return gotIdx
	}
}

// compressSelfTest performs a self-test to ensure that compression
// algorithms completes a roundtrip. If any algorithm
// produces an incorrect checksum it fails with a hard error.
//
// compressSelfTest tries to catch any issue in the compression implementation
// early instead of silently corrupting data.
func compressSelfTest() {
	// 4 MB block.
	// Approx runtime ~30ms