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make it possible to specify LDM parameters in any order

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This commit is contained in:
Yann Collet
2018-03-19 11:07:04 -07:00
parent cbc71e40f6
commit 9618c0c804
4 changed files with 33 additions and 40 deletions
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lib/zstd.h
+16 -21
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@@ -991,38 +991,33 @@ typedef enum {
* Special: value 0 means "do not change strategy". */
ZSTD_p_enableLongDistanceMatching=160, /* Enable long distance matching.
* This parameter is designed to improve the compression
* ratio for large inputs with long distance matches.
* This increases the memory usage as well as window size.
* Note: setting this parameter sets all the LDM parameters
* as well as ZSTD_p_windowLog. It should be set after
* ZSTD_p_compressionLevel and before ZSTD_p_windowLog and
* other LDM parameters. Setting the compression level
* after this parameter overrides the window log, though LDM
* will remain enabled until explicitly disabled. */
* This parameter is designed to improve compression ratio
* for large inputs, thanks to long distance matches.
* It increases memory usage and window size.
* Note: setting this parameter sets ZSTD_p_windowLog.
* Setting compression level after LDM overrides the window log,
* though LDM will remain enabled until explicitly disabled. */
ZSTD_p_ldmHashLog, /* Size of the table for long distance matching, as a power of 2.
* Larger values increase memory usage and compression ratio, but decrease
* compression speed.
* Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
* (default: windowlog - 7).
* Special: value 0 means "do not change ldmHashLog". */
* Special: value 0 means "automatically determine hashlog". */
ZSTD_p_ldmMinMatch, /* Minimum size of searched matches for long distance matcher.
* Larger/too small values usually decrease compression ratio.
* Must be clamped between ZSTD_LDM_MINMATCH_MIN
* and ZSTD_LDM_MINMATCH_MAX (default: 64).
* Special: value 0 means "do not change ldmMinMatch". */
* Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
* Special: value 0 means "use default value" (default: 64). */
ZSTD_p_ldmBucketSizeLog, /* Log size of each bucket in the LDM hash table for collision resolution.
* Larger values usually improve collision resolution but may decrease
* compression speed.
* The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX (default: 3).
* note : 0 is a valid value */
* Larger values improve collision resolution but decrease compression speed.
* The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX .
* Special: value 0 means "use default value" (default: 3). */
ZSTD_p_ldmHashEveryLog, /* Frequency of inserting/looking up entries in the LDM hash table.
* The default is MAX(0, (windowLog - ldmHashLog)) to
* optimize hash table usage.
* Larger values improve compression speed. Deviating far from the
* default value will likely result in a decrease in compression ratio.
* Must be clamped between 0 and ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN.
* note : 0 is a valid value */
* Larger values improve compression speed.
* Deviating far from default value will likely result in a compression ratio decrease.
* Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
* Special: value 0 means "automatically determine hashEveryLog". */
/* frame parameters */
ZSTD_p_contentSizeFlag=200, /* Content size will be written into frame header _whenever known_ (default:1)