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   1 /*
   2  * compress.h
   3  *
   4  * Functions useful for compression, mainly bitstreams.
   5  */
   6
   7 #ifndef _WIMLIB_COMPRESS_H
   8 #define _WIMLIB_COMPRESS_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         unsigned 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 static inline int bitstream_put_byte(struct output_bitstream *ostream,
  37                                      u8 n)
  38 {
  39         if (ostream->num_bytes_remaining < 1)
  40                 return 1;
  41         *ostream->output = n;
  42         ostream->output++;
  43         ostream->num_bytes_remaining--;
  44         return 0;
  45 }
  46
  47 static inline int bitstream_put_two_bytes(struct output_bitstream *ostream,
  48                                           u16 n)
  49 {
  50         if (ostream->num_bytes_remaining < 2)
  51                 return 1;
  52         *(u16*)ostream->output = cpu_to_le16(n);
  53         ostream->output += 2;
  54         ostream->num_bytes_remaining -= 2;
  55         return 0;
  56 }
  57
  58 struct lz_params {
  59         unsigned min_match;
  60         unsigned max_match;
  61         unsigned nice_match;
  62         unsigned good_match;
  63         unsigned max_chain_len;
  64         unsigned max_lazy_match;
  65         unsigned too_far;
  66 };
  67
  68 typedef unsigned (*lz_record_match_t)(unsigned, unsigned, void *, void *);
  69 typedef unsigned (*lz_record_literal_t)(u8, void *);
  70
  71 extern unsigned lz_analyze_block(const u8 uncompressed_data[],
  72                                  unsigned uncompressed_len,
  73                                  u32 match_tab[],
  74                                  lz_record_match_t record_match,
  75                                  lz_record_literal_t record_literal,
  76                                  void *record_match_arg1,
  77                                  void *record_match_arg2,
  78                                  void *record_literal_arg,
  79                                  const struct lz_params *params);
  80
  81 extern int bitstream_put_bits(struct output_bitstream *ostream,
  82                               output_bitbuf_t bits, unsigned num_bits);
  83
  84 extern void init_output_bitstream(struct output_bitstream *ostream,
  85                                   void *data, unsigned num_bytes);
  86
  87 extern int flush_output_bitstream(struct output_bitstream *ostream);
  88
  89 extern void make_canonical_huffman_code(unsigned num_syms,
  90                                         unsigned max_codeword_len,
  91                                         const u32 freq_tab[],
  92                                         u8 lens[],
  93                                         u16 codewords[]);
  94
  95 #endif /* _WIMLIB_COMPRESS_H */