Method tryWriteCopy

flate/dict_decoder.go:151–169

tryWriteCopy tries to copy a string at a given (distance, length) to the output. This specialized version is optimized for short distances. This method is designed to be inlined for performance reasons. This invariant must be kept: 0 < dist <= histSize()

(dist, length int)

//
// This invariant must be kept: 0 < dist <= histSize()
func (dd *dictDecoder) tryWriteCopy(dist, length int) int {
	dstPos := dd.wrPos
	endPos := dstPos + length
	if dstPos < dist || endPos > len(dd.hist) {
		return 0
	}
	dstBase := dstPos
	srcPos := dstPos - dist

	// Copy possibly overlapping section before destination position.
loop:
	dstPos += copy(dd.hist[dstPos:endPos], dd.hist[srcPos:dstPos])
	if dstPos < endPos {
		goto loop // Avoid for-loop so that this function can be inlined
	}

	dd.wrPos = dstPos
	return dstPos - dstBase
}

// appendWindow appends the current sliding window (up to len(hist) most recent
// bytes, oldest first) to dst.