7a04d1f662
The file_input_stream interface was messy: it was not fiber safe (e.g., code
doing seek() in the middle of an ongoing read_exactly()), and went against
the PIMPL philosophy.
So this patch removes the file_input_stream class, and replaces it with a
completely different design:
We now have in fstream.hh a global function:
input_stream<char>
make_file_input_stream(
lw_shared_ptr<file> file, uint64_t offset = 0,
uint64_t buffer_size = 8192);
In other words, instead of "seeking" in an input stream, we just open a new
input stream object at a particular offset of the given file. Multiple input
streams might be concurrently active on the same file.
Note how make_file_input_stream now returns a regular "input_stream", not a
subtype, and it can be used just like any normal input_stream to read the stream
starting at the given position.
This patch makes "input_stream" a "final" type: we no longer subclass it in our
code, and we shouldn't in the future because it goes against the PIMPL design
(the subclass should be of the inner workings, like the data_source_impl, not
of input_stream).
Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
69 lines
2.7 KiB
C++
69 lines
2.7 KiB
C++
/*
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* This file is open source software, licensed to you under the terms
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* of the Apache License, Version 2.0 (the "License"). See the NOTICE file
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* distributed with this work for additional information regarding copyright
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* ownership. You may not use this file except in compliance with the License.
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*
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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/*
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* Copyright (C) 2015 Cloudius Systems, Ltd.
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*/
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#include "fstream.hh"
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#include <malloc.h>
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class file_data_source_impl : public data_source_impl {
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lw_shared_ptr<file> _file;
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uint64_t _pos;
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size_t _buffer_size;
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public:
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file_data_source_impl(lw_shared_ptr<file> f, uint64_t pos, size_t buffer_size)
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: _file(std::move(f)), _pos(pos), _buffer_size(buffer_size) {}
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virtual future<temporary_buffer<char>> get() override {
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// must align allocation for dma
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auto p = ::memalign(std::min<size_t>(_buffer_size, 4096), _buffer_size);
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if (!p) {
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throw std::bad_alloc();
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}
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auto q = static_cast<char*>(p);
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temporary_buffer<char> buf(q, _buffer_size, make_free_deleter(p));
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auto old_pos = _pos;
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// dma_read needs to be aligned. It doesn't have to be page-aligned,
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// though, and we could get away with something much smaller. However, if
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// we start reading in things outside page boundaries, we will end up with
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// various pages around, some of them with overlapping ranges. Those would
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// be very challenging to cache.
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old_pos &= ~4095;
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auto front = _pos - old_pos;
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_pos += _buffer_size - front;
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return _file->dma_read(old_pos, q, _buffer_size).then(
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[buf = std::move(buf), front] (size_t size) mutable {
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buf.trim(size);
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buf.trim_front(front);
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return make_ready_future<temporary_buffer<char>>(std::move(buf));
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});
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}
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};
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class file_data_source : public data_source {
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public:
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file_data_source(lw_shared_ptr<file> f, uint64_t offset, size_t buffer_size)
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: data_source(std::make_unique<file_data_source_impl>(
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std::move(f), offset, buffer_size)) {}
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};
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input_stream<char> make_file_input_stream(
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lw_shared_ptr<file> f, uint64_t offset, size_t buffer_size) {
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return input_stream<char>(file_data_source(std::move(f), offset, buffer_size));
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}
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