fd2fba7c2c
Use smaller .mo files instead of .po, if gettext is available. Convert editor fonts to .woff2 format.
114 lines
4.6 KiB
C++
114 lines
4.6 KiB
C++
/* Copyright 2013 Google Inc. All Rights Reserved.
|
|
|
|
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 <brotli/port.h>
|
|
#include <brotli/types.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_ */
|