string.c

/**********************************************************************

  string.c -

  $Author$
  $Date$
  created at: Mon Aug  9 17:12:58 JST 1993

  Copyright (C) 1993-2003 Yukihiro Matsumoto
  Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
  Copyright (C) 2000  Information-technology Promotion Agency, Japan

**********************************************************************/

#include "ruby.h"
#include "re.h"
#include "version.h"

#define BEG(no) regs->beg[no]
#define END(no) regs->end[no]

#include <math.h>
#include <ctype.h>

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

VALUE rb_cString;

#define STR_ASSOC   FL_USER3

#define RESIZE_CAPA(str,capacity) do {\
    REALLOC_N(RSTRING(str)->ptr, char, (capacity)+1);\
    RSTRING(str)->aux.capa = (capacity);\
} while (0)

VALUE rb_fs;

static VALUE str_alloc _((VALUE));
static VALUE
str_alloc(klass)
    VALUE klass;
{
    NEWOBJ(str, struct RString);
    OBJSETUP(str, klass, T_STRING);

    str->ptr = 0;
    str->len = 0;
    str->aux.capa = 0;

    return (VALUE)str;
}

static VALUE
str_new(klass, ptr, len)
    VALUE klass;
    const char *ptr;
    long len;
{
    VALUE str;

    if (len < 0) {
	rb_raise(rb_eArgError, "negative string size (or size too big)");
    }

    str = str_alloc(klass);
    RSTRING(str)->len = len;
    RSTRING(str)->aux.capa = len;
    RSTRING(str)->ptr = ALLOC_N(char,len+1);
    if (ptr) {
	memcpy(RSTRING(str)->ptr, ptr, len);
    }
    RSTRING(str)->ptr[len] = '\0';
    return str;
}

VALUE
rb_str_new(ptr, len)
    const char *ptr;
    long len;
{
    return str_new(rb_cString, ptr, len);
}

VALUE
rb_str_new2(ptr)
    const char *ptr;
{
    if (!ptr) {
	rb_raise(rb_eArgError, "NULL pointer given");
    }
    return rb_str_new(ptr, strlen(ptr));
}

VALUE
rb_tainted_str_new(ptr, len)
    const char *ptr;
    long len;
{
    VALUE str = rb_str_new(ptr, len);

    OBJ_TAINT(str);
    return str;
}

VALUE
rb_tainted_str_new2(ptr)
    const char *ptr;
{
    VALUE str = rb_str_new2(ptr);

    OBJ_TAINT(str);
    return str;
}

static VALUE
str_new3(klass, str)
    VALUE klass, str;
{
    VALUE str2 = str_alloc(klass);

    RSTRING(str2)->len = RSTRING(str)->len;
    RSTRING(str2)->ptr = RSTRING(str)->ptr;
    RSTRING(str2)->aux.shared = str;
    FL_SET(str2, ELTS_SHARED);
    OBJ_INFECT(str2, str);

    return str2;
}

VALUE
rb_str_new3(str)
    VALUE str;
{
    return str_new3(rb_obj_class(str), str);
}

static VALUE
str_new4(klass, str)
    VALUE klass, str;
{
    VALUE str2 = str_alloc(klass);

    RSTRING(str2)->len = RSTRING(str)->len;
    RSTRING(str2)->ptr = RSTRING(str)->ptr;
    RSTRING(str)->aux.shared = str2;
    FL_SET(str, ELTS_SHARED);
    OBJ_INFECT(str2, str);

    return str2;
}

VALUE
rb_str_new4(orig)
    VALUE orig;
{
    VALUE klass, str;

    if (OBJ_FROZEN(orig)) return orig;
    klass = rb_obj_class(orig);
    if (FL_TEST(orig, ELTS_SHARED) && RSTRING(orig)->aux.shared) {
	long ofs;
	str = RSTRING(orig)->aux.shared;
	ofs = RSTRING(str)->len - RSTRING(orig)->len;
	if (ofs > 0) {
	    str = str_new3(klass, str);
	    RSTRING(str)->ptr += ofs;
	    RSTRING(str)->len -= ofs;
	}
    }
    else if (FL_TEST(orig, STR_ASSOC)) {
	str = str_new(klass, RSTRING(orig)->ptr, RSTRING(orig)->len);
	OBJ_INFECT(str, orig);
    }
    else {
	str = str_new4(klass, orig);
    }
    OBJ_FREEZE(str);
    return str;
}

VALUE
rb_str_new5(obj, ptr, len)
    VALUE obj;
    const char *ptr;
    long len;
{
    return str_new(rb_obj_class(obj), ptr, len);
}

#define STR_BUF_MIN_SIZE 128

VALUE
rb_str_buf_new(capa)
    long capa;
{
    VALUE str = str_alloc(rb_cString);

    if (capa < STR_BUF_MIN_SIZE) {
	capa = STR_BUF_MIN_SIZE;
    }
    RSTRING(str)->ptr = 0;
    RSTRING(str)->len = 0;
    RSTRING(str)->aux.capa = capa;
    RSTRING(str)->ptr = ALLOC_N(char, capa+1);
    RSTRING(str)->ptr[0] = '\0';

    return str;
}

VALUE
rb_str_buf_new2(ptr)
    const char *ptr;
{
    VALUE str;
    long len = strlen(ptr);

    str = rb_str_buf_new(len);
    rb_str_buf_cat(str, ptr, len);

    return str;
}

VALUE
rb_str_to_str(str)
    VALUE str;
{
    return rb_convert_type(str, T_STRING, "String", "to_str");
}

static void
rb_str_shared_replace(str, str2)
    VALUE str, str2;
{
    if (str == str2) return;
    if (!FL_TEST(str, ELTS_SHARED)) free(RSTRING(str)->ptr);
    if (NIL_P(str2)) {
	RSTRING(str)->ptr = 0;
	RSTRING(str)->len = 0;
	RSTRING(str)->aux.capa = 0;
	FL_UNSET(str, ELTS_SHARED|STR_ASSOC);
	return;
    }
    RSTRING(str)->ptr = RSTRING(str2)->ptr;
    RSTRING(str)->len = RSTRING(str2)->len;
    FL_UNSET(str, ELTS_SHARED|STR_ASSOC);
    if (FL_TEST(str2, ELTS_SHARED|STR_ASSOC)) {
	FL_SET(str, RBASIC(str2)->flags & (ELTS_SHARED|STR_ASSOC));
	RSTRING(str)->aux.shared = RSTRING(str2)->aux.shared;
    }
    else {
	RSTRING(str)->aux.capa = RSTRING(str2)->aux.capa;
    }
    RSTRING(str2)->ptr = 0;	/* abandon str2 */
    RSTRING(str2)->len = 0;
    RSTRING(str2)->aux.capa = 0;
    FL_UNSET(str2, ELTS_SHARED|STR_ASSOC);
    if (OBJ_TAINTED(str2)) OBJ_TAINT(str);
}

static ID id_to_s;

VALUE
rb_obj_as_string(obj)
    VALUE obj;
{
    VALUE str;

    if (TYPE(obj) == T_STRING) {
	return obj;
    }
    str = rb_funcall(obj, id_to_s, 0);
    if (TYPE(str) != T_STRING)
	return rb_any_to_s(obj);
    if (OBJ_TAINTED(obj)) OBJ_TAINT(str);
    return str;
}

static VALUE rb_str_replace _((VALUE, VALUE));

VALUE
rb_str_dup(str)
    VALUE str;
{
    VALUE dup = str_alloc(rb_obj_class(str));
    rb_str_replace(dup, str);
    return dup;
}

static VALUE
rb_str_init(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    VALUE orig;

    if (rb_scan_args(argc, argv, "01", &orig) == 1)
	rb_str_replace(str, orig);
    return str;
}

static VALUE
rb_str_length(str)
    VALUE str;
{
    return LONG2NUM(RSTRING(str)->len);
}

static VALUE
rb_str_empty(str)
    VALUE str;
{
    if (RSTRING(str)->len == 0)
	return Qtrue;
    return Qfalse;
}

VALUE
rb_str_plus(str1, str2)
    VALUE str1, str2;
{
    VALUE str3;

    StringValue(str2);
    str3 = rb_str_new(0, RSTRING(str1)->len+RSTRING(str2)->len);
    memcpy(RSTRING(str3)->ptr, RSTRING(str1)->ptr, RSTRING(str1)->len);
    memcpy(RSTRING(str3)->ptr + RSTRING(str1)->len,
	   RSTRING(str2)->ptr, RSTRING(str2)->len);
    RSTRING(str3)->ptr[RSTRING(str3)->len] = '\0';

    if (OBJ_TAINTED(str1) || OBJ_TAINTED(str2))
	OBJ_TAINT(str3);
    return str3;
}

VALUE
rb_str_times(str, times)
    VALUE str;
    VALUE times;
{
    VALUE str2;
    long i, len;

    len = NUM2LONG(times);
    if (len == 0) return rb_str_new5(str,0,0);
    if (len < 0) {
	rb_raise(rb_eArgError, "negative argument");
    }
    if (LONG_MAX/len <  RSTRING(str)->len) {
	rb_raise(rb_eArgError, "argument too big");
    }

    str2 = rb_str_new5(str,0, RSTRING(str)->len*len);
    for (i=0; i<len; i++) {
	memcpy(RSTRING(str2)->ptr+(i*RSTRING(str)->len),
	       RSTRING(str)->ptr, RSTRING(str)->len);
    }
    RSTRING(str2)->ptr[RSTRING(str2)->len] = '\0';

    OBJ_INFECT(str2, str);

    return str2;
}

static VALUE
rb_str_format(str, arg)
    VALUE str, arg;
{
    VALUE *argv;

    if (TYPE(arg) == T_ARRAY) {
	argv = ALLOCA_N(VALUE, RARRAY(arg)->len + 1);
	argv[0] = str;
	MEMCPY(argv+1, RARRAY(arg)->ptr, VALUE, RARRAY(arg)->len);
	return rb_f_sprintf(RARRAY(arg)->len+1, argv);
    }
    
    argv = ALLOCA_N(VALUE, 2);
    argv[0] = str;
    argv[1] = arg;
    return rb_f_sprintf(2, argv);
}

static int
str_independent(str)
    VALUE str;
{
    if (OBJ_FROZEN(str)) rb_error_frozen("string");
    if (!OBJ_TAINTED(str) && rb_safe_level() >= 4)
	rb_raise(rb_eSecurityError, "Insecure: can't modify string");
    if (!FL_TEST(str, ELTS_SHARED)) return 1;
    return 0;
}

static void
str_make_independent(str)
    VALUE str;
{
    char *ptr;

    ptr = ALLOC_N(char, RSTRING(str)->len+1);
    if (RSTRING(str)->ptr) {
	memcpy(ptr, RSTRING(str)->ptr, RSTRING(str)->len);
    }
    ptr[RSTRING(str)->len] = 0;
    RSTRING(str)->ptr = ptr;
    RSTRING(str)->aux.capa = RSTRING(str)->len;
    FL_UNSET(str, ELTS_SHARED|STR_ASSOC);
}

void
rb_str_modify(str)
    VALUE str;
{
    if (!str_independent(str))
	str_make_independent(str);
}

void
rb_str_associate(str, add)
    VALUE str, add;
{
    if (FL_TEST(str, STR_ASSOC)) {
	/* already associated */
	rb_ary_concat(RSTRING(str)->aux.shared, add);
    }
    else {
	if (FL_TEST(str, ELTS_SHARED)) {
	    str_make_independent(str);
	}
	else if (RSTRING(str)->aux.capa != RSTRING(str)->len) {
	    RESIZE_CAPA(str, RSTRING(str)->len);
	}
	RSTRING(str)->aux.shared = add;
	FL_SET(str, STR_ASSOC);
    }
}

VALUE
rb_str_associated(str)
    VALUE str;
{
    if (FL_TEST(str, STR_ASSOC)) {
	return RSTRING(str)->aux.shared;
    }
    return Qfalse;
}

static char *null_str = "";

VALUE
rb_string_value(ptr)
    volatile VALUE *ptr;
{
    VALUE s = *ptr;
    if (TYPE(s) != T_STRING) {
	s = rb_str_to_str(s);
	*ptr = s;
    }
    if (!RSTRING(s)->ptr) {
	FL_SET(s, ELTS_SHARED);
	RSTRING(s)->ptr = null_str;
    }
    return s;
}

char *
rb_string_value_ptr(ptr)
    volatile VALUE *ptr;
{
    return RSTRING(rb_string_value(ptr))->ptr;
}

char *
rb_string_value_cstr(ptr)
    volatile VALUE *ptr;
{
    VALUE str = rb_string_value(ptr);
    char *s = RSTRING(str)->ptr;

    if (!s || RSTRING(str)->len != strlen(s)) {
	rb_raise(rb_eArgError, "string contains null byte");
    }
    return s;
}

VALUE
rb_check_string_type(str)
    VALUE str;
{
    str = rb_check_convert_type(str, T_STRING, "String", "to_str");
    if (!NIL_P(str) && !RSTRING(str)->ptr) {
	FL_SET(str, ELTS_SHARED);
	RSTRING(str)->ptr = null_str;
    }
    return str;
}

VALUE
rb_str_substr(str, beg, len)
    VALUE str;
    long beg, len;
{
    VALUE str2;

    if (len < 0) return Qnil;
    if (beg > RSTRING(str)->len) return Qnil;
    if (beg < 0) {
	beg += RSTRING(str)->len;
	if (beg < 0) return Qnil;
    }
    if (beg + len > RSTRING(str)->len) {
	len = RSTRING(str)->len - beg;
    }
    if (len < 0) {
	len = 0;
    }
    if (len == 0) return rb_str_new5(str,0,0);

    if (len > sizeof(struct RString)/2 &&
	beg + len == RSTRING(str)->len &&
	!FL_TEST(str, STR_ASSOC)) {
	if (FL_TEST(str, ELTS_SHARED) && RSTRING(str)->aux.shared)
	    str = RSTRING(str)->aux.shared;
	else
	    str = str_new4(rb_obj_class(str), str);
	str2 = rb_str_new3(str);
	RSTRING(str2)->ptr += RSTRING(str2)->len - len;
	RSTRING(str2)->len = len;
    }
    else {
	str2 = rb_str_new5(str, RSTRING(str)->ptr+beg, len);
	OBJ_INFECT(str2, str);
    }

    return str2;
}

VALUE
rb_str_freeze(str)
    VALUE str;
{
    return rb_obj_freeze(str);
}

VALUE
rb_str_dup_frozen(str)
    VALUE str;
{
    if (FL_TEST(str, ELTS_SHARED) && RSTRING(str)->aux.shared) {
	VALUE shared = RSTRING(str)->aux.shared;
	if (RSTRING(shared)->len == RSTRING(str)->len) {
	    OBJ_FREEZE(shared);
	    return shared;
	}
    }
    if (OBJ_FROZEN(str)) return str;
    str = rb_str_dup(str);
    OBJ_FREEZE(str);
    return str;
}

VALUE
rb_str_resize(str, len)
    VALUE str;
    long len;
{
    if (len < 0) {
	rb_raise(rb_eArgError, "negative string size (or size too big)");
    }
	
    if (len != RSTRING(str)->len) {
	rb_str_modify(str);
	if (RSTRING(str)->len < len || RSTRING(str)->len - len > 1024) {
	    REALLOC_N(RSTRING(str)->ptr, char, len+1);
	    if (!FL_TEST(str, STR_ASSOC|ELTS_SHARED)) {
		RSTRING(str)->aux.capa = len;
	    }
	}
	RSTRING(str)->len = len;
	RSTRING(str)->ptr[len] = '\0';	/* sentinel */
    }
    return str;
}

VALUE
rb_str_buf_cat(str, ptr, len)
    VALUE str;
    const char *ptr;
    long len;
{
    long capa, total;

    if (len == 0) return str;
    if (len < 0) {
	rb_raise(rb_eArgError, "negative string size (or size too big)");
    }
    rb_str_modify(str);
    if (FL_TEST(str, STR_ASSOC)) {
	FL_UNSET(str, STR_ASSOC);
	capa = RSTRING(str)->aux.capa = RSTRING(str)->len;
    }
    else {
	capa = RSTRING(str)->aux.capa;
    }
    total = RSTRING(str)->len+len;
    if (capa <= total) {
	while (total > capa) {
	    capa = (capa + 1) * 2;
	}
	RESIZE_CAPA(str, capa);
    }
    memcpy(RSTRING(str)->ptr + RSTRING(str)->len, ptr, len);
    RSTRING(str)->len = total;
    RSTRING(str)->ptr[total] = '\0'; /* sentinel */

    return str;
}

VALUE
rb_str_buf_cat2(str, ptr)
    VALUE str;
    const char *ptr;
{
    return rb_str_buf_cat(str, ptr, strlen(ptr));
}

VALUE
rb_str_cat(str, ptr, len)
    VALUE str;
    const char *ptr;
    long len;
{
    if (len < 0) {
	rb_raise(rb_eArgError, "negative string size (or size too big)");
    }
    if (FL_TEST(str, STR_ASSOC)) {
	rb_str_modify(str);
	REALLOC_N(RSTRING(str)->ptr, char, RSTRING(str)->len+len);
	memcpy(RSTRING(str)->ptr + RSTRING(str)->len, ptr, len);
	RSTRING(str)->len += len;
	RSTRING(str)->ptr[RSTRING(str)->len] = '\0'; /* sentinel */
	return str;
    }

    return rb_str_buf_cat(str, ptr, len);
}

VALUE
rb_str_cat2(str, ptr)
    VALUE str;
    const char *ptr;
{
    return rb_str_cat(str, ptr, strlen(ptr));
}

VALUE
rb_str_buf_append(str, str2)
    VALUE str, str2;
{
    long capa, len;

    rb_str_modify(str);
    if (FL_TEST(str, STR_ASSOC)) {
	FL_UNSET(str, STR_ASSOC);
	capa = RSTRING(str)->aux.capa = RSTRING(str)->len;
    }
    else {
	capa = RSTRING(str)->aux.capa;
    }
    len = RSTRING(str)->len+RSTRING(str2)->len;
    if (capa <= len) {
	while (len > capa) {
	    capa = (capa + 1) * 2;
	}
	RESIZE_CAPA(str, capa);
    }
    memcpy(RSTRING(str)->ptr + RSTRING(str)->len,
	   RSTRING(str2)->ptr, RSTRING(str2)->len);
    RSTRING(str)->len += RSTRING(str2)->len;
    RSTRING(str)->ptr[RSTRING(str)->len] = '\0'; /* sentinel */
    OBJ_INFECT(str, str2);

    return str;
}

VALUE
rb_str_append(str, str2)
    VALUE str, str2;
{
    rb_str_modify(str);
    StringValue(str2);
    if (RSTRING(str2)->len > 0) {
	if (FL_TEST(str, STR_ASSOC)) {
	    long len = RSTRING(str)->len+RSTRING(str2)->len;
	    REALLOC_N(RSTRING(str)->ptr, char, len+1);
	    memcpy(RSTRING(str)->ptr + RSTRING(str)->len,
		   RSTRING(str2)->ptr, RSTRING(str2)->len);
	    RSTRING(str)->ptr[len] = '\0'; /* sentinel */
	    RSTRING(str)->len = len;
	}
	else {
	    return rb_str_buf_append(str, str2);
	}
    }
    OBJ_INFECT(str, str2);
    return str;
}

VALUE
rb_str_concat(str1, str2)
    VALUE str1, str2;
{
    if (FIXNUM_P(str2)) {
	int i = FIX2INT(str2);
	if (0 <= i && i <= 0xff) { /* byte */
	    char c = i;
	    return rb_str_cat(str1, &c, 1);
	}
    }
    str1 = rb_str_append(str1, str2);

    return str1;
}

int
rb_str_hash(str)
    VALUE str;
{
    register long len = RSTRING(str)->len;
    register char *p = RSTRING(str)->ptr;
    register int key = 0;

#ifdef HASH_ELFHASH
    register unsigned int g;

    while (len--) {
	key = (key << 4) + *p++;
	if (g = key & 0xF0000000)
	    key ^= g >> 24;
	key &= ~g;
    }
#elif HASH_PERL
    while (len--) {
	key = key*33 + *p++;
    }
    key = key + (key>>5);
#else
    while (len--) {
	key = key*65599 + *p;
	p++;
    }
    key = key + (key>>5);
#endif
    return key;
}

static VALUE
rb_str_hash_m(str)
    VALUE str;
{
    int key = rb_str_hash(str);
    return INT2FIX(key);
}

#define lesser(a,b) (((a)>(b))?(b):(a))

int
rb_str_cmp(str1, str2)
    VALUE str1, str2;
{
    long len;
    int retval;

    len = lesser(RSTRING(str1)->len, RSTRING(str2)->len);
    retval = rb_memcmp(RSTRING(str1)->ptr, RSTRING(str2)->ptr, len);
    if (retval == 0) {
	if (RSTRING(str1)->len == RSTRING(str2)->len) return 0;
	if (RSTRING(str1)->len > RSTRING(str2)->len) return 1;
	return -1;
    }
    if (retval > 0) return 1;
    return -1;
}

static VALUE
rb_str_equal(str1, str2)
    VALUE str1, str2;
{
    if (str1 == str2) return Qtrue;
    if (TYPE(str2) != T_STRING) {
	if (!rb_respond_to(str2, rb_intern("to_str"))) {
	    return Qnil;
	}
	return rb_equal(str2, str1);
    }
    if (RSTRING(str1)->len == RSTRING(str2)->len &&
	rb_str_cmp(str1, str2) == 0) {
	return Qtrue;
    }
    return Qfalse;
}

static VALUE
rb_str_eql(str1, str2)
    VALUE str1, str2;
{
    if (TYPE(str2) != T_STRING || RSTRING(str1)->len != RSTRING(str2)->len)
	return Qfalse;

    if (memcmp(RSTRING(str1)->ptr, RSTRING(str2)->ptr,
	       lesser(RSTRING(str1)->len, RSTRING(str2)->len)) == 0)
	return Qtrue;

    return Qfalse;
}

static VALUE
rb_str_cmp_m(str1, str2)
    VALUE str1, str2;
{
    long result;

    if (TYPE(str2) != T_STRING) {
	if (!rb_respond_to(str2, rb_intern("to_str"))) {
	    return Qnil;
	}
	else if (!rb_respond_to(str2, rb_intern("<=>"))) {
	    return Qnil;
	}
	else {
	    VALUE tmp = rb_funcall(str2, rb_intern("<=>"), 1, str1);

	    if (NIL_P(tmp)) return Qnil;
	    if (!FIXNUM_P(tmp)) {
		return rb_funcall(LONG2FIX(0), '-', 1, tmp);
	    }
	    result = -FIX2LONG(tmp);
	}
    }
    else {
	result = rb_str_cmp(str1, str2);
    }
    return LONG2NUM(result);
}

static VALUE
rb_str_casecmp(str1, str2)
    VALUE str1, str2;
{
    long len;
    int retval;

    StringValue(str2);
    len = lesser(RSTRING(str1)->len, RSTRING(str2)->len);
    retval = rb_memcicmp(RSTRING(str1)->ptr, RSTRING(str2)->ptr, len);
    if (retval == 0) {
	if (RSTRING(str1)->len == RSTRING(str2)->len) return INT2FIX(0);
	if (RSTRING(str1)->len > RSTRING(str2)->len) return INT2FIX(1);
	return INT2FIX(-1);
    }
    if (retval == 0) return INT2FIX(0);
    if (retval > 0) return INT2FIX(1);
    return INT2FIX(-1);
}

static long
rb_str_index(str, sub, offset)
    VALUE str, sub;
    long offset;
{
    long pos;

    if (offset < 0) {
	offset += RSTRING(str)->len;
	if (offset < 0) return -1;
    }
    if (RSTRING(str)->len - offset < RSTRING(sub)->len) return -1;
    if (RSTRING(sub)->len == 0) return offset;
    pos = rb_memsearch(RSTRING(sub)->ptr, RSTRING(sub)->len,
		       RSTRING(str)->ptr+offset, RSTRING(str)->len-offset);
    if (pos < 0) return pos;
    return pos + offset;
}

static VALUE
rb_str_index_m(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    VALUE sub;
    VALUE initpos;
    long pos;

    if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
	pos = NUM2LONG(initpos);
    }
    else {
	pos = 0;
    }
    if (pos < 0) {
	pos += RSTRING(str)->len;
	if (pos < 0) {
	    if (TYPE(sub) == T_REGEXP) {
		rb_backref_set(Qnil);
	    }
	    return Qnil;
	}
    }

    switch (TYPE(sub)) {
      case T_REGEXP:
	pos = rb_reg_adjust_startpos(sub, str, pos, 0);
	pos = rb_reg_search(sub, str, pos, 0);
	break;

      case T_FIXNUM:
      {
	  int c = FIX2INT(sub);
	  long len = RSTRING(str)->len;
	  char *p = RSTRING(str)->ptr;

	  for (;pos<len;pos++) {
	      if (p[pos] == c) return LONG2NUM(pos);
	  }
	  return Qnil;
      }

      default: {
	  VALUE tmp;

	  tmp = rb_check_string_type(sub);
	  if (NIL_P(tmp)) {
	      rb_raise(rb_eTypeError, "type mismatch: %s given",
		       rb_obj_classname(sub));
	  }
	  sub = tmp;
      }
	/* fall through */
      case T_STRING:
	pos = rb_str_index(str, sub, pos);
	break;
    }

    if (pos == -1) return Qnil;
    return LONG2NUM(pos);
}

static long
rb_str_rindex(str, sub, pos)
    VALUE str, sub;
    long pos;
{
    long len = RSTRING(sub)->len;
    char *s, *sbeg, *t;

    /* substring longer than string */
    if (RSTRING(str)->len < len) return -1;
    if (RSTRING(str)->len - pos < len) {
	pos = RSTRING(str)->len - len;
    }
    sbeg = RSTRING(str)->ptr;
    s = RSTRING(str)->ptr + pos;
    t = RSTRING(sub)->ptr;
    if (len) {
	while (sbeg <= s) {
	    if (rb_memcmp(s, t, len) == 0) {
		return s - RSTRING(str)->ptr;
	    }
	    s--;
	}
	return -1;
    }
    else {
	return pos;
    }
}

static VALUE
rb_str_rindex_m(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    VALUE sub;
    VALUE position;
    long pos;

    if (rb_scan_args(argc, argv, "11", &sub, &position) == 2) {
	pos = NUM2LONG(position);
        if (pos < 0) {
	    pos += RSTRING(str)->len;
	    if (pos < 0) {
		if (TYPE(sub) == T_REGEXP) {
		    rb_backref_set(Qnil);
		}
		return Qnil;
	    }
        }
	if (pos > RSTRING(str)->len) pos = RSTRING(str)->len;
    }
    else {
	pos = RSTRING(str)->len;
    }

    switch (TYPE(sub)) {
      case T_REGEXP:
	if (RREGEXP(sub)->len) {
	    pos = rb_reg_adjust_startpos(sub, str, pos, 1);
	    pos = rb_reg_search(sub, str, pos, 1);
	}
	if (pos >= 0) return LONG2NUM(pos);
	break;

      case T_STRING:
	pos = rb_str_rindex(str, sub, pos);
	if (pos >= 0) return LONG2NUM(pos);
	break;

      case T_FIXNUM:
      {
	  int c = FIX2INT(sub);
	  char *p = RSTRING(str)->ptr + pos;
	  char *pbeg = RSTRING(str)->ptr;

	  if (pos == RSTRING(str)->len) {
	      if (pos == 0) return Qnil;
	      --p;
	  }
	  while (pbeg <= p) {
	      if (*p == c) return LONG2NUM(p - RSTRING(str)->ptr);
	      p--;
	  }
	  return Qnil;
      }

      default:
	rb_raise(rb_eTypeError, "type mismatch: %s given",
		 rb_obj_classname(sub));
    }
    return Qnil;
}

static VALUE
rb_str_match(x, y)
    VALUE x, y;
{
    VALUE reg;
    long start;

    switch (TYPE(y)) {
      case T_REGEXP:
	return rb_reg_match(y, x);

      case T_STRING:
#if RUBY_VERSION_CODE < 181
	rb_warn("string =~ string will be obsolete; use explicit regexp");
#endif
	reg = rb_reg_regcomp(y);
	start = rb_reg_search(reg, x, 0, 0);
	if (start == -1) {
	    return Qnil;
	}
	return INT2NUM(start);

      default:
	return rb_funcall(y, rb_intern("=~"), 1, x);
    }
}

static VALUE
rb_str_match2(str)
    VALUE str;
{
    StringValue(str);
#if RUBY_VERSION_CODE < 181
	rb_warn("~string will be obsolete; use explicit regexp");
#endif
    return rb_reg_match2(rb_reg_regcomp(rb_reg_quote(str)));
}

static VALUE get_pat _((VALUE, int));

static VALUE
rb_str_match_m(str, re)
    VALUE str, re;
{
    return rb_funcall(get_pat(re, 0), rb_intern("match"), 1, str);
}

static char
succ_char(s)
    char *s;
{
    char c = *s;

    /* numerics */
    if ('0' <= c && c < '9') (*s)++;
    else if (c == '9') {
	*s = '0';
	return '1';
    }
    /* small alphabets */
    else if ('a' <= c && c < 'z') (*s)++;
    else if (c == 'z') {
	return *s = 'a';
    }
    /* capital alphabets */
    else if ('A' <= c && c < 'Z') (*s)++;
    else if (c == 'Z') {
	return *s = 'A';
    }
    return 0;
}

static VALUE
rb_str_succ(orig)
    VALUE orig;
{
    VALUE str;
    char *sbeg, *s;
    int c = -1;
    long n = 0;

    str = rb_str_new5(orig,RSTRING(orig)->ptr, RSTRING(orig)->len);
    OBJ_INFECT(str, orig);
    if (RSTRING(str)->len == 0) return str;

    sbeg = RSTRING(str)->ptr; s = sbeg + RSTRING(str)->len - 1;

    while (sbeg <= s) {
	if (ISALNUM(*s)) {
	    if ((c = succ_char(s)) == 0) break;
	    n = s - sbeg;
	}
	s--;
    }
    if (c == -1) {		/* str contains no alnum */
	sbeg = RSTRING(str)->ptr; s = sbeg + RSTRING(str)->len - 1;
	c = '\001';
	while (sbeg <= s) {
           if ((*s += 1) != 0) break;
           s--;
	}
    }
    if (s < sbeg) {
	RESIZE_CAPA(str, RSTRING(str)->len + 1);
	s = RSTRING(str)->ptr + n;
	memmove(s+1, s, RSTRING(str)->len - n);
	*s = c;
	RSTRING(str)->len += 1;
	RSTRING(str)->ptr[RSTRING(str)->len] = '\0';
    }

    return str;
}

static VALUE
rb_str_succ_bang(str)
    VALUE str;
{
    rb_str_modify(str);
    rb_str_shared_replace(str, rb_str_succ(str));

    return str;
}

VALUE
rb_str_upto(beg, end, excl)
    VALUE beg, end;
    int excl;
{
    VALUE current, after_end;
    ID succ = rb_intern("succ");

    StringValue(end);
    if (rb_str_cmp(beg, end) > 0) return beg;
    after_end = rb_funcall(end, succ, 0, 0);
    current = beg;
    while (!rb_str_equal(current, after_end)) {
	rb_yield(current);
	if (!excl && rb_str_equal(current, end)) break;
	current = rb_funcall(current, succ, 0, 0);
	if (excl && rb_str_equal(current, end)) break;
	if (RSTRING(current)->len > RSTRING(end)->len)
	    break;
    }

    return beg;
}

static VALUE
rb_str_upto_m(beg, end)
    VALUE beg, end;
{
    return rb_str_upto(beg, end, Qfalse);
}

static VALUE
rb_str_subpat(str, re, nth)
    VALUE str, re;
    int nth;
{
    if (rb_reg_search(re, str, 0, 0) >= 0) {
	return rb_reg_nth_match(nth, rb_backref_get());
    }
    return Qnil;
}
    
static VALUE
rb_str_aref(str, indx)
    VALUE str;
    VALUE indx;
{
    long idx;

    switch (TYPE(indx)) {
      case T_FIXNUM:
	idx = FIX2LONG(indx);

      num_index:
	if (idx < 0) {
	    idx = RSTRING(str)->len + idx;
	}
	if (idx < 0 || RSTRING(str)->len <= idx) {
	    return Qnil;
	}
	return INT2FIX(RSTRING(str)->ptr[idx] & 0xff);

      case T_REGEXP:
	return rb_str_subpat(str, indx, 0);

      case T_STRING:
	if (rb_str_index(str, indx, 0) != -1)
	    return rb_str_dup(indx);
	return Qnil;

      default:
	/* check if indx is Range */
	{
	    long beg, len;
	    switch (rb_range_beg_len(indx, &beg, &len, RSTRING(str)->len, 0)) {
	      case Qfalse:
		break;
	      case Qnil:
		return Qnil;
	      default:
		return rb_str_substr(str, beg, len);
	    }
	}
	idx = NUM2LONG(indx);
	goto num_index;
    }
    return Qnil;		/* not reached */
}

static VALUE
rb_str_aref_m(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    if (argc == 2) {
	if (TYPE(argv[0]) == T_REGEXP) {
	    return rb_str_subpat(str, argv[0], NUM2INT(argv[1]));
	}
	return rb_str_substr(str, NUM2LONG(argv[0]), NUM2LONG(argv[1]));
    }
    if (argc != 1) {
	rb_raise(rb_eArgError, "wrong number of arguments(%d for 1)", argc);
    }
    return rb_str_aref(str, argv[0]);
}

void
rb_str_update(str, beg, len, val)
    VALUE str;
    long beg, len;
    VALUE val;
{
    if (len < 0) rb_raise(rb_eIndexError, "negative length %ld", len);
    if (RSTRING(str)->len < beg) {
      out_of_range:
	rb_raise(rb_eIndexError, "index %ld out of string", beg);
    }
    if (beg < 0) {
	if (-beg > RSTRING(str)->len) {
	    goto out_of_range;
	}
	beg += RSTRING(str)->len;
    }
    if (RSTRING(str)->len < beg + len) {
	len = RSTRING(str)->len - beg;
    }

    StringValue(val);
    if (len < RSTRING(val)->len) {
	/* expand string */
	RESIZE_CAPA(str, RSTRING(str)->len + RSTRING(val)->len - len);
    }

    if (RSTRING(val)->len != len) {
	memmove(RSTRING(str)->ptr + beg + RSTRING(val)->len,
		RSTRING(str)->ptr + beg + len,
		RSTRING(str)->len - (beg + len));
    }
    if (RSTRING(str)->len < beg && len < 0) {
	MEMZERO(RSTRING(str)->ptr + RSTRING(str)->len, char, -len);
    }
    if (RSTRING(val)->len > 0) {
	memmove(RSTRING(str)->ptr+beg, RSTRING(val)->ptr, RSTRING(val)->len);
    }
    RSTRING(str)->len += RSTRING(val)->len - len;
    RSTRING(str)->ptr[RSTRING(str)->len] = '\0';
    OBJ_INFECT(str, val);
}

static void
rb_str_subpat_set(str, re, nth, val)
    VALUE str, re;
    int nth;
    VALUE val;
{
    VALUE match;
    long start, end, len;

    if (rb_reg_search(re, str, 0, 0) < 0) {
	rb_raise(rb_eIndexError, "regexp not matched");
    }
    match = rb_backref_get();
    if (nth >= RMATCH(match)->regs->num_regs) {
      out_of_range:
	rb_raise(rb_eIndexError, "index %d out of regexp", nth);
    }
    if (nth < 0) {
	if (-nth >= RMATCH(match)->regs->num_regs) {
	    goto out_of_range;
	}
	nth += RMATCH(match)->regs->num_regs;
    }

    start = RMATCH(match)->BEG(nth);
    if (start == -1) {
	rb_raise(rb_eIndexError, "regexp group %d not matched", nth);
    }
    end = RMATCH(match)->END(nth);
    len = end - start;
    rb_str_modify(str);
    rb_str_update(str, start, len, val);
}

static VALUE
rb_str_aset(str, indx, val)
    VALUE str;
    VALUE indx, val;
{
    long idx, beg;

    switch (TYPE(indx)) {
      case T_FIXNUM:
      num_index:
	idx = NUM2LONG(indx);
	if (RSTRING(str)->len <= idx) {
	  out_of_range:
	    rb_raise(rb_eIndexError, "index %ld out of string", idx);
	}
	if (idx < 0) {
	    if (-idx > RSTRING(str)->len)
		goto out_of_range;
	    idx += RSTRING(str)->len;
	}
	if (FIXNUM_P(val)) {
	    if (RSTRING(str)->len == idx) {
		RSTRING(str)->len += 1;
		RESIZE_CAPA(str, RSTRING(str)->len);
	    }
	    RSTRING(str)->ptr[idx] = NUM2INT(val) & 0xff;
	}
	else {
	    rb_str_update(str, idx, 1, val);
	}
	return val;

      case T_REGEXP:
	rb_str_subpat_set(str, indx, 0, val);
	return val;

      case T_STRING:
	beg = rb_str_index(str, indx, 0);
	if (beg < 0) {
	    rb_raise(rb_eIndexError, "string not matched");
	}
	rb_str_update(str, beg, RSTRING(indx)->len, val);
	return val;

      default:
	/* check if indx is Range */
	{
	    long beg, len;
	    if (rb_range_beg_len(indx, &beg, &len, RSTRING(str)->len, 2)) {
		rb_str_update(str, beg, len, val);
		return val;
	    }
	}
	idx = NUM2LONG(indx);
	goto num_index;
    }
}

static VALUE
rb_str_aset_m(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    rb_str_modify(str);
    if (argc == 3) {
	if (TYPE(argv[0]) == T_REGEXP) {
	    rb_str_subpat_set(str, argv[0], NUM2INT(argv[1]), argv[2]);
	}
	else {
	    rb_str_update(str, NUM2LONG(argv[0]), NUM2LONG(argv[1]), argv[2]);
	}
	return argv[2];
    }
    if (argc != 2) {
	rb_raise(rb_eArgError, "wrong number of arguments(%d for 2)", argc);
    }
    return rb_str_aset(str, argv[0], argv[1]);
}

static VALUE
rb_str_insert(str, idx, str2)
    VALUE str, idx, str2;
{
    long pos = NUM2LONG(idx);

    rb_str_modify(str);
    if (pos == -1) {
	pos = RSTRING(str)->len;
    }
    else if (pos < 0) {
	pos++;
    }
    rb_str_update(str, pos, 0, str2);
    return str;
}

static VALUE
rb_str_slice_bang(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    VALUE result;
    VALUE buf[3];
    int i;

    if (argc < 1 || 2 < argc) {
	rb_raise(rb_eArgError, "wrong number of arguments(%d for 1)", argc);
    }
    for (i=0; i<argc; i++) {
	buf[i] = argv[i];
    }
    buf[i] = rb_str_new(0,0);
    result = rb_str_aref_m(argc, buf, str);
    if (!NIL_P(result)) {
	rb_str_aset_m(argc+1, buf, str);
    }
    return result;
}

static VALUE
get_pat(pat, quote)
    VALUE pat;
    int quote;
{
    VALUE val;

    switch (TYPE(pat)) {
      case T_REGEXP:
	return pat;

      case T_STRING:
	break;

      default:
	val = rb_check_string_type(pat);
	if (NIL_P(val)) {
	    Check_Type(pat, T_REGEXP);
	}
	pat = val;
    }

    if (quote) {
	val = rb_reg_quote(pat);
#if RUBY_VERSION_CODE < 181
	if (val != pat && rb_str_cmp(val, pat) != 0) {
	    rb_warn("string pattern instead of regexp; metacharacters no longer effective");
	}
#endif
	pat = val;
    }

    return rb_reg_regcomp(pat);
}

static VALUE
rb_str_sub_bang(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    VALUE pat, repl, match;
    struct re_registers *regs;
    int iter = 0;
    int tainted = 0;
    long plen;

    if (argc == 1 && rb_block_given_p()) {
	iter = 1;
    }
    else if (argc == 2) {
	repl = argv[1];
	StringValue(repl);
	if (OBJ_TAINTED(repl)) tainted = 1;
    }
    else {
	rb_raise(rb_eArgError, "wrong number of arguments(%d for 2)", argc);
    }

    pat = get_pat(argv[0], 1);
    if (rb_reg_search(pat, str, 0, 0) >= 0) {
	rb_str_modify(str);
	match = rb_backref_get();
	regs = RMATCH(match)->regs;

	if (iter) {
	    rb_match_busy(match);
	    repl = rb_obj_as_string(rb_yield(rb_reg_nth_match(0, match)));
	    rb_backref_set(match);
	}
	else {
	    repl = rb_reg_regsub(repl, str, regs);
	}
	if (OBJ_TAINTED(repl)) tainted = 1;
	plen = END(0) - BEG(0);
	if (RSTRING(repl)->len > plen) {
	    RESIZE_CAPA(str, RSTRING(str)->len + RSTRING(repl)->len - plen);
	}
	if (RSTRING(repl)->len != plen) {
	    memmove(RSTRING(str)->ptr + BEG(0) + RSTRING(repl)->len,
		    RSTRING(str)->ptr + BEG(0) + plen,
		    RSTRING(str)->len - BEG(0) - plen);
	}
	memcpy(RSTRING(str)->ptr + BEG(0),
	       RSTRING(repl)->ptr, RSTRING(repl)->len);
	RSTRING(str)->len += RSTRING(repl)->len - plen;
	RSTRING(str)->ptr[RSTRING(str)->len] = '\0';
	if (tainted) OBJ_TAINT(str);

	return str;
    }
    return Qnil;
}

static VALUE
rb_str_sub(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_sub_bang(argc, argv, str);
    return str;
}

static VALUE
str_gsub(argc, argv, str, bang)
    int argc;
    VALUE *argv;
    VALUE str;
    int bang;
{
    VALUE pat, val, repl, match;
    struct re_registers *regs;
    long beg, n;
    long offset, blen, len;
    int iter = 0;
    char *buf, *bp, *cp;
    int tainted = 0;

    if (argc == 1 && rb_block_given_p()) {
	iter = 1;
    }
    else if (argc == 2) {
	repl = argv[1];
	StringValue(repl);
	if (OBJ_TAINTED(repl)) tainted = 1;
    }
    else {
	rb_raise(rb_eArgError, "wrong number of arguments(%d for 2)", argc);
    }

    pat = get_pat(argv[0], 1);
    offset=0; n=0; 
    beg = rb_reg_search(pat, str, 0, 0);
    if (beg < 0) {
	if (bang) return Qnil;	/* no match, no substitution */
	return rb_str_dup(str);
    }

    blen = RSTRING(str)->len + 30; /* len + margin */
    buf = ALLOC_N(char, blen);
    bp = buf;
    cp = RSTRING(str)->ptr;

    while (beg >= 0) {
	n++;
	match = rb_backref_get();
	regs = RMATCH(match)->regs;
	if (iter) {
	    rb_match_busy(match);
	    val = rb_obj_as_string(rb_yield(rb_reg_nth_match(0, match)));
	    rb_backref_set(match);
	}
	else {
	    val = rb_reg_regsub(repl, str, regs);
	}
	if (OBJ_TAINTED(val)) tainted = 1;
	len = (bp - buf) + (beg - offset) + RSTRING(val)->len + 3;
	if (blen < len) {
	    while (blen < len) blen *= 2;
	    len = bp - buf;
	    REALLOC_N(buf, char, blen);
	    bp = buf + len;
	}
	len = beg - offset;	/* copy pre-match substr */
	memcpy(bp, cp, len);
	bp += len;
	memcpy(bp, RSTRING(val)->ptr, RSTRING(val)->len);
	bp += RSTRING(val)->len;
       offset = END(0);
	if (BEG(0) == END(0)) {
	    /*
	     * Always consume at least one character of the input string
	     * in order to prevent infinite loops.
	     */
	    if (RSTRING(str)->len <= END(0)) break;
	    len = mbclen2(RSTRING(str)->ptr[END(0)], pat);
	    memcpy(bp, RSTRING(str)->ptr+END(0), len);
	    bp += len;
	    offset = END(0) + len;
	}
	cp = RSTRING(str)->ptr + offset;
	if (offset > RSTRING(str)->len) break;
	beg = rb_reg_search(pat, str, offset, 0);
    }
    if (RSTRING(str)->len > offset) {
	len = bp - buf;
	if (blen - len < RSTRING(str)->len - offset + 1) {
	    REALLOC_N(buf, char, len + RSTRING(str)->len - offset + 1);
	    bp = buf + len;
	}
	memcpy(bp, cp, RSTRING(str)->len - offset);
	bp += RSTRING(str)->len - offset;
    }
    rb_backref_set(match);
    if (bang) {
	if (str_independent(str)) {
	    free(RSTRING(str)->ptr);
	}
	FL_UNSET(str, ELTS_SHARED|STR_ASSOC);
    }
    else {
	VALUE dup = str_alloc(rb_obj_class(str));

	OBJ_INFECT(dup, str);
	str = dup;
    }
    RSTRING(str)->ptr = buf;
    RSTRING(str)->len = len = bp - buf;
    RSTRING(str)->ptr[len] = '\0';
    RSTRING(str)->aux.capa = len;

    if (tainted) OBJ_TAINT(str);
    return str;
}

static VALUE
rb_str_gsub_bang(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    return str_gsub(argc, argv, str, 1);
}

static VALUE
rb_str_gsub(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    return str_gsub(argc, argv, str, 0);
}

static VALUE
rb_str_replace(str, str2)
    VALUE str, str2;
{
    if (str == str2) return str;

    StringValue(str2);
    if (FL_TEST(str2, ELTS_SHARED)) {
	if (str_independent(str)) {
	    free(RSTRING(str)->ptr);
	}
	RSTRING(str)->len = RSTRING(str2)->len;
	RSTRING(str)->ptr = RSTRING(str2)->ptr;
	FL_SET(str, ELTS_SHARED);
	FL_UNSET(str, STR_ASSOC);
	RSTRING(str)->aux.shared = RSTRING(str2)->aux.shared;
    }
    else {
	rb_str_modify(str);
	rb_str_resize(str, RSTRING(str2)->len);
	memcpy(RSTRING(str)->ptr, RSTRING(str2)->ptr, RSTRING(str2)->len);
	if (FL_TEST(str2, STR_ASSOC)) {
	    FL_SET(str, STR_ASSOC);
	    RSTRING(str)->aux.shared = RSTRING(str2)->aux.shared;
	}
    }

    OBJ_INFECT(str, str2);
    return str;
}

static VALUE
uscore_get()
{
    VALUE line;

    line = rb_lastline_get();
    if (TYPE(line) != T_STRING) {
	rb_raise(rb_eTypeError, "$_ value need to be String (%s given)",
		 NIL_P(line) ? "nil" : rb_obj_classname(line));
    }
    return line;
}

static VALUE
rb_f_sub_bang(argc, argv)
    int argc;
    VALUE *argv;
{
    return rb_str_sub_bang(argc, argv, uscore_get());
}

static VALUE
rb_f_sub(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE str = rb_str_dup(uscore_get());

    if (NIL_P(rb_str_sub_bang(argc, argv, str)))
	return str;
    rb_lastline_set(str);
    return str;
}

static VALUE
rb_f_gsub_bang(argc, argv)
    int argc;
    VALUE *argv;
{
    return rb_str_gsub_bang(argc, argv, uscore_get());
}

static VALUE
rb_f_gsub(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE str = rb_str_dup(uscore_get());

    if (NIL_P(rb_str_gsub_bang(argc, argv, str)))
	return str;
    rb_lastline_set(str);
    return str;
}

static VALUE
rb_str_reverse_bang(str)
    VALUE str;
{
    char *s, *e;
    char c;

    if (RSTRING(str)->len <= 1) return Qnil;
    rb_str_modify(str);
    s = RSTRING(str)->ptr;
    e = s + RSTRING(str)->len - 1;
    while (s < e) {
	c = *s;
	*s++ = *e;
	*e-- = c;
    }

    return str;
}

static VALUE
rb_str_reverse(str)
    VALUE str;
{
    VALUE obj;
    char *s, *e, *p;

    if (RSTRING(str)->len <= 1) return rb_str_dup(str);

    obj = rb_str_new5(str, 0, RSTRING(str)->len);
    s = RSTRING(str)->ptr; e = s + RSTRING(str)->len - 1;
    p = RSTRING(obj)->ptr;

    while (e >= s) {
	*p++ = *e--;
    }
    OBJ_INFECT(obj, str);

    return obj;
}

static VALUE
rb_str_include(str, arg)
    VALUE str, arg;
{
    long i;

    if (FIXNUM_P(arg)) {
	int c = FIX2INT(arg);
	long len = RSTRING(str)->len;
	char *p = RSTRING(str)->ptr;

	for (i=0; i<len; i++) {
	    if (p[i] == c) {
		return Qtrue;
	    }
	}
	return Qfalse;
    }

    StringValue(arg);
    i = rb_str_index(str, arg, 0);

    if (i == -1) return Qfalse;
    return Qtrue;
}

static VALUE
rb_str_to_i(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    VALUE b;
    int base;

    rb_scan_args(argc, argv, "01", &b);
    if (argc == 0) base = 10;
    else base = NUM2INT(b);

    if (base < 0) {
	rb_raise(rb_eArgError, "illegal radix %d", base);
    }
    return rb_str_to_inum(str, base, Qfalse);
}

static VALUE
rb_str_to_f(str)
    VALUE str;
{
    return rb_float_new(rb_str_to_dbl(str, Qfalse));
}

static VALUE
rb_str_to_s(str)
    VALUE str;
{
    if (rb_obj_class(str) != rb_cString) {
	VALUE dup = str_alloc(rb_cString);
	rb_str_replace(dup, str);
	return dup;
    }
    return str;
}

VALUE
rb_str_inspect(str)
    VALUE str;
{
    char *p, *pend;
    VALUE result = rb_str_buf_new2("\"");
    char s[5];

    p = RSTRING(str)->ptr; pend = p + RSTRING(str)->len;
    while (p < pend) {
	char c = *p++;
	if (ismbchar(c) && p < pend) {
	    int len = mbclen(c);
	    rb_str_buf_cat(result, p - 1, len);
	    p += len - 1;
	}
	else if (c == '"'|| c == '\\') {
	    s[0] = '\\'; s[1] = c;
	    rb_str_buf_cat(result, s, 2);
	}
	else if (ISPRINT(c)) {
	    s[0] = c;
	    rb_str_buf_cat(result, s, 1);
	}
	else if (c == '\n') {
	    s[0] = '\\'; s[1] = 'n';
	    rb_str_buf_cat(result, s, 2);
	}
	else if (c == '\r') {
	    s[0] = '\\'; s[1] = 'r';
	    rb_str_buf_cat(result, s, 2);
	}
	else if (c == '\t') {
	    s[0] = '\\'; s[1] = 't';
	    rb_str_buf_cat(result, s, 2);
	}
	else if (c == '\f') {
	    s[0] = '\\'; s[1] = 'f';
	    rb_str_buf_cat(result, s, 2);
	}
	else if (c == '\013') {
	    s[0] = '\\'; s[1] = 'v';
	    rb_str_buf_cat(result, s, 2);
	}
	else if (c == '\007') {
	    s[0] = '\\'; s[1] = 'a';
	    rb_str_buf_cat(result, s, 2);
	}
	else if (c == 033) {
	    s[0] = '\\'; s[1] = 'e';
	    rb_str_buf_cat(result, s, 2);
	}
	else {
	    sprintf(s, "\\%03o", c & 0377);
	    rb_str_buf_cat2(result, s);
	}
    }
    rb_str_buf_cat2(result, "\"");

    OBJ_INFECT(result, str);
    return result;
}

VALUE
rb_str_dump(str)
    VALUE str;
{
    long len;
    char *p, *pend;
    char *q, *qend;
    VALUE result;

    len = 2;			/* "" */
    p = RSTRING(str)->ptr; pend = p + RSTRING(str)->len;
    while (p < pend) {
	char c = *p++;
	switch (c) {
	  case '"':  case '\\':
	  case '\n': case '\r':
	  case '\t': case '\f': case '#':
	  case '\013': case '\007': case '\033': 
	    len += 2;
	    break;

	  default:
	    if (ISPRINT(c)) {
		len++;
	    }
	    else {
		len += 4;		/* \nnn */
	    }
	    break;
	}
    }

    result = rb_str_new5(str, 0, len);
    p = RSTRING(str)->ptr; pend = p + RSTRING(str)->len;
    q = RSTRING(result)->ptr; qend = q + len;

    *q++ = '"';
    while (p < pend) {
	char c = *p++;

	if (c == '"' || c == '\\') {
	    *q++ = '\\';
	    *q++ = c;
	}
	else if (c == '#') {
	    *q++ = '\\';
	    *q++ = '#';
	}
	else if (ISPRINT(c)) {
	    *q++ = c;
	}
	else if (c == '\n') {
	    *q++ = '\\';
	    *q++ = 'n';
	}
	else if (c == '\r') {
	    *q++ = '\\';
	    *q++ = 'r';
	}
	else if (c == '\t') {
	    *q++ = '\\';
	    *q++ = 't';
	}
	else if (c == '\f') {
	    *q++ = '\\';
	    *q++ = 'f';
	}
	else if (c == '\013') {
	    *q++ = '\\';
	    *q++ = 'v';
	}
	else if (c == '\007') {
	    *q++ = '\\';
	    *q++ = 'a';
	}
	else if (c == '\033') {
	    *q++ = '\\';
	    *q++ = 'e';
	}
	else {
	    *q++ = '\\';
	    sprintf(q, "%03o", c&0xff);
	    q += 3;
	}
    }
    *q++ = '"';

    OBJ_INFECT(result, str);
    return result;
}

static VALUE
rb_str_upcase_bang(str)
    VALUE str;
{
    char *s, *send;
    int modify = 0;

    rb_str_modify(str);
    s = RSTRING(str)->ptr; send = s + RSTRING(str)->len;
    while (s < send) {
	if (ismbchar(*s)) {
	    s+=mbclen(*s) - 1;
	}
	else if (ISLOWER(*s)) {
	    *s = toupper(*s);
	    modify = 1;
	}
	s++;
    }

    if (modify) return str;
    return Qnil;
}

static VALUE
rb_str_upcase(str)
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_upcase_bang(str);
    return str;
}

static VALUE
rb_str_downcase_bang(str)
    VALUE str;
{
    char *s, *send;
    int modify = 0;

    rb_str_modify(str);
    s = RSTRING(str)->ptr; send = s + RSTRING(str)->len;
    while (s < send) {
	if (ismbchar(*s)) {
	    s+=mbclen(*s) - 1;
	}
	else if (ISUPPER(*s)) {
	    *s = tolower(*s);
	    modify = 1;
	}
	s++;
    }

    if (modify) return str;
    return Qnil;
}

static VALUE
rb_str_downcase(str)
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_downcase_bang(str);
    return str;
}

static VALUE
rb_str_capitalize_bang(str)
    VALUE str;
{
    char *s, *send;
    int modify = 0;

    rb_str_modify(str);
    if (RSTRING(str)->len == 0 || !RSTRING(str)->ptr) return Qnil;
    s = RSTRING(str)->ptr; send = s + RSTRING(str)->len;
    if (ISLOWER(*s)) {
	*s = toupper(*s);
	modify = 1;
    }
    while (++s < send) {
	if (ismbchar(*s)) {
	    s+=mbclen(*s) - 1;
	}
	else if (ISUPPER(*s)) {
	    *s = tolower(*s);
	    modify = 1;
	}
    }
    if (modify) return str;
    return Qnil;
}

static VALUE
rb_str_capitalize(str)
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_capitalize_bang(str);
    return str;
}

static VALUE
rb_str_swapcase_bang(str)
    VALUE str;
{
    char *s, *send;
    int modify = 0;

    rb_str_modify(str);
    s = RSTRING(str)->ptr; send = s + RSTRING(str)->len;
    while (s < send) {
	if (ismbchar(*s)) {
	    s+=mbclen(*s) - 1;
	}
	else if (ISUPPER(*s)) {
	    *s = tolower(*s);
	    modify = 1;
	}
	else if (ISLOWER(*s)) {
	    *s = toupper(*s);
	    modify = 1;
	}
	s++;
    }

    if (modify) return str;
    return Qnil;
}

static VALUE
rb_str_swapcase(str)
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_swapcase_bang(str);
    return str;
}

typedef unsigned char *USTR;

struct tr {
    int gen, now, max;
    char *p, *pend;
};

static int
trnext(t)
    struct tr *t;
{
    for (;;) {
	if (!t->gen) {
	    if (t->p == t->pend) return -1;
	    if (t->p < t->pend - 1 && *t->p == '\\') {
		t->p++;
	    }
	    t->now = *(USTR)t->p++;
	    if (t->p < t->pend - 1 && *t->p == '-') {
		t->p++;
		if (t->p < t->pend) {
		    if (t->now > *(USTR)t->p) {
			t->p++;
			continue;
		    }
		    t->gen = 1;
		    t->max = *(USTR)t->p++;
		}
	    }
	    return t->now;
	}
	else if (++t->now < t->max) {
	    return t->now;
	}
	else {
	    t->gen = 0;
	    return t->max;
	}
    }
}

static VALUE rb_str_delete_bang _((int,VALUE*,VALUE));

static VALUE
tr_trans(str, src, repl, sflag)
    VALUE str, src, repl;
    int sflag;
{
    struct tr trsrc, trrepl;
    int cflag = 0;
    int trans[256];
    int i, c, modify = 0;
    char *s, *send;

    rb_str_modify(str);
    StringValue(src);
    StringValue(repl);
    if (RSTRING(str)->len == 0 || !RSTRING(str)->ptr) return Qnil;
    trsrc.p = RSTRING(src)->ptr; trsrc.pend = trsrc.p + RSTRING(src)->len;
    if (RSTRING(src)->len >= 2 && RSTRING(src)->ptr[0] == '^') {
	cflag++;
	trsrc.p++;
    }
    if (RSTRING(repl)->len == 0) {
	return rb_str_delete_bang(1, &src, str);
    }
    trrepl.p = RSTRING(repl)->ptr;
    trrepl.pend = trrepl.p + RSTRING(repl)->len;
    trsrc.gen = trrepl.gen = 0;
    trsrc.now = trrepl.now = 0;
    trsrc.max = trrepl.max = 0;

    if (cflag) {
	for (i=0; i<256; i++) {
	    trans[i] = 1;
	}
	while ((c = trnext(&trsrc)) >= 0) {
	    trans[c & 0xff] = -1;
	}
	while ((c = trnext(&trrepl)) >= 0)
	    /* retrieve last replacer */;
	for (i=0; i<256; i++) {
	    if (trans[i] >= 0) {
		trans[i] = trrepl.now;
	    }
	}
    }
    else {
	int r;

	for (i=0; i<256; i++) {
	    trans[i] = -1;
	}
	while ((c = trnext(&trsrc)) >= 0) {
	    r = trnext(&trrepl);
	    if (r == -1) r = trrepl.now;
	    trans[c & 0xff] = r;
	}
    }

    s = RSTRING(str)->ptr; send = s + RSTRING(str)->len;
    if (sflag) {
	char *t = s;
	int c0, last = -1;

	while (s < send) {
	    c0 = *s++;
	    if ((c = trans[c0 & 0xff]) >= 0) {
		if (last == c) continue;
		last = c;
		*t++ = c & 0xff;
		modify = 1;
	    }
	    else {
		last = -1;
		*t++ = c0;
	    }
	}
	if (RSTRING(str)->len > (t - RSTRING(str)->ptr)) {
	    RSTRING(str)->len = (t - RSTRING(str)->ptr);
	    modify = 1;
	    *t = '\0';
	}
    }
    else {
	while (s < send) {
	    if ((c = trans[*s & 0xff]) >= 0) {
		*s = c & 0xff;
		modify = 1;
	    }
	    s++;
	}
    }

    if (modify) return str;
    return Qnil;
}

static VALUE
rb_str_tr_bang(str, src, repl)
    VALUE str, src, repl;
{
    return tr_trans(str, src, repl, 0);
}

static VALUE
rb_str_tr(str, src, repl)
    VALUE str, src, repl;
{
    str = rb_str_dup(str);
    tr_trans(str, src, repl, 0);
    return str;
}

static void
tr_setup_table(str, table, init)
    VALUE str;
    char table[256];
    int init;
{
    char buf[256];
    struct tr tr;
    int i, c;
    int cflag = 0;

    tr.p = RSTRING(str)->ptr; tr.pend = tr.p + RSTRING(str)->len;
    tr.gen = tr.now = tr.max = 0;
    if (RSTRING(str)->len > 1 && RSTRING(str)->ptr[0] == '^') {
	cflag = 1;
	tr.p++;
    }

    if (init) {
	for (i=0; i<256; i++) {
	    table[i] = 1;
	}
    }
    for (i=0; i<256; i++) {
	buf[i] = cflag;
    }
    while ((c = trnext(&tr)) >= 0) {
	buf[c & 0xff] = !cflag;
    }
    for (i=0; i<256; i++) {
	table[i] = table[i]&&buf[i];
    }
}

static VALUE
rb_str_delete_bang(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    char *s, *send, *t;
    char squeez[256];
    int modify = 0;
    int init = 1;
    int i;

    if (argc < 1) {
	rb_raise(rb_eArgError, "wrong number of arguments");
    }
    rb_str_modify(str);
    for (i=0; i<argc; i++) {
	VALUE s = argv[i];

	StringValue(s);
	tr_setup_table(s, squeez, init);
	init = 0;
    }

    s = t = RSTRING(str)->ptr;
    if (!s || RSTRING(str)->len == 0) return Qnil;
    send = s + RSTRING(str)->len;
    while (s < send) {
	if (squeez[*s & 0xff])
	    modify = 1;
	else
	    *t++ = *s;
	s++;
    }
    *t = '\0';
    RSTRING(str)->len = t - RSTRING(str)->ptr;

    if (modify) return str;
    return Qnil;
}

static VALUE
rb_str_delete(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_delete_bang(argc, argv, str);
    return str;
}

static VALUE
rb_str_squeeze_bang(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    char squeez[256];
    char *s, *send, *t;
    int c, save, modify = 0;
    int init = 1;
    int i;

    rb_str_modify(str);
    if (argc == 0) {
	for (i=0; i<256; i++) {
	    squeez[i] = 1;
	}
    }
    else {
	for (i=0; i<argc; i++) {
	    VALUE s = argv[i];

	    StringValue(s);
	    tr_setup_table(s, squeez, init);
	    init = 0;
	}
    }

    s = t = RSTRING(str)->ptr;
    if (!s || RSTRING(str)->len == 0) return Qnil;
    send = s + RSTRING(str)->len;
    save = -1;
    while (s < send) {
	c = *s++ & 0xff;
	if (c != save || !squeez[c]) {
	    *t++ = save = c;
	}
    }
    *t = '\0';
    if (t - RSTRING(str)->ptr != RSTRING(str)->len) {
	RSTRING(str)->len = t - RSTRING(str)->ptr;
	modify = 1;
    }

    if (modify) return str;
    return Qnil;
}

static VALUE
rb_str_squeeze(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_squeeze_bang(argc, argv, str);
    return str;
}

static VALUE
rb_str_tr_s_bang(str, src, repl)
    VALUE str, src, repl;
{
    return tr_trans(str, src, repl, 1);
}

static VALUE
rb_str_tr_s(str, src, repl)
    VALUE str, src, repl;
{
    str = rb_str_dup(str);
    tr_trans(str, src, repl, 1);
    return str;
}

static VALUE
rb_str_count(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    char table[256];
    char *s, *send;
    int init = 1;
    int i;

    if (argc < 1) {
	rb_raise(rb_eArgError, "wrong number of arguments");
    }
    for (i=0; i<argc; i++) {
	VALUE s = argv[i];

	StringValue(s);
	tr_setup_table(s, table, init);
	init = 0;
    }

    s = RSTRING(str)->ptr;
    if (!s || RSTRING(str)->len == 0) return INT2FIX(0);
    send = s + RSTRING(str)->len;
    i = 0;
    while (s < send) {
	if (table[*s++ & 0xff]) {
	    i++;
	}
    }
    return INT2NUM(i);
}

static VALUE
rb_str_split_m(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    VALUE spat;
    VALUE limit;
    int awk_split = Qfalse;
    long beg, end, i = 0;
    int lim = 0;
    VALUE result, tmp;

    if (rb_scan_args(argc, argv, "02", &spat, &limit) == 2) {
	lim = NUM2INT(limit);
	if (lim <= 0) limit = Qnil;
	else if (lim == 1) return rb_ary_new3(1, str);
	i = 1;
    }

    if (NIL_P(spat)) {
	if (!NIL_P(rb_fs)) {
	    spat = rb_fs;
	    goto fs_set;
	}
	awk_split = Qtrue;
    }
    else {
      fs_set:
	if (TYPE(spat) == T_STRING && RSTRING(spat)->len == 1) {
	    if (RSTRING(spat)->ptr[0] == ' ') {
		awk_split = Qtrue;
	    }
	    else {
		spat = rb_reg_regcomp(rb_reg_quote(spat));
	    }
	}
	else {
	    spat = get_pat(spat, 1);
	}
    }

    result = rb_ary_new();
    beg = 0;
    if (awk_split) {
	char *ptr = RSTRING(str)->ptr;
	long len = RSTRING(str)->len;
	char *eptr = ptr + len;
	int skip = 1;

	for (end = beg = 0; ptr<eptr; ptr++) {
	    if (skip) {
		if (ISSPACE(*ptr)) {
		    beg++;
		}
		else {
		    end = beg+1;
		    skip = 0;
		    if (!NIL_P(limit) && lim <= i) break;
		}
	    }
	    else {
		if (ISSPACE(*ptr)) {
		    rb_ary_push(result, rb_str_substr(str, beg, end-beg));
		    skip = 1;
		    beg = end + 1;
		    if (!NIL_P(limit)) ++i;
		}
		else {
		    end++;
		}
	    }
	}
    }
    else {
	long start = beg;
	long idx;
	int last_null = 0;
	struct re_registers *regs;

	while ((end = rb_reg_search(spat, str, start, 0)) >= 0) {
	    regs = RMATCH(rb_backref_get())->regs;
	    if (start == end && BEG(0) == END(0)) {
		if (!RSTRING(str)->ptr) {
		    rb_ary_push(result, rb_str_new("", 0));
		    break;
                }
		else if (last_null == 1) {
		    rb_ary_push(result, rb_str_substr(str, beg, mbclen2(RSTRING(str)->ptr[beg],spat)));
		    beg = start;
		}
		else {
		    start += mbclen2(RSTRING(str)->ptr[start],spat);
		    last_null = 1;
		    continue;
		}
	    }
	    else {
		rb_ary_push(result, rb_str_substr(str, beg, end-beg));
		beg = start = END(0);
	    }
	    last_null = 0;

	    for (idx=1; idx < regs->num_regs; idx++) {
		if (BEG(idx) == -1) continue;
		if (BEG(idx) == END(idx))
		    tmp = rb_str_new5(str, 0, 0);
		else
		    tmp = rb_str_substr(str, BEG(idx), END(idx)-BEG(idx));
		rb_ary_push(result, tmp);
	    }
	    if (!NIL_P(limit) && lim <= ++i) break;
	}
    }
    if (RSTRING(str)->len > 0 && (!NIL_P(limit) || RSTRING(str)->len > beg || lim < 0)) {
	if (RSTRING(str)->len == beg)
	    tmp = rb_str_new5(str, 0, 0);
	else
	    tmp = rb_str_substr(str, beg, RSTRING(str)->len-beg);
	rb_ary_push(result, tmp);
    }
    if (NIL_P(limit) && lim == 0) {
	while (RARRAY(result)->len > 0 &&
	       RSTRING(RARRAY(result)->ptr[RARRAY(result)->len-1])->len == 0)
	    rb_ary_pop(result);
    }

    return result;
}

VALUE
rb_str_split(str, sep0)
    VALUE str;
    const char *sep0;
{
    VALUE sep;

    StringValue(str);
    sep = rb_str_new2(sep0);
    return rb_str_split_m(1, &sep, str);
}

static VALUE
rb_f_split(argc, argv)
    int argc;
    VALUE *argv;
{
    return rb_str_split_m(argc, argv, uscore_get());
}

static VALUE
rb_str_each_line(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    VALUE rs;
    int newline;
    char *p = RSTRING(str)->ptr, *pend = p + RSTRING(str)->len, *s;
    char *ptr = p;
    long len = RSTRING(str)->len, rslen;
    VALUE line;

    if (rb_scan_args(argc, argv, "01", &rs) == 0) {
	rs = rb_rs;
    }

    if (NIL_P(rs)) {
	rb_yield(str);
	return str;
    }
    StringValue(rs);
    rslen = RSTRING(rs)->len;
    if (rslen == 0) {
	newline = '\n';
    }
    else {
	newline = RSTRING(rs)->ptr[rslen-1];
    }

    for (s = p, p += rslen; p < pend; p++) {
	if (rslen == 0 && *p == '\n') {
	    if (*++p != '\n') continue;
	    while (*p == '\n') p++;
	}
	if (RSTRING(str)->ptr < p && p[-1] == newline &&
	    (rslen <= 1 ||
	     rb_memcmp(RSTRING(rs)->ptr, p-rslen, rslen) == 0)) {
	    line = rb_str_new5(str, s, p - s);
	    OBJ_INFECT(line, str);
	    rb_yield(line);
	    if (RSTRING(str)->ptr != ptr || RSTRING(str)->len != len)
		rb_raise(rb_eArgError, "string modified");
	    s = p;
	}
    }

    if (s != pend) {
        if (p > pend) p = pend;
	line = rb_str_new5(str, s, p - s);
	OBJ_INFECT(line, str);
	rb_yield(line);
    }

    return str;
}

static VALUE
rb_str_each_byte(str)
    VALUE str;
{
    long i;

    for (i=0; i<RSTRING(str)->len; i++) {
	rb_yield(INT2FIX(RSTRING(str)->ptr[i] & 0xff));
    }
    return str;
}

static VALUE
rb_str_chop_bang(str)
    VALUE str;
{
    if (RSTRING(str)->len > 0) {
	rb_str_modify(str);
	RSTRING(str)->len--;
	if (RSTRING(str)->ptr[RSTRING(str)->len] == '\n') {
	    if (RSTRING(str)->len > 0 &&
		RSTRING(str)->ptr[RSTRING(str)->len-1] == '\r') {
		RSTRING(str)->len--;
	    }
	}
	RSTRING(str)->ptr[RSTRING(str)->len] = '\0';
	return str;
    }
    return Qnil;
}

static VALUE
rb_str_chop(str)
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_chop_bang(str);
    return str;
}

static VALUE
rb_f_chop_bang(str)
    VALUE str;
{
    return rb_str_chop_bang(uscore_get());
}

static VALUE
rb_f_chop()
{
    VALUE str = uscore_get();

    if (RSTRING(str)->len > 0) {
	str = rb_str_dup(str);
	rb_str_chop_bang(str);
	rb_lastline_set(str);
    }
    return str;
}

static VALUE
rb_str_chomp_bang(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    VALUE rs;
    int newline;
    char *p = RSTRING(str)->ptr;
    long len = RSTRING(str)->len, rslen;

    if (rb_scan_args(argc, argv, "01", &rs) == 0) {
	if (len == 0) return Qnil;
	rs = rb_rs;
	if (rs == rb_default_rs) {
	  smart_chomp:
	    rb_str_modify(str);
	    if (RSTRING(str)->ptr[len-1] == '\n') {
		RSTRING(str)->len--;
		if (RSTRING(str)->len > 0 &&
		    RSTRING(str)->ptr[RSTRING(str)->len-1] == '\r') {
		    RSTRING(str)->len--;
		}
	    }
	    else if (RSTRING(str)->ptr[len-1] == '\r') {
		RSTRING(str)->len--;
	    }
	    else {
		return Qnil;
	    }
	    RSTRING(str)->ptr[RSTRING(str)->len] = '\0';
	    return str;
	}
    }
    if (NIL_P(rs)) return Qnil;
    if (len == 0) return Qnil;

    StringValue(rs);
    rb_str_modify(str);
    rslen = RSTRING(rs)->len;
    if (rslen == 0) {
	while (len>0 && p[len-1] == '\n') {
	    len--;
	    if (len>0 && p[len-1] == '\r')
		len--;
	}
	if (len < RSTRING(str)->len) {
	    rb_str_modify(str);
	    RSTRING(str)->len = len;
	    RSTRING(str)->ptr[len] = '\0';
	    return str;
	}
	return Qnil;
    }
    if (rslen > len) return Qnil;
    newline = RSTRING(rs)->ptr[rslen-1];
    if (rslen == 1 && newline == '\n')
	goto smart_chomp;

    if (p[len-1] == newline &&
	(rslen <= 1 ||
	 rb_memcmp(RSTRING(rs)->ptr, p+len-rslen, rslen) == 0)) {
	rb_str_modify(str);
	RSTRING(str)->len -= rslen;
	RSTRING(str)->ptr[RSTRING(str)->len] = '\0';
	return str;
    }
    return Qnil;
}

static VALUE
rb_str_chomp(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_chomp_bang(argc, argv, str);
    return str;
}

static VALUE
rb_f_chomp_bang(argc, argv)
    int argc;
    VALUE *argv;
{
    return rb_str_chomp_bang(argc, argv, uscore_get());
}

static VALUE
rb_f_chomp(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE str = uscore_get();
    VALUE dup = rb_str_dup(str);

    if (NIL_P(rb_str_chomp_bang(argc, argv, dup)))
	return str;
    rb_lastline_set(dup);
    return dup;
}

static VALUE
rb_str_lstrip_bang(str)
    VALUE str;
{
    char *s, *t, *e;

    rb_str_modify(str);
    s = RSTRING(str)->ptr;
    if (!s || RSTRING(str)->len == 0) return Qnil;
    e = t = s + RSTRING(str)->len;
    /* remove spaces at head */
    while (s < t && (ISSPACE(*s) || !*s)) s++;

    RSTRING(str)->len = t-s;
    if (s > RSTRING(str)->ptr) {
	memmove(RSTRING(str)->ptr, s, RSTRING(str)->len);
	RSTRING(str)->ptr[RSTRING(str)->len] = '\0';
	return str;
    }
    return Qnil;
}

static VALUE
rb_str_lstrip(str)
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_lstrip_bang(str);
    return str;
}

static VALUE
rb_str_rstrip_bang(str)
    VALUE str;
{
    char *s, *t, *e;

    rb_str_modify(str);
    s = RSTRING(str)->ptr;
    if (!s || RSTRING(str)->len == 0) return Qnil;
    e = t = s + RSTRING(str)->len;

    /* remove trailing spaces */
    while (s < t && (ISSPACE(*(t-1)) || !*(t-1))) t--;

    RSTRING(str)->len = t-s;
    if (t < e) {
	RSTRING(str)->ptr[RSTRING(str)->len] = '\0';
	return str;
    }
    return Qnil;
}

static VALUE
rb_str_rstrip(str)
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_rstrip_bang(str);
    return str;
}

static VALUE
rb_str_strip_bang(str)
    VALUE str;
{
    VALUE l = rb_str_lstrip_bang(str);
    VALUE r = rb_str_rstrip_bang(str);

    if (NIL_P(l) && NIL_P(r)) return Qnil;
    return str;
}

static VALUE
rb_str_strip(str)
    VALUE str;
{
    str = rb_str_dup(str);
    rb_str_strip_bang(str);
    return str;
}

static VALUE
scan_once(str, pat, start)
    VALUE str, pat;
    long *start;
{
    VALUE result, match;
    struct re_registers *regs;
    long i;

    if (rb_reg_search(pat, str, *start, 0) >= 0) {
	match = rb_backref_get();
	regs = RMATCH(match)->regs;
	if (BEG(0) == END(0)) {
	    /*
	     * Always consume at least one character of the input string
	     */
	    if (RSTRING(str)->len < END(0))
		*start = END(0)+mbclen2(RSTRING(str)->ptr[END(0)],pat);
	    else
		*start = END(0)+1;
	}
	else {
	    *start = END(0);
	}
	if (regs->num_regs == 1) {
	    return rb_reg_nth_match(0, match);
	}
	result = rb_ary_new2(regs->num_regs);
	for (i=1; i < regs->num_regs; i++) {
	    rb_ary_push(result, rb_reg_nth_match(i, match));
	}

	return result;
    }
    return Qnil;
}

static VALUE
rb_str_scan(str, pat)
    VALUE str, pat;
{
    VALUE result;
    long start = 0;
    VALUE match = Qnil;

    pat = get_pat(pat, 1);
    if (!rb_block_given_p()) {
	VALUE ary = rb_ary_new();

	while (!NIL_P(result = scan_once(str, pat, &start))) {
	    match = rb_backref_get();
	    rb_ary_push(ary, result);
	}
	rb_backref_set(match);
	return ary;
    }
    
    while (!NIL_P(result = scan_once(str, pat, &start))) {
	match = rb_backref_get();
	rb_match_busy(match);
	rb_yield(result);
	rb_backref_set(match);	/* restore $~ value */
    }
    rb_backref_set(match);
    return str;
}

static VALUE
rb_f_scan(self, pat)
    VALUE self, pat;
{
    return rb_str_scan(uscore_get(), pat);
}

static VALUE
rb_str_hex(str)
    VALUE str;
{
    return rb_str_to_inum(str, 16, Qfalse);
}

static VALUE
rb_str_oct(str)
    VALUE str;
{
    return rb_str_to_inum(str, -8, Qfalse);
}

static VALUE
rb_str_crypt(str, salt)
    VALUE str, salt;
{
    extern char *crypt();
    VALUE result;
    char *s;

    StringValue(salt);
    if (RSTRING(salt)->len < 2)
	rb_raise(rb_eArgError, "salt too short(need >=2 bytes)");

    if (RSTRING(str)->ptr) s = RSTRING(str)->ptr;
    else s = "";
    result = rb_str_new2(crypt(s, RSTRING(salt)->ptr));
    OBJ_INFECT(result, str);
    OBJ_INFECT(result, salt);
    return result;
}

VALUE
rb_str_intern(str)
    VALUE str;
{
    ID id;

    if (!RSTRING(str)->ptr || RSTRING(str)->len == 0) {
	rb_raise(rb_eArgError, "interning empty string");
    }
    if (strlen(RSTRING(str)->ptr) != RSTRING(str)->len)
	rb_raise(rb_eArgError, "symbol string may not contain `\\0'");
    id = rb_intern(RSTRING(str)->ptr);
    return ID2SYM(id);
}

static VALUE
rb_str_sum(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    VALUE vbits;
    int bits;
    char *p, *pend;

    if (rb_scan_args(argc, argv, "01", &vbits) == 0) {
	bits = 16;
    }
    else bits = NUM2INT(vbits);

    p = RSTRING(str)->ptr; pend = p + RSTRING(str)->len;
    if (bits > sizeof(long)*CHAR_BIT) {
	VALUE res = INT2FIX(0);
	VALUE mod;

	mod = rb_funcall(INT2FIX(1), rb_intern("<<"), 1, INT2FIX(bits));
	mod = rb_funcall(mod, '-', 1, INT2FIX(1));

	while (p < pend) {
	    res = rb_funcall(res, '+', 1, INT2FIX((unsigned int)*p));
	    p++;
	}
	res = rb_funcall(res, '&', 1, mod);
	return res;
    }
    else {
	unsigned int res = 0;
	unsigned int mod = (1<<bits)-1;

	if (mod == 0) {
	    mod = -1;
	}
	while (p < pend) {
	    res += (unsigned int)*p;
	    p++;
	}
	res &= mod;
	return rb_int2inum(res);
    }
}

static VALUE
rb_str_justify(argc, argv, str, jflag)
    int argc;
    VALUE *argv;
    VALUE str;
    char jflag;
{
    VALUE w;
    long width, flen = 0;
    VALUE res;
    char *p, *pend, *f = " ";
    long n;
    VALUE pad;

    if (rb_scan_args(argc, argv, "11", &w, &pad) == 2) {
        if (!NIL_P(pad)) {
            StringValue(pad);
            if (RSTRING(pad)->len > 0) {
                f = RSTRING(pad)->ptr;
                flen = RSTRING(pad)->len;
            }
        }
    }
    width = NUM2LONG(w);
    if (width < 0 || RSTRING(str)->len >= width) return rb_str_dup(str);
    res = rb_str_new5(str, 0, width);
    p = RSTRING(res)->ptr;
    if (jflag != 'l') {
        n = width - RSTRING(str)->len;
        pend = p + ((jflag == 'r') ? n : n/2);
        if (flen <= 1) {
            while (p < pend) {
                *p++ = *f;
            }
        }
        else {
            char *q = f;
            while (p + flen <= pend) {
                memcpy(p,f,flen);
                p += flen;
            }
            while (p < pend) {
                *p++ = *q++;
            }
        }
    }
    memcpy(p, RSTRING(str)->ptr, RSTRING(str)->len);
    if (jflag != 'r') {
        p += RSTRING(str)->len; pend = RSTRING(res)->ptr + width;
        if (flen <= 1) {
            while (p < pend) {
                *p++ = *f;
            }
        }
        else {
            while (p + flen <= pend) {
                memcpy(p,f,flen);
                p += flen;
            }
            while (p < pend) {
                *p++ = *f++;
            }
        }
    }
    OBJ_INFECT(res, str);
    if (flen > 0) OBJ_INFECT(res, pad);
    return res;
}

static VALUE
rb_str_ljust(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    return rb_str_justify(argc, argv, str, 'l');
}

static VALUE
rb_str_rjust(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    return rb_str_justify(argc, argv, str, 'r');
}

static VALUE
rb_str_center(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    return rb_str_justify(argc, argv, str, 'c');
}

void
rb_str_setter(val, id, var)
    VALUE val;
    ID id;
    VALUE *var;
{
    if (!NIL_P(val) && TYPE(val) != T_STRING) {
	rb_raise(rb_eTypeError, "value of %s must be String", rb_id2name(id));
    }
    *var = val;
}

void
Init_String()
{
    rb_cString  = rb_define_class("String", rb_cObject);
    rb_include_module(rb_cString, rb_mComparable);
    rb_include_module(rb_cString, rb_mEnumerable);
    rb_define_alloc_func(rb_cString, str_alloc);
    rb_define_method(rb_cString, "initialize", rb_str_init, -1);
    rb_define_method(rb_cString, "initialize_copy", rb_str_replace, 1); 
    rb_define_method(rb_cString, "<=>", rb_str_cmp_m, 1);
    rb_define_method(rb_cString, "==", rb_str_equal, 1);
    rb_define_method(rb_cString, "eql?", rb_str_eql, 1);
    rb_define_method(rb_cString, "hash", rb_str_hash_m, 0);
    rb_define_method(rb_cString, "casecmp", rb_str_casecmp, 1);
    rb_define_method(rb_cString, "+", rb_str_plus, 1);
    rb_define_method(rb_cString, "*", rb_str_times, 1);
    rb_define_method(rb_cString, "%", rb_str_format, 1);
    rb_define_method(rb_cString, "[]", rb_str_aref_m, -1);
    rb_define_method(rb_cString, "[]=", rb_str_aset_m, -1);
    rb_define_method(rb_cString, "insert", rb_str_insert, 2);
    rb_define_method(rb_cString, "length", rb_str_length, 0);
    rb_define_method(rb_cString, "size", rb_str_length, 0);
    rb_define_method(rb_cString, "empty?", rb_str_empty, 0);
    rb_define_method(rb_cString, "=~", rb_str_match, 1);
    rb_define_method(rb_cString, "~", rb_str_match2, 0);
    rb_define_method(rb_cString, "match", rb_str_match_m, 1);
    rb_define_method(rb_cString, "succ", rb_str_succ, 0);
    rb_define_method(rb_cString, "succ!", rb_str_succ_bang, 0);
    rb_define_method(rb_cString, "next", rb_str_succ, 0);
    rb_define_method(rb_cString, "next!", rb_str_succ_bang, 0);
    rb_define_method(rb_cString, "upto", rb_str_upto_m, 1);
    rb_define_method(rb_cString, "index", rb_str_index_m, -1);
    rb_define_method(rb_cString, "rindex", rb_str_rindex_m, -1);
    rb_define_method(rb_cString, "replace", rb_str_replace, 1);

    rb_define_method(rb_cString, "to_i", rb_str_to_i, -1);
    rb_define_method(rb_cString, "to_f", rb_str_to_f, 0);
    rb_define_method(rb_cString, "to_s", rb_str_to_s, 0);
    rb_define_method(rb_cString, "to_str", rb_str_to_s, 0);
    rb_define_method(rb_cString, "inspect", rb_str_inspect, 0);
    rb_define_method(rb_cString, "dump", rb_str_dump, 0);

    rb_define_method(rb_cString, "upcase", rb_str_upcase, 0);
    rb_define_method(rb_cString, "downcase", rb_str_downcase, 0);
    rb_define_method(rb_cString, "capitalize", rb_str_capitalize, 0);
    rb_define_method(rb_cString, "swapcase", rb_str_swapcase, 0);

    rb_define_method(rb_cString, "upcase!", rb_str_upcase_bang, 0);
    rb_define_method(rb_cString, "downcase!", rb_str_downcase_bang, 0);
    rb_define_method(rb_cString, "capitalize!", rb_str_capitalize_bang, 0);
    rb_define_method(rb_cString, "swapcase!", rb_str_swapcase_bang, 0);

    rb_define_method(rb_cString, "hex", rb_str_hex, 0);
    rb_define_method(rb_cString, "oct", rb_str_oct, 0);
    rb_define_method(rb_cString, "split", rb_str_split_m, -1);
    rb_define_method(rb_cString, "reverse", rb_str_reverse, 0);
    rb_define_method(rb_cString, "reverse!", rb_str_reverse_bang, 0);
    rb_define_method(rb_cString, "concat", rb_str_concat, 1);
    rb_define_method(rb_cString, "<<", rb_str_concat, 1);
    rb_define_method(rb_cString, "crypt", rb_str_crypt, 1);
    rb_define_method(rb_cString, "intern", rb_str_intern, 0);
    rb_define_method(rb_cString, "to_sym", rb_str_intern, 0);

    rb_define_method(rb_cString, "include?", rb_str_include, 1);

    rb_define_method(rb_cString, "scan", rb_str_scan, 1);

    rb_define_method(rb_cString, "ljust", rb_str_ljust, -1);
    rb_define_method(rb_cString, "rjust", rb_str_rjust, -1);
    rb_define_method(rb_cString, "center", rb_str_center, -1);

    rb_define_method(rb_cString, "sub", rb_str_sub, -1);
    rb_define_method(rb_cString, "gsub", rb_str_gsub, -1);
    rb_define_method(rb_cString, "chop", rb_str_chop, 0);
    rb_define_method(rb_cString, "chomp", rb_str_chomp, -1);
    rb_define_method(rb_cString, "strip", rb_str_strip, 0);
    rb_define_method(rb_cString, "lstrip", rb_str_lstrip, 0);
    rb_define_method(rb_cString, "rstrip", rb_str_rstrip, 0);

    rb_define_method(rb_cString, "sub!", rb_str_sub_bang, -1);
    rb_define_method(rb_cString, "gsub!", rb_str_gsub_bang, -1);
    rb_define_method(rb_cString, "chop!", rb_str_chop_bang, 0);
    rb_define_method(rb_cString, "chomp!", rb_str_chomp_bang, -1);
    rb_define_method(rb_cString, "strip!", rb_str_strip_bang, 0);
    rb_define_method(rb_cString, "lstrip!", rb_str_lstrip_bang, 0);
    rb_define_method(rb_cString, "rstrip!", rb_str_rstrip_bang, 0);

    rb_define_method(rb_cString, "tr", rb_str_tr, 2);
    rb_define_method(rb_cString, "tr_s", rb_str_tr_s, 2);
    rb_define_method(rb_cString, "delete", rb_str_delete, -1);
    rb_define_method(rb_cString, "squeeze", rb_str_squeeze, -1);
    rb_define_method(rb_cString, "count", rb_str_count, -1);

    rb_define_method(rb_cString, "tr!", rb_str_tr_bang, 2);
    rb_define_method(rb_cString, "tr_s!", rb_str_tr_s_bang, 2);
    rb_define_method(rb_cString, "delete!", rb_str_delete_bang, -1);
    rb_define_method(rb_cString, "squeeze!", rb_str_squeeze_bang, -1);

    rb_define_method(rb_cString, "each_line", rb_str_each_line, -1);
    rb_define_method(rb_cString, "each", rb_str_each_line, -1);
    rb_define_method(rb_cString, "each_byte", rb_str_each_byte, 0);

    rb_define_method(rb_cString, "sum", rb_str_sum, -1);

    rb_define_global_function("sub", rb_f_sub, -1);
    rb_define_global_function("gsub", rb_f_gsub, -1);

    rb_define_global_function("sub!", rb_f_sub_bang, -1);
    rb_define_global_function("gsub!", rb_f_gsub_bang, -1);

    rb_define_global_function("chop", rb_f_chop, 0);
    rb_define_global_function("chop!", rb_f_chop_bang, 0);

    rb_define_global_function("chomp", rb_f_chomp, -1);
    rb_define_global_function("chomp!", rb_f_chomp_bang, -1);

    rb_define_global_function("split", rb_f_split, -1);
    rb_define_global_function("scan", rb_f_scan, 1);

    rb_define_method(rb_cString, "slice", rb_str_aref_m, -1);
    rb_define_method(rb_cString, "slice!", rb_str_slice_bang, -1);

    id_to_s = rb_intern("to_s");

    rb_fs = Qnil;
    rb_define_hooked_variable("$;", &rb_fs, 0, rb_str_setter);
    rb_define_hooked_variable("$-F", &rb_fs, 0, rb_str_setter);
}