Rev 4709: Restructure the internals to be a bit more understandable. in http://bazaar.launchpad.net/~jameinel/bzr/2.0-490228-gc-segfault

[John Arbash Meinel]

At http://bazaar.launchpad.net/~jameinel/bzr/2.0-490228-gc-segfault

------------------------------------------------------------
revno: 4709
revision-id: john at arbash-meinel.com-20091214155442-tm43um6g8xofx4rs
parent: john at arbash-meinel.com-20091214155224-6av92htxukvp69jk
committer: John Arbash Meinel <john at arbash-meinel.com>
branch nick: 2.0-490228-gc-segfault
timestamp: Mon 2009-12-14 09:54:42 -0600
message:
  Restructure the internals to be a bit more understandable.
  
  This is just renaming variables and assigning to local temp variables
  rather than accessing through pointers and array offsets.
-------------- next part --------------
=== modified file 'bzrlib/diff-delta.c'
--- a/bzrlib/diff-delta.c	2009-12-14 15:52:24 +0000
+++ b/bzrlib/diff-delta.c	2009-12-14 15:54:42 +0000
@@ -688,7 +688,7 @@
     const unsigned char *data, *buffer, *top;
     unsigned char cmd;
     struct delta_index *new_index;
-    struct index_entry *entry, *entries, *old_entry;
+    struct index_entry *entry, *entries;
 
     if (!src->buf || !src->size)
         return NULL;
@@ -789,6 +789,7 @@
     entry = entries;
     num_inserted = 0;
     for (; num_entries > 0; --num_entries, ++entry) {
+        struct index_entry *next_bucket_entry, *cur_entry, *bucket_first_entry;
         hash_offset = (entry->val & old_index->hash_mask);
         /* The basic structure is a hash => packed_entries that fit in that
          * hash bucket. Things are structured such that the hash-pointers are
@@ -797,15 +798,19 @@
          * forward. If there are no NULL targets, then we know because
          * entry->ptr will not be NULL.
          */
-        old_entry = old_index->hash[hash_offset + 1];
-        old_entry--;
-        while (old_entry->ptr == NULL
-               && old_entry >= old_index->hash[hash_offset]) {
-            old_entry--;
+        // The start of the next bucket, this may point past the end of the
+        // entry table if hash_offset is the last bucket.
+        next_bucket_entry = old_index->hash[hash_offset + 1];
+        // First entry in this bucket
+        bucket_first_entry = old_index->hash[hash_offset];
+        cur_entry = next_bucket_entry - 1;
+        while (cur_entry->ptr == NULL && cur_entry >= bucket_first_entry) {
+            cur_entry--;
         }
-        old_entry++;
-        if (old_entry >= old_index->hash[hash_offset + 1]
-            || old_entry->ptr != NULL) {
+        // cur_entry now either points at the first NULL, or it points to
+        // next_bucket_entry if there were no blank spots.
+        cur_entry++;
+        if (cur_entry >= next_bucket_entry || cur_entry->ptr != NULL) {
             /* There is no room for this entry, we have to resize */
             // char buff[128];
             // get_text(buff, entry->ptr);
@@ -822,7 +827,7 @@
             break;
         }
         num_inserted++;
-        *old_entry = *entry;
+        *cur_entry = *entry;
         /* For entries which we *do* manage to insert into old_index, we don't
          * want them double copied into the final output.
          */