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152 lines
3.0 KiB
Go
152 lines
3.0 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Buffered reading and decoding of DWARF data streams.
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package util
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import (
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"debug/dwarf"
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"fmt"
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)
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// Data buffer being decoded.
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type buf struct {
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dwarf *dwarf.Data
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format dataFormat
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name string
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off dwarf.Offset
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data []byte
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Err error
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}
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// Data format, other than byte order. This affects the handling of
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// certain field formats.
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type dataFormat interface {
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// DWARF version number. Zero means unknown.
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version() int
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// 64-bit DWARF format?
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dwarf64() (dwarf64 bool, isKnown bool)
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// Size of an address, in bytes. Zero means unknown.
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addrsize() int
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}
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// Some parts of DWARF have no data format, e.g., abbrevs.
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type UnknownFormat struct{}
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func (u UnknownFormat) version() int {
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return 0
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}
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func (u UnknownFormat) dwarf64() (bool, bool) {
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return false, false
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}
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func (u UnknownFormat) addrsize() int {
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return 0
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}
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func MakeBuf(d *dwarf.Data, format dataFormat, name string, off dwarf.Offset, data []byte) buf {
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return buf{d, format, name, off, data, nil}
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}
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func (b *buf) slice(length int) buf {
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n := *b
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data := b.data
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b.skip(length) // Will validate length.
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n.data = data[:length]
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return n
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}
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func (b *buf) Uint8() uint8 {
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if len(b.data) < 1 {
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b.error("underflow")
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return 0
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}
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val := b.data[0]
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b.data = b.data[1:]
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b.off++
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return val
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}
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func (b *buf) bytes(n int) []byte {
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if len(b.data) < n {
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b.error("underflow")
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return nil
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}
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data := b.data[0:n]
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b.data = b.data[n:]
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b.off += dwarf.Offset(n)
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return data
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}
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func (b *buf) skip(n int) { b.bytes(n) }
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// string returns the NUL-terminated (C-like) string at the start of the buffer.
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// The terminal NUL is discarded.
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func (b *buf) string() string {
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for i := 0; i < len(b.data); i++ {
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if b.data[i] == 0 {
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s := string(b.data[0:i])
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b.data = b.data[i+1:]
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b.off += dwarf.Offset(i + 1)
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return s
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}
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}
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b.error("underflow")
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return ""
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}
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// Read a varint, which is 7 bits per byte, little endian.
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// the 0x80 bit means read another byte.
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func (b *buf) Varint() (c uint64, bits uint) {
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for i := 0; i < len(b.data); i++ {
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byte := b.data[i]
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c |= uint64(byte&0x7F) << bits
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bits += 7
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if byte&0x80 == 0 {
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b.off += dwarf.Offset(i + 1)
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b.data = b.data[i+1:]
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return c, bits
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}
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}
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return 0, 0
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}
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// Unsigned int is just a varint.
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func (b *buf) Uint() uint64 {
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x, _ := b.Varint()
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return x
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}
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// Signed int is a sign-extended varint.
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func (b *buf) Int() int64 {
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ux, bits := b.Varint()
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x := int64(ux)
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if x&(1<<(bits-1)) != 0 {
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x |= -1 << bits
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}
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return x
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}
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// AssertEmpty checks that everything has been read from b.
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func (b *buf) AssertEmpty() {
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if len(b.data) == 0 {
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return
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}
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if len(b.data) > 5 {
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b.error(fmt.Sprintf("unexpected extra data: %x...", b.data[0:5]))
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}
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b.error(fmt.Sprintf("unexpected extra data: %x", b.data))
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}
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func (b *buf) error(s string) {
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if b.Err == nil {
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b.data = nil
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b.Err = dwarf.DecodeError{b.name, b.off, s}
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}
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}
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