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Diffstat (limited to 'programs/zstd.1.md')
| -rw-r--r-- | programs/zstd.1.md | 63 |
1 files changed, 62 insertions, 1 deletions
diff --git a/programs/zstd.1.md b/programs/zstd.1.md index 4310afa1aaf8..eea68548982e 100644 --- a/programs/zstd.1.md +++ b/programs/zstd.1.md @@ -105,6 +105,16 @@ the last one takes effect. * `--ultra`: unlocks high compression levels 20+ (maximum 22), using a lot more memory. Note that decompression will also require more memory when using these levels. +* `--long[=#]`: + enables long distance matching with `#` `windowLog`, if not `#` is not + present it defaults to `27`. + This increases the window size (`windowLog`) and memory usage for both the + compressor and decompressor. + This setting is designed to improve the compression ratio for files with + long matches at a large distance. + + Note: If `windowLog` is set to larger than 27, `--long=windowLog` or + `--memory=windowSize` needs to be passed to the decompressor. * `-T#`, `--threads=#`: Compress using `#` threads (default: 1). If `#` is 0, attempt to detect and use the number of physical CPU cores. @@ -137,6 +147,10 @@ the last one takes effect. This is the default behavior. * `-r`: operate recursively on dictionaries +* `--format=FORMAT`: + compress and decompress in other formats. If compiled with + support, zstd can compress to or decompress from other compression algorithm + formats. Possibly available options are `gzip`, `xz`, `lzma`, and `lz4`. * `-h`/`-H`, `--help`: display help/long help and exit * `-V`, `--version`: @@ -178,6 +192,8 @@ Typical gains range from 10% (at 64KB) to x5 better (at <1KB). Dictionary saved into `file` (default name: dictionary). * `--maxdict=#`: Limit dictionary to specified size (default: 112640). +* `-B#`: + Split input files in blocks of size # (default: no split) * `--dictID=#`: A dictionary ID is a locally unique ID that a decoder can use to verify it is using the right dictionary. @@ -267,7 +283,11 @@ The list of available _options_: The higher number of increases the chance to find a match which usually improves compression ratio. It also increases memory requirements for the compressor and decompressor. - The minimum _wlog_ is 10 (1 KiB) and the maximum is 27 (128 MiB). + The minimum _wlog_ is 10 (1 KiB) and the maximum is 30 (1 GiB) on 32-bit + platforms and 31 (2 GiB) on 64-bit platforms. + + Note: If `windowLog` is set to larger than 27, `--long=windowLog` or + `--memory=windowSize` needs to be passed to the decompressor. - `hashLog`=_hlog_, `hlog`=_hlog_: Specify the maximum number of bits for a hash table. @@ -327,6 +347,47 @@ The list of available _options_: Default _ovlog_ is 6, which means "reload `windowSize / 8`". Exception : the maximum compression level (22) has a default _ovlog_ of 9. +- `ldmHashLog`=_ldmhlog_, `ldmhlog`=_ldmhlog_: + Specify the maximum size for a hash table used for long distance matching. + + This option is ignored unless long distance matching is enabled. + + Bigger hash tables usually improve compression ratio at the expense of more + memory during compression and a decrease in compression speed. + + The minimum _ldmhlog_ is 6 and the maximum is 26 (default: 20). + +- `ldmSearchLength`=_ldmslen_, `ldmslen`=_ldmslen_: + Specify the minimum searched length of a match for long distance matching. + + This option is ignored unless long distance matching is enabled. + + Larger/very small values usually decrease compression ratio. + + The minumum _ldmslen_ is 4 and the maximum is 4096 (default: 64). + +- `ldmBucketSizeLog`=_ldmblog_, `ldmblog`=_ldmblog_: + Specify the size of each bucket for the hash table used for long distance + matching. + + This option is ignored unless long distance matching is enabled. + + Larger bucket sizes improve collision resolution but decrease compression + speed. + + The minimum _ldmblog_ is 0 and the maximum is 8 (default: 3). + +- `ldmHashEveryLog`=_ldmhevery_, `ldmhevery`=_ldmhevery_: + Specify the frequency of inserting entries into the long distance matching + hash table. + + This option is ignored unless long distance matching is enabled. + + Larger values will improve compression speed. Deviating far from the + default value will likely result in a decrease in compression ratio. + + The default value is `wlog - ldmhlog`. + ### -B#: Select the size of each compression job. This parameter is available only when multi-threading is enabled. |