1 files changed, 205 insertions, 0 deletions
diff --git a/src/debug/dwarf/buf.go b/src/debug/dwarf/buf.go
new file mode 100644
index 0000000..7ac53ef
--- /dev/null
+++ b/src/debug/dwarf/buf.go
@@ -0,0 +1,205 @@
+// 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 (
+	"bytes"
+	"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 n < 0 || 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 {
+	i := bytes.IndexByte(b.data, 0)
+	if i < 0 {
+		b.error("underflow")
+		return ""
+	}
+
+	s := string(b.data[0:i])
+	b.data = b.data[i+1:]
+	b.off += Offset(i + 1)
+	return s
+}
+
+func (b *buf) uint16() uint16 {
+	a := b.bytes(2)
+	if a == nil {
+		return 0
+	}
+	return b.order.Uint16(a)
+}
+
+func (b *buf) uint24() uint32 {
+	a := b.bytes(3)
+	if a == nil {
+		return 0
+	}
+	if b.dwarf.bigEndian {
+		return uint32(a[2]) | uint32(a[1])<<8 | uint32(a[0])<<16
+	} else {
+		return uint32(a[0]) | uint32(a[1])<<8 | uint32(a[2])<<16
+	}
+}
+
+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 b.uint64()
+	}
+	b.error("unknown address size")
+	return 0
+}
+
+func (b *buf) unitLength() (length Offset, dwarf64 bool) {
+	length = Offset(b.uint32())
+	if length == 0xffffffff {
+		dwarf64 = true
+		length = Offset(b.uint64())
+	} else if length >= 0xfffffff0 {
+		b.error("unit length has reserved value")
+	}
+	return
+}
+
+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
+}