1 files changed, 110 insertions, 0 deletions
diff --git a/src/cmpvers.c b/src/cmpvers.c
new file mode 100644
index 0000000..42014e8
--- /dev/null
+++ b/src/cmpvers.c
@@ -0,0 +1,110 @@
+
+/**********************************************************************
+
+  Copyright 2019 Andrey V.Kosteltsev
+
+  Licensed under the Radix.pro License, Version 1.0 (the "License");
+  you may not use this file  except  in compliance with the License.
+  You may obtain a copy of the License at
+
+     https://radix.pro/licenses/LICENSE-1.0-en_US.txt
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+  implied.
+
+ **********************************************************************/
+
+#include <config.h>
+
+#include <stdint.h>
+#include <string.h>
+#include <ctype.h>
+
+/* states: S_N: normal, S_I: comparing integral part, S_F: comparing
+           fractionnal parts, S_Z: idem but with leading Zeroes only */
+#define  S_N    0x0
+#define  S_I    0x3
+#define  S_F    0x6
+#define  S_Z    0x9
+
+/* result_type: CMP: return diff; LEN: compare using len_diff/diff */
+#define  CMP    2
+#define  LEN    3
+
+
+/* Compare S1 and S2 as strings holding indices/version numbers,
+   returning less than, equal to or greater than zero if S1 is less than,
+   equal to or greater than S2 (for more info, see the texinfo doc).
+*/
+
+int cmp_version( const char *s1, const char *s2 )
+{
+  const unsigned char *p1 = (const unsigned char *)s1;
+  const unsigned char *p2 = (const unsigned char *)s2;
+
+  /* Symbol(s)    0       [1-9]   others
+     Transition   (10) 0  (01) d  (00) x   */
+  static const uint8_t next_state[] =
+  {
+      /* state    x    d    0  */
+      /* S_N */  S_N, S_I, S_Z,
+      /* S_I */  S_N, S_I, S_I,
+      /* S_F */  S_N, S_F, S_F,
+      /* S_Z */  S_N, S_F, S_Z
+  };
+
+  static const int8_t result_type[] =
+  {
+      /* state   x/x  x/d  x/0  d/x  d/d  d/0  0/x  0/d  0/0  */
+
+      /* S_N */  CMP, CMP, CMP, CMP, LEN, CMP, CMP, CMP, CMP,
+      /* S_I */  CMP, -1,  -1,  +1,  LEN, LEN, +1,  LEN, LEN,
+      /* S_F */  CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
+      /* S_Z */  CMP, +1,  +1,  -1,  CMP, CMP, -1,  CMP, CMP
+  };
+
+  if( p1 == p2 ) return 0;
+
+  unsigned char c1 = *p1++;
+  unsigned char c2 = *p2++;
+  /* Hint: '0' is a digit too.  */
+  int state = S_N + ((c1 == '0') + (isdigit (c1) != 0));
+
+  int diff;
+  while( (diff = c1 - c2) == 0 )
+    {
+      if( c1 == '\0' ) return diff;
+
+      state  = next_state[state];
+      c1     = *p1++;
+      c2     = *p2++;
+      state += (c1 == '0') + (isdigit (c1) != 0);
+    }
+
+  state = result_type[state * 3 + (((c2 == '0') + (isdigit (c2) != 0)))];
+
+  switch (state)
+  {
+    case CMP:
+      return diff;
+
+    case LEN:
+      while( isdigit (*p1++) )
+        if( !isdigit (*p2++) )
+          return 1;
+
+      return isdigit (*p2) ? -1 : diff;
+
+    default:
+      return state;
+  }
+}
+
+
+const char *max_version( const char *s1, const char *s2 )
+{
+  if( cmp_version( s1, s2 ) < 0 ) return s2;
+  else                            return s1;
+}