func()

in flexflate/deflate.go [150:204]

• 44 lines of code
• 17 McCabe index (conditional complexity)

func (d *compressor) findMatch(pos int, prevHead int, prevLength int, lookahead int) (length, offset int, ok bool) {
	minMatchLook := maxMatchLength
	if lookahead < minMatchLook {
		minMatchLook = lookahead
	}

	win := d.window[0 : pos+minMatchLook]

	// We quit when we get a match that's at least nice long
	nice := len(win) - pos
	if d.nice < nice {
		nice = d.nice
	}

	// If we've got a match that's good enough, only look in 1/4 the chain.
	tries := d.chain
	length = prevLength
	if length >= d.good {
		tries >>= 2
	}

	w0 := win[pos]
	w1 := win[pos+1]
	wEnd := win[pos+length]
	minIndex := pos - windowSize

	for i := prevHead; tries > 0; tries-- {
		if w0 == win[i] && w1 == win[i+1] && wEnd == win[i+length] {
			// The hash function ensures that if win[i] and win[i+1] match, win[i+2] matches

			n := 3
			for pos+n < len(win) && win[i+n] == win[pos+n] {
				n++
			}
			if n > length && (n > 3 || pos-i <= 4096) {
				length = n
				offset = pos - i
				ok = true
				if n >= nice {
					// The match is good enough that we don't try to find a better one.
					break
				}
				wEnd = win[pos+n]
			}
		}
		if i == minIndex {
			// hashPrev[i & windowMask] has already been overwritten, so stop now.
			break
		}
		if i = d.hashPrev[i&windowMask] - d.hashOffset; i < minIndex || i < 0 {
			break
		}
	}
	return
}