Method handleProcInstEncoding

xmlparser/decoder.go:456–489

handleProcInstEncoding replaces the encoding declaration in the processing instruction data with "UTF-8" and returns the updated data. It also recreates the reader with defined encoding.

(data []byte)

// with "UTF-8" and returns the updated data.
// It also recreates the reader with defined encoding.
func (d *Decoder) handleProcInstEncoding(data []byte) []byte {
	matches := encodingRE.FindSubmatch(data)
	if matches == nil {
		// No encoding declaration found, return original data without changes
		return data
	}

	// Get the encoding from the processing instruction data
	encoding := bytes.Trim(matches[2], `"'`)

	if bytes.EqualFold(encoding, []byte("utf-8")) || bytes.EqualFold(encoding, []byte("utf8")) {
		// No need for special handling if encoding is already UTF-8
		return data
	}

	// Recreate the reader with defined encoding.
	// If the encoding is UTF-16/32, we have already handled it in the BOM check.
	if len(encoding) < 3 || !bytes.EqualFold(encoding[:3], []byte("utf")) {
		if !d.setEncoding(string(encoding)) {
			return data
		}
	}

	// Build the updated data with "UTF-8" encoding.
	// We write it to the buffer that already contains the processing instruction data,
	// so we mark the position of the updated data start.
	start := d.buf.Len()
	d.buf.Write(matches[1])        // Up to encoding=
	d.buf.Write([]byte(`"UTF-8"`)) // New encoding
	d.buf.Write(matches[3])        // After encoding declaration
	updated := d.buf.Bytes()[start:]

	return updated
}

// readComment reads a comment (until `-->`).
func (d *Decoder) readComment() ([]byte, bool) {