third_party/brotli/dec/context.h - Issue 960873002: Update from https://crrev.com/318214

Unified Diff: third_party/brotli/dec/context.h

Issue 960873002: Update from https://crrev.com/318214 (Closed) Base URL: https://github.com/domokit/mojo.git@master

Patch Set: Created 5 years, 10 months ago

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Index: third_party/brotli/dec/context.h

diff --git a/third_party/brotli/dec/context.h b/third_party/brotli/dec/context.h

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+ Licensed under the Apache License, Version 2.0 (the "License");

+ you may not use this file except in compliance with the License.

+ You may obtain a copy of the License at

+ http://www.apache.org/licenses/LICENSE-2.0

+ Unless required by applicable law or agreed to in writing, software

+ distributed under the License is distributed on an "AS IS" BASIS,

+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

+ See the License for the specific language governing permissions and

+ limitations under the License.

+ 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.

+ The context id for the UTF8 context model is calculated as follows. If p1

+ and p2 are the previous two bytes, we calcualte the context as

+ context = kContextLookup[p1] | kContextLookup[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-) |

+ |=============|===================|=====================|==================|

+ | (0-127) | context: 4 - 63 | | context: 2 - 3 |

+ |-------------|-------------------|---------------------|------------------|

+ |-------------|-------------------|---------------------|------------------|

+ | (192-207) | | context: 0 - 1 | |

+ |-------------|-------------------|---------------------|------------------|

+ | (208-) | | context: 2 - 3 | |

+ |-------------|-------------------|---------------------|------------------|

+ The context id for the signed context mode is calculated as:

+ context = (kContextLookup[512 + p1] << 3) | kContextLookup[512 + p2].

+ For any context modeling modes, the context ids can be calculated by |-ing

+ together two lookups from one table using context model dependent offsets:

+ context = kContextLookup[offset1 + p1] | kContextLookup[offset2 + p2].

+ where offset1 and offset2 are dependent on the context mode.

+*/

+#ifndef BROTLI_DEC_CONTEXT_H_

+#define BROTLI_DEC_CONTEXT_H_

+#include "./types.h"

+enum ContextType {

+ CONTEXT_LSB6 = 0,

+ CONTEXT_MSB6 = 1,

+ CONTEXT_UTF8 = 2,

+ CONTEXT_SIGNED = 3

+};

+/* Common context lookup table for all context modes. */

+static const uint8_t kContextLookup[1792] = {

+ /* CONTEXT_UTF8, 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,

+ /* UTF8 lead byte range. */

+ 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3,

+ /* CONTEXT_UTF8 second last byte. */

+ /* ASCII range. */

+ 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,

+ /* UTF8 lead byte range. */

+ 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,

+ /* CONTEXT_SIGNED, second last byte. */

+ 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,

+ 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,

+ 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,

+ /* CONTEXT_SIGNED, last byte, same as the above values shifted by 3 bits. */

+ 0, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,

+ 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,

+ 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,

+ 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32,

+ 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40,

+ 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 56,

+ /* CONTEXT_LSB6, last byte. */

+ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,

+ 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,

+ 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,

+ 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,

+ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,

+ 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,

+ 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,

+ 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,

+ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,

+ 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,

+ 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,

+ 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,

+ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,

+ 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,

+ 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,

+ 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,

+ /* CONTEXT_MSB6, last byte. */

+ 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3,

+ 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7,

+ 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11,

+ 12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14, 15, 15, 15, 15,

+ 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 19, 19, 19, 19,

+ 20, 20, 20, 20, 21, 21, 21, 21, 22, 22, 22, 22, 23, 23, 23, 23,

+ 24, 24, 24, 24, 25, 25, 25, 25, 26, 26, 26, 26, 27, 27, 27, 27,

+ 28, 28, 28, 28, 29, 29, 29, 29, 30, 30, 30, 30, 31, 31, 31, 31,

+ 32, 32, 32, 32, 33, 33, 33, 33, 34, 34, 34, 34, 35, 35, 35, 35,

+ 36, 36, 36, 36, 37, 37, 37, 37, 38, 38, 38, 38, 39, 39, 39, 39,

+ 40, 40, 40, 40, 41, 41, 41, 41, 42, 42, 42, 42, 43, 43, 43, 43,

+ 44, 44, 44, 44, 45, 45, 45, 45, 46, 46, 46, 46, 47, 47, 47, 47,

+ 48, 48, 48, 48, 49, 49, 49, 49, 50, 50, 50, 50, 51, 51, 51, 51,

+ 52, 52, 52, 52, 53, 53, 53, 53, 54, 54, 54, 54, 55, 55, 55, 55,

+ 56, 56, 56, 56, 57, 57, 57, 57, 58, 58, 58, 58, 59, 59, 59, 59,

+ 60, 60, 60, 60, 61, 61, 61, 61, 62, 62, 62, 62, 63, 63, 63, 63,

+ /* CONTEXT_{M,L}SB6, second last byte, */

+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

+};

+static const int kContextLookupOffsets[8] = {

+ /* CONTEXT_LSB6 */

+ 1024, 1536,

+ /* CONTEXT_MSB6 */

+ 1280, 1536,

+ /* CONTEXT_UTF8 */

+ 0, 256,

+ /* CONTEXT_SIGNED */

+ 768, 512,

+};

+#endif /* BROTLI_DEC_CONTEXT_H_ */

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