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Source file src/debug/pe/string.go

Documentation: debug/pe

  // 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 (
  	"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 {
  	var i int
  	for i = 0; i < len(b) && b[i] != 0; i++ {
  	}
  	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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