enhanced for wpx response transformer

transform.go

@@ -0,0 +1,82 @@
+package hodu
+
+import "bytes"
+import "golang.org/x/text/transform"
+
+type Transformer struct {
+	replacement []byte
+	needle []byte
+	needle_len int
+}
+
+func NewBytesTransformer(needle []byte, replacement []byte) *Transformer {
+	return &Transformer{needle: needle, replacement: replacement, needle_len: len(needle)}
+}
+
+func NewStringTransformer(needle string, replacement string) *Transformer {
+	return NewBytesTransformer([]byte(needle), []byte(replacement))
+}
+
+func (t *Transformer) Reset() {
+	// do nothing
+}
+
+func (t *Transformer) Transform(dst []byte, src []byte, at_eof bool) (int, int, error) {
+	var n int
+	var i int
+	var ndst int
+	var nsrc int
+	var rem int
+	var err error
+
+	if t.needle_len <= 0 {
+		n, err = t.copy_all(dst, src)
+		return n, n, err
+	}
+
+	nsrc = 0; ndst = 0
+	for {
+		i = bytes.Index(src[nsrc:], t.needle)
+		if i == -1 { break }
+
+		// copy the part before the match
+		n, err = t.copy_all(dst[ndst:], src[nsrc:nsrc+i])
+		nsrc += n; ndst += n
+		if err != nil { goto done }
+
+		// copy the new value in place of the match
+		n, err = t.copy_all(dst[ndst:], t.replacement)
+		if err != nil { goto done }
+		ndst += n; nsrc += t.needle_len
+	}
+
+	if at_eof {
+		n, err = t.copy_all(dst[ndst:], src[nsrc:])
+		ndst += n; nsrc += n
+		goto done
+	}
+
+	rem = len(src[nsrc:])
+	if rem >= t.needle_len {
+		n, err = t.copy_all(dst[ndst:], src[nsrc: nsrc + (rem - t.needle_len) + 1])
+		nsrc += n; ndst += n
+		if err != nil { goto done }
+	}
+
+	// ErrShortSrc means that the source buffer has insufficient data to
+	// complete the transformation.
+	err = transform.ErrShortSrc
+
+done:
+	return ndst, nsrc, err 
+}
+
+func (t *Transformer) copy_all(dst []byte, src []byte) (int, error) {
+	var n int
+	var err error
+	n = copy(dst, src)
+	// ErrShortDst means that the destination buffer was too short to
+	// receive all of the transformed bytes.
+	if n < len(src) { err = transform.ErrShortDst }
+	return n, err
+}