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|
% Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
% License for the specific language governing permissions and limitations under
% the License.
-module(couch_stream).
-behaviour(gen_server).
-define(FILE_POINTER_BYTES, 8).
-define(FILE_POINTER_BITS, 8*(?FILE_POINTER_BYTES)).
-define(STREAM_OFFSET_BYTES, 4).
-define(STREAM_OFFSET_BITS, 8*(?STREAM_OFFSET_BYTES)).
-define(HUGE_CHUNK, 1000000000). % Huge chuck size when reading all in one go
-define(DEFAULT_STREAM_CHUNK, 16#00100000). % 1 meg chunks when streaming data
-export([test/0]).
-export([open/1, close/1, write/2, foldl/4, old_foldl/5,old_copy_to_new_stream/4]).
-export([copy_to_new_stream/3,old_read_term/2]).
-export([init/1, terminate/2, handle_call/3]).
-export([handle_cast/2,code_change/3,handle_info/2]).
-include("couch_db.hrl").
-record(stream,
{fd = 0,
written_pointers=[],
buffer_list = [],
buffer_len = 0,
max_buffer = 4096,
written_len = 0
}).
%%% Interface functions %%%
open(Fd) ->
gen_server:start_link(couch_stream, Fd, []).
close(Pid) ->
gen_server:call(Pid, close, infinity).
copy_to_new_stream(Fd, PosList, DestFd) ->
{ok, Dest} = open(DestFd),
foldl(Fd, PosList,
fun(Bin, _) ->
ok = write(Dest, Bin)
end, ok),
close(Dest).
% 09 UPGRADE CODE
old_copy_to_new_stream(Fd, Pos, Len, DestFd) ->
{ok, Dest} = open(DestFd),
old_foldl(Fd, Pos, Len,
fun(Bin, _) ->
ok = write(Dest, Bin)
end, ok),
close(Dest).
% 09 UPGRADE CODE
old_foldl(_Fd, null, 0, _Fun, Acc) ->
Acc;
old_foldl(Fd, OldPointer, Len, Fun, Acc) when is_tuple(OldPointer)->
old_stream_data(Fd, OldPointer, Len, ?DEFAULT_STREAM_CHUNK, Fun, Acc).
foldl(_Fd, [], _Fun, Acc) ->
Acc;
foldl(Fd, [Pos|Rest], Fun, Acc) ->
{ok, Bin} = couch_file:pread_iolist(Fd, Pos),
foldl(Fd, Rest, Fun, Fun(Bin, Acc)).
write(_Pid, <<>>) ->
ok;
write(Pid, Bin) ->
gen_server:call(Pid, {write, Bin}, infinity).
init(Fd) ->
{ok, #stream{fd = Fd}}.
terminate(_Reason, _Stream) ->
ok.
handle_call({write, Bin}, _From, Stream) ->
BinSize = iolist_size(Bin),
#stream{
fd = Fd,
written_len = WrittenLen,
written_pointers = Written,
buffer_len = BufferLen,
buffer_list = Buffer,
max_buffer = Max} = Stream,
if BinSize + BufferLen > Max ->
{ok, Pos} = couch_file:append_binary(Fd, lists:reverse(Buffer, [Bin])),
{reply, ok, Stream#stream{
written_len=WrittenLen + BufferLen + BinSize,
written_pointers=[Pos|Written],
buffer_list=[],
buffer_len=0}};
true ->
{reply, ok, Stream#stream{
buffer_list=[Bin|Buffer],
buffer_len=BufferLen + BinSize}}
end;
handle_call(close, _From, Stream) ->
#stream{
fd = Fd,
written_len = WrittenLen,
written_pointers = Written,
buffer_len = BufferLen,
buffer_list = Buffer} = Stream,
case Buffer of
[] ->
Result = {lists:reverse(Written), WrittenLen};
_ ->
{ok, Pos} = couch_file:append_binary(Fd, lists:reverse(Buffer)),
Result = {lists:reverse(Written, [Pos]), WrittenLen + BufferLen}
end,
{stop, normal, Result, Stream}.
handle_cast(_Msg, State) ->
{noreply,State}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
handle_info(_Info, State) ->
{noreply, State}.
% 09 UPGRADE CODE
old_read_term(Fd, Sp) ->
{ok, <<TermLen:(?STREAM_OFFSET_BITS)>>, Sp2}
= old_read(Fd, Sp, ?STREAM_OFFSET_BYTES),
{ok, Bin, _Sp3} = old_read(Fd, Sp2, TermLen),
{ok, binary_to_term(Bin)}.
old_read(Fd, Sp, Num) ->
{ok, RevBin, Sp2} = old_stream_data(Fd, Sp, Num, ?HUGE_CHUNK, fun(Bin, Acc) -> [Bin | Acc] end, []),
Bin = list_to_binary(lists:reverse(RevBin)),
{ok, Bin, Sp2}.
% 09 UPGRADE CODE
old_stream_data(_Fd, Sp, 0, _MaxChunk, _Fun, Acc) ->
{ok, Acc, Sp};
old_stream_data(Fd, {Pos, 0}, Num, MaxChunk, Fun, Acc) ->
{ok, <<NextPos:(?FILE_POINTER_BITS), NextOffset:(?STREAM_OFFSET_BITS)>>}
= couch_file:old_pread(Fd, Pos, ?FILE_POINTER_BYTES + ?STREAM_OFFSET_BYTES),
Sp = {NextPos, NextOffset},
% Check NextPos is past current Pos (this is always true in a stream)
% Guards against potential infinite loops caused by corruption.
case NextPos > Pos of
true -> ok;
false -> throw({error, stream_corruption})
end,
old_stream_data(Fd, Sp, Num, MaxChunk, Fun, Acc);
old_stream_data(Fd, {Pos, Offset}, Num, MaxChunk, Fun, Acc) ->
ReadAmount = lists:min([MaxChunk, Num, Offset]),
{ok, Bin} = couch_file:old_pread(Fd, Pos, ReadAmount),
Sp = {Pos + ReadAmount, Offset - ReadAmount},
old_stream_data(Fd, Sp, Num - ReadAmount, MaxChunk, Fun, Fun(Bin, Acc)).
%%% Tests %%%
read_all(Fd, PosList) ->
iolist_to_binary(foldl(Fd, PosList,
fun(Bin, Acc) ->
[Bin, Acc]
end, [])).
test() ->
{ok, Fd} = couch_file:open("foo", [create,overwrite]),
ok = couch_file:write_header(Fd, {howdy, howdy}),
Bin = <<"damienkatz">>,
{ok, Pos} = couch_file:append_binary(Fd, Bin),
{ok, Bin} = couch_file:pread_binary(Fd, Pos),
{ok, {howdy, howdy}} = couch_file:read_header(Fd),
ok = couch_file:write_header(Fd, {foo, foo}),
{ok, {foo, foo}} = couch_file:read_header(Fd),
{ok, Stream} = open(Fd),
ok = write(Stream, <<"food">>),
ok = write(Stream, <<"foob">>),
{PosList, 8} = close(Stream),
<<"foodfoob">> = read_all(Fd, PosList),
{ok, Stream2} = open(Fd),
OneBits = <<1:(8*10)>>,
ZeroBits = <<0:(8*10)>>,
ok = write(Stream2, OneBits),
ok = write(Stream2, ZeroBits),
{PosList2, 20} = close(Stream2),
AllBits = iolist_to_binary([OneBits,ZeroBits]),
AllBits = read_all(Fd, PosList2),
couch_file:close(Fd),
PosList2.
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