hmath.h

#ifndef HV_MATH_H_
#define HV_MATH_H_

#include <math.h>

static inline unsigned long floor2e(unsigned long num) {
    unsigned long n = num;
    int e = 0;
    while (n>>=1) ++e;
    unsigned long ret = 1;
    while (e--) ret<<=1;
    return ret;
}

static inline unsigned long ceil2e(unsigned long num) {
    // 2**0 = 1
    if (num == 0 || num == 1)   return 1;
    unsigned long n = num - 1;
    int e = 1;
    while (n>>=1) ++e;
    unsigned long ret = 1;
    while (e--) ret<<=1;
    return ret;
}

// varint little-endian
// MSB
static inline int varint_encode(long long value, unsigned char* buf) {
    unsigned char ch;
    unsigned char *p = buf;
    int bytes = 0;
    do {
        ch = value & 0x7F;
        value >>= 7;
        *p++ = value == 0 ? ch : (ch | 0x80);
        ++bytes;
    } while (value);
    return bytes;
}

// @param[IN|OUT] len: in=>buflen, out=>varint bytesize
static inline long long varint_decode(const unsigned char* buf, int* len) {
    long long ret = 0;
    int bytes = 0, bits = 0;
    const unsigned char *p = buf;
    do {
        if (len && *len && bytes == *len) {
            // Not enough length
            *len = 0;
            return 0;
        }
        ret |= ((long long)(*p & 0x7F)) << bits;
        ++bytes;
        if ((*p & 0x80) == 0) {
            // Found end
            if (len) *len = bytes;
            return ret;
        }
        ++p;
        bits += 7;
    } while(bytes < 10);

    // Not found end
    if (len) *len = -1;
    return ret;
}

#endif // HV_MATH_H_