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Unified Diff: debug/dwarf/buf.go

Issue 81640043: code review 81640043: ogle: copy debug/dwarf into our repo (Closed)
Patch Set: diff -r b0fd2d1d31aa https://code.google.com/p/ogle Created 10 years ago
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Index: debug/dwarf/buf.go
===================================================================
new file mode 100644
--- /dev/null
+++ b/debug/dwarf/buf.go
@@ -0,0 +1,181 @@
+// 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
+}
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