hash-lookup: rename from sha1-lookup

[thirdparty/git.git] / sha1-lookup.c

diff --git a/sha1-lookup.c b/sha1-lookup.c
deleted file mode 100644 (file)
index 45489ed..0000000
--- a/sha1-lookup.c
+++ /dev/null
@@ -1,129 +0,0 @@
-#include "cache.h"
-#include "sha1-lookup.h"
-
-static uint32_t take2(const unsigned char *sha1)
-{
-       return ((sha1[0] << 8) | sha1[1]);
-}
-
-/*
- * Conventional binary search loop looks like this:
- *
- *      do {
- *              int mi = lo + (hi - lo) / 2;
- *              int cmp = "entry pointed at by mi" minus "target";
- *              if (!cmp)
- *                      return (mi is the wanted one)
- *              if (cmp > 0)
- *                      hi = mi; "mi is larger than target"
- *              else
- *                      lo = mi+1; "mi is smaller than target"
- *      } while (lo < hi);
- *
- * The invariants are:
- *
- * - When entering the loop, lo points at a slot that is never
- *   above the target (it could be at the target), hi points at a
- *   slot that is guaranteed to be above the target (it can never
- *   be at the target).
- *
- * - We find a point 'mi' between lo and hi (mi could be the same
- *   as lo, but never can be the same as hi), and check if it hits
- *   the target.  There are three cases:
- *
- *    - if it is a hit, we are happy.
- *
- *    - if it is strictly higher than the target, we update hi with
- *      it.
- *
- *    - if it is strictly lower than the target, we update lo to be
- *      one slot after it, because we allow lo to be at the target.
- *
- * When choosing 'mi', we do not have to take the "middle" but
- * anywhere in between lo and hi, as long as lo <= mi < hi is
- * satisfied.  When we somehow know that the distance between the
- * target and lo is much shorter than the target and hi, we could
- * pick mi that is much closer to lo than the midway.
- */
-/*
- * The table should contain "nr" elements.
- * The hash of element i (between 0 and nr - 1) should be returned
- * by "fn(i, table)".
- */
-int hash_pos(const unsigned char *hash, void *table, size_t nr,
-            hash_access_fn fn)
-{
-       size_t hi = nr;
-       size_t lo = 0;
-       size_t mi = 0;
-
-       if (!nr)
-               return -1;
-
-       if (nr != 1) {
-               size_t lov, hiv, miv, ofs;
-
-               for (ofs = 0; ofs < the_hash_algo->rawsz - 2; ofs += 2) {
-                       lov = take2(fn(0, table) + ofs);
-                       hiv = take2(fn(nr - 1, table) + ofs);
-                       miv = take2(hash + ofs);
-                       if (miv < lov)
-                               return -1;
-                       if (hiv < miv)
-                               return index_pos_to_insert_pos(nr);
-                       if (lov != hiv) {
-                               /*
-                                * At this point miv could be equal
-                                * to hiv (but hash could still be higher);
-                                * the invariant of (mi < hi) should be
-                                * kept.
-                                */
-                               mi = (nr - 1) * (miv - lov) / (hiv - lov);
-                               if (lo <= mi && mi < hi)
-                                       break;
-                               BUG("assertion failed in binary search");
-                       }
-               }
-       }
-
-       do {
-               int cmp;
-               cmp = hashcmp(fn(mi, table), hash);
-               if (!cmp)
-                       return mi;
-               if (cmp > 0)
-                       hi = mi;
-               else
-                       lo = mi + 1;
-               mi = lo + (hi - lo) / 2;
-       } while (lo < hi);
-       return index_pos_to_insert_pos(lo);
-}
-
-int bsearch_hash(const unsigned char *sha1, const uint32_t *fanout_nbo,
-                const unsigned char *table, size_t stride, uint32_t *result)
-{
-       uint32_t hi, lo;
-
-       hi = ntohl(fanout_nbo[*sha1]);
-       lo = ((*sha1 == 0x0) ? 0 : ntohl(fanout_nbo[*sha1 - 1]));
-
-       while (lo < hi) {
-               unsigned mi = lo + (hi - lo) / 2;
-               int cmp = hashcmp(table + mi * stride, sha1);
-
-               if (!cmp) {
-                       if (result)
-                               *result = mi;
-                       return 1;
-               }
-               if (cmp > 0)
-                       hi = mi;
-               else
-                       lo = mi + 1;
-       }
-
-       if (result)
-               *result = lo;
-       return 0;
-}