diff --git a/lib/std/compress/zlib.zig b/lib/std/compress/zlib.zig index 722047812b..554f6f894b 100644 --- a/lib/std/compress/zlib.zig +++ b/lib/std/compress/zlib.zig @@ -64,3 +64,38 @@ pub const store = struct { return deflate.store.compressor(.zlib, writer); } }; + +test "should not overshoot" { + const std = @import("std"); + + // Compressed zlib data with extra 4 bytes at the end. + const data = [_]u8{ + 0x78, 0x9c, 0x73, 0xce, 0x2f, 0xa8, 0x2c, 0xca, 0x4c, 0xcf, 0x28, 0x51, 0x08, 0xcf, 0xcc, 0xc9, + 0x49, 0xcd, 0x55, 0x28, 0x4b, 0xcc, 0x53, 0x08, 0x4e, 0xce, 0x48, 0xcc, 0xcc, 0xd6, 0x51, 0x08, + 0xce, 0xcc, 0x4b, 0x4f, 0x2c, 0xc8, 0x2f, 0x4a, 0x55, 0x30, 0xb4, 0xb4, 0x34, 0xd5, 0xb5, 0x34, + 0x03, 0x00, 0x8b, 0x61, 0x0f, 0xa4, 0x52, 0x5a, 0x94, 0x12, + }; + + var stream = std.io.fixedBufferStream(data[0..]); + const reader = stream.reader(); + + var dcp = decompressor(reader); + var out: [128]u8 = undefined; + + // Decompress + var n = try dcp.reader().readAll(out[0..]); + + // Expected decompressed data + try std.testing.expectEqual(46, n); + try std.testing.expectEqualStrings("Copyright Willem van Schaik, Singapore 1995-96", out[0..n]); + + // Decompressor don't overshoot underlying reader. + // It is leaving it at the end of compressed data chunk. + try std.testing.expectEqual(data.len - 4, stream.getPos()); + try std.testing.expectEqual(0, dcp.unreadBytes()); + + // 4 bytes after compressed chunk are available in reader. + n = try reader.readAll(out[0..]); + try std.testing.expectEqual(n, 4); + try std.testing.expectEqualSlices(u8, data[data.len - 4 .. data.len], out[0..n]); +}