✏️ 编辑：stream_flags.h
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/usr/include/lzma/stream_flags.h
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/** * \file lzma/stream_flags.h * \brief .xz Stream Header and Stream Footer encoder and decoder */ /* * Author: Lasse Collin * * This file has been put into the public domain. * You can do whatever you want with this file. * * See ../lzma.h for information about liblzma as a whole. */ #ifndef LZMA_H_INTERNAL # error Never include this file directly. Use <lzma.h> instead. #endif /** * \brief Size of Stream Header and Stream Footer * * Stream Header and Stream Footer have the same size and they are not * going to change even if a newer version of the .xz file format is * developed in future. */ #define LZMA_STREAM_HEADER_SIZE 12 /** * \brief Options for encoding/decoding Stream Header and Stream Footer */ typedef struct { /** * \brief Stream Flags format version * * To prevent API and ABI breakages if new features are needed in * Stream Header or Stream Footer, a version number is used to * indicate which fields in this structure are in use. For now, * version must always be zero. With non-zero version, the * lzma_stream_header_encode() and lzma_stream_footer_encode() * will return LZMA_OPTIONS_ERROR. * * lzma_stream_header_decode() and lzma_stream_footer_decode() * will always set this to the lowest value that supports all the * features indicated by the Stream Flags field. The application * must check that the version number set by the decoding functions * is supported by the application. Otherwise it is possible that * the application will decode the Stream incorrectly. */ uint32_t version; /** * \brief Backward Size * * Backward Size must be a multiple of four bytes. In this Stream * format version, Backward Size is the size of the Index field. * * Backward Size isn't actually part of the Stream Flags field, but * it is convenient to include in this structure anyway. Backward * Size is present only in the Stream Footer. There is no need to * initialize backward_size when encoding Stream Header. * * lzma_stream_header_decode() always sets backward_size to * LZMA_VLI_UNKNOWN so that it is convenient to use * lzma_stream_flags_compare() when both Stream Header and Stream * Footer have been decoded. */ lzma_vli backward_size; # define LZMA_BACKWARD_SIZE_MIN 4 # define LZMA_BACKWARD_SIZE_MAX (LZMA_VLI_C(1) << 34) /** * \brief Check ID * * This indicates the type of the integrity check calculated from * uncompressed data. */ lzma_check check; /* * Reserved space to allow possible future extensions without * breaking the ABI. You should not touch these, because the * names of these variables may change. * * (We will never be able to use all of these since Stream Flags * is just two bytes plus Backward Size of four bytes. But it's * nice to have the proper types when they are needed.) */ lzma_reserved_enum reserved_enum1; lzma_reserved_enum reserved_enum2; lzma_reserved_enum reserved_enum3; lzma_reserved_enum reserved_enum4; lzma_bool reserved_bool1; lzma_bool reserved_bool2; lzma_bool reserved_bool3; lzma_bool reserved_bool4; lzma_bool reserved_bool5; lzma_bool reserved_bool6; lzma_bool reserved_bool7; lzma_bool reserved_bool8; uint32_t reserved_int1; uint32_t reserved_int2; } lzma_stream_flags; /** * \brief Encode Stream Header * * \param options Stream Header options to be encoded. * options->backward_size is ignored and doesn't * need to be initialized. * \param out Beginning of the output buffer of * LZMA_STREAM_HEADER_SIZE bytes. * * \return - LZMA_OK: Encoding was successful. * - LZMA_OPTIONS_ERROR: options->version is not supported by * this liblzma version. * - LZMA_PROG_ERROR: Invalid options. */ extern LZMA_API(lzma_ret) lzma_stream_header_encode( const lzma_stream_flags *options, uint8_t *out) lzma_nothrow lzma_attr_warn_unused_result; /** * \brief Encode Stream Footer * * \param options Stream Footer options to be encoded. * \param out Beginning of the output buffer of * LZMA_STREAM_HEADER_SIZE bytes. * * \return - LZMA_OK: Encoding was successful. * - LZMA_OPTIONS_ERROR: options->version is not supported by * this liblzma version. * - LZMA_PROG_ERROR: Invalid options. */ extern LZMA_API(lzma_ret) lzma_stream_footer_encode( const lzma_stream_flags *options, uint8_t *out) lzma_nothrow lzma_attr_warn_unused_result; /** * \brief Decode Stream Header * * \param options Target for the decoded Stream Header options. * \param in Beginning of the input buffer of * LZMA_STREAM_HEADER_SIZE bytes. * * options->backward_size is always set to LZMA_VLI_UNKNOWN. This is to * help comparing Stream Flags from Stream Header and Stream Footer with * lzma_stream_flags_compare(). * * \return - LZMA_OK: Decoding was successful. * - LZMA_FORMAT_ERROR: Magic bytes don't match, thus the given * buffer cannot be Stream Header. * - LZMA_DATA_ERROR: CRC32 doesn't match, thus the header * is corrupt. * - LZMA_OPTIONS_ERROR: Unsupported options are present * in the header. * * \note When decoding .xz files that contain multiple Streams, it may * make sense to print "file format not recognized" only if * decoding of the Stream Header of the _first_ Stream gives * LZMA_FORMAT_ERROR. If non-first Stream Header gives * LZMA_FORMAT_ERROR, the message used for LZMA_DATA_ERROR is * probably more appropriate. * * For example, Stream decoder in liblzma uses LZMA_DATA_ERROR if * LZMA_FORMAT_ERROR is returned by lzma_stream_header_decode() * when decoding non-first Stream. */ extern LZMA_API(lzma_ret) lzma_stream_header_decode( lzma_stream_flags *options, const uint8_t *in) lzma_nothrow lzma_attr_warn_unused_result; /** * \brief Decode Stream Footer * * \param options Target for the decoded Stream Header options. * \param in Beginning of the input buffer of * LZMA_STREAM_HEADER_SIZE bytes. * * \return - LZMA_OK: Decoding was successful. * - LZMA_FORMAT_ERROR: Magic bytes don't match, thus the given * buffer cannot be Stream Footer. * - LZMA_DATA_ERROR: CRC32 doesn't match, thus the Stream Footer * is corrupt. * - LZMA_OPTIONS_ERROR: Unsupported options are present * in Stream Footer. * * \note If Stream Header was already decoded successfully, but * decoding Stream Footer returns LZMA_FORMAT_ERROR, the * application should probably report some other error message * than "file format not recognized", since the file more likely * is corrupt (possibly truncated). Stream decoder in liblzma * uses LZMA_DATA_ERROR in this situation. */ extern LZMA_API(lzma_ret) lzma_stream_footer_decode( lzma_stream_flags *options, const uint8_t *in) lzma_nothrow lzma_attr_warn_unused_result; /** * \brief Compare two lzma_stream_flags structures * * backward_size values are compared only if both are not * LZMA_VLI_UNKNOWN. * * \return - LZMA_OK: Both are equal. If either had backward_size set * to LZMA_VLI_UNKNOWN, backward_size values were not * compared or validated. * - LZMA_DATA_ERROR: The structures differ. * - LZMA_OPTIONS_ERROR: version in either structure is greater * than the maximum supported version (currently zero). * - LZMA_PROG_ERROR: Invalid value, e.g. invalid check or * backward_size. */ extern LZMA_API(lzma_ret) lzma_stream_flags_compare( const lzma_stream_flags *a, const lzma_stream_flags *b) lzma_nothrow lzma_attr_pure;
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