parsers: use base-16 trie for faster node->rev mapping This greatly speeds up node->rev lookups, with results that are often user-perceptible: for instance, "hg --time log" of the node associated with rev 1000 on a linux-2.6 repo improves from 0.3 seconds to 0.03. I have not found any instances of slowdowns. The new perfnodelookup command in contrib/perf.py demonstrates the speedup more dramatically, since it performs no I/O. For a single lookup, the new code is about 40x faster. These changes also prepare the ground for the possibility of further improving the performance of prefix-based node lookups.

--- a/tests/test-parseindex2.py	Thu Apr 12 20:22:18 2012 -0500
+++ b/tests/test-parseindex2.py	Thu Apr 12 14:05:59 2012 -0700
@@ -110,6 +110,13 @@
     if py_res_2 != c_res_2:
         print "Parse index result (no inlined data) differs!"
 
+    ix = parsers.parse_index2(data_inlined, True)[0]
+    for i, r in enumerate(ix):
+        if r[7] == nullid:
+            i = -1
+        if ix[r[7]] != i:
+            print 'Reverse lookup inconsistent for %r' % r[7].encode('hex')
+
     print "done"
 
 runtest()