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?? ..
?? .libs
?? constants.c(619 B)
?? constants.dep(371 B)
?? constants.h(7.79 KB)
?? constants.lo(286 B)
?? context.c(7.8 KB)
?? context.dep(365 B)
?? context.h(4.53 KB)
?? context.lo(282 B)
?? dictionary.c(1.52 KB)
?? dictionary.dep(446 B)
?? dictionary.h(1.88 KB)
?? dictionary.lo(288 B)
?? dictionary_inc.h(459.41 KB)
?? platform.c(465 B)
?? platform.dep(302 B)
?? platform.h(23.2 KB)
?? platform.lo(284 B)
?? shared_dictionary.c(16.94 KB)
?? shared_dictionary.dep(622 B)
?? shared_dictionary.lo(302 B)
?? shared_dictionary_internal.h(2.35 KB)
?? static_init.h(1.95 KB)
?? transform.c(10.53 KB)
?? transform.dep(371 B)
?? transform.h(3.11 KB)
?? transform.lo(286 B)
?? version.h(1.68 KB)

Editing: context.h

Distributed under MIT license.
   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/

/* Lookup table to map the previous two bytes to a context id.

There are four different context modeling modes defined here:
    CONTEXT_LSB6: context id is the least significant 6 bits of the last byte,
    CONTEXT_MSB6: context id is the most significant 6 bits of the last byte,
    CONTEXT_UTF8: second-order context model tuned for UTF8-encoded text,
    CONTEXT_SIGNED: second-order context model tuned for signed integers.

If |p1| and |p2| are the previous two bytes, and |mode| is current context
  mode, we calculate the context as:

context = ContextLut(mode)[p1] | ContextLut(mode)[p2 + 256].

For CONTEXT_UTF8 mode, if the previous two bytes are ASCII characters
  (i.e. < 128), this will be equivalent to

context = 4 * context1(p1) + context2(p2),

where context1 is based on the previous byte in the following way:

0  : non-ASCII control
    1  : \t, \n, \r
    2  : space
    3  : other punctuation
    4  : " '
    5  : %
    6  : ( < [ {
    7  : ) > ] }
    8  : , ; :
    9  : .
    10 : =
    11 : number
    12 : upper-case vowel
    13 : upper-case consonant
    14 : lower-case vowel
    15 : lower-case consonant

and context2 is based on the second last byte:

0 : control, space
    1 : punctuation
    2 : upper-case letter, number
    3 : lower-case letter

If the last byte is ASCII, and the second last byte is not (in a valid UTF8
  stream it will be a continuation byte, value between 128 and 191), the
  context is the same as if the second last byte was an ASCII control or space.

If the last byte is a UTF8 lead byte (value >= 192), then the next byte will
  be a continuation byte and the context id is 2 or 3 depending on the LSB of
  the last byte and to a lesser extent on the second last byte if it is ASCII.

If the last byte is a UTF8 continuation byte, the second last byte can be:
    - continuation byte: the next byte is probably ASCII or lead byte (assuming
      4-byte UTF8 characters are rare) and the context id is 0 or 1.
    - lead byte (192 - 207): next byte is ASCII or lead byte, context is 0 or 1
    - lead byte (208 - 255): next byte is continuation byte, context is 2 or 3

The possible value combinations of the previous two bytes, the range of
  context ids and the type of the next byte is summarized in the table below:

|--------\-----------------------------------------------------------------|
  |         \                         Last byte                              |
  | Second   \---------------------------------------------------------------|
  | last byte \    ASCII            |   cont. byte        |   lead byte      |
  |            \   (0-127)          |   (128-191)         |   (192-)         |
  |=============|===================|=====================|==================|
  |  ASCII      | next: ASCII/lead  |  not valid          |  next: cont.     |
  |  (0-127)    | context: 4 - 63   |                     |  context: 2 - 3  |
  |-------------|-------------------|---------------------|------------------|
  |  cont. byte | next: ASCII/lead  |  next: ASCII/lead   |  next: cont.     |
  |  (128-191)  | context: 4 - 63   |  context: 0 - 1     |  context: 2 - 3  |
  |-------------|-------------------|---------------------|------------------|
  |  lead byte  | not valid         |  next: ASCII/lead   |  not valid       |
  |  (192-207)  |                   |  context: 0 - 1     |                  |
  |-------------|-------------------|---------------------|------------------|
  |  lead byte  | not valid         |  next: cont.        |  not valid       |
  |  (208-)     |                   |  context: 2 - 3     |                  |
  |-------------|-------------------|---------------------|------------------|
*/

#ifndef BROTLI_COMMON_CONTEXT_H_
#define BROTLI_COMMON_CONTEXT_H_

#include "platform.h"

typedef enum ContextType {
  CONTEXT_LSB6 = 0,
  CONTEXT_MSB6 = 1,
  CONTEXT_UTF8 = 2,
  CONTEXT_SIGNED = 3
} ContextType;

/* "Soft-private", it is exported, but not "advertised" as API. */
/* Common context lookup table for all context modes. */
BROTLI_COMMON_API extern const uint8_t _kBrotliContextLookupTable[2048];

typedef const uint8_t* ContextLut;

/* typeof(MODE) == ContextType; returns ContextLut */
#define BROTLI_CONTEXT_LUT(MODE) (&_kBrotliContextLookupTable[(MODE) << 9])

/* typeof(LUT) == ContextLut */
#define BROTLI_CONTEXT(P1, P2, LUT) ((LUT)[P1] | ((LUT) + 256)[P2])

#endif  /* BROTLI_COMMON_CONTEXT_H_ */

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