118 lines
2.3 KiB
Go
118 lines
2.3 KiB
Go
// Copyright 2018 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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package osp
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import (
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"encoding/binary"
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"errors"
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"io"
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)
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const (
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maxInt6 = 1<<5 - 1
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maxInt14 = 1<<13 - 1
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maxInt30 = 1<<29 - 1
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maxInt62 = 1<<63 - 1
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)
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// https://tools.ietf.org/html/draft-ietf-quic-transport-16#section-16
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func ReadVaruint(r io.Reader) (uint64, error) {
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b0, err := readByte(r)
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if err != nil {
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return 0, err
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}
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var a [8]byte
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b := a[:]
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e := binary.BigEndian
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b[0] = last6Bits(b0)
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switch first2Bits(b0) {
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case 0:
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return uint64(b[0]), nil
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case 1:
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err = readBytes(r, b[1:2])
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return uint64(e.Uint16(b)), err
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case 2:
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err = readBytes(r, b[1:4])
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return uint64(e.Uint32(b)), err
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case 3:
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err = readBytes(r, b[1:8])
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return uint64(e.Uint64(b)), err
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}
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return 0, nil
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}
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// https://tools.ietf.org/html/draft-ietf-quic-transport-16#section-16
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func WriteVaruint(v uint64, w io.Writer) error {
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var a [8]byte
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b := a[:]
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e := binary.BigEndian
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if v <= maxInt6 {
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b[0] = byte(v)
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setFirst2Bits(0, b)
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return writeBytes(b[:1], w)
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} else if v <= maxInt14 {
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e.PutUint16(b, uint16(v))
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setFirst2Bits(1, b)
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return writeBytes(b[:2], w)
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} else if v <= maxInt30 {
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e.PutUint32(b, uint32(v))
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setFirst2Bits(2, b)
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return writeBytes(b[:4], w)
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} else if v <= maxInt62 {
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e.PutUint64(b, v)
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setFirst2Bits(3, b)
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return writeBytes(b[:8], w)
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}
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return errors.New("Too big")
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}
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func first2Bits(b byte) byte {
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return b >> 6
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}
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func last6Bits(b byte) byte {
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return b & 0x3f // 0b00111111
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}
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func setFirst2Bits(first byte, b []byte) {
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b[0] = (first << 6) | b[0]
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}
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func readByte(r io.Reader) (byte, error) {
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var b [1]byte
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err := readBytes(r, b[:])
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return b[0], err
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}
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// Read len(b) bytes from r into b
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// If you hit an error (of the end), propogate the error from r.Read
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func readBytes(r io.Reader, b []byte) error {
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start := 0
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end := len(b)
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for start < end {
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n, err := r.Read(b[start:end])
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if err != nil {
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return err
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}
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start += n
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}
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return nil
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}
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// Write len(b) bytes from b to w
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// If you hit an error, propogate the error from w.Write
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func writeBytes(b []byte, w io.Writer) error {
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start := 0
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end := len(b)
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for start < end {
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n, err := w.Write(b[start:end])
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if err != nil {
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return err
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}
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start += n
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}
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return nil
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}
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