init: dec-music 项目初始化

decrypt/ximalaya/ximalaya.go

@@ -0,0 +1,57 @@
+package ximalaya
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	"jsuse.com/dev/dec-music/decrypt"
+	"jsuse.com/dev/dec-music/internal/sniff"
+)
+
+type decoder struct {
+	rd     io.ReadSeeker
+	offset int
+
+	audio io.Reader
+}
+
+func newDecoder(p *decrypt.DecoderParams) decrypt.Decoder {
+	return &decoder{rd: p.Reader}
+}
+
+func (d *decoder) Validate() error {
+	encryptedHeader := make([]byte, x2mHeaderSize)
+	if _, err := io.ReadFull(d.rd, encryptedHeader); err != nil {
+		return fmt.Errorf("ximalaya read header: %w", err)
+	}
+
+	{ // try to decode with x2m
+		header := decryptX2MHeader(encryptedHeader)
+		if _, ok := sniff.AudioExtension(header); ok {
+			d.audio = io.MultiReader(bytes.NewReader(header), d.rd)
+			return nil
+		}
+	}
+
+	{ // try to decode with x3m
+		// not read file again, since x2m and x3m have the same header size
+		header := decryptX3MHeader(encryptedHeader)
+		if _, ok := sniff.AudioExtension(header); ok {
+			d.audio = io.MultiReader(bytes.NewReader(header), d.rd)
+			return nil
+		}
+	}
+
+	return fmt.Errorf("ximalaya: unknown format")
+}
+
+func (d *decoder) Read(p []byte) (n int, err error) {
+	return d.audio.Read(p)
+}
+
+func init() {
+	decrypt.RegisterDecoder("x2m", false , newDecoder)
+	decrypt.RegisterDecoder("x3m", false , newDecoder)
+	decrypt.RegisterDecoder("xm", false , newDecoder)
+}