zip.c

   1 #define ZIP_BIGLEN 254
   2 #define ZIP_END 255
   3
   4 /* The following macro returns the number of bytes needed to encode the length
   5  * for the integer value _l, that is, 1 byte for lengths < ZIP_BIGLEN and
   6  * 5 bytes for all the other lengths. */
   7 #define ZIP_LEN_BYTES(_l) (((_l) < ZIP_BIGLEN) ? 1 : sizeof(unsigned int)+1)
   8
   9 /* Decode the encoded length pointed by 'p' */
  10 static unsigned int zipDecodeLength(unsigned char *p) {
  11     unsigned int len = *p;
  12
  13     if (len < ZIP_BIGLEN) return len;
  14     memcpy(&len,p+1,sizeof(unsigned int));
  15     return len;
  16 }
  17
  18 /* Encode the length 'l' writing it in 'p'. If p is NULL it just returns
  19  * the amount of bytes required to encode such a length. */
  20 static unsigned int zipEncodeLength(unsigned char *p, unsigned int len) {
  21     if (p == NULL) {
  22         return ZIP_LEN_BYTES(len);
  23     } else {
  24         if (len < ZIP_BIGLEN) {
  25             p[0] = len;
  26             return 1;
  27         } else {
  28             p[0] = ZIP_BIGLEN;
  29             memcpy(p+1,&len,sizeof(len));
  30             return 1+sizeof(len);
  31         }
  32     }
  33 }
  34
  35 /* Return the total amount used by an entry (encoded length + payload). */
  36 static unsigned int zipRawEntryLength(unsigned char *p) {
  37     unsigned int l = zipDecodeLength(p);
  38     return zipEncodeLength(NULL,l) + l;
  39 }
  40
  41 /* Resize the zip* structure. */
  42 static unsigned char *zipResize(unsigned char *z, unsigned int len) {
  43     z = zrealloc(z,len);
  44     z[len-1] = ZIP_END;
  45     return z;
  46 }