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// Copyright 2016 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.
package pe
import (
"bytes"
"encoding/binary"
"fmt"
"io"
)
// cstring converts ASCII byte sequence b to string.
// It stops once it finds 0 or reaches end of b.
func cstring(b []byte) string {
i := bytes.IndexByte(b, 0)
if i == -1 {
i = len(b)
}
return string(b[:i])
}
// StringTable is a COFF string table.
type StringTable []byte
func readStringTable(fh *FileHeader, r io.ReadSeeker) (StringTable, error) {
// COFF string table is located right after COFF symbol table.
if fh.PointerToSymbolTable <= 0 {
return nil, nil
}
offset := fh.PointerToSymbolTable + COFFSymbolSize*fh.NumberOfSymbols
_, err := r.Seek(int64(offset), seekStart)
if err != nil {
return nil, fmt.Errorf("fail to seek to string table: %v", err)
}
var l uint32
err = binary.Read(r, binary.LittleEndian, &l)
if err != nil {
return nil, fmt.Errorf("fail to read string table length: %v", err)
}
// string table length includes itself
if l <= 4 {
return nil, nil
}
l -= 4
buf := make([]byte, l)
_, err = io.ReadFull(r, buf)
if err != nil {
return nil, fmt.Errorf("fail to read string table: %v", err)
}
return StringTable(buf), nil
}
// TODO(brainman): decide if start parameter should be int instead of uint32
// String extracts string from COFF string table st at offset start.
func (st StringTable) String(start uint32) (string, error) {
// start includes 4 bytes of string table length
if start < 4 {
return "", fmt.Errorf("offset %d is before the start of string table", start)
}
start -= 4
if int(start) > len(st) {
return "", fmt.Errorf("offset %d is beyond the end of string table", start)
}
return cstring(st[start:]), nil
}
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