varint.c

   1 #include "varint.h"
   2
   3 uintmax_t decode_varint(const unsigned char **bufp)
   4 {
   5         const unsigned char *buf = *bufp;
   6         unsigned char c = *buf++;
   7         uintmax_t val = c & 127;
   8         while (c & 128) {
   9                 val += 1;
  10                 if (!val || MSB(val, 7))
  11                         return 0; /* overflow */
  12                 c = *buf++;
  13                 val = (val << 7) + (c & 127);
  14         }
  15         *bufp = buf;
  16         return val;
  17 }
  18
  19 int encode_varint(uintmax_t value, unsigned char *buf)
  20 {
  21         unsigned char varint[16];
  22         unsigned pos = sizeof(varint) - 1;
  23         varint[pos] = value & 127;
  24         while (value >>= 7)
  25                 varint[--pos] = 128 | (--value & 127);
  26         if (buf)
  27                 memcpy(buf, varint + pos, sizeof(varint) - pos);
  28         return sizeof(varint) - pos;
  29 }