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1// Copyright 2014 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// Defensive debug-only utility to track that functions run on the
6// goroutine that they're supposed to.
7
8package http2
9
10import (
11	"bytes"
12	"errors"
13	"fmt"
14	"os"
15	"runtime"
16	"strconv"
17	"sync"
18)
19
20var DebugGoroutines = os.Getenv("DEBUG_HTTP2_GOROUTINES") == "1"
21
22type goroutineLock uint64
23
24func newGoroutineLock() goroutineLock {
25	if !DebugGoroutines {
26		return 0
27	}
28	return goroutineLock(curGoroutineID())
29}
30
31func (g goroutineLock) check() {
32	if !DebugGoroutines {
33		return
34	}
35	if curGoroutineID() != uint64(g) {
36		panic("running on the wrong goroutine")
37	}
38}
39
40func (g goroutineLock) checkNotOn() {
41	if !DebugGoroutines {
42		return
43	}
44	if curGoroutineID() == uint64(g) {
45		panic("running on the wrong goroutine")
46	}
47}
48
49var goroutineSpace = []byte("goroutine ")
50
51func curGoroutineID() uint64 {
52	bp := littleBuf.Get().(*[]byte)
53	defer littleBuf.Put(bp)
54	b := *bp
55	b = b[:runtime.Stack(b, false)]
56	// Parse the 4707 out of "goroutine 4707 ["
57	b = bytes.TrimPrefix(b, goroutineSpace)
58	i := bytes.IndexByte(b, ' ')
59	if i < 0 {
60		panic(fmt.Sprintf("No space found in %q", b))
61	}
62	b = b[:i]
63	n, err := parseUintBytes(b, 10, 64)
64	if err != nil {
65		panic(fmt.Sprintf("Failed to parse goroutine ID out of %q: %v", b, err))
66	}
67	return n
68}
69
70var littleBuf = sync.Pool{
71	New: func() interface{} {
72		buf := make([]byte, 64)
73		return &buf
74	},
75}
76
77// parseUintBytes is like strconv.ParseUint, but using a []byte.
78func parseUintBytes(s []byte, base int, bitSize int) (n uint64, err error) {
79	var cutoff, maxVal uint64
80
81	if bitSize == 0 {
82		bitSize = int(strconv.IntSize)
83	}
84
85	s0 := s
86	switch {
87	case len(s) < 1:
88		err = strconv.ErrSyntax
89		goto Error
90
91	case 2 <= base && base <= 36:
92		// valid base; nothing to do
93
94	case base == 0:
95		// Look for octal, hex prefix.
96		switch {
97		case s[0] == '0' && len(s) > 1 && (s[1] == 'x' || s[1] == 'X'):
98			base = 16
99			s = s[2:]
100			if len(s) < 1 {
101				err = strconv.ErrSyntax
102				goto Error
103			}
104		case s[0] == '0':
105			base = 8
106		default:
107			base = 10
108		}
109
110	default:
111		err = errors.New("invalid base " + strconv.Itoa(base))
112		goto Error
113	}
114
115	n = 0
116	cutoff = cutoff64(base)
117	maxVal = 1<<uint(bitSize) - 1
118
119	for i := 0; i < len(s); i++ {
120		var v byte
121		d := s[i]
122		switch {
123		case '0' <= d && d <= '9':
124			v = d - '0'
125		case 'a' <= d && d <= 'z':
126			v = d - 'a' + 10
127		case 'A' <= d && d <= 'Z':
128			v = d - 'A' + 10
129		default:
130			n = 0
131			err = strconv.ErrSyntax
132			goto Error
133		}
134		if int(v) >= base {
135			n = 0
136			err = strconv.ErrSyntax
137			goto Error
138		}
139
140		if n >= cutoff {
141			// n*base overflows
142			n = 1<<64 - 1
143			err = strconv.ErrRange
144			goto Error
145		}
146		n *= uint64(base)
147
148		n1 := n + uint64(v)
149		if n1 < n || n1 > maxVal {
150			// n+v overflows
151			n = 1<<64 - 1
152			err = strconv.ErrRange
153			goto Error
154		}
155		n = n1
156	}
157
158	return n, nil
159
160Error:
161	return n, &strconv.NumError{Func: "ParseUint", Num: string(s0), Err: err}
162}
163
164// Return the first number n such that n*base >= 1<<64.
165func cutoff64(base int) uint64 {
166	if base < 2 {
167		return 0
168	}
169	return (1<<64-1)/uint64(base) + 1
170}
171