X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;ds=sidebyside;f=lib%2Fstr-two-way.h;h=7dcb38721139e18e6ac5c22a8ba6ca958b8bb502;hb=b344de996cd51f8a2f2558a3172016b64d99c622;hp=5f150af6afb6681e7647a892911e6e653518bc4d;hpb=c823199df2cc03b6bd70d0a2fef5999af82792fe;p=gnulib.git

diff --git a/lib/str-two-way.h b/lib/str-two-way.h
index 5f150af6a..7dcb38721 100644
--- a/lib/str-two-way.h
+++ b/lib/str-two-way.h
@@ -1,5 +1,5 @@
 /* Byte-wise substring search, using the Two-Way algorithm.
-   Copyright (C) 2008, 2009, 2010 Free Software Foundation, Inc.
+   Copyright (C) 2008-2011 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Written by Eric Blake <ebb9@byu.net>, 2008.
 
@@ -44,14 +44,15 @@
 #include <limits.h>
 #include <stdint.h>
 
-/* We use the Two-Way string matching algorithm, which guarantees
-   linear complexity with constant space.  Additionally, for long
-   needles, we also use a bad character shift table similar to the
-   Boyer-Moore algorithm to achieve improved (potentially sub-linear)
-   performance.
+/* We use the Two-Way string matching algorithm (also known as
+   Chrochemore-Perrin), which guarantees linear complexity with
+   constant space.  Additionally, for long needles, we also use a bad
+   character shift table similar to the Boyer-Moore algorithm to
+   achieve improved (potentially sub-linear) performance.
 
-   See http://www-igm.univ-mlv.fr/~lecroq/string/node26.html#SECTION00260
-   and http://en.wikipedia.org/wiki/Boyer-Moore_string_search_algorithm
+   See http://www-igm.univ-mlv.fr/~lecroq/string/node26.html#SECTION00260,
+   http://en.wikipedia.org/wiki/Boyer-Moore_string_search_algorithm,
+   http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.34.6641&rep=rep1&type=pdf
 */
 
 /* Point at which computing a bad-byte shift table is likely to be
@@ -108,7 +109,7 @@ static size_t
 critical_factorization (const unsigned char *needle, size_t needle_len,
                         size_t *period)
 {
-  /* Index of last byte of left half.  */
+  /* Index of last byte of left half, or SIZE_MAX.  */
   size_t max_suffix, max_suffix_rev;
   size_t j; /* Index into NEEDLE for current candidate suffix.  */
   size_t k; /* Offset into current period.  */
@@ -124,8 +125,8 @@ critical_factorization (const unsigned char *needle, size_t needle_len,
     }
 
   /* Invariants:
-     1 <= j < NEEDLE_LEN - 1
-     0 <= max_suffix{,_rev} < j
+     0 <= j < NEEDLE_LEN - 1
+     -1 <= max_suffix{,_rev} < j (treating SIZE_MAX as if it were signed)
      min(max_suffix, max_suffix_rev) < global period of NEEDLE
      1 <= p <= global period of NEEDLE
      p == global period of the substring NEEDLE[max_suffix{,_rev}+1...j]
@@ -133,8 +134,9 @@ critical_factorization (const unsigned char *needle, size_t needle_len,
   */
 
   /* Perform lexicographic search.  */
-  max_suffix = 0;
-  j = k = p = 1;
+  max_suffix = SIZE_MAX;
+  j = 0;
+  k = p = 1;
   while (j + k < needle_len)
     {
       a = CANON_ELEMENT (needle[j + k]);
@@ -167,8 +169,9 @@ critical_factorization (const unsigned char *needle, size_t needle_len,
   *period = p;
 
   /* Perform reverse lexicographic search.  */
-  max_suffix_rev = 0;
-  j = k = p = 1;
+  max_suffix_rev = SIZE_MAX;
+  j = 0;
+  k = p = 1;
   while (j + k < needle_len)
     {
       a = CANON_ELEMENT (needle[j + k]);