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   1 /*
   2  * compress.h
   3  *
   4  * Header for compression code shared by multiple compression formats.
   5  */
   6
   7 #ifndef _WIMLIB_COMPRESS_H
   8 #define _WIMLIB_COMPRESS_H
   9
  10 #include "wimlib/types.h"
  11
  12 /* Variable type that can represent all possible window positions.  */
  13 #ifndef INPUT_IDX_T_DEFINED
  14 #define INPUT_IDX_T_DEFINED
  15 typedef u32 input_idx_t;
  16 #endif
  17
  18 /* Structure to keep track of the current state sending bits and bytes to the
  19  * compressed output buffer.  */
  20 struct output_bitstream {
  21
  22         /* Variable that holds up to 16 bits that haven't yet been flushed to
  23          * the output.  */
  24         u16 bitbuf;
  25
  26         /* Number of free bits in @bitbuf; that is, 16 minus the number of valid
  27          * bits in @bitbuf.  */
  28         unsigned free_bits;
  29
  30         /* Pointer to the start of the output buffer.  */
  31         u8 *output_start;
  32
  33         /* Position at which to write the next 16 bits.  */
  34         u8 *bit_output;
  35
  36         /* Next position to write 16 bits, after they are written to bit_output.
  37          * This is after @next_bit_output and may be separated from @bit_output
  38          * by literal bytes.  */
  39         u8 *next_bit_output;
  40
  41         /* Next position to write literal bytes.  This is after @bit_output and
  42          * @next_bit_output, and may be separated from them by literal bytes.
  43          */
  44         u8 *output;
  45
  46         /* Number of bytes remaining in the @output buffer.  */
  47         input_idx_t bytes_remaining;
  48
  49         /* Set to true if the buffer has been exhausted.  */
  50         bool overrun;
  51 };
  52
  53 extern void
  54 init_output_bitstream(struct output_bitstream *ostream,
  55                       void *data, unsigned num_bytes);
  56
  57 extern input_idx_t
  58 flush_output_bitstream(struct output_bitstream *ostream);
  59
  60 extern void
  61 bitstream_put_bits(struct output_bitstream *ostream,
  62                    u32 bits, unsigned num_bits);
  63
  64 extern void
  65 bitstream_put_byte(struct output_bitstream *ostream, u8 n);
  66
  67 struct lz_params {
  68         unsigned min_match;
  69         unsigned max_match;
  70         unsigned max_offset;
  71         unsigned nice_match;
  72         unsigned good_match;
  73         unsigned max_chain_len;
  74         unsigned max_lazy_match;
  75         unsigned too_far;
  76 };
  77
  78 typedef void (*lz_record_match_t)(unsigned len, unsigned offset, void *ctx);
  79 typedef void (*lz_record_literal_t)(u8 lit, void *ctx);
  80
  81 extern void
  82 lz_analyze_block(const u8 window[restrict],
  83                  input_idx_t window_size,
  84                  lz_record_match_t record_match,
  85                  lz_record_literal_t record_literal,
  86                  void *record_ctx,
  87                  const struct lz_params *params,
  88                  input_idx_t prev_tab[restrict]);
  89
  90 extern void
  91 make_canonical_huffman_code(unsigned num_syms,
  92                             unsigned max_codeword_len,
  93                             const input_idx_t freq_tab[restrict],
  94                             u8 lens[restrict],
  95                             u16 codewords[restrict]);
  96
  97 #endif /* _WIMLIB_COMPRESS_H */