245 lines
9.4 KiB
C
245 lines
9.4 KiB
C
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/**
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* \file lzma/vli.h
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* \brief Variable-length integer handling
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*
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* \author Copyright (C) 1999-2006 Igor Pavlov
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* \author Copyright (C) 2007 Lasse Collin
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*/
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#ifndef LZMA_H_INTERNAL
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# error Never include this file directly. Use <lzma.h> instead.
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#endif
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/**
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* \brief Maximum supported value of variable-length integer
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*/
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#define LZMA_VLI_VALUE_MAX (UINT64_MAX / 2)
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/**
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* \brief VLI value to denote that the value is unknown
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*/
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#define LZMA_VLI_VALUE_UNKNOWN UINT64_MAX
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/**
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* \brief Maximum supported length of variable length integers
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*/
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#define LZMA_VLI_BYTES_MAX 9
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/**
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* \brief VLI constant suffix
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*/
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#define LZMA_VLI_C(n) UINT64_C(n)
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/**
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* \brief Variable-length integer type
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*
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* This will always be unsigned integer. Valid VLI values are in the range
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* [0, LZMA_VLI_VALUE_MAX]. Unknown value is indicated with
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* LZMA_VLI_VALUE_UNKNOWN, which is the maximum value of the underlaying
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* integer type (this feature is useful in several situations).
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*
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* In future, even if lzma_vli is typdefined to something else than uint64_t,
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* it is guaranteed that 2 * LZMA_VLI_VALUE_MAX will not overflow lzma_vli.
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* This simplifies integer overflow detection.
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*/
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typedef uint64_t lzma_vli;
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/**
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* \brief Simple macro to validate variable-length integer
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*
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* This is useful to test that application has given acceptable values
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* for example in the uncompressed_size and compressed_size variables.
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*
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* \return True if the integer is representable as VLI or if it
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* indicates unknown value.
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*/
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#define lzma_vli_is_valid(vli) \
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((vli) <= LZMA_VLI_VALUE_MAX || (vli) == LZMA_VLI_VALUE_UNKNOWN)
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/**
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* \brief Sets VLI to given value with error checking
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*
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* \param dest Target variable which must have type of lzma_vli.
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* \param src New value to be stored to dest.
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* \param limit Maximum allowed value for src.
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*
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* \return False on success, true on error. If an error occurred,
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* dest is left in undefined state (i.e. it's possible that
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* it will be different in newer liblzma versions).
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*/
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#define lzma_vli_set_lim(dest, src, limit) \
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((src) > (limit) || ((dest) = (src)) > (limit))
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/**
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* \brief
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*/
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#define lzma_vli_add_lim(dest, src, limit) \
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((src) > (limit) || ((dest) += (src)) > (limit))
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#define lzma_vli_add2_lim(dest, src1, src2, limit) \
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(lzma_vli_add_lim(dest, src1, limit) \
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|| lzma_vli_add_lim(dest, src2, limit))
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#define lzma_vli_add3_lim(dest, src1, src2, src3, limit) \
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(lzma_vli_add_lim(dest, src1, limit) \
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|| lzma_vli_add_lim(dest, src2, limit) \
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|| lzma_vli_add_lim(dest, src3, limit))
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#define lzma_vli_add4_lim(dest, src1, src2, src3, src4, limit) \
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(lzma_vli_add_lim(dest, src1, limit) \
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|| lzma_vli_add_lim(dest, src2, limit) \
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|| lzma_vli_add_lim(dest, src3, limit) \
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|| lzma_vli_add_lim(dest, src4, limit))
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#define lzma_vli_sum_lim(dest, src1, src2, limit) \
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(lzma_vli_set_lim(dest, src1, limit) \
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|| lzma_vli_add_lim(dest, src2, limit))
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#define lzma_vli_sum3_lim(dest, src1, src2, src3, limit) \
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(lzma_vli_set_lim(dest, src1, limit) \
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|| lzma_vli_add_lim(dest, src2, limit) \
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|| lzma_vli_add_lim(dest, src3, limit))
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#define lzma_vli_sum4_lim(dest, src1, src2, src3, src4, limit) \
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(lzma_vli_set_lim(dest, src1, limit) \
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|| lzma_vli_add_lim(dest, src2, limit) \
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|| lzma_vli_add_lim(dest, src3, limit) \
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|| lzma_vli_add_lim(dest, src4, limit))
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#define lzma_vli_set(dest, src) lzma_vli_set_lim(dest, src, LZMA_VLI_VALUE_MAX)
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#define lzma_vli_add(dest, src) lzma_vli_add_lim(dest, src, LZMA_VLI_VALUE_MAX)
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#define lzma_vli_add2(dest, src1, src2) \
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lzma_vli_add2_lim(dest, src1, src2, LZMA_VLI_VALUE_MAX)
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#define lzma_vli_add3(dest, src1, src2, src3) \
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lzma_vli_add3_lim(dest, src1, src2, src3, LZMA_VLI_VALUE_MAX)
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#define lzma_vli_add4(dest, src1, src2, src3, src4) \
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lzma_vli_add4_lim(dest, src1, src2, src3, src4, LZMA_VLI_VALUE_MAX)
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#define lzma_vli_sum(dest, src1, src2) \
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lzma_vli_sum_lim(dest, src1, src2, LZMA_VLI_VALUE_MAX)
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#define lzma_vli_sum3(dest, src1, src2, src3) \
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lzma_vli_sum3_lim(dest, src1, src2, src3, LZMA_VLI_VALUE_MAX)
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#define lzma_vli_sum4(dest, src1, src2, src3, src4) \
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lzma_vli_sum4_lim(dest, src1, src2, src3, src4, LZMA_VLI_VALUE_MAX)
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/**
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* \brief Encodes variable-length integer
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*
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* In the new .lzma format, most integers are encoded in variable-length
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* representation. This saves space when smaller values are more likely
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* than bigger values.
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*
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* The encoding scheme encodes seven bits to every byte, using minimum
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* number of bytes required to represent the given value. In other words,
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* it puts 7-63 bits into 1-9 bytes. This implementation limits the number
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* of bits used to 63, thus num must be at maximum of INT64_MAX / 2. You
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* may use LZMA_VLI_VALUE_MAX for clarity.
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*
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* \param vli Integer to be encoded
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* \param vli_pos How many bytes have already been written out. This
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* must be less than 9 before calling this function.
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* \param vli_size Minimum size that the variable-length representation
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* must take. This is useful if you want to use
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* variable-length integers as padding. Usually you want
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* to set this to zero. The maximum allowed value is 9.
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* \param out Beginning of the output buffer
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* \param out_pos The next byte will be written to out[*out_pos].
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* \param out_size Size of the out buffer; the first byte into
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* which no data is written to is out[out_size].
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*
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* \return - LZMA_OK: So far all OK, but the integer is not
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* completely written out yet.
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* - LZMA_STREAM_END: Integer successfully encoded.
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* - LZMA_BUF_ERROR: No output space (*out_pos == out_size)
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* - LZMA_PROG_ERROR: Arguments are not sane.
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*/
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extern lzma_ret lzma_vli_encode(
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lzma_vli vli, size_t *lzma_restrict vli_pos, size_t vli_size,
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uint8_t *lzma_restrict out, size_t *lzma_restrict out_pos,
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size_t out_size);
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/**
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* \brief Decodes variable-length integer
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*
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* \param vli Pointer to decoded integer. The decoder will
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* initialize it to zero when *vli_pos == 0, so
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* application isn't required to initialize *vli.
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* \param vli_pos How many bytes have already been decoded. When
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* starting to decode a new integer, *vli_pos must
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* be initialized to zero.
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* \param in Beginning of the input buffer
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* \param in_pos The next byte will be read from in[*in_pos].
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* \param in_size Size of the input buffer; the first byte that
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* won't be read is in[in_size].
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*
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* \return - LZMA_OK: So far all OK, but the integer is not
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* completely decoded yet.
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* - LZMA_STREAM_END: Integer successfully decoded.
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* - LZMA_BUF_ERROR: No input data (*in_pos == in_size)
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* - LZMA_DATA_ERROR: Integer is longer than nine bytes.
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* - LZMA_PROG_ERROR: Arguments are not sane.
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*/
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extern lzma_ret lzma_vli_decode(lzma_vli *lzma_restrict vli,
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size_t *lzma_restrict vli_pos, const uint8_t *lzma_restrict in,
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size_t *lzma_restrict in_pos, size_t in_size);
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/**
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* \brief Decodes variable-length integer reading buffer backwards
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*
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* The variable-length integer encoding is designed so that it can be read
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* either from the beginning to the end, or from the end to the beginning.
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* This feature is needed to make the Stream parseable backwards;
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* specifically, to read the Backward Size field in Stream Footer.
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*
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* \param vli Pointer to variable to hold the decoded integer.
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* \param in Beginning of the input buffer
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* \param in_size Number of bytes available in the in[] buffer.
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* On successful decoding, this is updated to match
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* the number of bytes used. (in[*in_size - 1] is the
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* first byte to process. After successful decoding,
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* in[*in_size] will point to the first byte of the
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* variable-length integer.)
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*
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* \return - LZMA_OK: Decoding successful
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* - LZMA_DATA_ERROR: No valid variable-length integer was found.
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* - LZMA_BUF_ERROR: Not enough input. Note that in practice,
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* this tends to be a sign of broken input, because the
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* applications usually do give as much input to this function
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* as the applications have available.
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*/
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extern lzma_ret lzma_vli_reverse_decode(
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lzma_vli *vli, const uint8_t *in, size_t *in_size);
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/**
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* \brief Gets the minimum number of bytes required to encode vli
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*
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* \return Number of bytes on success (1-9). If vli isn't valid,
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* zero is returned.
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*/
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extern size_t lzma_vli_size(lzma_vli vli);
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