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///////////////////////////////////////////////////////////////////////////////
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//
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/// \file stream_flags_decoder.c
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/// \brief Decodes Stream Header and Stream Footer from .xz files
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//
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// Author: Lasse Collin
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//
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// This file has been put into the public domain.
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// You can do whatever you want with this file.
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//
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///////////////////////////////////////////////////////////////////////////////
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#include "stream_flags_common.h"
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static bool
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stream_flags_decode(lzma_stream_flags *options, const uint8_t *in)
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{
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// Reserved bits must be unset.
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if (in[0] != 0x00 || (in[1] & 0xF0))
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return true;
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options->version = 0;
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options->check = in[1] & 0x0F;
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return false;
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}
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extern LZMA_API(lzma_ret)
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lzma_stream_header_decode(lzma_stream_flags *options, const uint8_t *in)
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{
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// Magic
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if (memcmp(in, lzma_header_magic, sizeof(lzma_header_magic)) != 0)
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return LZMA_FORMAT_ERROR;
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// Verify the CRC32 so we can distinguish between corrupt
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// and unsupported files.
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const uint32_t crc = lzma_crc32(in + sizeof(lzma_header_magic),
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LZMA_STREAM_FLAGS_SIZE, 0);
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if (crc != unaligned_read32le(in + sizeof(lzma_header_magic)
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+ LZMA_STREAM_FLAGS_SIZE))
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return LZMA_DATA_ERROR;
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// Stream Flags
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if (stream_flags_decode(options, in + sizeof(lzma_header_magic)))
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return LZMA_OPTIONS_ERROR;
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// Set Backward Size to indicate unknown value. That way
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// lzma_stream_flags_compare() can be used to compare Stream Header
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// and Stream Footer while keeping it useful also for comparing
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// two Stream Footers.
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options->backward_size = LZMA_VLI_UNKNOWN;
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return LZMA_OK;
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}
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extern LZMA_API(lzma_ret)
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lzma_stream_footer_decode(lzma_stream_flags *options, const uint8_t *in)
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{
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// Magic
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if (memcmp(in + sizeof(uint32_t) * 2 + LZMA_STREAM_FLAGS_SIZE,
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lzma_footer_magic, sizeof(lzma_footer_magic)) != 0)
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return LZMA_FORMAT_ERROR;
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// CRC32
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const uint32_t crc = lzma_crc32(in + sizeof(uint32_t),
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sizeof(uint32_t) + LZMA_STREAM_FLAGS_SIZE, 0);
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if (crc != unaligned_read32le(in))
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return LZMA_DATA_ERROR;
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// Stream Flags
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if (stream_flags_decode(options, in + sizeof(uint32_t) * 2))
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return LZMA_OPTIONS_ERROR;
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// Backward Size
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options->backward_size = unaligned_read32le(in + sizeof(uint32_t));
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options->backward_size = (options->backward_size + 1) * 4;
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return LZMA_OK;
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}
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