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   1 /*
   2  * comp.h
   3  *
   4  * Functions useful for compression, mainly bitstreams.
   5  */
   6
   7 #ifndef _WIMLIB_COMP_H
   8 #define _WIMLIB_COMP_H
   9
  10 #include "util.h"
  11 #include "endianness.h"
  12
  13 typedef u16 output_bitbuf_t;
  14
  15 /* Structure to keep track of the current position in the compressed output. */
  16 struct output_bitstream {
  17
  18         /* A variable to buffer writing bits to the output and is flushed to the
  19          * compressed output when full. */
  20         output_bitbuf_t bitbuf;
  21
  22         /* Number of free bits in @bitbuf */
  23         uint free_bits;
  24
  25         u8 *bit_output;
  26         u8 *next_bit_output;
  27
  28         /* Pointer to the next byte in the compressed output. */
  29         u8 *output;
  30
  31
  32         /* Number of bytes left in the memory pointed to by @output. */
  33         int num_bytes_remaining;
  34 };
  35
  36
  37 static inline int bitstream_put_byte(struct output_bitstream *ostream,
  38                                      u8 n)
  39 {
  40         if (ostream->num_bytes_remaining < 1)
  41                 return 1;
  42         *ostream->output = n;
  43         ostream->output++;
  44         ostream->num_bytes_remaining--;
  45         return 0;
  46 }
  47
  48 static inline int bitstream_put_two_bytes(struct output_bitstream *ostream,
  49                                           u16 n)
  50 {
  51         if (ostream->num_bytes_remaining < 2)
  52                 return 1;
  53         *(u16*)ostream->output = cpu_to_le16(n);
  54         ostream->output += 2;
  55         ostream->num_bytes_remaining -= 2;
  56         return 0;
  57 }
  58
  59
  60 struct lz_params {
  61         uint min_match;
  62         uint max_match;
  63         uint nice_match;
  64         uint good_match;
  65         uint max_chain_len;
  66         uint max_lazy_match;
  67         uint too_far;
  68 };
  69
  70 typedef uint (*lz_record_match_t)(uint, uint, void *, void *);
  71 typedef uint (*lz_record_literal_t)(u8, void *);
  72
  73 extern uint lz_analyze_block(const u8 uncompressed_data[],
  74                              uint uncompressed_len,
  75                              u32 match_tab[],
  76                              lz_record_match_t record_match,
  77                              lz_record_literal_t record_literal,
  78                              void *record_match_arg1,
  79                              void *record_match_arg2,
  80                              void *record_literal_arg,
  81                              const struct lz_params *params);
  82
  83 extern int bitstream_put_bits(struct output_bitstream *ostream,
  84                               output_bitbuf_t bits, unsigned num_bits);
  85
  86 extern void init_output_bitstream(struct output_bitstream *ostream,
  87                                   void *data, unsigned num_bytes);
  88
  89 extern int flush_output_bitstream(struct output_bitstream *ostream);
  90
  91 extern void make_canonical_huffman_code(uint num_syms, uint max_codeword_len,
  92                                         const u32 freq_tab[], u8 lens[],
  93                                         u16 codewords[]);
  94
  95 #endif /* _WIMLIB_COMP_H */