Constants

All constants are exposed as top-level aliases (not under zstd.constants).

Top-Level Aliases

pub const MAGICNUMBER: u32 = 0xFD2FB528;
pub const MAGIC_DICTIONARY: u32 = 0xEC30A437;
pub const MAGIC_SKIPPABLE_START: u32 = 0x184D2A50;
pub const MAGIC_SKIPPABLE_MASK: u32 = 0xFFFFFFF0;
pub const BLOCKSIZE_MAX: usize = 1 << 17; // 131072
pub const CONTENTSIZE_UNKNOWN: u64 = 0xFFFFFFFFFFFFFFFF - 1;
pub const CONTENTSIZE_ERROR: u64 = 0xFFFFFFFFFFFFFFFF - 2;
pub const CLEVEL_DEFAULT: i32 = 3;
pub const MAX_INPUT_SIZE: usize = 0xFF00FF00FF00FF00 (64-bit) or 0xFF00FF00 (32-bit);

Usage:

const zstd = @import("zstd");

if (data.len >= 4) {
    const magic = std.mem.readInt(u32, data[0..4], .little);
    if (magic == zstd.MAGICNUMBER) { /* zstd frame */ }
    if ((magic & zstd.MAGIC_SKIPPABLE_MASK) == zstd.MAGIC_SKIPPABLE_START) { /* skippable */ }
}
const max_block = zstd.BLOCKSIZE_MAX; // 131072
if (zstd.getFrameContentSize(data) == zstd.CONTENTSIZE_UNKNOWN) { /* ... */ }

Magic Numbers

Constant	Value	Description
magic_number	0xFD2FB528	Zstandard frame magic number
magic_dictionary	0xEC30A437	Dictionary format magic number
magic_skippable_start	0x184D2A50	Skippable frame start magic
magic_skippable_mask	0xFFFFFFF0	Mask for skippable frame detection

Sizes and Limits

Constant	Value	Description
blockSizeMax	131072 (128 KB)	Maximum block size (1 << 17)
block_size_log_max	17	Log2 of maximum block size
contentsize_unknown	0xFFFFFFFFFFFFFFFF - 1	Sentinel for unknown content size
contentsize_error	0xFFFFFFFFFFFFFFFF - 2	Sentinel for content size error
max_input_size	platform-dependent	Maximum input size
window_log_min/max	10 / 30 (32-bit) or 31 (64-bit)	Window log range
c_level_min/max/default	-131072 / 22 / 3	Compression level range

Version (, 134-151)

pub const version: []const u8 = "1.6.0";
pub const version_number: u32 = 1*100*100 + 6*100 + 0; // 10600

pub fn versionString() []const u8 // "1.6.0"
pub fn versionNumber() u32         // 10600
pub fn minCLevel() i32             // -131072
pub fn maxCLevel() i32             // 22
pub fn defaultCLevel() i32         // 3

std.debug.print("Version: {s}\n", .{zstd.versionString()});
std.debug.print("Number: {d}\n", .{zstd.versionNumber()});
std.debug.print("Default level: {d}\n", .{zstd.defaultCLevel()});

Version Constants

Constant	Value	Description
zstd.version	"0.0.4"	This library's release version, as a comptime string
zstd.versionString()	"0.0.4"	The same string, as a function
zstd.versionNumber()	4	major*100*100 + minor*100 + patch for 0.0.4
zstd.specVersionString()	"1.6.0"	Zstandard format specification implemented
zstd.specVersionNumber()	10600	major*100*100 + minor*100 + patch for 1.6.0

zstd.version and zstd.versionString() both report the library; the spec* pair reports the format it reads and writes. They move independently, so a reader that needs the format version must use the spec* pair.

Level Constants

Constant	Value	Description
zstd.minCLevel()	-131072	Lowest accepted level (fastest)
zstd.maxCLevel()	22	Highest accepted level
zstd.defaultCLevel()	3	Level used when none is given
zstd.CLEVEL_DEFAULT	3	The same default, as a constant

Levels are plain i32, not an enum, matching the specification's own range.