src/varint.c

   1 /*
   2  * Copyright (C) the libgit2 contributors. All rights reserved.
   3  *
   4  * This file is part of libgit2, distributed under the GNU GPL v2 with
   5  * a Linking Exception. For full terms see the included COPYING file.
   6  */
   7
   8 #include "varint.h"
   9
  10 uintmax_t git_decode_varint(const unsigned char *bufp, size_t *varint_len)
  11 {
  12         const unsigned char *buf = bufp;
  13         unsigned char c = *buf++;
  14         uintmax_t val = c & 127;
  15         while (c & 128) {
  16                 val += 1;
  17                 if (!val || MSB(val, 7)) {
  18                         /* This is not a valid varint_len, so it signals
  19                            the error */
  20                         *varint_len = 0;
  21                         return 0; /* overflow */
  22                 }
  23                 c = *buf++;
  24                 val = (val << 7) + (c & 127);
  25         }
  26         *varint_len = buf - bufp;
  27         return val;
  28 }
  29
  30 int git_encode_varint(unsigned char *buf, size_t bufsize, uintmax_t value)
  31 {
  32         unsigned char varint[16];
  33         unsigned pos = sizeof(varint) - 1;
  34         varint[pos] = value & 127;
  35         while (value >>= 7)
  36                 varint[--pos] = 128 | (--value & 127);
  37         if (buf) {
  38                 if (bufsize < (sizeof(varint) - pos))
  39                         return -1;
  40                 memcpy(buf, varint + pos, sizeof(varint) - pos);
  41         }
  42         return sizeof(varint) - pos;
  43 }