選択できるのは25トピックまでです。
トピックは、先頭が英数字で、英数字とダッシュ('-')を使用した35文字以内のものにしてください。
106 行
3.1 KiB
106 行
3.1 KiB
%% Copyright (c) 2017-Present Pivotal Software, Inc. All rights reserved.
|
|
%%
|
|
%% This package, Looking Glass, is double-licensed under the Mozilla
|
|
%% Public License 1.1 ("MPL") and the Apache License version 2
|
|
%% ("ASL"). For the MPL, please see LICENSE-MPL-RabbitMQ. For the ASL,
|
|
%% please see LICENSE-APACHE2.
|
|
%%
|
|
%% This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND,
|
|
%% either express or implied. See the LICENSE file for specific language governing
|
|
%% rights and limitations of this software.
|
|
%%
|
|
%% If you have any questions regarding licensing, please contact us at
|
|
%% info@rabbitmq.com.
|
|
|
|
-module(lg_file_reader).
|
|
|
|
-export([fold/3]).
|
|
-export([foreach/2]).
|
|
|
|
-export([open/1]).
|
|
-export([read_event/1]).
|
|
-export([close/1]).
|
|
|
|
-record(state, {
|
|
io_device :: file:io_device(),
|
|
ctx :: lz4f:dctx(),
|
|
buffer = <<>> :: binary(),
|
|
offset = 0 :: non_neg_integer(),
|
|
uncompressed_offset = 0 :: non_neg_integer()
|
|
}).
|
|
|
|
%% High level API.
|
|
|
|
fold(Fun, Acc, Filename) ->
|
|
{ok, IoDevice} = open(Filename),
|
|
Ctx = lz4f:create_decompression_context(),
|
|
Ret = fold1(#state{io_device=IoDevice, ctx=Ctx}, Fun, Acc),
|
|
ok = close(IoDevice),
|
|
Ret.
|
|
|
|
fold1(State0, Fun, Acc0) ->
|
|
case read_event(State0) of
|
|
{ok, Event, State} ->
|
|
Acc = Fun(Event, Acc0),
|
|
fold1(State, Fun, Acc);
|
|
eof ->
|
|
{ok, Acc0};
|
|
Error = {error, _, _} ->
|
|
Error
|
|
end.
|
|
|
|
foreach(Fun, Filename) ->
|
|
{ok, IoDevice} = open(Filename),
|
|
Ctx = lz4f:create_decompression_context(),
|
|
Ret = foreach1(#state{io_device=IoDevice, ctx=Ctx}, Fun),
|
|
ok = close(IoDevice),
|
|
Ret.
|
|
|
|
foreach1(State0, Fun) ->
|
|
case read_event(State0) of
|
|
{ok, Event, State} ->
|
|
_ = Fun(Event),
|
|
foreach1(State, Fun);
|
|
eof ->
|
|
ok;
|
|
Error = {error, _, _} ->
|
|
Error
|
|
end.
|
|
|
|
%% Low level API.
|
|
|
|
open(Filename) ->
|
|
file:open(Filename, [read, binary]).
|
|
|
|
read_event(State=#state{buffer=Buffer}) ->
|
|
case Buffer of
|
|
<<Size:32, Bin:Size/binary, Rest/bits>> ->
|
|
convert_event_body(State#state{buffer=Rest}, Bin);
|
|
_ ->
|
|
read_file(State)
|
|
end.
|
|
|
|
read_file(State=#state{io_device=IoDevice, ctx=Ctx, buffer=Buffer, offset=Offset}) ->
|
|
case file:read(IoDevice, 1000) of
|
|
{ok, Data0} ->
|
|
Data = iolist_to_binary(lz4f:decompress(Ctx, Data0)),
|
|
read_event(State#state{buffer= <<Buffer/binary, Data/binary>>,
|
|
offset=Offset + byte_size(Data0)});
|
|
eof ->
|
|
eof;
|
|
{error, Reason} ->
|
|
{error, Reason,
|
|
'An error occurred while trying to read from the file.'}
|
|
end.
|
|
|
|
convert_event_body(State=#state{offset=Offset, uncompressed_offset=UnOffset}, Bin) ->
|
|
try binary_to_term(Bin) of
|
|
Term ->
|
|
{ok, Term, State#state{uncompressed_offset=UnOffset + byte_size(Bin)}}
|
|
catch Class:Reason ->
|
|
{error, {crash, Class, Reason, Offset, UnOffset},
|
|
'The binary form of an event could not be decoded to an Erlang term.'}
|
|
end.
|
|
|
|
close(IoDevice) ->
|
|
file:close(IoDevice).
|