Function Unescape

escape.go:135–182

unescape unescapes the string contained in 'in' and returns it as a slice. If 'in' contains no escaped characters: Returns 'in'. Else, if 'out' is of sufficient capacity (guaranteed if cap(out) >= len(in)): 'out' is used to build the unescaped string and is returned with no extra allocation Else: A

(in, out []byte)

// Else:
//   A new slice is allocated and returned.
func Unescape(in, out []byte) ([]byte, error) {
	firstBackslash := bytes.IndexByte(in, '\\')
	if firstBackslash == -1 {
		return in, nil
	}

	// Get a buffer of sufficient size (allocate if needed)
	if cap(out) < len(in) {
		out = make([]byte, len(in))
	} else {
		out = out[0:len(in)]
	}

	// Copy the first sequence of unescaped bytes to the output and obtain a buffer pointer (subslice)
	copy(out, in[:firstBackslash])
	in = in[firstBackslash:]
	buf := out[firstBackslash:]

	// The loop always exits via break: either on error (MalformedStringEscapeError)
	// or after copying the final non-escaped tail. The former `for len(in) > 0`
	// guard was structurally always true on re-entry since the else branch always
	// leaves at least the backslash character in `in`.
	for {
		// Unescape the next escaped character
		inLen, bufLen := unescapeToUTF8(in, buf)
		if inLen == -1 {
			return nil, MalformedStringEscapeError
		}

		in = in[inLen:]
		buf = buf[bufLen:]

		// Copy everything up until the next backslash
		nextBackslash := bytes.IndexByte(in, '\\')
		if nextBackslash == -1 {
			copy(buf, in)
			buf = buf[len(in):]
			break
		} else {
			copy(buf, in[:nextBackslash])
			buf = buf[nextBackslash:]
			in = in[nextBackslash:]
		}
	}

	// Trim the out buffer to the amount that was actually emitted
	return out[:len(out)-len(buf)], nil
}