github.com/geraldss/go/src@v0.0.0-20210511222824-ac7d0ebfc235/debug/pe/string.go (about) 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 }