Enum WriteFilter 

#[non_exhaustive]
pub enum WriteFilter {
    None,
    BcjX86,
    BcjArm,
    BcjArm64,
    BcjArmThumb,
    BcjPpc,
    BcjSparc,
    BcjIa64,
    BcjRiscv,
    Bcj2,
    Delta {
        distance: u8,
    },
}

Pre-compression filter for improving compression of specific data types.

BCJ (Branch/Call/Jump) filters transform executable code addresses from relative to absolute form before compression. This improves compression ratios by 5-15% for executable files because the resulting byte patterns compress better.

The Delta filter computes differences between consecutive samples, improving compression for audio, image, and other structured data.

Example

use zesven::write::{WriteOptions, WriteFilter};

// Use BCJ x86 filter for compressing Windows/Linux executables
let options = WriteOptions::new().filter(WriteFilter::BcjX86);

// Use Delta filter for audio data (2-byte samples)
let options = WriteOptions::new().filter(WriteFilter::Delta { distance: 2 });

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

None

No filter applied.

BcjX86

BCJ x86 filter for 32-bit and 64-bit x86 executables.

BcjArm

BCJ ARM filter for 32-bit ARM executables.

BcjArm64

BCJ ARM64/AArch64 filter for 64-bit ARM executables.

BcjArmThumb

BCJ ARM Thumb filter for ARM Thumb mode executables.

BcjPpc

BCJ PowerPC filter.

BcjSparc

BCJ SPARC filter.

BcjIa64

BCJ IA-64 (Itanium) filter.

BcjRiscv

BCJ RISC-V filter.

Bcj2

BCJ2 4-stream filter for x86 executables.

BCJ2 splits x86 code into 4 streams (main, call, jump, range) for improved compression. Unlike simple BCJ filters, BCJ2 uses a complex 4-input coder structure.

Note: BCJ2 is only supported in non-solid mode.

Delta

Delta filter for structured data (audio, images).

The distance parameter specifies the sample size in bytes. Common values:

• 1: byte-level differences
• 2: 16-bit audio samples
• 4: 32-bit values or RGBA pixels

Use WriteFilter::delta() to construct with validation.

Fields

distance: u8

Sample distance in bytes (1-255).

Implementations

impl WriteFilter

pub fn delta(distance: u8) -> Self

Creates a Delta filter with the given sample distance.

Arguments

• distance - Sample size in bytes (1-255)

Panics

Panics if distance is 0. Use a non-zero distance value.

Example

use zesven::write::WriteFilter;

let filter = WriteFilter::delta(2); // 16-bit samples

impl WriteFilter

pub fn method_id(&self) -> Option<&'static [u8]>

Returns the 7z method ID bytes for this filter.

pub fn is_bcj2(&self) -> bool

Returns whether this is the BCJ2 filter.

BCJ2 requires special handling as it produces 4 output streams.

pub fn is_active(&self) -> bool

Returns whether this filter is active (not None).

pub fn properties(&self) -> Option<Vec<u8>>

Returns the filter properties to encode in the archive header.

Most BCJ filters have no properties. Delta filter has a 1-byte property encoding distance - 1 (so distance 1 is stored as 0, distance 255 as 254).

Trait Implementations

impl Clone for WriteFilter

fn clone(&self) -> WriteFilter

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for WriteFilter

impl Debug for WriteFilter

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for WriteFilter

fn default() -> WriteFilter

Returns the “default value” for a type.

impl Eq for WriteFilter

impl PartialEq for WriteFilter

fn eq(&self, other: &WriteFilter) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for WriteFilter