Method MaxEncodedSize

zstd/encoder.go:843–873

MaxEncodedSize returns the expected maximum size of an encoded block or stream.

(size int)

// MaxEncodedSize returns the expected maximum
// size of an encoded block or stream.
func (e *Encoder) MaxEncodedSize(size int) int {
	frameHeader := 4 + 2 // magic + frame header & window descriptor
	if e.o.dict != nil {
		frameHeader += 4
	}
	// Frame content size:
	if size < 256 {
		frameHeader++
	} else if size < 65536+256 {
		frameHeader += 2
	} else if size < math.MaxInt32 {
		frameHeader += 4
	} else {
		frameHeader += 8
	}
	// Final crc
	if e.o.crc {
		frameHeader += 4
	}

	// Max overhead is 3 bytes/block.
	// There cannot be 0 blocks.
	blocks := (size + e.o.blockSize) / e.o.blockSize

	// Combine, add padding.
	maxSz := frameHeader + 3*blocks + size
	if e.o.pad > 1 {
		maxSz += calcSkippableFrame(int64(maxSz), int64(e.o.pad))
	}
	return maxSz
}