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134 lines
3.2 KiB
134 lines
3.2 KiB
/*
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* Copyright 2023 jacqueline <me@jacqueline.id.au>
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*
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* SPDX-License-Identifier: GPL-3.0-only
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*/
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#pragma once
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#include <cstddef>
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#include <cstdint>
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#include <memory>
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#include <optional>
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#include <span>
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#include <string>
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#include <utility>
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#include "result.hpp"
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#include "sample.hpp"
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#include "types.hpp"
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#include "memory_resource.hpp"
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namespace codecs {
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/*
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* Interface for an abstract source of file-like data.
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*/
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class IStream {
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public:
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IStream(StreamType t) : t_(t) {}
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virtual ~IStream() {}
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auto type() -> StreamType { return t_; }
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virtual auto Read(std::span<std::byte> dest) -> ssize_t = 0;
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virtual auto CanSeek() -> bool = 0;
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enum class SeekFrom {
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kStartOfStream,
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kEndOfStream,
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kCurrentPosition,
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};
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virtual auto SeekTo(int64_t destination, SeekFrom from) -> void = 0;
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virtual auto CurrentPosition() -> int64_t = 0;
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virtual auto Size() -> std::optional<int64_t> = 0;
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/*
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* Called by codecs to indicate that they've finished parsing any header data
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* within this stream, and are about to begin decoding.
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*
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* Currently used as a hint to the readahead stream to begin prefetching file
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* data.
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*/
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virtual auto SetPreambleFinished() -> void {}
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protected:
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StreamType t_;
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};
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/*
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* Common interface to be implemented by all audio decoders.
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*/
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class ICodec {
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public:
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virtual ~ICodec() {}
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/* Errors that may be returned by codecs. */
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enum class Error {
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// Indicates that more data is required before this codec can finish its
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// operation. E.g. the input buffer ends with a truncated frame.
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kOutOfInput,
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// Indicates that the data within the input buffer is fatally malformed.
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kMalformedData,
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// Indicated that the format is unsupported
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kUnsupportedFormat,
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kInternalError,
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};
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static auto ErrorString(Error err) -> std::pmr::string {
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switch (err) {
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case Error::kOutOfInput:
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return "out of input";
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case Error::kMalformedData:
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return "malformed data";
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case Error::kInternalError:
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return "internal error";
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case Error::kUnsupportedFormat:
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return "unsupported format";
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}
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return "uhh";
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}
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/*
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* Alias for more readable return types. All codec methods, success or
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* failure, should also return the number of bytes they consumed.
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*/
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template <typename T>
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using Result = std::pair<std::size_t, cpp::result<T, Error>>;
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struct OutputFormat {
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uint8_t num_channels;
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uint32_t sample_rate_hz;
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std::optional<uint32_t> total_samples;
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bool operator==(const OutputFormat&) const = default;
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};
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/*
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* Decodes metadata or headers from the given input stream, and returns the
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* format for the samples that will be decoded from it.
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*/
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virtual auto OpenStream(std::shared_ptr<IStream> input, uint32_t offset)
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-> cpp::result<OutputFormat, Error> = 0;
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struct OutputInfo {
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std::size_t samples_written;
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bool is_stream_finished;
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};
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/*
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* Writes PCM samples to the given output buffer.
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*/
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virtual auto DecodeTo(std::span<sample::Sample> destination)
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-> cpp::result<OutputInfo, Error> = 0;
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};
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auto CreateCodecForType(StreamType type) -> std::optional<ICodec*>;
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} // namespace codecs
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