X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Funistr%2Fu8-strchr.c;h=ea931a9153072c415981dc6fb23dd137060e5cde;hb=d462d9f08cc8fd534ccae14c878f9c7c18112237;hp=3ee246521e7779b76310173e55a28dcfb27e3b36;hpb=e240ab433593692f27c804c26ec1730a0dd27e5d;p=gnulib.git

diff --git a/lib/unistr/u8-strchr.c b/lib/unistr/u8-strchr.c
index 3ee246521..ea931a915 100644
--- a/lib/unistr/u8-strchr.c
+++ b/lib/unistr/u8-strchr.c
@@ -1,5 +1,5 @@
 /* Search character in UTF-8 string.
-   Copyright (C) 1999, 2002, 2006-2007, 2009-2010 Free Software Foundation,
+   Copyright (C) 1999, 2002, 2006-2007, 2009-2012 Free Software Foundation,
    Inc.
    Written by Bruno Haible <bruno@clisp.org>, 2002.
 
@@ -35,14 +35,15 @@ u8_strchr (const uint8_t *s, ucs4_t uc)
       if (false)
         {
           /* Unoptimized code.  */
-          for (;; s++)
+          for (;;)
             {
-              if (*s == c0)
+              uint8_t s0 = *s;
+              if (s0 == c0)
+                return (uint8_t *) s;
+              s++;
+              if (s0 == 0)
                 break;
-              if (*s == 0)
-                goto notfound;
             }
-          return (uint8_t *) s;
         }
       else
         {
@@ -53,64 +54,187 @@ u8_strchr (const uint8_t *s, ucs4_t uc)
         }
     }
   else
+      /* Loops equivalent to strstr, optimized for a specific length (2, 3, 4)
+         of the needle.  We use an algorithm similar to Boyer-Moore which
+         is documented in lib/unistr/u8-chr.c.  There is additional
+         complication because we need to check after every byte for
+         a NUL byte, but the idea is the same. */
     switch (u8_uctomb_aux (c, uc, 6))
       {
-      /* Loops equivalent to strstr, optimized for a specific length (2, 3, 4)
-         of the needle.  */
       case 2:
-        if (*s == 0)
-          goto notfound;
+        if (*s == 0 || s[1] == 0)
+          break;
         {
           uint8_t c0 = c[0];
           uint8_t c1 = c[1];
+          /* Search for { c0, c1 }.  */
+          uint8_t s1 = s[1];
 
-          for (;; s++)
+          for (;;)
             {
+              /* Here s[0] != 0, s[1] != 0.
+                 Test whether s[0..1] == { c0, c1 }.  */
+              if (s1 == c1)
+                {
+                  if (*s == c0)
+                    return (uint8_t *) s;
+                  else
+                    /* Skip the search at s + 1, because s[1] = c1 < c0.  */
+                    goto case2_skip2;
+                }
+              else
+                {
+                  if (s1 == c0)
+                    goto case2_skip1;
+                  else
+                    /* Skip the search at s + 1, because s[1] != c0.  */
+                    goto case2_skip2;
+                }
+             case2_skip2:
+              s++;
+              s1 = s[1];
+              if (s[1] == 0)
+                break;
+             case2_skip1:
+              s++;
+              s1 = s[1];
               if (s[1] == 0)
-                goto notfound;
-              if (s[1] == c1 && *s == c0)
                 break;
             }
-          return (uint8_t *) s;
         }
+        break;
 
       case 3:
-        if (*s == 0 || s[1] == 0)
-          goto notfound;
+        if (*s == 0 || s[1] == 0 || s[2] == 0)
+          break;
         {
           uint8_t c0 = c[0];
           uint8_t c1 = c[1];
           uint8_t c2 = c[2];
+          /* Search for { c0, c1, c2 }.  */
+          uint8_t s2 = s[2];
 
-          for (;; s++)
+          for (;;)
             {
+              /* Here s[0] != 0, s[1] != 0, s[2] != 0.
+                 Test whether s[0..2] == { c0, c1, c2 }.  */
+              if (s2 == c2)
+                {
+                  if (s[1] == c1 && *s == c0)
+                    return (uint8_t *) s;
+                  else
+                    /* If c2 != c1:
+                         Skip the search at s + 1, because s[2] == c2 != c1.
+                       Skip the search at s + 2, because s[2] == c2 < c0.  */
+                    if (c2 == c1)
+                      goto case3_skip1;
+                    else
+                      goto case3_skip3;
+                }
+              else
+                {
+                  if (s2 == c1)
+                    goto case3_skip1;
+                  else if (s2 == c0)
+                    /* Skip the search at s + 1, because s[2] != c1.  */
+                    goto case3_skip2;
+                  else
+                    /* Skip the search at s + 1, because s[2] != c1.
+                       Skip the search at s + 2, because s[2] != c0.  */
+                    goto case3_skip3;
+                }
+             case3_skip3:
+              s++;
+              s2 = s[2];
+              if (s[2] == 0)
+                break;
+             case3_skip2:
+              s++;
+              s2 = s[2];
+              if (s[2] == 0)
+                break;
+             case3_skip1:
+              s++;
+              s2 = s[2];
               if (s[2] == 0)
-                goto notfound;
-              if (s[2] == c2 && s[1] == c1 && *s == c0)
                 break;
             }
-          return (uint8_t *) s;
         }
+        break;
 
       case 4:
-        if (*s == 0 || s[1] == 0 || s[2] == 0)
-          goto notfound;
+        if (*s == 0 || s[1] == 0 || s[2] == 0 || s[3] == 0)
+          break;
         {
           uint8_t c0 = c[0];
           uint8_t c1 = c[1];
           uint8_t c2 = c[2];
           uint8_t c3 = c[3];
+          /* Search for { c0, c1, c2, c3 }.  */
+          uint8_t s3 = s[3];
 
-          for (;; s++)
+          for (;;)
             {
+              /* Here s[0] != 0, s[1] != 0, s[2] != 0, s[3] != 0.
+                 Test whether s[0..3] == { c0, c1, c2, c3 }.  */
+              if (s3 == c3)
+                {
+                  if (s[2] == c2 && s[1] == c1 && *s == c0)
+                    return (uint8_t *) s;
+                  else
+                    /* If c3 != c2:
+                         Skip the search at s + 1, because s[3] == c3 != c2.
+                       If c3 != c1:
+                         Skip the search at s + 2, because s[3] == c3 != c1.
+                       Skip the search at s + 3, because s[3] == c3 < c0.  */
+                    if (c3 == c2)
+                      goto case4_skip1;
+                    else if (c3 == c1)
+                      goto case4_skip2;
+                    else
+                      goto case4_skip4;
+                }
+              else
+                {
+                  if (s3 == c2)
+                    goto case4_skip1;
+                  else if (s3 == c1)
+                    /* Skip the search at s + 1, because s[3] != c2.  */
+                    goto case4_skip2;
+                  else if (s3 == c0)
+                    /* Skip the search at s + 1, because s[3] != c2.
+                       Skip the search at s + 2, because s[3] != c1.  */
+                    goto case4_skip3;
+                  else
+                    /* Skip the search at s + 1, because s[3] != c2.
+                       Skip the search at s + 2, because s[3] != c1.
+                       Skip the search at s + 3, because s[3] != c0.  */
+                    goto case4_skip4;
+                }
+             case4_skip4:
+              s++;
+              s3 = s[3];
+              if (s[3] == 0)
+                break;
+             case4_skip3:
+              s++;
+              s3 = s[3];
+              if (s[3] == 0)
+                break;
+             case4_skip2:
+              s++;
+              s3 = s[3];
+              if (s[3] == 0)
+                break;
+             case4_skip1:
+              s++;
+              s3 = s[3];
               if (s[3] == 0)
-                goto notfound;
-              if (s[3] == c3 && s[2] == c2 && s[1] == c1 && *s == c0)
                 break;
             }
-          return (uint8_t *) s;
         }
+        break;
       }
-notfound:
+
   return NULL;
 }