github.com/Schaudge/grailbase@v0.0.0-20240223061707-44c758a471c0/compress/libdeflate/deflate_constants.h (about)

     1  /*
     2   * deflate_constants.h - constants for the DEFLATE compression format
     3   */
     4  
     5  #ifndef LIB_DEFLATE_CONSTANTS_H
     6  #define LIB_DEFLATE_CONSTANTS_H
     7  
     8  /* Valid block types  */
     9  #define DEFLATE_BLOCKTYPE_UNCOMPRESSED		0
    10  #define DEFLATE_BLOCKTYPE_STATIC_HUFFMAN	1
    11  #define DEFLATE_BLOCKTYPE_DYNAMIC_HUFFMAN	2
    12  
    13  /* Minimum and maximum supported match lengths (in bytes)  */
    14  #define DEFLATE_MIN_MATCH_LEN			3
    15  #define DEFLATE_MAX_MATCH_LEN			258
    16  
    17  /* Minimum and maximum supported match offsets (in bytes)  */
    18  #define DEFLATE_MIN_MATCH_OFFSET		1
    19  #define DEFLATE_MAX_MATCH_OFFSET		32768
    20  
    21  #define DEFLATE_MAX_WINDOW_SIZE			32768
    22  
    23  /* Number of symbols in each Huffman code.  Note: for the literal/length
    24   * and offset codes, these are actually the maximum values; a given block
    25   * might use fewer symbols.  */
    26  #define DEFLATE_NUM_PRECODE_SYMS		19
    27  #define DEFLATE_NUM_LITLEN_SYMS			288
    28  #define DEFLATE_NUM_OFFSET_SYMS			32
    29  
    30  /* The maximum number of symbols across all codes  */
    31  #define DEFLATE_MAX_NUM_SYMS			288
    32  
    33  /* Division of symbols in the literal/length code  */
    34  #define DEFLATE_NUM_LITERALS			256
    35  #define DEFLATE_END_OF_BLOCK			256
    36  #define DEFLATE_NUM_LEN_SYMS			31
    37  
    38  /* Maximum codeword length, in bits, within each Huffman code  */
    39  #define DEFLATE_MAX_PRE_CODEWORD_LEN		7
    40  #define DEFLATE_MAX_LITLEN_CODEWORD_LEN		15
    41  #define DEFLATE_MAX_OFFSET_CODEWORD_LEN		15
    42  
    43  /* The maximum codeword length across all codes  */
    44  #define DEFLATE_MAX_CODEWORD_LEN		15
    45  
    46  /* Maximum possible overrun when decoding codeword lengths  */
    47  #define DEFLATE_MAX_LENS_OVERRUN		137
    48  
    49  /*
    50   * Maximum number of extra bits that may be required to represent a match
    51   * length or offset.
    52   *
    53   * TODO: are we going to have full DEFLATE64 support?  If so, up to 16
    54   * length bits must be supported.
    55   */
    56  #define DEFLATE_MAX_EXTRA_LENGTH_BITS		5
    57  #define DEFLATE_MAX_EXTRA_OFFSET_BITS		14
    58  
    59  /* The maximum number of bits in which a match can be represented.  This
    60   * is the absolute worst case, which assumes the longest possible Huffman
    61   * codewords and the maximum numbers of extra bits.  */
    62  #define DEFLATE_MAX_MATCH_BITS	\
    63  	(DEFLATE_MAX_LITLEN_CODEWORD_LEN + DEFLATE_MAX_EXTRA_LENGTH_BITS + \
    64  	DEFLATE_MAX_OFFSET_CODEWORD_LEN + DEFLATE_MAX_EXTRA_OFFSET_BITS)
    65  
    66  #endif /* LIB_DEFLATE_CONSTANTS_H */