root / lab4 / .minix-src / include / lzma / vli.h @ 13
History | View | Annotate | Download (6.39 KB)
| 1 | 13 | up20180614 | /**
|
|---|---|---|---|
| 2 | * \file lzma/vli.h
|
||
| 3 | * \brief Variable-length integer handling
|
||
| 4 | *
|
||
| 5 | * In the .xz format, most integers are encoded in a variable-length
|
||
| 6 | * representation, which is sometimes called little endian base-128 encoding.
|
||
| 7 | * This saves space when smaller values are more likely than bigger values.
|
||
| 8 | *
|
||
| 9 | * The encoding scheme encodes seven bits to every byte, using minimum
|
||
| 10 | * number of bytes required to represent the given value. Encodings that use
|
||
| 11 | * non-minimum number of bytes are invalid, thus every integer has exactly
|
||
| 12 | * one encoded representation. The maximum number of bits in a VLI is 63,
|
||
| 13 | * thus the vli argument must be less than or equal to UINT64_MAX / 2. You
|
||
| 14 | * should use LZMA_VLI_MAX for clarity.
|
||
| 15 | */
|
||
| 16 | |||
| 17 | /*
|
||
| 18 | * Author: Lasse Collin
|
||
| 19 | *
|
||
| 20 | * This file has been put into the public domain.
|
||
| 21 | * You can do whatever you want with this file.
|
||
| 22 | *
|
||
| 23 | * See ../lzma.h for information about liblzma as a whole.
|
||
| 24 | */
|
||
| 25 | |||
| 26 | #ifndef LZMA_H_INTERNAL
|
||
| 27 | # error Never include this file directly. Use <lzma.h> instead.
|
||
| 28 | #endif
|
||
| 29 | |||
| 30 | |||
| 31 | /**
|
||
| 32 | * \brief Maximum supported value of a variable-length integer
|
||
| 33 | */
|
||
| 34 | #define LZMA_VLI_MAX (UINT64_MAX / 2) |
||
| 35 | |||
| 36 | /**
|
||
| 37 | * \brief VLI value to denote that the value is unknown
|
||
| 38 | */
|
||
| 39 | #define LZMA_VLI_UNKNOWN UINT64_MAX
|
||
| 40 | |||
| 41 | /**
|
||
| 42 | * \brief Maximum supported encoded length of variable length integers
|
||
| 43 | */
|
||
| 44 | #define LZMA_VLI_BYTES_MAX 9 |
||
| 45 | |||
| 46 | /**
|
||
| 47 | * \brief VLI constant suffix
|
||
| 48 | */
|
||
| 49 | #define LZMA_VLI_C(n) UINT64_C(n)
|
||
| 50 | |||
| 51 | |||
| 52 | /**
|
||
| 53 | * \brief Variable-length integer type
|
||
| 54 | *
|
||
| 55 | * Valid VLI values are in the range [0, LZMA_VLI_MAX]. Unknown value is
|
||
| 56 | * indicated with LZMA_VLI_UNKNOWN, which is the maximum value of the
|
||
| 57 | * underlaying integer type.
|
||
| 58 | *
|
||
| 59 | * lzma_vli will be uint64_t for the foreseeable future. If a bigger size
|
||
| 60 | * is needed in the future, it is guaranteed that 2 * LZMA_VLI_MAX will
|
||
| 61 | * not overflow lzma_vli. This simplifies integer overflow detection.
|
||
| 62 | */
|
||
| 63 | typedef uint64_t lzma_vli;
|
||
| 64 | |||
| 65 | |||
| 66 | /**
|
||
| 67 | * \brief Validate a variable-length integer
|
||
| 68 | *
|
||
| 69 | * This is useful to test that application has given acceptable values
|
||
| 70 | * for example in the uncompressed_size and compressed_size variables.
|
||
| 71 | *
|
||
| 72 | * \return True if the integer is representable as VLI or if it
|
||
| 73 | * indicates unknown value.
|
||
| 74 | */
|
||
| 75 | #define lzma_vli_is_valid(vli) \
|
||
| 76 | ((vli) <= LZMA_VLI_MAX || (vli) == LZMA_VLI_UNKNOWN) |
||
| 77 | |||
| 78 | |||
| 79 | /**
|
||
| 80 | * \brief Encode a variable-length integer
|
||
| 81 | *
|
||
| 82 | * This function has two modes: single-call and multi-call. Single-call mode
|
||
| 83 | * encodes the whole integer at once; it is an error if the output buffer is
|
||
| 84 | * too small. Multi-call mode saves the position in *vli_pos, and thus it is
|
||
| 85 | * possible to continue encoding if the buffer becomes full before the whole
|
||
| 86 | * integer has been encoded.
|
||
| 87 | *
|
||
| 88 | * \param vli Integer to be encoded
|
||
| 89 | * \param vli_pos How many VLI-encoded bytes have already been written
|
||
| 90 | * out. When starting to encode a new integer in
|
||
| 91 | * multi-call mode, *vli_pos must be set to zero.
|
||
| 92 | * To use single-call encoding, set vli_pos to NULL.
|
||
| 93 | * \param out Beginning of the output buffer
|
||
| 94 | * \param out_pos The next byte will be written to out[*out_pos].
|
||
| 95 | * \param out_size Size of the out buffer; the first byte into
|
||
| 96 | * which no data is written to is out[out_size].
|
||
| 97 | *
|
||
| 98 | * \return Slightly different return values are used in multi-call and
|
||
| 99 | * single-call modes.
|
||
| 100 | *
|
||
| 101 | * Single-call (vli_pos == NULL):
|
||
| 102 | * - LZMA_OK: Integer successfully encoded.
|
||
| 103 | * - LZMA_PROG_ERROR: Arguments are not sane. This can be due
|
||
| 104 | * to too little output space; single-call mode doesn't use
|
||
| 105 | * LZMA_BUF_ERROR, since the application should have checked
|
||
| 106 | * the encoded size with lzma_vli_size().
|
||
| 107 | *
|
||
| 108 | * Multi-call (vli_pos != NULL):
|
||
| 109 | * - LZMA_OK: So far all OK, but the integer is not
|
||
| 110 | * completely written out yet.
|
||
| 111 | * - LZMA_STREAM_END: Integer successfully encoded.
|
||
| 112 | * - LZMA_BUF_ERROR: No output space was provided.
|
||
| 113 | * - LZMA_PROG_ERROR: Arguments are not sane.
|
||
| 114 | */
|
||
| 115 | extern LZMA_API(lzma_ret) lzma_vli_encode(lzma_vli vli, size_t *vli_pos,
|
||
| 116 | uint8_t *out, size_t *out_pos, size_t out_size) lzma_nothrow; |
||
| 117 | |||
| 118 | |||
| 119 | /**
|
||
| 120 | * \brief Decode a variable-length integer
|
||
| 121 | *
|
||
| 122 | * Like lzma_vli_encode(), this function has single-call and multi-call modes.
|
||
| 123 | *
|
||
| 124 | * \param vli Pointer to decoded integer. The decoder will
|
||
| 125 | * initialize it to zero when *vli_pos == 0, so
|
||
| 126 | * application isn't required to initialize *vli.
|
||
| 127 | * \param vli_pos How many bytes have already been decoded. When
|
||
| 128 | * starting to decode a new integer in multi-call
|
||
| 129 | * mode, *vli_pos must be initialized to zero. To
|
||
| 130 | * use single-call decoding, set vli_pos to NULL.
|
||
| 131 | * \param in Beginning of the input buffer
|
||
| 132 | * \param in_pos The next byte will be read from in[*in_pos].
|
||
| 133 | * \param in_size Size of the input buffer; the first byte that
|
||
| 134 | * won't be read is in[in_size].
|
||
| 135 | *
|
||
| 136 | * \return Slightly different return values are used in multi-call and
|
||
| 137 | * single-call modes.
|
||
| 138 | *
|
||
| 139 | * Single-call (vli_pos == NULL):
|
||
| 140 | * - LZMA_OK: Integer successfully decoded.
|
||
| 141 | * - LZMA_DATA_ERROR: Integer is corrupt. This includes hitting
|
||
| 142 | * the end of the input buffer before the whole integer was
|
||
| 143 | * decoded; providing no input at all will use LZMA_DATA_ERROR.
|
||
| 144 | * - LZMA_PROG_ERROR: Arguments are not sane.
|
||
| 145 | *
|
||
| 146 | * Multi-call (vli_pos != NULL):
|
||
| 147 | * - LZMA_OK: So far all OK, but the integer is not
|
||
| 148 | * completely decoded yet.
|
||
| 149 | * - LZMA_STREAM_END: Integer successfully decoded.
|
||
| 150 | * - LZMA_DATA_ERROR: Integer is corrupt.
|
||
| 151 | * - LZMA_BUF_ERROR: No input was provided.
|
||
| 152 | * - LZMA_PROG_ERROR: Arguments are not sane.
|
||
| 153 | */
|
||
| 154 | extern LZMA_API(lzma_ret) lzma_vli_decode(lzma_vli *vli, size_t *vli_pos,
|
||
| 155 | const uint8_t *in, size_t *in_pos, size_t in_size)
|
||
| 156 | lzma_nothrow; |
||
| 157 | |||
| 158 | |||
| 159 | /**
|
||
| 160 | * \brief Get the number of bytes required to encode a VLI
|
||
| 161 | *
|
||
| 162 | * \return Number of bytes on success (1-9). If vli isn't valid,
|
||
| 163 | * zero is returned.
|
||
| 164 | */
|
||
| 165 | extern LZMA_API(uint32_t) lzma_vli_size(lzma_vli vli)
|
||
| 166 | lzma_nothrow lzma_attr_pure; |