root / lab4 / .minix-src / include / lzma / vli.h @ 14
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| 1 | 13 | up20180614 | /**
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| 2 | * \file lzma/vli.h
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| 3 | * \brief Variable-length integer handling
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| 4 | *
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| 5 | * In the .xz format, most integers are encoded in a variable-length
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| 6 | * representation, which is sometimes called little endian base-128 encoding.
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| 7 | * This saves space when smaller values are more likely than bigger values.
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| 8 | *
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| 9 | * The encoding scheme encodes seven bits to every byte, using minimum
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| 10 | * number of bytes required to represent the given value. Encodings that use
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| 11 | * non-minimum number of bytes are invalid, thus every integer has exactly
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| 12 | * one encoded representation. The maximum number of bits in a VLI is 63,
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| 13 | * thus the vli argument must be less than or equal to UINT64_MAX / 2. You
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| 14 | * should use LZMA_VLI_MAX for clarity.
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| 15 | */
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| 16 | |||
| 17 | /*
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| 18 | * Author: Lasse Collin
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| 19 | *
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| 20 | * This file has been put into the public domain.
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| 21 | * You can do whatever you want with this file.
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| 22 | *
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| 23 | * See ../lzma.h for information about liblzma as a whole.
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| 24 | */
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| 25 | |||
| 26 | #ifndef LZMA_H_INTERNAL
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| 27 | # error Never include this file directly. Use <lzma.h> instead.
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| 28 | #endif
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| 29 | |||
| 30 | |||
| 31 | /**
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| 32 | * \brief Maximum supported value of a variable-length integer
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| 33 | */
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| 34 | #define LZMA_VLI_MAX (UINT64_MAX / 2) |
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| 35 | |||
| 36 | /**
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| 37 | * \brief VLI value to denote that the value is unknown
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| 38 | */
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| 39 | #define LZMA_VLI_UNKNOWN UINT64_MAX
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| 40 | |||
| 41 | /**
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| 42 | * \brief Maximum supported encoded length of variable length integers
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| 43 | */
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| 44 | #define LZMA_VLI_BYTES_MAX 9 |
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| 45 | |||
| 46 | /**
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| 47 | * \brief VLI constant suffix
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| 48 | */
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| 49 | #define LZMA_VLI_C(n) UINT64_C(n)
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| 50 | |||
| 51 | |||
| 52 | /**
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| 53 | * \brief Variable-length integer type
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| 54 | *
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| 55 | * Valid VLI values are in the range [0, LZMA_VLI_MAX]. Unknown value is
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| 56 | * indicated with LZMA_VLI_UNKNOWN, which is the maximum value of the
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| 57 | * underlaying integer type.
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| 58 | *
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| 59 | * lzma_vli will be uint64_t for the foreseeable future. If a bigger size
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| 60 | * is needed in the future, it is guaranteed that 2 * LZMA_VLI_MAX will
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| 61 | * not overflow lzma_vli. This simplifies integer overflow detection.
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| 62 | */
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| 63 | typedef uint64_t lzma_vli;
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| 64 | |||
| 65 | |||
| 66 | /**
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| 67 | * \brief Validate a variable-length integer
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| 68 | *
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| 69 | * This is useful to test that application has given acceptable values
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| 70 | * for example in the uncompressed_size and compressed_size variables.
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| 71 | *
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| 72 | * \return True if the integer is representable as VLI or if it
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| 73 | * indicates unknown value.
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| 74 | */
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| 75 | #define lzma_vli_is_valid(vli) \
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| 76 | ((vli) <= LZMA_VLI_MAX || (vli) == LZMA_VLI_UNKNOWN) |
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| 77 | |||
| 78 | |||
| 79 | /**
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| 80 | * \brief Encode a variable-length integer
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| 81 | *
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| 82 | * This function has two modes: single-call and multi-call. Single-call mode
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| 83 | * encodes the whole integer at once; it is an error if the output buffer is
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| 84 | * too small. Multi-call mode saves the position in *vli_pos, and thus it is
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| 85 | * possible to continue encoding if the buffer becomes full before the whole
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| 86 | * integer has been encoded.
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| 87 | *
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| 88 | * \param vli Integer to be encoded
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| 89 | * \param vli_pos How many VLI-encoded bytes have already been written
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| 90 | * out. When starting to encode a new integer in
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| 91 | * multi-call mode, *vli_pos must be set to zero.
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| 92 | * To use single-call encoding, set vli_pos to NULL.
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| 93 | * \param out Beginning of the output buffer
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| 94 | * \param out_pos The next byte will be written to out[*out_pos].
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| 95 | * \param out_size Size of the out buffer; the first byte into
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| 96 | * which no data is written to is out[out_size].
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| 97 | *
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| 98 | * \return Slightly different return values are used in multi-call and
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| 99 | * single-call modes.
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| 100 | *
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| 101 | * Single-call (vli_pos == NULL):
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| 102 | * - LZMA_OK: Integer successfully encoded.
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| 103 | * - LZMA_PROG_ERROR: Arguments are not sane. This can be due
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| 104 | * to too little output space; single-call mode doesn't use
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| 105 | * LZMA_BUF_ERROR, since the application should have checked
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| 106 | * the encoded size with lzma_vli_size().
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| 107 | *
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| 108 | * Multi-call (vli_pos != NULL):
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| 109 | * - LZMA_OK: So far all OK, but the integer is not
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| 110 | * completely written out yet.
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| 111 | * - LZMA_STREAM_END: Integer successfully encoded.
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| 112 | * - LZMA_BUF_ERROR: No output space was provided.
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| 113 | * - LZMA_PROG_ERROR: Arguments are not sane.
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| 114 | */
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| 115 | extern LZMA_API(lzma_ret) lzma_vli_encode(lzma_vli vli, size_t *vli_pos,
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| 116 | uint8_t *out, size_t *out_pos, size_t out_size) lzma_nothrow; |
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| 117 | |||
| 118 | |||
| 119 | /**
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| 120 | * \brief Decode a variable-length integer
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| 121 | *
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| 122 | * Like lzma_vli_encode(), this function has single-call and multi-call modes.
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| 123 | *
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| 124 | * \param vli Pointer to decoded integer. The decoder will
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| 125 | * initialize it to zero when *vli_pos == 0, so
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| 126 | * application isn't required to initialize *vli.
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| 127 | * \param vli_pos How many bytes have already been decoded. When
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| 128 | * starting to decode a new integer in multi-call
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| 129 | * mode, *vli_pos must be initialized to zero. To
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| 130 | * use single-call decoding, set vli_pos to NULL.
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| 131 | * \param in Beginning of the input buffer
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| 132 | * \param in_pos The next byte will be read from in[*in_pos].
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| 133 | * \param in_size Size of the input buffer; the first byte that
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| 134 | * won't be read is in[in_size].
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| 135 | *
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| 136 | * \return Slightly different return values are used in multi-call and
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| 137 | * single-call modes.
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| 138 | *
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| 139 | * Single-call (vli_pos == NULL):
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| 140 | * - LZMA_OK: Integer successfully decoded.
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| 141 | * - LZMA_DATA_ERROR: Integer is corrupt. This includes hitting
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| 142 | * the end of the input buffer before the whole integer was
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| 143 | * decoded; providing no input at all will use LZMA_DATA_ERROR.
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| 144 | * - LZMA_PROG_ERROR: Arguments are not sane.
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| 145 | *
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| 146 | * Multi-call (vli_pos != NULL):
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| 147 | * - LZMA_OK: So far all OK, but the integer is not
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| 148 | * completely decoded yet.
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| 149 | * - LZMA_STREAM_END: Integer successfully decoded.
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| 150 | * - LZMA_DATA_ERROR: Integer is corrupt.
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| 151 | * - LZMA_BUF_ERROR: No input was provided.
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| 152 | * - LZMA_PROG_ERROR: Arguments are not sane.
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| 153 | */
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| 154 | extern LZMA_API(lzma_ret) lzma_vli_decode(lzma_vli *vli, size_t *vli_pos,
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| 155 | const uint8_t *in, size_t *in_pos, size_t in_size)
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| 156 | lzma_nothrow; |
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| 157 | |||
| 158 | |||
| 159 | /**
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| 160 | * \brief Get the number of bytes required to encode a VLI
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| 161 | *
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| 162 | * \return Number of bytes on success (1-9). If vli isn't valid,
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| 163 | * zero is returned.
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| 164 | */
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| 165 | extern LZMA_API(uint32_t) lzma_vli_size(lzma_vli vli)
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| 166 | lzma_nothrow lzma_attr_pure; |