(mergefps): Use binary search rather than linear one

when comparing new line to lines already in main memory.

diff --git a/src/sort.c b/src/sort.c
index 61071ac61e2e15c0bb55e6eb5e576ebee3066440..d8cbfbae1d5b6839b126aa3ed7bd01a2bd43ccb1 100644 (file)
--- a/src/sort.c
+++ b/src/sort.c
@@ -1,5 +1,5 @@
 /* sort - sort lines of text (with all kinds of options).
-   Copyright (C) 88, 1991-2004 Free Software Foundation, Inc.
+   Copyright (C) 1988, 1991-2005 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
@@ -1778,18 +1778,31 @@ mergefps (char **files, size_t ntemps, size_t nfiles,
        }
 
       /* The new line just read in may be larger than other lines
-        already in core; push it back in the queue until we encounter
-        a line larger than it. */
-      for (i = 1; i < nfiles; ++i)
-       {
-         int cmp = compare (cur[ord[0]], cur[ord[i]]);
-         if (cmp < 0 || (cmp == 0 && ord[0] < ord[i]))
-           break;
-       }
-      t = ord[0];
-      for (j = 1; j < i; ++j)
-       ord[j - 1] = ord[j];
-      ord[i - 1] = t;
+        already in main memory; push it back in the queue until we
+        encounter a line larger than it.  Optimize for the common
+        case where the new line is smallest.  */
+      {
+       size_t lo = 1;
+       size_t hi = nfiles;
+       size_t probe = lo;
+       size_t ord0 = ord[0];
+       size_t count_of_smaller_lines;
+
+       while (lo < hi)
+         {
+           int cmp = compare (cur[ord0], cur[ord[probe]]);
+           if (cmp < 0 || (cmp == 0 && ord0 < ord[probe]))
+             hi = probe;
+           else
+             lo = probe + 1;
+           probe = (lo + hi) / 2;
+         }
+
+       count_of_smaller_lines = lo - 1;
+       for (j = 0; j < count_of_smaller_lines; j++)
+         ord[j] = ord[j + 1];
+       ord[count_of_smaller_lines] = ord0;
+      }
     }
 
   if (unique && savedline)