init: dec-music 项目初始化

mmkv/internal/protobuffer.go

@@ -0,0 +1,41 @@
+package internal
+
+// ProtoBuffer decodes a subset of the protobuf wire format for MMKV payloads.
+
+type ProtoBuffer struct {
+	buf []byte
+	idx int
+}
+
+// NewProtoBuffer returns a buffer whose unread portion is buf.
+func NewProtoBuffer(buf []byte) *ProtoBuffer {
+	return &ProtoBuffer{buf: buf}
+}
+
+// DecodeStringBytes consumes a length-prefixed string.
+func (b *ProtoBuffer) DecodeStringBytes() (string, error) {
+	v, n := ConsumeString(b.buf[b.idx:])
+	if n < 0 {
+		return "", parseError(n)
+	}
+	b.idx += n
+	return v, nil
+}
+
+// DecodeRawBytes consumes a length-prefixed bytes field.
+func (b *ProtoBuffer) DecodeRawBytes(alloc bool) ([]byte, error) {
+	v, n := ConsumeBytes(b.buf[b.idx:])
+	if n < 0 {
+		return nil, parseError(n)
+	}
+	b.idx += n
+	if alloc {
+		v = append([]byte(nil), v...)
+	}
+	return v, nil
+}
+
+// Unread returns the unread portion of the buffer.
+func (b *ProtoBuffer) Unread() []byte {
+	return b.buf[b.idx:]
+}

mmkv/internal/wire.go

@@ -0,0 +1,65 @@
+package internal
+
+// Minimal protobuf wire helpers (bytes/string fields only).
+
+const (
+	errCodeOverflow = -2
+	errCodeTruncated = -1
+)
+
+func consumeVarint(b []byte) (uint64, int) {
+	var x uint64
+	var s uint
+	for i, c := range b {
+		if c < 0x80 {
+			if i > 9 || i == 9 && c > 1 {
+				return 0, errCodeOverflow
+			}
+			return x | uint64(c)<<s, i + 1
+		}
+		x |= uint64(c&0x7f) << s
+		s += 7
+	}
+	return 0, errCodeTruncated
+}
+
+// ConsumeBytes parses a length-delimited bytes field.
+func ConsumeBytes(b []byte) ([]byte, int) {
+	v, n := consumeVarint(b)
+	if n < 0 {
+		return nil, n
+	}
+	if v > uint64(len(b)-n) {
+		return nil, errCodeOverflow
+	}
+	return b[n : n+int(v)], n + int(v)
+}
+
+// ConsumeString parses a length-delimited string field.
+func ConsumeString(b []byte) (string, int) {
+	v, n := ConsumeBytes(b)
+	if n < 0 {
+		return "", n
+	}
+	return string(v), n
+}
+
+func parseError(code int) error {
+	switch code {
+	case errCodeOverflow:
+		return errOverflow
+	case errCodeTruncated:
+		return errTruncated
+	default:
+		return errTruncated
+	}
+}
+
+var (
+	errOverflow  = &parseErr{"overflow"}
+	errTruncated = &parseErr{"truncated"}
+)
+
+type parseErr struct{ msg string }
+
+func (e *parseErr) Error() string { return "protowire: " + e.msg }