(Reporter) How does one import a byte of binary file into the value of N byte? (C/C ++) (c)

Abstract
In order to protect their intellectual property rights, the company will define its own legal format, and its header area will define each byte representing a certain level of information, therefore, it is often necessary to directly import a byte of binary classification, and then directly Import several bytes to indicate a certain amount of data.

Introduction
Environment: Windows XP SP3 + visual c ++ 6.0 SP6

Add the cursor to the 0x33 byte value of WF. Bin.

 1   /*   
  2   (C) oomusou 2011  Http://oomusou.cnblogs.com  
  3   
  4   Filename: writenbyte. c
 5   Compiler: Visual C + + 6.0
  6   Description: How to Write n byte value with N-byte position?
  7   Release: oct.31, 2011 1.0
  8   */ 
 9  
 10 # Include <stdio. h>
 11  
 12   Int Main (){
13 File * FP;
 14     Int Filesize;
 15 Unsigned Char Buff [ 4 ];
 16      
 17 Fp = fopen ( "  ./WF. Bin  " , "  RB +  " );
 18     If (! FP ){
 19 Fclose (FP );
 20       Return - 1 ;
 21 }
 22       
 23 Buff [ 0 ] = 0xac ;
 24 Buff [1 ] = 0xff ;
 25 Buff [ 2 ] = 0x1b ;
 26 Buff [ 3 ] = 0xaa ;
 27      
 28 Fseek (FP, 0x33 , Seek_set );
 29 Fwrite (buff,Sizeof (Unsigned Char ), 4 , FP );
 30      
 31 Fclose (FP );
 32          
 33     Return   0 ;
 34 }

15 rows

 
UnsignedCharBuff [4];
 

4 byte char array.

17 rows

Fp = fopen ("./WF. Bin","RB +");
 

Because we want to modify the currently enabled binary F ile, how can we import a byte value of binary file using RB + or Alibaba Cloud? (C/C ++) (c ).

23 rows

 
Buff [0] =0xac;
Buff [1] =0xff;
Buff [2] =0x1b;
Buff [3] =0xaa;
 

Set the value of each byte separately.

28 rows

 
Fseek (FP,0x33, Seek_set );
 

Use fseek to move the location of binary file to 0x33. seek_set indicates that the offset starts from the beginning.

29 rows

 
Fwrite (buff,Sizeof(UnsignedChar),4, FP );
 

The official use of fwrite will put the buff into the limit case, because the single bit is unsigned char, so the size is 4.

See also
(Reporter) How to import a byte value of binary file? (C/C ++) (c)