filevercmp: new module

[gnulib.git] / lib / filevercmp.c

diff --git a/lib/filevercmp.c b/lib/filevercmp.c
new file mode 100644 (file)
index 0000000..856f30f
--- /dev/null
+++ b/lib/filevercmp.c
@@ -0,0 +1,154 @@
+/*
+   Copyright (C) 1995 Ian Jackson <iwj10@cus.cam.ac.uk>
+   Copyright (C) 2001 Anthony Towns <aj@azure.humbug.org.au>
+   Copyright (C) 2008 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>. */
+
+#include <config.h>
+#include "filevercmp.h"
+
+#include <sys/types.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <c-ctype.h>
+#include <limits.h>
+
+/* Match a file suffix defined by this regular expression:
+   /(\.[A-Za-z][A-Za-z0-9]*)*$/
+   Scan the string *STR and return a pointer to the matching suffix, or
+   NULL if not found.  Upon return, *STR points to terminating NUL.  */
+static const char *
+match_suffix (const char **str)
+{
+  const char *match = NULL;
+  bool read_alpha = false;
+  while (**str)
+    {
+      if (read_alpha)
+        {
+          read_alpha = false;
+          if (!c_isalpha (**str))
+            match = NULL;
+        }
+      else if ('.' == **str)
+        {
+          read_alpha = true;
+          if (!match)
+            match = *str;
+        }
+      else if (!c_isalnum (**str))
+        match = NULL;
+      (*str)++;
+    }
+  return match;
+}
+
+/* verrevcmp helper function */
+static inline int
+order (unsigned char c)
+{
+  if (c_isdigit (c))
+    return 0;
+  else if (c_isalpha (c))
+    return c;
+  else if (c == '~')
+    return -1;
+  else
+    return (int) c + UCHAR_MAX + 1;
+}
+
+/* slightly modified verrevcmp function from dpkg
+   S1, S2 - compared string
+   S1_LEN, S2_LEN - length of strings to be scanned
+
+   This implements the algorithm for comparison of version strings
+   specified by Debian and now widely adopted.  The detailed
+   specification can be found in the Debian Policy Manual in the
+   section on the `Version' control field.  This version of the code
+   implements that from s5.6.12 of Debian Policy v3.8.0.1
+   http://www.debian.org/doc/debian-policy/ch-controlfields.html#s-f-Version */
+static int
+verrevcmp (const char *s1, size_t s1_len, const char *s2, size_t s2_len)
+{
+  size_t s1_pos = 0;
+  size_t s2_pos = 0;
+  while (s1_pos < s1_len || s2_pos < s2_len)
+    {
+      int first_diff = 0;
+      while ((s1_pos < s1_len && !c_isdigit (s1[s1_pos]))
+            || (s2_pos < s2_len && !c_isdigit (s2[s2_pos])))
+       {
+         int s1_c = (s1_pos == s1_len) ? 0 : order (s1[s1_pos]);
+         int s2_c = (s2_pos == s2_len) ? 0 : order (s2[s2_pos]);
+         if (s1_c != s2_c)
+           return s1_c - s2_c;
+         s1_pos++;
+         s2_pos++;
+       }
+      while (s1[s1_pos] == '0')
+       s1_pos++;
+      while (s2[s2_pos] == '0')
+       s2_pos++;
+      while (c_isdigit (s1[s1_pos]) && c_isdigit (s2[s2_pos]))
+       {
+         if (!first_diff)
+           first_diff = s1[s1_pos] - s2[s2_pos];
+         s1_pos++;
+         s2_pos++;
+       }
+      if (c_isdigit (s1[s1_pos]))
+       return 1;
+      if (c_isdigit (s2[s2_pos]))
+       return -1;
+      if (first_diff)
+       return first_diff;
+    }
+  return 0;
+}
+
+/* Compare version strings S1 and S2.
+   See filevercmp.h for function description.  */
+int
+filevercmp (const char *s1, const char *s2)
+{
+  const char *s1_pos = s1;
+  const char *s2_pos = s2;
+  const char *s1_suffix, *s2_suffix;
+  size_t s1_len, s2_len;
+  int result;
+
+  /* easy comparison to see if strings are identical */
+  int simple_cmp = strcmp (s1, s2);
+  if (simple_cmp == 0)
+    return 0;
+
+  /* "cut" file suffixes */
+  s1_suffix = match_suffix (&s1_pos);
+  s2_suffix = match_suffix (&s2_pos);
+  s1_len = (s1_suffix ? s1_suffix : s1_pos) - s1;
+  s2_len = (s2_suffix ? s2_suffix : s2_pos) - s2;
+
+  /* restore file suffixes if strings are identical after "cut" */
+  if ((s1_suffix || s2_suffix) && (s1_len == s2_len)
+      && 0 == strncmp (s1, s2, s1_len))
+    {
+      s1_len = s1_pos - s1;
+      s2_len = s2_pos - s2;
+    }
+
+  result = verrevcmp (s1, s1_len, s2, s2_len);
+  return result == 0 ? simple_cmp : result;
+}