Struct deflate::CompressionOptions [−][src]
pub struct CompressionOptions { pub max_hash_checks: u16, pub lazy_if_less_than: u16, pub matching_type: MatchingType, pub special: SpecialOptions, }
A struct describing the options for a compressor or compression function.
These values are not stable and still subject to change!
Fields
max_hash_checks: u16
The maximum number of checks to make in the hash table for matches.
Higher numbers mean slower, but better compression. Very high (say >1024
) values
will impact compression speed a lot. The maximum match length is 2^15, so values higher than
this won't make any difference, and will be truncated to 2^15 by the compression
function/writer.
Default value: 128
lazy_if_less_than: u16
Only lazy match if we have a length less than this value.
Higher values degrade compression slightly, but improve compression speed.
0
: Never lazy match. (Same effect as setting MatchingType to greedy, but may be slower).1...257
: Only check for a better match if the first match was shorter than this value.258
: Always lazy match.
As the maximum length of a match is 258
, values higher than this will have
no further effect.
- Default value:
32
matching_type: MatchingType
Whether to use lazy or greedy matching.
Lazy matching will provide better compression, at the expense of compression speed.
As a special case, if max_hash_checks is set to 0, and matching_type is set to lazy, compression using only run-length encoding (i.e maximum match distance of 1) is performed. (This may be changed in the future but is defined like this at the moment to avoid API breakage.
- Default value:
MatchingType::Lazy
special: SpecialOptions
Force fixed/stored blocks (Not implemented yet).
- Default value:
SpecialOptions::Normal
Methods
impl CompressionOptions
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impl CompressionOptions
pub fn high() -> CompressionOptions
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pub fn high() -> CompressionOptions
Returns compression settings rouhgly corresponding to the HIGH(9)
setting in miniz.
pub fn fast() -> CompressionOptions
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pub fn fast() -> CompressionOptions
Returns a fast set of compression settings
Ideally this should roughly correspond to the FAST(1)
setting in miniz.
However, that setting makes miniz use a somewhat different algorhithm,
so currently hte fast level in this library is slower and better compressing
than the corresponding level in miniz.
pub fn huffman_only() -> CompressionOptions
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pub fn huffman_only() -> CompressionOptions
Returns a set of compression settings that makes the compressor only compress using huffman coding. (Ignoring any length/distance matching)
This will normally have the worst compression ratio (besides only using uncompressed data), but may be the fastest method in some cases.
pub fn rle() -> CompressionOptions
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pub fn rle() -> CompressionOptions
Returns a set of compression settings that makes the compressor compress only using run-length encoding (i.e only looking for matches one byte back).
This is very fast, but tends to compress worse than looking for more matches using hash chains that the slower settings do. Works best on data that has runs of equivialent bytes, like binary or simple images, less good for text.
Trait Implementations
impl Copy for CompressionOptions
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impl Copy for CompressionOptions
impl Clone for CompressionOptions
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impl Clone for CompressionOptions
fn clone(&self) -> CompressionOptions
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fn clone(&self) -> CompressionOptions
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
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fn clone_from(&mut self, source: &Self)
Performs copy-assignment from source
. Read more
impl Debug for CompressionOptions
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impl Debug for CompressionOptions
fn fmt(&self, f: &mut Formatter) -> Result
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fn fmt(&self, f: &mut Formatter) -> Result
Formats the value using the given formatter. Read more
impl Eq for CompressionOptions
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impl Eq for CompressionOptions
impl PartialEq for CompressionOptions
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impl PartialEq for CompressionOptions
fn eq(&self, other: &CompressionOptions) -> bool
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fn eq(&self, other: &CompressionOptions) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
fn ne(&self, other: &CompressionOptions) -> bool
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fn ne(&self, other: &CompressionOptions) -> bool
This method tests for !=
.
impl Hash for CompressionOptions
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impl Hash for CompressionOptions
fn hash<__H: Hasher>(&self, state: &mut __H)
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fn hash<__H: Hasher>(&self, state: &mut __H)
Feeds this value into the given [Hasher
]. Read more
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
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fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
Feeds a slice of this type into the given [Hasher
]. Read more
impl Default for CompressionOptions
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impl Default for CompressionOptions
fn default() -> CompressionOptions
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fn default() -> CompressionOptions
Returns the options describing the default compression level.
impl From<Compression> for CompressionOptions
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impl From<Compression> for CompressionOptions
fn from(compression: Compression) -> CompressionOptions
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fn from(compression: Compression) -> CompressionOptions
Performs the conversion.
Auto Trait Implementations
impl Send for CompressionOptions
impl Send for CompressionOptions
impl Sync for CompressionOptions
impl Sync for CompressionOptions