96d02a3e75
Previously, a libc-like out-of-line error information was used in the loader and its plugins. Now, all functions that may fail to do their job return some sort of Result. The universally-used error type ist the new LoaderError, which can contain information about the general error category (such as file format, I/O, unimplemented features), an error description, and location information, such as file index or sample index. Additionally, the loader plugins try to do as little work as possible in their constructors. Right after being constructed, a user should call initialize() and check the errors returned from there. (This is done transparently by Loader itself.) If a constructor caused an error, the call to initialize should check and return it immediately. This opportunity was used to rework a lot of the internal error propagation in both loader classes, especially FlacLoader. Therefore, a couple of other refactorings may have sneaked in as well. The adoption of LibAudio users is minimal. Piano's adoption is not important, as the code will receive major refactoring in the near future anyways. SoundPlayer's adoption is also less important, as changes to refactor it are in the works as well. aplay's adoption is the best and may serve as an example for other users. It also includes new buffering behavior. Buffer also gets some attention, making it OOM-safe and thereby also propagating its errors to the user.
83 lines
2.9 KiB
C++
83 lines
2.9 KiB
C++
/*
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* Copyright (c) 2018-2021, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/ByteBuffer.h>
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#include <AK/NonnullOwnPtr.h>
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#include <AK/NonnullRefPtr.h>
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#include <AK/RefCounted.h>
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#include <AK/RefPtr.h>
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#include <AK/Result.h>
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#include <AK/StringView.h>
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#include <AK/Try.h>
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#include <LibAudio/Buffer.h>
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#include <LibAudio/LoaderError.h>
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#include <LibCore/File.h>
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namespace Audio {
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static const String empty_string = "";
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static String no_plugin_error = "No loader plugin available";
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using LoaderSamples = Result<NonnullRefPtr<Buffer>, LoaderError>;
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using MaybeLoaderError = Result<void, LoaderError>;
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class LoaderPlugin {
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public:
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virtual ~LoaderPlugin() { }
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virtual MaybeLoaderError initialize() = 0;
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virtual LoaderSamples get_more_samples(size_t max_bytes_to_read_from_input = 128 * KiB) = 0;
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virtual MaybeLoaderError reset() = 0;
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virtual MaybeLoaderError seek(const int sample_index) = 0;
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// total_samples() and loaded_samples() should be independent
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// of the number of channels.
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//
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// For example, with a three-second-long, stereo, 44.1KHz audio file:
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// num_channels() should return 2
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// sample_rate() should return 44100 (each channel is sampled at this rate)
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// total_samples() should return 132300 (sample_rate * three seconds)
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virtual int loaded_samples() = 0;
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virtual int total_samples() = 0;
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virtual u32 sample_rate() = 0;
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virtual u16 num_channels() = 0;
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virtual PcmSampleFormat pcm_format() = 0;
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virtual RefPtr<Core::File> file() = 0;
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};
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class Loader : public RefCounted<Loader> {
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public:
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static Result<NonnullRefPtr<Loader>, LoaderError> create(StringView path) { return adopt_ref(*new Loader(TRY(try_create(path)))); }
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static Result<NonnullRefPtr<Loader>, LoaderError> create(ByteBuffer const& buffer) { return adopt_ref(*new Loader(TRY(try_create(buffer)))); }
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LoaderSamples get_more_samples(size_t max_bytes_to_read_from_input = 128 * KiB) const { return m_plugin->get_more_samples(max_bytes_to_read_from_input); }
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MaybeLoaderError reset() const { return m_plugin->reset(); }
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MaybeLoaderError seek(const int position) const { return m_plugin->seek(position); }
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int loaded_samples() const { return m_plugin->loaded_samples(); }
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int total_samples() const { return m_plugin->total_samples(); }
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u32 sample_rate() const { return m_plugin->sample_rate(); }
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u16 num_channels() const { return m_plugin->num_channels(); }
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u16 bits_per_sample() const { return pcm_bits_per_sample(m_plugin->pcm_format()); }
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RefPtr<Core::File> file() const { return m_plugin->file(); }
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private:
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static Result<NonnullOwnPtr<LoaderPlugin>, LoaderError> try_create(StringView path);
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static Result<NonnullOwnPtr<LoaderPlugin>, LoaderError> try_create(ByteBuffer const& buffer);
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explicit Loader(NonnullOwnPtr<LoaderPlugin>);
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mutable NonnullOwnPtr<LoaderPlugin> m_plugin;
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};
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}
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