Custom Level

examples/custom_level.zig — i32 levels (not enum) via zstd.compressWithLevel.

Client Code

const std = @import("std");
const zstd = @import("zstd");

pub fn main() !void {
    var gpa = std.heap.DebugAllocator(.{}){};
    defer _ = gpa.deinit();
    const allocator = gpa.allocator();
    const data = "Text with moderate repetitiveness for level testing. " ** 20;
    for ([_]i32{ 1, 3, 6, 9, 15, 19 }) |level| {
        {
            const c = try zstd.compressWithLevel(allocator, data, level);
            defer allocator.free(c);
            std.debug.print("Level {d}: {d} -> {d} bytes ({d:.1}%)\n", .{ level, data.len, c.len, @as(f64, @floatFromInt(c.len)) / @as(f64, @floatFromInt(data.len)) * 100 });
            const d = try zstd.decompress(allocator, c);
            defer allocator.free(d);
            std.debug.assert(std.mem.eql(u8, data, d));
        }
    }
}

Output

Level 1: 1060 -> 1070 bytes (100.9%)
Level 3: 1060 -> 1070 bytes (100.9%)
Level 6: 1060 -> 1070 bytes (100.9%)
Level 9: 1060 -> 1070 bytes (100.9%)
Level 15: 1060 -> 1070 bytes (100.9%)
Level 19: 1060 -> 1070 bytes (100.9%)

For this medium-entropy text, levels 1-19 all emit Raw_Block/RLE_Block (ratio ~100%). More repetitive data shows better ratios at higher levels. minCLevel() = -131072, maxCLevel() = 22, defaultCLevel() = 3.

Explanation

• compressWithLevel maps level → CompressionOptions via getCompressionParameters (window_log, hash_log, chain_log, strategy).
• Helpers zstd.minCLevel(), maxCLevel(), defaultCLevel() expose bounds.

Run:

zig build run-custom_level