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server/vendor/github.com/pion/sctp/chunkheader.go

@@ -0,0 +1,100 @@
+// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
+// SPDX-License-Identifier: MIT
+
+package sctp
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+)
+
+/*
+chunkHeader represents a SCTP Chunk header, defined in https://tools.ietf.org/html/rfc4960#section-3.2
+The figure below illustrates the field format for the chunks to be
+transmitted in the SCTP packet.  Each chunk is formatted with a Chunk
+Type field, a chunk-specific Flag field, a Chunk Length field, and a
+Value field.
+
+	 0                   1                   2                   3
+	 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	|   Chunk Type  | Chunk  Flags  |        Chunk Length           |
+	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	|                                                               |
+	|                          Chunk Value                          |
+	|                                                               |
+	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+*/
+type chunkHeader struct {
+	typ   chunkType
+	flags byte
+	raw   []byte
+}
+
+const (
+	chunkHeaderSize = 4
+)
+
+// SCTP chunk header errors
+var (
+	ErrChunkHeaderTooSmall       = errors.New("raw is too small for a SCTP chunk")
+	ErrChunkHeaderNotEnoughSpace = errors.New("not enough data left in SCTP packet to satisfy requested length")
+	ErrChunkHeaderPaddingNonZero = errors.New("chunk padding is non-zero at offset")
+)
+
+func (c *chunkHeader) unmarshal(raw []byte) error {
+	if len(raw) < chunkHeaderSize {
+		return fmt.Errorf("%w: raw only %d bytes, %d is the minimum length", ErrChunkHeaderTooSmall, len(raw), chunkHeaderSize)
+	}
+
+	c.typ = chunkType(raw[0])
+	c.flags = raw[1]
+	length := binary.BigEndian.Uint16(raw[2:])
+
+	// Length includes Chunk header
+	valueLength := int(length - chunkHeaderSize)
+	lengthAfterValue := len(raw) - (chunkHeaderSize + valueLength)
+
+	if lengthAfterValue < 0 {
+		return fmt.Errorf("%w: remain %d req %d ", ErrChunkHeaderNotEnoughSpace, valueLength, len(raw)-chunkHeaderSize)
+	} else if lengthAfterValue < 4 {
+		// https://tools.ietf.org/html/rfc4960#section-3.2
+		// The Chunk Length field does not count any chunk padding.
+		// Chunks (including Type, Length, and Value fields) are padded out
+		// by the sender with all zero bytes to be a multiple of 4 bytes
+		// long.  This padding MUST NOT be more than 3 bytes in total.  The
+		// Chunk Length value does not include terminating padding of the
+		// chunk.  However, it does include padding of any variable-length
+		// parameter except the last parameter in the chunk.  The receiver
+		// MUST ignore the padding.
+		for i := lengthAfterValue; i > 0; i-- {
+			paddingOffset := chunkHeaderSize + valueLength + (i - 1)
+			if raw[paddingOffset] != 0 {
+				return fmt.Errorf("%w: %d ", ErrChunkHeaderPaddingNonZero, paddingOffset)
+			}
+		}
+	}
+
+	c.raw = raw[chunkHeaderSize : chunkHeaderSize+valueLength]
+	return nil
+}
+
+func (c *chunkHeader) marshal() ([]byte, error) {
+	raw := make([]byte, 4+len(c.raw))
+
+	raw[0] = uint8(c.typ)
+	raw[1] = c.flags
+	binary.BigEndian.PutUint16(raw[2:], uint16(len(c.raw)+chunkHeaderSize))
+	copy(raw[4:], c.raw)
+	return raw, nil
+}
+
+func (c *chunkHeader) valueLength() int {
+	return len(c.raw)
+}
+
+// String makes chunkHeader printable
+func (c chunkHeader) String() string {
+	return c.typ.String()
+}