func()

in flexflate/deflate.go [228:360]

• 115 lines of code
• 42 McCabe index (conditional complexity)

func (d *compressor) deflate() {
	if d.windowEnd-d.index < minMatchLength+maxMatchLength && !d.sync {
		return
	}

	d.maxInsertIndex = d.windowEnd - (minMatchLength - 1)
	if d.index < d.maxInsertIndex {
		d.hash = int(d.window[d.index])<<hashShift + int(d.window[d.index+1])
	}

Loop:
	for {
		if d.index > d.windowEnd {
			panic("index > windowEnd")
		}
		lookahead := d.windowEnd - d.index
		if lookahead < minMatchLength+maxMatchLength {
			if !d.sync {
				break Loop
			}
			if d.index > d.windowEnd {
				panic("index > windowEnd")
			}
			if lookahead == 0 {
				// Flush current output block if any.
				if d.byteAvailable {
					// There is still one pending token that needs to be flushed
					d.tokens = append(d.tokens, literalToken(uint32(d.window[d.index-1])))
					d.byteAvailable = false
				}
				if len(d.tokens) > 0 {
					if d.err = d.writeBlock(d.tokens, d.index, false); d.err != nil {
						return
					}
					d.tokens = d.tokens[:0]
				}
				break Loop
			}
		}
		if d.index < d.maxInsertIndex {
			// Update the hash
			d.hash = (d.hash<<hashShift + int(d.window[d.index+2])) & hashMask
			d.chainHead = d.hashHead[d.hash]
			d.hashPrev[d.index&windowMask] = d.chainHead
			d.hashHead[d.hash] = d.index + d.hashOffset
		}
		prevLength := d.length
		prevOffset := d.offset
		d.length = minMatchLength - 1
		d.offset = 0
		minIndex := d.index - windowSize
		if minIndex < 0 {
			minIndex = 0
		}

		if d.chainHead-d.hashOffset >= minIndex &&
			(d.fastSkipHashing != skipNever && lookahead > minMatchLength-1 ||
				d.fastSkipHashing == skipNever && lookahead > prevLength && prevLength < d.lazy) {
			if newLength, newOffset, ok := d.findMatch(d.index, d.chainHead-d.hashOffset, minMatchLength-1, lookahead); ok {
				d.length = newLength
				d.offset = newOffset
			}
		}
		if d.fastSkipHashing != skipNever && d.length >= minMatchLength ||
			d.fastSkipHashing == skipNever && prevLength >= minMatchLength && d.length <= prevLength {
			// There was a match at the previous step, and the current match is
			// not better. Output the previous match.
			if d.fastSkipHashing != skipNever {
				d.tokens = append(d.tokens, matchToken(uint32(d.length-minMatchLength), uint32(d.offset-minOffsetSize)))
			} else {
				d.tokens = append(d.tokens, matchToken(uint32(prevLength-minMatchLength), uint32(prevOffset-minOffsetSize)))
			}
			// Insert in the hash table all strings up to the end of the match.
			// index and index-1 are already inserted. If there is not enough
			// lookahead, the last two strings are not inserted into the hash
			// table.
			if d.length <= d.fastSkipHashing {
				var newIndex int
				if d.fastSkipHashing != skipNever {
					newIndex = d.index + d.length
				} else {
					newIndex = d.index + prevLength - 1
				}
				for d.index++; d.index < newIndex; d.index++ {
					if d.index < d.maxInsertIndex {
						d.hash = (d.hash<<hashShift + int(d.window[d.index+2])) & hashMask
						// Get previous value with the same hash.
						// Our chain should point to the previous value.
						d.hashPrev[d.index&windowMask] = d.hashHead[d.hash]
						// Set the head of the hash chain to us.
						d.hashHead[d.hash] = d.index + d.hashOffset
					}
				}
				if d.fastSkipHashing == skipNever {
					d.byteAvailable = false
					d.length = minMatchLength - 1
				}
			} else {
				// For matches this long, we don't bother inserting each individual
				// item into the table.
				d.index += d.length
				if d.index < d.maxInsertIndex {
					d.hash = (int(d.window[d.index])<<hashShift + int(d.window[d.index+1]))
				}
			}
			if len(d.tokens) == maxFlateBlockTokens {
				// The block includes the current character
				if d.err = d.writeBlock(d.tokens, d.index, false); d.err != nil {
					return
				}
				d.tokens = d.tokens[:0]
			}
		} else {
			if d.fastSkipHashing != skipNever || d.byteAvailable {
				i := d.index - 1
				if d.fastSkipHashing != skipNever {
					i = d.index
				}
				d.tokens = append(d.tokens, literalToken(uint32(d.window[i])))
				if len(d.tokens) == maxFlateBlockTokens {
					if d.err = d.writeBlock(d.tokens, i+1, false); d.err != nil {
						return
					}
					d.tokens = d.tokens[:0]
				}
			}
			d.index++
			if d.fastSkipHashing == skipNever {
				d.byteAvailable = true
			}
		}
	}
}