CompressionContext

A reusable compression context. Create once, compress multiple buffers with the same settings. Defined in src/compress/context.zig:6 and re-exported as zstd.CompressionContext (src/zstd.zig:23).

Definition

pub const CompressionContext = struct {
    allocator: std.mem.Allocator,
    options: CompressionOptions,
    stream: StreamingCompressor,
    // ...
};

Methods

init

Create with default level (3):

pub fn init(allocator: std.mem.Allocator) CompressionContext

var cctx = zstd.CompressionContext.init(allocator);
defer cctx.deinit();

initWithLevel

Create with numeric i32 level:

pub fn initWithLevel(allocator: std.mem.Allocator, level: i32) CompressionContext

var cctx = zstd.CompressionContext.initWithLevel(allocator, 9);
defer cctx.deinit();

deinit

Release streaming buffer:

pub fn deinit(self: *CompressionContext) void

setLevel

Change compression level:

pub fn setLevel(self: *CompressionContext, level: i32) void

cctx.setLevel(5);

setChecksum

Enable/disable checksum:

pub fn setChecksum(self: *CompressionContext, flag: bool) void

setWindowLog

Set window log override:

pub fn setWindowLog(self: *CompressionContext, log: u8) void

setPledgedSrcSize

Set content size for frame header:

pub fn setPledgedSrcSize(self: *CompressionContext, size: ?u64) void

cctx.setPledgedSrcSize(@as(?u64, data.len));
cctx.setPledgedSrcSize(null); // unknown

compress

Compress into pre-allocated buffer:

pub fn compress(self: *CompressionContext, dst: []u8, src: []const u8) !usize

var buf: [4096]u8 = undefined;
const written = try cctx.compress(&buf, data);

compressAlloc

Compress with allocator (convenience):

pub fn compressAlloc(self: *CompressionContext, src: []const u8) anyerror![]u8

const compressed = try cctx.compressAlloc(data);
defer allocator.free(compressed);

reset

Reset streaming state for reuse:

pub fn reset(self: *CompressionContext) void

cctx.reset();

Example

var cctx = zstd.CompressionContext.init(allocator);
defer cctx.deinit();

// First compression (default 3)
const c1 = try cctx.compressAlloc(data1);
defer allocator.free(c1);

// Change level and compress again
cctx.setLevel(9);
cctx.setChecksum(true);
const c2 = try cctx.compressAlloc(data2);
defer allocator.free(c2);

// Into fixed buffer
var buf: [8192]u8 = undefined;
const n = try cctx.compress(&buf, data3);

Removed names: old Compressor, Compressor.init(opts: CompressOptions), compressAlloc(alloc,src), compress2(dst,src), setParameter(.compression_level, .checksum_flag), reset(ResetDirective) are replaced by the CompressionContext API above.