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From fdman...@apache.org
Subject svn commit: r1033714 - /couchdb/trunk/src/couchdb/couch_file.erl
Date Wed, 10 Nov 2010 21:14:01 GMT
Author: fdmanana
Date: Wed Nov 10 21:14:00 2010
New Revision: 1033714

URL: http://svn.apache.org/viewvc?rev=1033714&view=rev
Log:
Micro optimization: faster header reads (read the whole block at once, so far headers are
always smaller than a block). Read time is basically reduced to half.

Modified:
    couchdb/trunk/src/couchdb/couch_file.erl

Modified: couchdb/trunk/src/couchdb/couch_file.erl
URL: http://svn.apache.org/viewvc/couchdb/trunk/src/couchdb/couch_file.erl?rev=1033714&r1=1033713&r2=1033714&view=diff
==============================================================================
--- couchdb/trunk/src/couchdb/couch_file.erl (original)
+++ couchdb/trunk/src/couchdb/couch_file.erl Wed Nov 10 21:14:00 2010
@@ -486,11 +486,18 @@ find_header(Fd, Block) ->
     end.
 
 load_header(Fd, Block) ->
-    {ok, <<1>>} = file:pread(Fd, Block*?SIZE_BLOCK, 1),
-    {ok, <<HeaderLen:32/integer>>} = file:pread(Fd, (Block*?SIZE_BLOCK) + 1,
4),
+    {ok, <<1, HeaderLen:32/integer, RestBlock/binary>>} =
+        file:pread(Fd, Block * ?SIZE_BLOCK, ?SIZE_BLOCK),
     TotalBytes = calculate_total_read_len(1, HeaderLen),
-    {ok, <<RawBin:TotalBytes/binary>>} =
-            file:pread(Fd, (Block*?SIZE_BLOCK) + 5, TotalBytes),
+    case TotalBytes > byte_size(RestBlock) of
+    false ->
+        <<RawBin:TotalBytes/binary, _/binary>> = RestBlock;
+    true ->
+        {ok, Missing} = file:pread(
+            Fd, (Block * ?SIZE_BLOCK) + 5 + byte_size(RestBlock),
+            TotalBytes - byte_size(RestBlock)),
+        RawBin = <<RestBlock/binary, Missing/binary>>
+    end,
     <<Md5Sig:16/binary, HeaderBin/binary>> =
         iolist_to_binary(remove_block_prefixes(1, RawBin)),
     Md5Sig = couch_util:md5(HeaderBin),



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