Basic Compression

examples/basic_compression.zig - the simplest zstd.compress / zstd.decompress usage.

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();

    // One allocator for the whole program; the library never creates its own.
    var input: std.ArrayList(u8) = .empty;
    defer input.deinit(allocator);
    try input.appendSlice(allocator, "Hello, Zstandard! This is a basic compression example with some repetitive data. ");
    for (0..5) |_| try input.appendSlice(allocator, "Hello, Zstandard! ");

    const compressed = try zstd.compress(allocator, input.items);
    defer allocator.free(compressed);
    std.debug.print("Original: {d} bytes\nCompressed: {d} bytes\nRatio: {d:.2}%\n", .{ input.items.len, compressed.len, @as(f64, @floatFromInt(compressed.len)) / @as(f64, @floatFromInt(input.items.len)) * 100 });
    const decompressed = try zstd.decompress(allocator, compressed);
    defer allocator.free(decompressed);
    std.debug.assert(std.mem.eql(u8, input.items, decompressed));
    std.debug.print("Round-trip verified: {d} bytes\n", .{decompressed.len});
}

Output

Original: 171 bytes
Compressed: 85 bytes
Ratio: 49.71%
Round-trip verified: 171 bytes

Note: small payloads may expand slightly due to frame header (magic, FHD, window) - ratio >100% is expected for tiny inputs. Larger inputs compress well.

Explanation

1. zstd.compress(allocator, input) - one-shot compression with default level 3, emits a full Zstandard frame (0xFD2FB528 magic, FHD, optional Frame_Content_Size, Window_Descriptor, Block_Header, Checksum).
2. zstd.decompress(allocator, compressed) - validates magic, parses FHD, decompresses Raw_Block/RLE_Block and verifies Content_Checksum if present.
3. Round-trip assert proves lossless.

Run:

zig build run-basic_compression