/* Copyright 2013 Google Inc. All Rights Reserved.

   Distributed under MIT license.

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

*/

/* Functions to map previous bytes into a context id. */

#ifndef BROTLI_ENC_CONTEXT_H_

#define BROTLI_ENC_CONTEXT_H_

#include <brotli/port.h>

#include <brotli/types.h>

#if defined(__cplusplus) || defined(c_plusplus)

extern "C" {

#endif

/* Second-order context lookup table for UTF8 byte streams.

   If p1 and p2 are the previous two bytes, we calculate the context as

     context = kUTF8ContextLookup[p1] | kUTF8ContextLookup[p2 + 256].

   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     |                  |

   |-------------|-------------------|---------------------|------------------|

*/

static const uint8_t kUTF8ContextLookup[512] = {

  /* Last byte. */

  /* */

  /* ASCII range. */

   0,  0,  0,  0,  0,  0,  0,  0,  0,  4,  4,  0,  0,  4,  0,  0,

   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,

   8, 12, 16, 12, 12, 20, 12, 16, 24, 28, 12, 12, 32, 12, 36, 12,

  44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 32, 32, 24, 40, 28, 12,

  12, 48, 52, 52, 52, 48, 52, 52, 52, 48, 52, 52, 52, 52, 52, 48,

  52, 52, 52, 52, 52, 48, 52, 52, 52, 52, 52, 24, 12, 28, 12, 12,

  12, 56, 60, 60, 60, 56, 60, 60, 60, 56, 60, 60, 60, 60, 60, 56,

  60, 60, 60, 60, 60, 56, 60, 60, 60, 60, 60, 24, 12, 28, 12,  0,

  /* UTF8 continuation byte range. */

  0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1,

  0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1,

  0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1,

  0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1,

  /* UTF8 lead byte range. */

  2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3,

  2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3,

  2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3,

  2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3,

  /* Second last byte. */

  /* */

  /* ASCII range. */

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,

  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1,

  1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,

  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1,

  1, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,

  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 1, 1, 1, 1, 0,

  /* UTF8 continuation byte range. */

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  /* UTF8 lead byte range. */

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,

  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,

};

/* Context lookup table for small signed integers. */

static const uint8_t kSigned3BitContextLookup[] = {

  0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,

  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,

  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,

  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,

  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,

  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,

  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,

  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,

  4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,

  4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,

  4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,

  4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,

  5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,

  5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,

  5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,

  6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7,

};

typedef enum ContextType {

  CONTEXT_LSB6         = 0,

  CONTEXT_MSB6         = 1,

  CONTEXT_UTF8         = 2,

  CONTEXT_SIGNED       = 3

} ContextType;

static BROTLI_INLINE uint8_t Context(uint8_t p1, uint8_t p2, ContextType mode) {

  switch (mode) {

    case CONTEXT_LSB6:

      return p1 & 0x3f;

    case CONTEXT_MSB6:

      return (uint8_t)(p1 >> 2);

    case CONTEXT_UTF8:

      return kUTF8ContextLookup[p1] | kUTF8ContextLookup[p2 + 256];

    case CONTEXT_SIGNED:

      return (uint8_t)((kSigned3BitContextLookup[p1] << 3) +

                       kSigned3BitContextLookup[p2]);

    default:

      return 0;

  }

}

Unexecuted instantiation: bit_cost.c:Context

Unexecuted instantiation: block_splitter.c:Context

Unexecuted instantiation: brotli_bit_stream.c:Context

Unexecuted instantiation: cluster.c:Context

Unexecuted instantiation: compress_fragment.c:Context

Unexecuted instantiation: compress_fragment_two_pass.c:Context

Unexecuted instantiation: encode.c:Context

Unexecuted instantiation: histogram.c:Context

Unexecuted instantiation: metablock.c:Context

#if defined(__cplusplus) || defined(c_plusplus)

}  /* extern "C" */

#endif

#endif  /* BROTLI_ENC_CONTEXT_H_ */