mirror of
https://github.com/torvalds/linux.git
synced 2024-12-05 18:41:23 +00:00
d89775fc92
Rationale: Reduces attack surface on kernel devs opening the links for MITM as HTTPS traffic is much harder to manipulate. Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Coly Li <colyli@suse.de> [crc64.c] Link: http://lkml.kernel.org/r/20200726112154.16510-1-grandmaster@al2klimov.de Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
205 lines
6.0 KiB
C
205 lines
6.0 KiB
C
/*
|
|
* LZMA2 definitions
|
|
*
|
|
* Authors: Lasse Collin <lasse.collin@tukaani.org>
|
|
* Igor Pavlov <https://7-zip.org/>
|
|
*
|
|
* This file has been put into the public domain.
|
|
* You can do whatever you want with this file.
|
|
*/
|
|
|
|
#ifndef XZ_LZMA2_H
|
|
#define XZ_LZMA2_H
|
|
|
|
/* Range coder constants */
|
|
#define RC_SHIFT_BITS 8
|
|
#define RC_TOP_BITS 24
|
|
#define RC_TOP_VALUE (1 << RC_TOP_BITS)
|
|
#define RC_BIT_MODEL_TOTAL_BITS 11
|
|
#define RC_BIT_MODEL_TOTAL (1 << RC_BIT_MODEL_TOTAL_BITS)
|
|
#define RC_MOVE_BITS 5
|
|
|
|
/*
|
|
* Maximum number of position states. A position state is the lowest pb
|
|
* number of bits of the current uncompressed offset. In some places there
|
|
* are different sets of probabilities for different position states.
|
|
*/
|
|
#define POS_STATES_MAX (1 << 4)
|
|
|
|
/*
|
|
* This enum is used to track which LZMA symbols have occurred most recently
|
|
* and in which order. This information is used to predict the next symbol.
|
|
*
|
|
* Symbols:
|
|
* - Literal: One 8-bit byte
|
|
* - Match: Repeat a chunk of data at some distance
|
|
* - Long repeat: Multi-byte match at a recently seen distance
|
|
* - Short repeat: One-byte repeat at a recently seen distance
|
|
*
|
|
* The symbol names are in from STATE_oldest_older_previous. REP means
|
|
* either short or long repeated match, and NONLIT means any non-literal.
|
|
*/
|
|
enum lzma_state {
|
|
STATE_LIT_LIT,
|
|
STATE_MATCH_LIT_LIT,
|
|
STATE_REP_LIT_LIT,
|
|
STATE_SHORTREP_LIT_LIT,
|
|
STATE_MATCH_LIT,
|
|
STATE_REP_LIT,
|
|
STATE_SHORTREP_LIT,
|
|
STATE_LIT_MATCH,
|
|
STATE_LIT_LONGREP,
|
|
STATE_LIT_SHORTREP,
|
|
STATE_NONLIT_MATCH,
|
|
STATE_NONLIT_REP
|
|
};
|
|
|
|
/* Total number of states */
|
|
#define STATES 12
|
|
|
|
/* The lowest 7 states indicate that the previous state was a literal. */
|
|
#define LIT_STATES 7
|
|
|
|
/* Indicate that the latest symbol was a literal. */
|
|
static inline void lzma_state_literal(enum lzma_state *state)
|
|
{
|
|
if (*state <= STATE_SHORTREP_LIT_LIT)
|
|
*state = STATE_LIT_LIT;
|
|
else if (*state <= STATE_LIT_SHORTREP)
|
|
*state -= 3;
|
|
else
|
|
*state -= 6;
|
|
}
|
|
|
|
/* Indicate that the latest symbol was a match. */
|
|
static inline void lzma_state_match(enum lzma_state *state)
|
|
{
|
|
*state = *state < LIT_STATES ? STATE_LIT_MATCH : STATE_NONLIT_MATCH;
|
|
}
|
|
|
|
/* Indicate that the latest state was a long repeated match. */
|
|
static inline void lzma_state_long_rep(enum lzma_state *state)
|
|
{
|
|
*state = *state < LIT_STATES ? STATE_LIT_LONGREP : STATE_NONLIT_REP;
|
|
}
|
|
|
|
/* Indicate that the latest symbol was a short match. */
|
|
static inline void lzma_state_short_rep(enum lzma_state *state)
|
|
{
|
|
*state = *state < LIT_STATES ? STATE_LIT_SHORTREP : STATE_NONLIT_REP;
|
|
}
|
|
|
|
/* Test if the previous symbol was a literal. */
|
|
static inline bool lzma_state_is_literal(enum lzma_state state)
|
|
{
|
|
return state < LIT_STATES;
|
|
}
|
|
|
|
/* Each literal coder is divided in three sections:
|
|
* - 0x001-0x0FF: Without match byte
|
|
* - 0x101-0x1FF: With match byte; match bit is 0
|
|
* - 0x201-0x2FF: With match byte; match bit is 1
|
|
*
|
|
* Match byte is used when the previous LZMA symbol was something else than
|
|
* a literal (that is, it was some kind of match).
|
|
*/
|
|
#define LITERAL_CODER_SIZE 0x300
|
|
|
|
/* Maximum number of literal coders */
|
|
#define LITERAL_CODERS_MAX (1 << 4)
|
|
|
|
/* Minimum length of a match is two bytes. */
|
|
#define MATCH_LEN_MIN 2
|
|
|
|
/* Match length is encoded with 4, 5, or 10 bits.
|
|
*
|
|
* Length Bits
|
|
* 2-9 4 = Choice=0 + 3 bits
|
|
* 10-17 5 = Choice=1 + Choice2=0 + 3 bits
|
|
* 18-273 10 = Choice=1 + Choice2=1 + 8 bits
|
|
*/
|
|
#define LEN_LOW_BITS 3
|
|
#define LEN_LOW_SYMBOLS (1 << LEN_LOW_BITS)
|
|
#define LEN_MID_BITS 3
|
|
#define LEN_MID_SYMBOLS (1 << LEN_MID_BITS)
|
|
#define LEN_HIGH_BITS 8
|
|
#define LEN_HIGH_SYMBOLS (1 << LEN_HIGH_BITS)
|
|
#define LEN_SYMBOLS (LEN_LOW_SYMBOLS + LEN_MID_SYMBOLS + LEN_HIGH_SYMBOLS)
|
|
|
|
/*
|
|
* Maximum length of a match is 273 which is a result of the encoding
|
|
* described above.
|
|
*/
|
|
#define MATCH_LEN_MAX (MATCH_LEN_MIN + LEN_SYMBOLS - 1)
|
|
|
|
/*
|
|
* Different sets of probabilities are used for match distances that have
|
|
* very short match length: Lengths of 2, 3, and 4 bytes have a separate
|
|
* set of probabilities for each length. The matches with longer length
|
|
* use a shared set of probabilities.
|
|
*/
|
|
#define DIST_STATES 4
|
|
|
|
/*
|
|
* Get the index of the appropriate probability array for decoding
|
|
* the distance slot.
|
|
*/
|
|
static inline uint32_t lzma_get_dist_state(uint32_t len)
|
|
{
|
|
return len < DIST_STATES + MATCH_LEN_MIN
|
|
? len - MATCH_LEN_MIN : DIST_STATES - 1;
|
|
}
|
|
|
|
/*
|
|
* The highest two bits of a 32-bit match distance are encoded using six bits.
|
|
* This six-bit value is called a distance slot. This way encoding a 32-bit
|
|
* value takes 6-36 bits, larger values taking more bits.
|
|
*/
|
|
#define DIST_SLOT_BITS 6
|
|
#define DIST_SLOTS (1 << DIST_SLOT_BITS)
|
|
|
|
/* 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
|
|
* distance slot itself is the same as the actual distance. DIST_MODEL_START
|
|
* indicates the first distance slot where at least one additional bit is
|
|
* needed.
|
|
*/
|
|
#define DIST_MODEL_START 4
|
|
|
|
/*
|
|
* 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.
|
|
*
|
|
* The distance slot value of 14 is for distances 128-191.
|
|
*/
|
|
#define DIST_MODEL_END 14
|
|
|
|
/* Distance slots that indicate a distance <= 127. */
|
|
#define FULL_DISTANCES_BITS (DIST_MODEL_END / 2)
|
|
#define FULL_DISTANCES (1 << FULL_DISTANCES_BITS)
|
|
|
|
/*
|
|
* For match distances greater than 127, only the highest two bits and the
|
|
* lowest four bits (alignment) is encoded using probabilities.
|
|
*/
|
|
#define ALIGN_BITS 4
|
|
#define ALIGN_SIZE (1 << ALIGN_BITS)
|
|
#define ALIGN_MASK (ALIGN_SIZE - 1)
|
|
|
|
/* Total number of all probability variables */
|
|
#define PROBS_TOTAL (1846 + LITERAL_CODERS_MAX * LITERAL_CODER_SIZE)
|
|
|
|
/*
|
|
* LZMA remembers the four most recent match distances. Reusing these
|
|
* distances tends to take less space than re-encoding the actual
|
|
* distance value.
|
|
*/
|
|
#define REPS 4
|
|
|
|
#endif
|