Function resizeMap

msgp/edit.go:189–242

delta is delta on map size

(raw []byte, delta int64)

// delta is delta on map size
func resizeMap(raw []byte, delta int64) []byte {
	var sz int64
	switch raw[0] {
	case mmap16:
		sz = int64(big.Uint16(raw[1:]))
		if sz+delta <= math.MaxUint16 {
			big.PutUint16(raw[1:], uint16(sz+delta))
			return raw
		}
		if cap(raw)-len(raw) >= 2 {
			raw = raw[0 : len(raw)+2]
			copy(raw[5:], raw[3:])
			raw[0] = mmap32
			big.PutUint32(raw[1:], uint32(sz+delta))
			return raw
		}
		n := make([]byte, 0, len(raw)+5)
		n = AppendMapHeader(n, uint32(sz+delta))
		return append(n, raw[3:]...)

	case mmap32:
		sz = int64(big.Uint32(raw[1:]))
		big.PutUint32(raw[1:], uint32(sz+delta))
		return raw

	default:
		sz = int64(rfixmap(raw[0]))
		if sz+delta < 16 {
			raw[0] = wfixmap(uint8(sz + delta))
			return raw
		} else if sz+delta <= math.MaxUint16 {
			if cap(raw)-len(raw) >= 2 {
				raw = raw[0 : len(raw)+2]
				copy(raw[3:], raw[1:])
				raw[0] = mmap16
				big.PutUint16(raw[1:], uint16(sz+delta))
				return raw
			}
			n := make([]byte, 0, len(raw)+5)
			n = AppendMapHeader(n, uint32(sz+delta))
			return append(n, raw[1:]...)
		}
		if cap(raw)-len(raw) >= 4 {
			raw = raw[0 : len(raw)+4]
			copy(raw[5:], raw[1:])
			raw[0] = mmap32
			big.PutUint32(raw[1:], uint32(sz+delta))
			return raw
		}
		n := make([]byte, 0, len(raw)+5)
		n = AppendMapHeader(n, uint32(sz+delta))
		return append(n, raw[1:]...)
	}
}