From 9a3bbe128403a6bd6f8dd53f11dec991cfc7d526 Mon Sep 17 00:00:00 2001
From: Matthew Sackman <matthew@lshift.net>
Date: Wed, 8 Apr 2009 17:42:44 +0100
Subject: Seem to be able to reliable read and write...

---
 src/rabbit_disk_queue.erl | 75 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 src/rabbit_disk_queue.erl

diff --git a/src/rabbit_disk_queue.erl b/src/rabbit_disk_queue.erl
new file mode 100644
index 00000000..24c9db7d
--- /dev/null
+++ b/src/rabbit_disk_queue.erl
@@ -0,0 +1,75 @@
+%%   The contents of this file are subject to the Mozilla Public License
+%%   Version 1.1 (the "License"); you may not use this file except in
+%%   compliance with the License. You may obtain a copy of the License at
+%%   http://www.mozilla.org/MPL/
+%%
+%%   Software distributed under the License is distributed on an "AS IS"
+%%   basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
+%%   License for the specific language governing rights and limitations
+%%   under the License.
+%%
+%%   The Original Code is RabbitMQ.
+%%
+%%   The Initial Developers of the Original Code are LShift Ltd,
+%%   Cohesive Financial Technologies LLC, and Rabbit Technologies Ltd.
+%%
+%%   Portions created before 22-Nov-2008 00:00:00 GMT by LShift Ltd,
+%%   Cohesive Financial Technologies LLC, or Rabbit Technologies Ltd
+%%   are Copyright (C) 2007-2008 LShift Ltd, Cohesive Financial
+%%   Technologies LLC, and Rabbit Technologies Ltd.
+%%
+%%   Portions created by LShift Ltd are Copyright (C) 2007-2009 LShift
+%%   Ltd. Portions created by Cohesive Financial Technologies LLC are
+%%   Copyright (C) 2007-2009 Cohesive Financial Technologies
+%%   LLC. Portions created by Rabbit Technologies Ltd are Copyright
+%%   (C) 2007-2009 Rabbit Technologies Ltd.
+%%
+%%   All Rights Reserved.
+%%
+%%   Contributor(s): ______________________________________.
+%%
+
+-module(rabbit_disk_queue).
+
+-compile(export_all). %% CHANGE ME
+
+-define(WRITE_OK_SIZE_BITS, 8).
+-define(WRITE_OK, 255).
+-define(INTEGER_SIZE_BYTES, 8).
+-define(INTEGER_SIZE_BITS, 8 * ?INTEGER_SIZE_BYTES).
+
+base_filename() ->
+    mnesia:system_info(directory) ++ "/rabbit_disk_queue/".
+
+append_message(FileHdl, MsgId, MsgBody) when is_binary(MsgBody) ->
+    BodySize = size(MsgBody),
+    MsgIdBin = term_to_binary(MsgId),
+    MsgIdBinSize = size(MsgIdBin),
+    TotalSize = BodySize + MsgIdBinSize,
+    case file:write(FileHdl, <<TotalSize:(?INTEGER_SIZE_BITS),
+			       MsgIdBinSize:(?INTEGER_SIZE_BITS),
+			       MsgIdBin:MsgIdBinSize/binary, MsgBody:BodySize/binary>>) of
+	ok -> file:write(FileHdl, <<(?WRITE_OK):(?WRITE_OK_SIZE_BITS)>>);
+	KO -> KO
+    end.
+
+read_message_at_offset(FileHdl, Offset) ->
+    case file:position(FileHdl, {bof, Offset}) of
+	{ok, Offset} ->
+	    case file:read(FileHdl, 2 * (?INTEGER_SIZE_BYTES)) of
+		{ok, <<TotalSize:(?INTEGER_SIZE_BITS), MsgIdBinSize:(?INTEGER_SIZE_BITS)>>} ->
+		    ExpectedAbsPos = Offset + (2 * (?INTEGER_SIZE_BYTES)) + MsgIdBinSize,
+		    case file:position(FileHdl, {cur, MsgIdBinSize}) of
+			{ok, ExpectedAbsPos} ->
+			    BodySize = TotalSize - MsgIdBinSize,
+			    case file:read(FileHdl, 1 + BodySize) of
+				{ok, <<MsgBody:BodySize/binary, 255:(?WRITE_OK_SIZE_BITS)>>} ->
+				    {ok, MsgBody, BodySize};
+				KO -> KO
+			    end;
+			KO -> KO
+		    end;
+		KO -> KO
+	    end;
+	KO -> KO
+    end.
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