1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
|
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Buffered reading and decoding of DWARF data streams.
package dwarf
import (
"encoding/binary"
"strconv"
)
// Data buffer being decoded.
type buf struct {
dwarf *Data
order binary.ByteOrder
format dataFormat
name string
off Offset
data []byte
err error
}
// Data format, other than byte order. This affects the handling of
// certain field formats.
type dataFormat interface {
// DWARF version number. Zero means unknown.
version() int
// 64-bit DWARF format?
dwarf64() (dwarf64 bool, isKnown bool)
// Size of an address, in bytes. Zero means unknown.
addrsize() int
}
// Some parts of DWARF have no data format, e.g., abbrevs.
type unknownFormat struct{}
func (u unknownFormat) version() int {
return 0
}
func (u unknownFormat) dwarf64() (bool, bool) {
return false, false
}
func (u unknownFormat) addrsize() int {
return 0
}
func makeBuf(d *Data, format dataFormat, name string, off Offset, data []byte) buf {
return buf{d, d.order, format, name, off, data, nil}
}
func (b *buf) uint8() uint8 {
if len(b.data) < 1 {
b.error("underflow")
return 0
}
val := b.data[0]
b.data = b.data[1:]
b.off++
return val
}
func (b *buf) bytes(n int) []byte {
if len(b.data) < n {
b.error("underflow")
return nil
}
data := b.data[0:n]
b.data = b.data[n:]
b.off += Offset(n)
return data
}
func (b *buf) skip(n int) { b.bytes(n) }
func (b *buf) string() string {
for i := 0; i < len(b.data); i++ {
if b.data[i] == 0 {
s := string(b.data[0:i])
b.data = b.data[i+1:]
b.off += Offset(i + 1)
return s
}
}
b.error("underflow")
return ""
}
func (b *buf) uint16() uint16 {
a := b.bytes(2)
if a == nil {
return 0
}
return b.order.Uint16(a)
}
func (b *buf) uint32() uint32 {
a := b.bytes(4)
if a == nil {
return 0
}
return b.order.Uint32(a)
}
func (b *buf) uint64() uint64 {
a := b.bytes(8)
if a == nil {
return 0
}
return b.order.Uint64(a)
}
// Read a varint, which is 7 bits per byte, little endian.
// the 0x80 bit means read another byte.
func (b *buf) varint() (c uint64, bits uint) {
for i := 0; i < len(b.data); i++ {
byte := b.data[i]
c |= uint64(byte&0x7F) << bits
bits += 7
if byte&0x80 == 0 {
b.off += Offset(i + 1)
b.data = b.data[i+1:]
return c, bits
}
}
return 0, 0
}
// Unsigned int is just a varint.
func (b *buf) uint() uint64 {
x, _ := b.varint()
return x
}
// Signed int is a sign-extended varint.
func (b *buf) int() int64 {
ux, bits := b.varint()
x := int64(ux)
if x&(1<<(bits-1)) != 0 {
x |= -1 << bits
}
return x
}
// Address-sized uint.
func (b *buf) addr() uint64 {
switch b.format.addrsize() {
case 1:
return uint64(b.uint8())
case 2:
return uint64(b.uint16())
case 4:
return uint64(b.uint32())
case 8:
return uint64(b.uint64())
}
b.error("unknown address size")
return 0
}
func (b *buf) error(s string) {
if b.err == nil {
b.data = nil
b.err = DecodeError{b.name, b.off, s}
}
}
type DecodeError struct {
Name string
Offset Offset
Err string
}
func (e DecodeError) Error() string {
return "decoding dwarf section " + e.Name + " at offset 0x" + strconv.FormatInt(int64(e.Offset), 16) + ": " + e.Err
}
|
