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d748edd994
This compression scheme was quite popular during the 80's, and we can still find it in use inside file formats such as TIFF or PDF.
45 lines
1.4 KiB
C++
45 lines
1.4 KiB
C++
/*
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* Copyright (c) 2023, Lucas Chollet <lucas.chollet@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "PackBitsDecoder.h"
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#include <AK/MemoryStream.h>
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namespace Compress::PackBits {
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ErrorOr<ByteBuffer> decode_all(ReadonlyBytes bytes, Optional<u64> expected_output_size, CompatibilityMode mode)
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{
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// This implementation uses unsigned values for the selector, as described in the PDF spec.
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// Note that this remains compatible with other implementations based on signed numbers.
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auto memory_stream = make<FixedMemoryStream>(bytes);
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ByteBuffer decoded_bytes;
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if (expected_output_size.has_value())
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TRY(decoded_bytes.try_ensure_capacity(*expected_output_size));
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while (memory_stream->remaining() > 0 && decoded_bytes.size() < expected_output_size.value_or(NumericLimits<u64>::max())) {
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auto const length = TRY(memory_stream->read_value<u8>());
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if (length < 128) {
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for (u8 i = 0; i <= length; ++i)
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TRY(decoded_bytes.try_append(TRY(memory_stream->read_value<u8>())));
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} else if (length > 128) {
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auto const next_byte = TRY(memory_stream->read_value<u8>());
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for (u8 i = 0; i < 257 - length; ++i)
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TRY(decoded_bytes.try_append(next_byte));
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} else {
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VERIFY(length == 128);
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if (mode == CompatibilityMode::PDF)
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break;
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}
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}
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return decoded_bytes;
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}
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}
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