versioncmp.c

   1 #include "cache.h"
   2
   3 /*
   4  * versioncmp(): copied from string/strverscmp.c in glibc commit
   5  * ee9247c38a8def24a59eb5cfb7196a98bef8cfdc, reformatted to Git coding
   6  * style. The implementation is under LGPL-2.1 and Git relicenses it
   7  * to GPLv2.
   8  */
   9
  10 /*
  11  * states: S_N: normal, S_I: comparing integral part, S_F: comparing
  12  * fractionnal parts, S_Z: idem but with leading Zeroes only
  13  */
  14 #define  S_N    0x0
  15 #define  S_I    0x3
  16 #define  S_F    0x6
  17 #define  S_Z    0x9
  18
  19 /* result_type: CMP: return diff; LEN: compare using len_diff/diff */
  20 #define  CMP    2
  21 #define  LEN    3
  22
  23
  24 /*
  25  * Compare S1 and S2 as strings holding indices/version numbers,
  26  * returning less than, equal to or greater than zero if S1 is less
  27  * than, equal to or greater than S2 (for more info, see the texinfo
  28  * doc).
  29  */
  30
  31 int versioncmp(const char *s1, const char *s2)
  32 {
  33         const unsigned char *p1 = (const unsigned char *) s1;
  34         const unsigned char *p2 = (const unsigned char *) s2;
  35         unsigned char c1, c2;
  36         int state, diff;
  37
  38         /*
  39          * Symbol(s)    0       [1-9]   others
  40          * Transition   (10) 0  (01) d  (00) x
  41          */
  42         static const uint8_t next_state[] = {
  43                 /* state    x    d    0  */
  44                 /* S_N */  S_N, S_I, S_Z,
  45                 /* S_I */  S_N, S_I, S_I,
  46                 /* S_F */  S_N, S_F, S_F,
  47                 /* S_Z */  S_N, S_F, S_Z
  48         };
  49
  50         static const int8_t result_type[] = {
  51                 /* state   x/x  x/d  x/0  d/x  d/d  d/0  0/x  0/d  0/0  */
  52
  53                 /* S_N */  CMP, CMP, CMP, CMP, LEN, CMP, CMP, CMP, CMP,
  54                 /* S_I */  CMP, -1,  -1,  +1,  LEN, LEN, +1,  LEN, LEN,
  55                 /* S_F */  CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
  56                 /* S_Z */  CMP, +1,  +1,  -1,  CMP, CMP, -1,  CMP, CMP
  57         };
  58
  59         if (p1 == p2)
  60                 return 0;
  61
  62         c1 = *p1++;
  63         c2 = *p2++;
  64         /* Hint: '0' is a digit too.  */
  65         state = S_N + ((c1 == '0') + (isdigit (c1) != 0));
  66
  67         while ((diff = c1 - c2) == 0) {
  68                 if (c1 == '\0')
  69                         return diff;
  70
  71                 state = next_state[state];
  72                 c1 = *p1++;
  73                 c2 = *p2++;
  74                 state += (c1 == '0') + (isdigit (c1) != 0);
  75         }
  76
  77         state = result_type[state * 3 + (((c2 == '0') + (isdigit (c2) != 0)))];
  78
  79         switch (state) {
  80         case CMP:
  81                 return diff;
  82
  83         case LEN:
  84                 while (isdigit (*p1++))
  85                         if (!isdigit (*p2++))
  86                                 return 1;
  87
  88                 return isdigit (*p2) ? -1 : diff;
  89
  90         default:
  91                 return state;
  92         }
  93 }