string.go

Documentation: debug/pe

		 1  // Copyright 2016 The Go Authors. All rights reserved.
		 2  // Use of this source code is governed by a BSD-style
		 3  // license that can be found in the LICENSE file.
		 4  
		 5  package pe
		 6  
		 7  import (
		 8  	"bytes"
		 9  	"encoding/binary"
		10  	"fmt"
		11  	"io"
		12  )
		13  
		14  // cstring converts ASCII byte sequence b to string.
		15  // It stops once it finds 0 or reaches end of b.
		16  func cstring(b []byte) string {
		17  	i := bytes.IndexByte(b, 0)
		18  	if i == -1 {
		19  		i = len(b)
		20  	}
		21  	return string(b[:i])
		22  }
		23  
		24  // StringTable is a COFF string table.
		25  type StringTable []byte
		26  
		27  func readStringTable(fh *FileHeader, r io.ReadSeeker) (StringTable, error) {
		28  	// COFF string table is located right after COFF symbol table.
		29  	if fh.PointerToSymbolTable <= 0 {
		30  		return nil, nil
		31  	}
		32  	offset := fh.PointerToSymbolTable + COFFSymbolSize*fh.NumberOfSymbols
		33  	_, err := r.Seek(int64(offset), seekStart)
		34  	if err != nil {
		35  		return nil, fmt.Errorf("fail to seek to string table: %v", err)
		36  	}
		37  	var l uint32
		38  	err = binary.Read(r, binary.LittleEndian, &l)
		39  	if err != nil {
		40  		return nil, fmt.Errorf("fail to read string table length: %v", err)
		41  	}
		42  	// string table length includes itself
		43  	if l <= 4 {
		44  		return nil, nil
		45  	}
		46  	l -= 4
		47  	buf := make([]byte, l)
		48  	_, err = io.ReadFull(r, buf)
		49  	if err != nil {
		50  		return nil, fmt.Errorf("fail to read string table: %v", err)
		51  	}
		52  	return StringTable(buf), nil
		53  }
		54  
		55  // TODO(brainman): decide if start parameter should be int instead of uint32
		56  
		57  // String extracts string from COFF string table st at offset start.
		58  func (st StringTable) String(start uint32) (string, error) {
		59  	// start includes 4 bytes of string table length
		60  	if start < 4 {
		61  		return "", fmt.Errorf("offset %d is before the start of string table", start)
		62  	}
		63  	start -= 4
		64  	if int(start) > len(st) {
		65  		return "", fmt.Errorf("offset %d is beyond the end of string table", start)
		66  	}
		67  	return cstring(st[start:]), nil
		68  }
		69
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