Function patchDelta

plumbing/format/packfile/patch_delta.go:251–324

(dst *bytes.Buffer, src, delta []byte)

}

func patchDelta(dst *bytes.Buffer, src, delta []byte) error {
	srcSz, delta, err := decodeLEB128(delta)
	if err != nil {
		return fmt.Errorf("%w: %w", ErrInvalidDelta, err)
	}
	if srcSz != uint(len(src)) {
		return ErrInvalidDelta
	}

	targetSz, delta, err := decodeLEB128(delta)
	if err != nil {
		return fmt.Errorf("%w: %w", ErrInvalidDelta, err)
	}
	remainingTargetSz := targetSz

	growSz := min(targetSz, maxPatchPreemptionSize)
	dst.Grow(int(growSz))

	for remainingTargetSz > 0 {
		if len(delta) == 0 {
			return ErrInvalidDelta
		}

		cmd := delta[0]
		delta = delta[1:]

		switch {
		case isCopyFromSrc(cmd):
			var offset, sz uint
			var err error
			offset, delta, err = decodeOffset(cmd, delta)
			if err != nil {
				return err
			}

			sz, delta, err = decodeSize(cmd, delta)
			if err != nil {
				return err
			}

			if invalidSize(sz, remainingTargetSz) ||
				invalidOffsetSize(offset, sz, srcSz) {
				return ErrInvalidDelta
			}
			dst.Write(src[offset : offset+sz])
			remainingTargetSz -= sz

		case isCopyFromDelta(cmd):
			sz := uint(cmd) // cmd is the size itself
			if invalidSize(sz, remainingTargetSz) {
				return ErrInvalidDelta
			}

			if uint(len(delta)) < sz {
				return ErrInvalidDelta
			}

			dst.Write(delta[0:sz])