Method EncodeNoHist

zstd/enc_fast.go:294–531

EncodeNoHist will encode a block with no history and no following blocks. Most notable difference is that src will not be copied for history and we do not need to check for max match length.

(blk *blockEnc, src []byte)

// Most notable difference is that src will not be copied for history and
// we do not need to check for max match length.
func (e *fastEncoder) EncodeNoHist(blk *blockEnc, src []byte) {
	const (
		inputMargin            = 8
		minNonLiteralBlockSize = 1 + 1 + inputMargin
	)
	if debugEncoder {
		if len(src) > maxCompressedBlockSize {
			panic("src too big")
		}
	}

	// Protect against e.cur wraparound.
	if e.cur >= e.bufferReset {
		for i := range e.table[:] {
			e.table[i] = tableEntry{}
		}
		e.cur = e.maxMatchOff
	}

	s := int32(0)
	blk.size = len(src)
	if len(src) < minNonLiteralBlockSize {
		blk.extraLits = len(src)
		blk.literals = blk.literals[:len(src)]
		copy(blk.literals, src)
		return
	}

	sLimit := int32(len(src)) - inputMargin
	// stepSize is the number of bytes to skip on every main loop iteration.
	// It should be >= 2.
	const stepSize = 2

	// TEMPLATE
	const hashLog = tableBits
	// seems global, but would be nice to tweak.
	const kSearchStrength = 6

	// nextEmit is where in src the next emitLiteral should start from.
	nextEmit := s
	cv := load6432(src, s)

	// Relative offsets
	offset1 := int32(blk.recentOffsets[0])
	offset2 := int32(blk.recentOffsets[1])

	addLiterals := func(s *seq, until int32) {
		if until == nextEmit {
			return
		}
		blk.literals = append(blk.literals, src[nextEmit:until]...)
		s.litLen = uint32(until - nextEmit)
	}
	if debugEncoder {
		println("recent offsets:", blk.recentOffsets)
	}

encodeLoop: