1 files changed, 588 insertions, 0 deletions
diff --git a/apps/couch/src/couch_file.erl b/apps/couch/src/couch_file.erl
new file mode 100644
index 00000000..0a891712
--- /dev/null
+++ b/apps/couch/src/couch_file.erl
@@ -0,0 +1,588 @@
+% 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_file).
+-behaviour(gen_server).
+
+-include("couch_db.hrl").
+
+-define(SIZE_BLOCK, 4096).
+
+-record(file, {
+    fd,
+    tail_append_begin = 0, % 09 UPGRADE CODE
+    eof = 0
+    }).
+
+-export([open/1, open/2, close/1, bytes/1, sync/1, append_binary/2,old_pread/3]).
+-export([append_term/2, pread_term/2, pread_iolist/2, write_header/2]).
+-export([pread_binary/2, read_header/1, truncate/2, upgrade_old_header/2]).
+-export([append_term_md5/2,append_binary_md5/2]).
+-export([init/1, terminate/2, handle_call/3, handle_cast/2, code_change/3, handle_info/2]).
+-export([delete/2,delete/3,init_delete_dir/1]).
+
+%%----------------------------------------------------------------------
+%% Args:   Valid Options are [create] and [create,overwrite].
+%%  Files are opened in read/write mode.
+%% Returns: On success, {ok, Fd}
+%%  or {error, Reason} if the file could not be opened.
+%%----------------------------------------------------------------------
+
+open(Filepath) ->
+    open(Filepath, []).
+
+open(Filepath, Options) ->
+    case gen_server:start_link(couch_file,
+            {Filepath, Options, self(), Ref = make_ref()}, []) of
+    {ok, Fd} ->
+        {ok, Fd};
+    ignore ->
+        % get the error
+        receive
+        {Ref, Pid, Error} ->
+            case process_info(self(), trap_exit) of
+            {trap_exit, true} -> receive {'EXIT', Pid, _} -> ok end;
+            {trap_exit, false} -> ok
+            end,
+            Error
+        end;
+    Error ->
+        Error
+    end.
+
+
+%%----------------------------------------------------------------------
+%% Purpose: To append an Erlang term to the end of the file.
+%% Args:    Erlang term to serialize and append to the file.
+%% Returns: {ok, Pos} where Pos is the file offset to the beginning the
+%%  serialized  term. Use pread_term to read the term back.
+%%  or {error, Reason}.
+%%----------------------------------------------------------------------
+
+append_term(Fd, Term) ->
+    append_binary(Fd, term_to_binary(Term)).
+    
+append_term_md5(Fd, Term) ->
+    append_binary_md5(Fd, term_to_binary(Term)).
+
+
+%%----------------------------------------------------------------------
+%% Purpose: To append an Erlang binary to the end of the file.
+%% Args:    Erlang term to serialize and append to the file.
+%% Returns: {ok, Pos} where Pos is the file offset to the beginning the
+%%  serialized  term. Use pread_term to read the term back.
+%%  or {error, Reason}.
+%%----------------------------------------------------------------------
+
+append_binary(Fd, Bin) ->
+    Size = iolist_size(Bin),
+    gen_server:call(Fd, {append_bin,
+            [<<0:1/integer,Size:31/integer>>, Bin]}, infinity).
+    
+append_binary_md5(Fd, Bin) ->
+    Size = iolist_size(Bin),
+    gen_server:call(Fd, {append_bin,
+            [<<1:1/integer,Size:31/integer>>, couch_util:md5(Bin), Bin]}, infinity).
+
+
+%%----------------------------------------------------------------------
+%% Purpose: Reads a term from a file that was written with append_term
+%% Args:    Pos, the offset into the file where the term is serialized.
+%% Returns: {ok, Term}
+%%  or {error, Reason}.
+%%----------------------------------------------------------------------
+
+
+pread_term(Fd, Pos) ->
+    {ok, Bin} = pread_binary(Fd, Pos),
+    {ok, binary_to_term(Bin)}.
+
+
+%%----------------------------------------------------------------------
+%% Purpose: Reads a binrary from a file that was written with append_binary
+%% Args:    Pos, the offset into the file where the term is serialized.
+%% Returns: {ok, Term}
+%%  or {error, Reason}.
+%%----------------------------------------------------------------------
+
+pread_binary(Fd, Pos) ->
+    {ok, L} = pread_iolist(Fd, Pos),
+    {ok, iolist_to_binary(L)}.
+
+
+pread_iolist(Fd, Pos) ->
+    gen_server:call(Fd, {pread_iolist, Pos}, infinity).
+
+%%----------------------------------------------------------------------
+%% Purpose: The length of a file, in bytes.
+%% Returns: {ok, Bytes}
+%%  or {error, Reason}.
+%%----------------------------------------------------------------------
+
+% length in bytes
+bytes(Fd) ->
+    gen_server:call(Fd, bytes, infinity).
+
+%%----------------------------------------------------------------------
+%% Purpose: Truncate a file to the number of bytes.
+%% Returns: ok
+%%  or {error, Reason}.
+%%----------------------------------------------------------------------
+
+truncate(Fd, Pos) ->
+    gen_server:call(Fd, {truncate, Pos}, infinity).
+
+%%----------------------------------------------------------------------
+%% Purpose: Ensure all bytes written to the file are flushed to disk.
+%% Returns: ok
+%%  or {error, Reason}.
+%%----------------------------------------------------------------------
+
+sync(Filepath) when is_list(Filepath) ->
+    {ok, Fd} = file:open(Filepath, [append, raw]),
+    try file:sync(Fd) after file:close(Fd) end;
+sync(Fd) ->
+    gen_server:call(Fd, sync, infinity).
+
+%%----------------------------------------------------------------------
+%% Purpose: Close the file.
+%% Returns: ok
+%%----------------------------------------------------------------------
+close(Fd) ->
+    MRef = erlang:monitor(process, Fd),
+    try
+        catch unlink(Fd),
+        catch exit(Fd, shutdown),
+        receive
+        {'DOWN', MRef, _, _, _} ->
+            ok
+        end
+    after
+        erlang:demonitor(MRef, [flush])
+    end.
+
+
+delete(RootDir, Filepath) ->
+    delete(RootDir, Filepath, true).
+
+
+delete(RootDir, Filepath, Async) ->
+    DelFile = filename:join([RootDir,".delete", ?b2l(couch_uuids:random())]),
+    case file:rename(Filepath, DelFile) of
+    ok ->
+        if (Async) ->
+            spawn(file, delete, [DelFile]),
+            ok;
+        true ->
+            file:delete(DelFile)
+        end;
+    Error ->
+        Error
+    end.
+
+
+init_delete_dir(RootDir) ->
+    Dir = filename:join(RootDir,".delete"),
+    % note: ensure_dir requires an actual filename companent, which is the
+    % reason for "foo".
+    filelib:ensure_dir(filename:join(Dir,"foo")),
+    filelib:fold_files(Dir, ".*", true,
+        fun(Filename, _) ->
+            ok = file:delete(Filename)
+        end, ok).
+
+
+% 09 UPGRADE CODE
+old_pread(Fd, Pos, Len) ->
+    {ok, <<RawBin:Len/binary>>, false} = gen_server:call(Fd, {pread, Pos, Len}, infinity),
+    {ok, RawBin}.
+
+% 09 UPGRADE CODE
+upgrade_old_header(Fd, Sig) ->
+    gen_server:call(Fd, {upgrade_old_header, Sig}, infinity).
+
+
+read_header(Fd) ->
+    case gen_server:call(Fd, find_header, infinity) of
+    {ok, Bin} ->
+        {ok, binary_to_term(Bin)};
+    Else ->
+        Else
+    end.
+
+write_header(Fd, Data) ->
+    Bin = term_to_binary(Data),
+    Md5 = couch_util:md5(Bin),
+    % now we assemble the final header binary and write to disk
+    FinalBin = <<Md5/binary, Bin/binary>>,
+    gen_server:call(Fd, {write_header, FinalBin}, infinity).
+
+
+
+
+init_status_error(ReturnPid, Ref, Error) ->
+    ReturnPid ! {Ref, self(), Error},
+    ignore.
+
+% server functions
+
+init({Filepath, Options, ReturnPid, Ref}) ->
+    process_flag(trap_exit, true),
+    case lists:member(create, Options) of
+    true ->
+        filelib:ensure_dir(Filepath),
+        case file:open(Filepath, [read, append, raw, binary]) of
+        {ok, Fd} ->
+            {ok, Length} = file:position(Fd, eof),
+            case Length > 0 of
+            true ->
+                % this means the file already exists and has data.
+                % FYI: We don't differentiate between empty files and non-existant
+                % files here.
+                case lists:member(overwrite, Options) of
+                true ->
+                    {ok, 0} = file:position(Fd, 0),
+                    ok = file:truncate(Fd),
+                    ok = file:sync(Fd),
+                    maybe_track_open_os_files(Options),
+                    {ok, #file{fd=Fd}};
+                false ->
+                    ok = file:close(Fd),
+                    init_status_error(ReturnPid, Ref, file_exists)
+                end;
+            false ->
+                maybe_track_open_os_files(Options),
+                {ok, #file{fd=Fd}}
+            end;
+        Error ->
+            init_status_error(ReturnPid, Ref, Error)
+        end;
+    false ->
+        % open in read mode first, so we don't create the file if it doesn't exist.
+        case file:open(Filepath, [read, raw]) of
+        {ok, Fd_Read} ->
+            {ok, Fd} = file:open(Filepath, [read, append, raw, binary]),
+            ok = file:close(Fd_Read),
+            maybe_track_open_os_files(Options),
+            {ok, Length} = file:position(Fd, eof),
+            {ok, #file{fd=Fd, eof=Length}};
+        Error ->
+            init_status_error(ReturnPid, Ref, Error)
+        end
+    end.
+
+maybe_track_open_os_files(FileOptions) ->
+    case lists:member(sys_db, FileOptions) of
+    true ->
+        ok;
+    false ->
+        couch_stats_collector:track_process_count({couchdb, open_os_files})
+    end.
+
+terminate(_Reason, _Fd) ->
+    ok.
+
+
+handle_call({pread_iolist, Pos}, _From, File) ->
+    {LenIolist, NextPos} = read_raw_iolist_int(File, Pos, 4),
+    case iolist_to_binary(LenIolist) of
+    <<1:1/integer,Len:31/integer>> -> % an MD5-prefixed term
+        {Md5AndIoList, _} = read_raw_iolist_int(File, NextPos, Len+16),
+        {Md5, IoList} = extract_md5(Md5AndIoList),
+        case couch_util:md5(IoList) of
+        Md5 ->
+            {reply, {ok, IoList}, File};
+        _ ->
+            {stop, file_corruption, {error,file_corruption}, File}
+        end;
+    <<0:1/integer,Len:31/integer>> ->
+        {Iolist, _} = read_raw_iolist_int(File, NextPos, Len),
+        {reply, {ok, Iolist}, File}
+    end;
+handle_call({pread, Pos, Bytes}, _From, #file{fd=Fd,tail_append_begin=TailAppendBegin}=File) ->
+    {ok, Bin} = file:pread(Fd, Pos, Bytes),
+    {reply, {ok, Bin, Pos >= TailAppendBegin}, File};
+handle_call(bytes, _From, #file{eof=Length}=File) ->
+    {reply, {ok, Length}, File};
+handle_call(sync, _From, #file{fd=Fd}=File) ->
+    {reply, file:sync(Fd), File};
+handle_call({truncate, Pos}, _From, #file{fd=Fd}=File) ->
+    {ok, Pos} = file:position(Fd, Pos),
+    case file:truncate(Fd) of
+    ok ->
+        {reply, ok, File#file{eof=Pos}};
+    Error ->
+        {reply, Error, File}
+    end;
+handle_call({append_bin, Bin}, _From, #file{fd=Fd, eof=Pos}=File) ->
+    Blocks = make_blocks(Pos rem ?SIZE_BLOCK, Bin),
+    case file:write(Fd, Blocks) of
+    ok ->
+        {reply, {ok, Pos}, File#file{eof=Pos+iolist_size(Blocks)}};
+    Error ->
+        {reply, Error, File}
+    end;
+handle_call({write_header, Bin}, _From, #file{fd=Fd, eof=Pos}=File) ->
+    BinSize = size(Bin),
+    case Pos rem ?SIZE_BLOCK of
+    0 ->
+        Padding = <<>>;
+    BlockOffset ->
+        Padding = <<0:(8*(?SIZE_BLOCK-BlockOffset))>>
+    end,
+    FinalBin = [Padding, <<1, BinSize:32/integer>> | make_blocks(5, [Bin])],
+    case file:write(Fd, FinalBin) of
+    ok ->
+        {reply, ok, File#file{eof=Pos+iolist_size(FinalBin)}};
+    Error ->
+        {reply, Error, File}
+    end;
+
+
+handle_call({upgrade_old_header, Prefix}, _From, #file{fd=Fd}=File) ->
+    case (catch read_old_header(Fd, Prefix)) of
+    {ok, Header} ->
+        TailAppendBegin = File#file.eof,
+        Bin = term_to_binary(Header),
+        Md5 = couch_util:md5(Bin),
+        % now we assemble the final header binary and write to disk
+        FinalBin = <<Md5/binary, Bin/binary>>,
+        {reply, ok, _} = handle_call({write_header, FinalBin}, ok, File),
+        ok = write_old_header(Fd, <<"upgraded">>, TailAppendBegin),
+        {reply, ok, File#file{tail_append_begin=TailAppendBegin}};
+    _Error ->
+        case (catch read_old_header(Fd, <<"upgraded">>)) of
+        {ok, TailAppendBegin} ->
+            {reply, ok, File#file{tail_append_begin = TailAppendBegin}};
+        _Error2 ->
+            {reply, ok, File}
+        end
+    end;
+
+
+handle_call(find_header, _From, #file{fd=Fd, eof=Pos}=File) ->
+    {reply, find_header(Fd, Pos div ?SIZE_BLOCK), File}.
+
+% 09 UPGRADE CODE
+-define(HEADER_SIZE, 2048). % size of each segment of the doubly written header
+
+% 09 UPGRADE CODE
+read_old_header(Fd, Prefix) ->
+    {ok, Bin} = file:pread(Fd, 0, 2*(?HEADER_SIZE)),
+    <<Bin1:(?HEADER_SIZE)/binary, Bin2:(?HEADER_SIZE)/binary>> = Bin,
+    Result =
+    % read the first header
+    case extract_header(Prefix, Bin1) of
+    {ok, Header1} ->
+        case extract_header(Prefix, Bin2) of
+        {ok, Header2} ->
+            case Header1 == Header2 of
+            true ->
+                % Everything is completely normal!
+                {ok, Header1};
+            false ->
+                % To get here we must have two different header versions with signatures intact.
+                % It's weird but possible (a commit failure right at the 2k boundary). Log it and take the first.
+                ?LOG_INFO("Header version differences.~nPrimary Header: ~p~nSecondary Header: ~p", [Header1, Header2]),
+                {ok, Header1}
+            end;
+        Error ->
+            % error reading second header. It's ok, but log it.
+            ?LOG_INFO("Secondary header corruption (error: ~p). Using primary header.", [Error]),
+            {ok, Header1}
+        end;
+    Error ->
+        % error reading primary header
+        case extract_header(Prefix, Bin2) of
+        {ok, Header2} ->
+            % log corrupt primary header. It's ok since the secondary is still good.
+            ?LOG_INFO("Primary header corruption (error: ~p). Using secondary header.", [Error]),
+            {ok, Header2};
+        _ ->
+            % error reading secondary header too
+            % return the error, no need to log anything as the caller will be responsible for dealing with the error.
+            Error
+        end
+    end,
+    case Result of
+    {ok, {pointer_to_header_data, Ptr}} ->
+        pread_term(Fd, Ptr);
+    _ ->
+        Result
+    end.
+
+% 09 UPGRADE CODE
+extract_header(Prefix, Bin) ->
+    SizeOfPrefix = size(Prefix),
+    SizeOfTermBin = ?HEADER_SIZE -
+                    SizeOfPrefix -
+                    16,     % md5 sig
+
+    <<HeaderPrefix:SizeOfPrefix/binary, TermBin:SizeOfTermBin/binary, Sig:16/binary>> = Bin,
+
+    % check the header prefix
+    case HeaderPrefix of
+    Prefix ->
+        % check the integrity signature
+        case couch_util:md5(TermBin) == Sig of
+        true ->
+            Header = binary_to_term(TermBin),
+            {ok, Header};
+        false ->
+            header_corrupt
+        end;
+    _ ->
+        unknown_header_type
+    end.
+
+
+% 09 UPGRADE CODE
+write_old_header(Fd, Prefix, Data) ->
+    TermBin = term_to_binary(Data),
+    % the size of all the bytes written to the header, including the md5 signature (16 bytes)
+    FilledSize = byte_size(Prefix) + byte_size(TermBin) + 16,
+    {TermBin2, FilledSize2} =
+    case FilledSize > ?HEADER_SIZE of
+    true ->
+        % too big!
+        {ok, Pos} = append_binary(Fd, TermBin),
+        PtrBin = term_to_binary({pointer_to_header_data, Pos}),
+        {PtrBin, byte_size(Prefix) + byte_size(PtrBin) + 16};
+    false ->
+        {TermBin, FilledSize}
+    end,
+    ok = file:sync(Fd),
+    % pad out the header with zeros, then take the md5 hash
+    PadZeros = <<0:(8*(?HEADER_SIZE - FilledSize2))>>,
+    Sig = couch_util:md5([TermBin2, PadZeros]),
+    % now we assemble the final header binary and write to disk
+    WriteBin = <<Prefix/binary, TermBin2/binary, PadZeros/binary, Sig/binary>>,
+    ?HEADER_SIZE = size(WriteBin), % sanity check
+    DblWriteBin = [WriteBin, WriteBin],
+    ok = file:pwrite(Fd, 0, DblWriteBin),
+    ok = file:sync(Fd).
+
+
+handle_cast(close, Fd) ->
+    {stop,normal,Fd}.
+
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
+
+handle_info({'EXIT', _, normal}, Fd) ->
+    {noreply, Fd};
+handle_info({'EXIT', _, Reason}, Fd) ->
+    {stop, Reason, Fd}.
+
+
+find_header(_Fd, -1) ->
+    no_valid_header;
+find_header(Fd, Block) ->
+    case (catch load_header(Fd, Block)) of
+    {ok, Bin} ->
+        {ok, Bin};
+    _Error ->
+        find_header(Fd, Block -1)
+    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),
+    TotalBytes = calculate_total_read_len(1, HeaderLen),
+    {ok, <<RawBin:TotalBytes/binary>>} =
+            file:pread(Fd, (Block*?SIZE_BLOCK) + 5, TotalBytes),
+    <<Md5Sig:16/binary, HeaderBin/binary>> =
+        iolist_to_binary(remove_block_prefixes(1, RawBin)),
+    Md5Sig = couch_util:md5(HeaderBin),
+    {ok, HeaderBin}.
+
+-spec read_raw_iolist_int(#file{}, Pos::non_neg_integer(), Len::non_neg_integer()) ->
+    {Data::iolist(), CurPos::non_neg_integer()}.
+read_raw_iolist_int(#file{fd=Fd, tail_append_begin=TAB}, Pos, Len) ->
+    BlockOffset = Pos rem ?SIZE_BLOCK,
+    TotalBytes = calculate_total_read_len(BlockOffset, Len),
+    {ok, <<RawBin:TotalBytes/binary>>} = file:pread(Fd, Pos, TotalBytes),
+    if Pos >= TAB ->
+        {remove_block_prefixes(BlockOffset, RawBin), Pos + TotalBytes};
+    true ->
+        % 09 UPGRADE CODE
+        <<ReturnBin:Len/binary, _/binary>> = RawBin,
+        {[ReturnBin], Pos + Len}
+    end.
+
+-spec extract_md5(iolist()) -> {binary(), iolist()}.
+extract_md5(FullIoList) ->
+    {Md5List, IoList} = split_iolist(FullIoList, 16, []),
+    {iolist_to_binary(Md5List), IoList}.
+
+calculate_total_read_len(0, FinalLen) ->
+    calculate_total_read_len(1, FinalLen) + 1;
+calculate_total_read_len(BlockOffset, FinalLen) ->
+    case ?SIZE_BLOCK - BlockOffset of
+    BlockLeft when BlockLeft >= FinalLen ->
+        FinalLen;
+    BlockLeft ->
+        FinalLen + ((FinalLen - BlockLeft) div (?SIZE_BLOCK -1)) +
+            if ((FinalLen - BlockLeft) rem (?SIZE_BLOCK -1)) =:= 0 -> 0;
+                true -> 1 end
+    end.
+
+remove_block_prefixes(_BlockOffset, <<>>) ->
+    [];
+remove_block_prefixes(0, <<_BlockPrefix,Rest/binary>>) ->
+    remove_block_prefixes(1, Rest);
+remove_block_prefixes(BlockOffset, Bin) ->
+    BlockBytesAvailable = ?SIZE_BLOCK - BlockOffset,
+    case size(Bin) of
+    Size when Size > BlockBytesAvailable ->
+        <<DataBlock:BlockBytesAvailable/binary,Rest/binary>> = Bin,
+        [DataBlock | remove_block_prefixes(0, Rest)];
+    _Size ->
+        [Bin]
+    end.
+
+make_blocks(_BlockOffset, []) ->
+    [];
+make_blocks(0, IoList) ->
+    [<<0>> | make_blocks(1, IoList)];
+make_blocks(BlockOffset, IoList) ->
+    case split_iolist(IoList, (?SIZE_BLOCK - BlockOffset), []) of
+    {Begin, End} ->
+        [Begin | make_blocks(0, End)];
+    _SplitRemaining ->
+        IoList
+    end.
+
+%% @doc Returns a tuple where the first element contains the leading SplitAt
+%% bytes of the original iolist, and the 2nd element is the tail. If SplitAt
+%% is larger than byte_size(IoList), return the difference.
+-spec split_iolist(IoList::iolist(), SplitAt::non_neg_integer(), Acc::list()) ->
+    {iolist(), iolist()} | non_neg_integer().
+split_iolist(List, 0, BeginAcc) ->
+    {lists:reverse(BeginAcc), List};
+split_iolist([], SplitAt, _BeginAcc) ->
+    SplitAt;
+split_iolist([<<Bin/binary>> | Rest], SplitAt, BeginAcc) when SplitAt > byte_size(Bin) ->
+    split_iolist(Rest, SplitAt - byte_size(Bin), [Bin | BeginAcc]);
+split_iolist([<<Bin/binary>> | Rest], SplitAt, BeginAcc) ->
+    <<Begin:SplitAt/binary,End/binary>> = Bin,
+    split_iolist([End | Rest], 0, [Begin | BeginAcc]);
+split_iolist([Sublist| Rest], SplitAt, BeginAcc) when is_list(Sublist) ->
+    case split_iolist(Sublist, SplitAt, BeginAcc) of
+    {Begin, End} ->
+        {Begin, [End | Rest]};
+    SplitRemaining ->
+        split_iolist(Rest, SplitAt - (SplitAt - SplitRemaining), [Sublist | BeginAcc])
+    end;
+split_iolist([Byte | Rest], SplitAt, BeginAcc) when is_integer(Byte) ->
+    split_iolist(Rest, SplitAt - 1, [Byte | BeginAcc]).