Function report

Linux Kernel

v5.5.9

Brick Technologies Co., Ltd

Source Code:lib\xz\xz_dec_lzma2.c Create Date:2022-07-28 07:08:42
Last Modify:2020-03-12 14:18:49 Copyright©Brick
home page Tree
Annotation kernel can get tool activityDownload SCCTChinese

Name:Decode a match. The distance will be stored in s->lzma.rep0.

Proto:static void lzma_match(struct xz_dec_lzma2 *s, uint32_t pos_state)

Type:void

Parameter:

TypeParameterName
struct xz_dec_lzma2 *s
uint32_tpos_state
652  Indicate that the latest symbol was a match.
654  rep3 = rep2
655  rep2 = rep1
656  rep1 = Distances of latest four matches
658  Decode the length of the match into s->lzma.len.
660  probs = * Probability tree for the highest two bits of the match * distance. There is a separate probability tree for match * lengths of 2 (i.e. MATCH_LEN_MIN), 3, 4, and [5, 273].[Get the index of the appropriate probability array for decoding* the distance slot.]
661  dist_slot = Decode a bittree starting from the most significant bit. - DIST_SLOTS
663  If dist_slot < Match distances up to 127 are fully encoded using probabilities. Since* the highest two bits (distance slot) are always encoded using six bits,* the distances 0-3 don't need any additional bits to encode, since the Then
664  Distances of latest four matches = dist_slot
665  Else
666  limit = (dist_slot >> 1) - 1
667  Distances of latest four matches = 2 + (dist_slot & 1)
669  If dist_slot < Match distances greater than 127 are encoded in three pieces:* - distance slot: the highest two bits* - direct bits: 2-26 bits below the highest two bits* - alignment bits: four lowest bits* Direct bits don't use any probabilities. Then
670  Distances of latest four matches <<= limit
671  probs = * Probility trees for additional bits for match distance * when the distance is in the range [4, 127]. + Distances of latest four matches - dist_slot - 1
673  Decode a bittree starting from the least significant bit.
675  Else
676  Decode direct bits (fixed fifty-fifty probability)
677  Distances of latest four matches <<= For match distances greater than 127, only the highest two bits and the* lowest four bits (alignment) is encoded using probabilities.
678  Decode a bittree starting from the least significant bit.
Caller
NameDescribe
lzma_mainLZMA decoder core