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45 lines
1.1 KiB
45 lines
1.1 KiB
3 years ago
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package codec
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import (
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"encoding/binary"
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"io"
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"github.com/go-faster/errors"
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"github.com/gotd/td/bin"
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)
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// Codec is MTProto transport protocol encoding abstraction.
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type Codec interface {
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// WriteHeader sends protocol tag if needed.
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WriteHeader(w io.Writer) error
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// ReadHeader reads protocol tag if needed.
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ReadHeader(r io.Reader) error
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// Write encode to writer message from given buffer.
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Write(w io.Writer, b *bin.Buffer) error
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// Read fills buffer with received message.
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Read(r io.Reader, b *bin.Buffer) error
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}
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// TaggedCodec is codec with protocol tag.
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type TaggedCodec interface {
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Codec
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// ObfuscatedTag returns protocol tag for obfuscation.
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ObfuscatedTag() [4]byte
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}
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// readLen reads 32-bit integer and validates it as message length.
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func readLen(r io.Reader, b *bin.Buffer) (int, error) {
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b.ResetN(bin.Word)
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if _, err := io.ReadFull(r, b.Buf[:bin.Word]); err != nil {
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return 0, errors.Wrap(err, "read length")
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}
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n := int(binary.LittleEndian.Uint32(b.Buf[:bin.Word]))
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if n <= 0 || n > maxMessageSize {
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return 0, invalidMsgLenErr{n: n}
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}
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return n, nil
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}
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