Errors

lz4.zig returns typed, structured errors from the unified lz4.Error error set:

pub const Error = CompressionError || DecompressionError || FrameError;

---

lz4.CompressionError

Error	Description
DstCapacityTooSmall	Destination buffer is too small to receive compressed output.
InputTooLarge	Uncompressed input exceeds format limits (2,113,929,216 bytes).
CorruptInput	Input contains invalid sequences for the selected compression mode.
OutOfMemory	System allocator failed to allocate internal context buffers.

---

lz4.DecompressionError

Error	Description
MalformedInput	Input is corrupted, has illegal tokens, or violates LZ4 grammar.
OffsetOutOfBounds	Back-reference match offset is zero or points before the start of available history.
CorruptLiteralLength	Variable-length literal run was truncated or overflowed.
CorruptMatchLength	Variable-length match extension was truncated or overflowed.
DstCapacityTooSmall	Caller output buffer capacity exhausted before decompression completed.
SourceBufferExhausted	Compressed input ended abruptly in the middle of a sequence.
UnexpectedEndOfStream	Unexpected termination or missing required 5 trailing literal bytes.
OutOfMemory	System allocator failed during buffer growth.

---

lz4.FrameError

Error	Description
InvalidMagic	First 4 bytes do not match 0x184D2204 or skippable frame magics.
UnsupportedVersion	Frame version field is not 01b.
ReservedBitsNonZero	Reserved descriptor bits were non-zero.
HeaderChecksumMismatch	1-byte descriptor checksum failed verification.
BlockChecksumMismatch	4-byte block checksum failed verification.
ContentChecksumMismatch	4-byte content xxHash-32 failed verification.
InvalidBlockMaxSize	Descriptor block max size is not in 4..7 (64KB..4MB).
BlockSizeTooLarge	Block size declared in frame exceeds descriptor limit.
MissingEndMark	Expected 4-byte 0x00000000 EndMark was not found.
PrematureEndOfFrame	Frame truncated before reading block, EndMark, or footer.
DictionaryMismatch	Frame requires a dictionary ID that does not match provided dictionary.
CorruptFrame	Corrupt block payload inside frame container.

---

Idiomatic Error Handling

const std = @import("std");
const lz4 = @import("lz4");

pub fn processInput(allocator: std.mem.Allocator, data: []const u8) !void {
    const uncompressed = lz4.decompress(allocator, data) catch |err| switch (err) {
        error.InvalidMagic => {
            std.debug.print("Not an LZ4 file or unsupported header\n", .{});
            return;
        },
        error.ContentChecksumMismatch, error.BlockChecksumMismatch => {
            std.debug.print("Data integrity check failed: corrupt payload\n", .{});
            return;
        },
        error.MalformedInput, error.OffsetOutOfBounds => {
            std.debug.print("Malformed LZ4 block data\n", .{});
            return;
        },
        error.OutOfMemory => return err,
        else => {
            std.debug.print("Decompression error: {}\n", .{err});
            return err;
        },
    };
    defer allocator.free(uncompressed);
}