dwelling-radio/pkg/oggtag/oggtag.go

package oggtag

/* oggtag is a naive implementation of OGG tag's reader that is just looking
for certain tag names ending with an = character, e.g. artist= and title=.
*/

import (
	"bytes"
	"strings"
)

// OggGetTag is searching for a certain tag in a given buffer buf and returns
// its value.
//
// It is a simple implementation that doesn't parse a header and instead just
// looking for a certain tag preceded with three zero bytes and ends with
// an = character.
func OggGetTag(buf []byte, tag string) string {
	tagIdx := bytes.Index(buf, append([]byte{0, 0, 0}, (tag+"=")...))
	if tagIdx == -1 {
		tagIdx = bytes.Index(buf, append([]byte{0, 0, 0}, (strings.ToUpper(tag)+"=")...))
		if tagIdx == -1 {
			return ""
		}
	}
	tagIdx += 3
	tagNameLen := len(tag) + 1
	valStart := tagIdx + tagNameLen
	valLen := int(buf[tagIdx-4]) - tagNameLen
	return string(buf[valStart : valStart+valLen])
}