app-init

internal/navicat/parser.go

@@ -0,0 +1,116 @@
+package navicat
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+)
+
+type reader struct {
+	buf []byte
+	off int
+}
+
+func newReader(b []byte) *reader {
+	return &reader{buf: b}
+}
+
+func (r *reader) remaining() int {
+	return len(r.buf) - r.off
+}
+
+func (r *reader) peek() (byte, error) {
+	if r.off >= len(r.buf) {
+		return 0, io.EOF
+	}
+	return r.buf[r.off], nil
+}
+
+func (r *reader) readByte() (byte, error) {
+	if r.off >= len(r.buf) {
+		return 0, io.ErrUnexpectedEOF
+	}
+	b := r.buf[r.off]
+	r.off++
+	return b, nil
+}
+
+func (r *reader) readN(n int) ([]byte, error) {
+	if n < 0 {
+		return nil, fmt.Errorf("negative length")
+	}
+	if r.off+n > len(r.buf) {
+		return nil, io.ErrUnexpectedEOF
+	}
+	s := r.buf[r.off : r.off+n]
+	r.off += n
+	return s, nil
+}
+
+func (r *reader) u16() (uint16, error) {
+	b, err := r.readN(2)
+	if err != nil {
+		return 0, err
+	}
+	return binary.BigEndian.Uint16(b), nil
+}
+
+func (r *reader) u32() (uint32, error) {
+	b, err := r.readN(4)
+	if err != nil {
+		return 0, err
+	}
+	return binary.BigEndian.Uint32(b), nil
+}
+
+// block reads GetBlock. nullable allows 0xFF as SQL NULL (EchoData only).
+func (r *reader) block(nullable bool) (val []byte, isNull bool, err error) {
+	if r.off >= len(r.buf) {
+		return nil, false, io.ErrUnexpectedEOF
+	}
+	first := r.buf[r.off]
+	if nullable && first == markNull {
+		r.off++
+		return nil, true, nil
+	}
+	r.off++
+	var n int
+	if first < 254 {
+		n = int(first)
+	} else if first == markLong {
+		ln, err := r.u32()
+		if err != nil {
+			return nil, false, err
+		}
+		if ln > 64<<20 {
+			return nil, false, fmt.Errorf("block length %d exceeds 64MiB limit", ln)
+		}
+		n = int(ln)
+	} else {
+		return nil, false, fmt.Errorf("invalid block marker 0x%02x", first)
+	}
+	b, err := r.readN(n)
+	if err != nil {
+		return nil, false, err
+	}
+	return b, false, nil
+}
+
+func (r *reader) blockBytes() ([]byte, error) {
+	b, isNull, err := r.block(false)
+	if err != nil {
+		return nil, err
+	}
+	if isNull {
+		return nil, fmt.Errorf("unexpected NULL block")
+	}
+	return b, nil
+}
+
+func (r *reader) blockString() (string, error) {
+	b, err := r.blockBytes()
+	if err != nil {
+		return "", err
+	}
+	return string(b), nil
+}