Skip to content

Commit

Permalink
lib/string_helpers.c: refactor string_escape_mem
Browse files Browse the repository at this point in the history 
When printf is given the format specifier %pE, it needs a way of obtaining
the total output size that would be generated if the buffer was large
enough, and string_escape_mem doesn't easily provide that.  This is a
refactorization of string_escape_mem in preparation of changing its
external API to provide that information.

The somewhat ugly early returns and subsequent seemingly redundant
conditionals are to make the following patch touch as little as possible
in string_helpers.c while still preserving the current behaviour of never
outputting partial escape sequences.  That behaviour must also change for
%pE to work as one expects from every other printf specifier.

Signed-off-by: Rasmus Villemoes <[email protected]>
Acked-by: Andy Shevchenko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
  • Loading branch information
@Villemoes @torvalds
Villemoes authored and torvalds committed Apr 15, 2015
1 parent 9c98f23 commit 3aeddc7
Showing 1 changed file with 105 additions and 103 deletions.
208 changes: 105 additions & 103 deletions lib/string_helpers.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -239,29 +239,21 @@ int string_unescape(char *src, char *dst, size_t size, unsigned int flags)
}
EXPORT_SYMBOL(string_unescape);

static int escape_passthrough(unsigned char c, char **dst, size_t *osz)
static bool escape_passthrough(unsigned char c, char **dst, char *end)
{
char *out = *dst;

if (*osz < 1)
return -ENOMEM;

*out++ = c;

*dst = out;
*osz -= 1;

return 1;
if (out < end)
*out = c;
*dst = out + 1;
return true;
}

static int escape_space(unsigned char c, char **dst, size_t *osz)
static bool escape_space(unsigned char c, char **dst, char *end)
{
char *out = *dst;
unsigned char to;

if (*osz < 2)
return -ENOMEM;

switch (c) {
case '\n':
to = 'n';
Expand All @@ -279,26 +271,30 @@ static int escape_space(unsigned char c, char **dst, size_t *osz)
to = 'f';
break;
default:
return 0;
return false;
}

*out++ = '\\';
*out++ = to;
if (out + 2 > end) {
*dst = out + 2;
return true;
}

*dst = out;
*osz -= 2;
if (out < end)
*out = '\\';
++out;
if (out < end)
*out = to;
++out;

return 1;
*dst = out;
return true;
}

static int escape_special(unsigned char c, char **dst, size_t *osz)
static bool escape_special(unsigned char c, char **dst, char *end)
{
char *out = *dst;
unsigned char to;

if (*osz < 2)
return -ENOMEM;

switch (c) {
case '\\':
to = '\\';
Expand All @@ -310,71 +306,98 @@ static int escape_special(unsigned char c, char **dst, size_t *osz)
to = 'e';
break;
default:
return 0;
return false;
}

*out++ = '\\';
*out++ = to;
if (out + 2 > end) {
*dst = out + 2;
return true;
}

*dst = out;
*osz -= 2;
if (out < end)
*out = '\\';
++out;
if (out < end)
*out = to;
++out;

return 1;
*dst = out;
return true;
}

static int escape_null(unsigned char c, char **dst, size_t *osz)
static bool escape_null(unsigned char c, char **dst, char *end)
{
char *out = *dst;

if (*osz < 2)
return -ENOMEM;

if (c)
return 0;
return false;

*out++ = '\\';
*out++ = '0';
if (out + 2 > end) {
*dst = out + 2;
return true;
}

*dst = out;
*osz -= 2;
if (out < end)
*out = '\\';
++out;
if (out < end)
*out = '0';
++out;

return 1;
*dst = out;
return true;
}

static int escape_octal(unsigned char c, char **dst, size_t *osz)
static bool escape_octal(unsigned char c, char **dst, char *end)
{
char *out = *dst;

if (*osz < 4)
return -ENOMEM;
if (out + 4 > end) {
*dst = out + 4;
return true;
}

*out++ = '\\';
*out++ = ((c >> 6) & 0x07) + '0';
*out++ = ((c >> 3) & 0x07) + '0';
*out++ = ((c >> 0) & 0x07) + '0';
if (out < end)
*out = '\\';
++out;
if (out < end)
*out = ((c >> 6) & 0x07) + '0';
++out;
if (out < end)
*out = ((c >> 3) & 0x07) + '0';
++out;
if (out < end)
*out = ((c >> 0) & 0x07) + '0';
++out;

*dst = out;
*osz -= 4;

return 1;
return true;
}

static int escape_hex(unsigned char c, char **dst, size_t *osz)
static bool escape_hex(unsigned char c, char **dst, char *end)
{
char *out = *dst;

if (*osz < 4)
return -ENOMEM;
if (out + 4 > end) {
*dst = out + 4;
return true;
}

*out++ = '\\';
*out++ = 'x';
*out++ = hex_asc_hi(c);
*out++ = hex_asc_lo(c);
if (out < end)
*out = '\\';
++out;
if (out < end)
*out = 'x';
++out;
if (out < end)
*out = hex_asc_hi(c);
++out;
if (out < end)
*out = hex_asc_lo(c);
++out;

*dst = out;
*osz -= 4;

return 1;
return true;
}

/**
Expand Down Expand Up @@ -436,9 +459,10 @@ static int escape_hex(unsigned char c, char **dst, size_t *osz)
int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz,
unsigned int flags, const char *esc)
{
char *out = *dst, *p = out;
char *p = *dst;
char *end = p + osz;
bool is_dict = esc && *esc;
int ret = 0;
int ret;

while (isz--) {
unsigned char c = *src++;
Expand All @@ -458,55 +482,33 @@ int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz,
(is_dict && !strchr(esc, c))) {
/* do nothing */
} else {
if (flags & ESCAPE_SPACE) {
ret = escape_space(c, &p, &osz);
if (ret < 0)
break;
if (ret > 0)
continue;
}

if (flags & ESCAPE_SPECIAL) {
ret = escape_special(c, &p, &osz);
if (ret < 0)
break;
if (ret > 0)
continue;
}

if (flags & ESCAPE_NULL) {
ret = escape_null(c, &p, &osz);
if (ret < 0)
break;
if (ret > 0)
continue;
}
if (flags & ESCAPE_SPACE && escape_space(c, &p, end))
continue;

if (flags & ESCAPE_SPECIAL && escape_special(c, &p, end))
continue;

if (flags & ESCAPE_NULL && escape_null(c, &p, end))
continue;

/* ESCAPE_OCTAL and ESCAPE_HEX always go last */
if (flags & ESCAPE_OCTAL) {
ret = escape_octal(c, &p, &osz);
if (ret < 0)
break;
if (flags & ESCAPE_OCTAL && escape_octal(c, &p, end))
continue;
}
if (flags & ESCAPE_HEX) {
ret = escape_hex(c, &p, &osz);
if (ret < 0)
break;

if (flags & ESCAPE_HEX && escape_hex(c, &p, end))
continue;
}
}

ret = escape_passthrough(c, &p, &osz);
if (ret < 0)
break;
escape_passthrough(c, &p, end);
}

*dst = p;

if (ret < 0)
return ret;
if (p > end) {
*dst = end;
return -ENOMEM;
}

return p - out;
ret = p - *dst;
*dst = p;
return ret;
}
EXPORT_SYMBOL(string_escape_mem);

0 comments on commit 3aeddc7

Please sign in to comment.