82 lines
1.7 KiB
Go
82 lines
1.7 KiB
Go
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package loclist
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import (
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"encoding/binary"
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)
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// Reader parses and presents DWARF loclist information.
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type Reader struct {
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data []byte
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cur int
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ptrSz int
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}
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// New returns an initialized loclist Reader.
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func New(data []byte, ptrSz int) *Reader {
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return &Reader{data: data, ptrSz: ptrSz}
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}
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// Empty returns true if this reader has no data.
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func (rdr *Reader) Empty() bool {
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return rdr.data == nil
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}
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// Seek moves the data pointer to the specified offset.
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func (rdr *Reader) Seek(off int) {
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rdr.cur = off
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}
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// Next advances the reader to the next loclist entry, returning
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// the entry and true if successful, or nil, false if not.
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func (rdr *Reader) Next(e *Entry) bool {
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e.LowPC = rdr.oneAddr()
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e.HighPC = rdr.oneAddr()
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if e.LowPC == 0 && e.HighPC == 0 {
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return false
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}
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if e.BaseAddressSelection() {
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e.Instr = nil
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return true
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}
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instrlen := binary.LittleEndian.Uint16(rdr.read(2))
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e.Instr = rdr.read(int(instrlen))
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return true
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}
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func (rdr *Reader) read(sz int) []byte {
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r := rdr.data[rdr.cur : rdr.cur+sz]
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rdr.cur += sz
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return r
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}
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func (rdr *Reader) oneAddr() uint64 {
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switch rdr.ptrSz {
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case 4:
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addr := binary.LittleEndian.Uint32(rdr.read(rdr.ptrSz))
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if addr == ^uint32(0) {
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return ^uint64(0)
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}
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return uint64(addr)
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case 8:
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addr := uint64(binary.LittleEndian.Uint64(rdr.read(rdr.ptrSz)))
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return addr
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default:
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panic("bad address size")
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}
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}
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// Entry represents a single entry in the loclist section.
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type Entry struct {
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LowPC, HighPC uint64
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Instr []byte
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}
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// BaseAddressSelection returns true if entry.highpc should
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// be used as the base address for subsequent entries.
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func (e *Entry) BaseAddressSelection() bool {
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return e.LowPC == ^uint64(0)
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}
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