How can I convert a binary file to the text declaring a C/C++ array with that content?

Question

I need to include the contents of a binary file in my C/C++ source code as the text for the declaration of an array initialized to the content of the file. I'm not looking to read the file dynamically at runtime. I want to perform the operation once and then use the generated array declaration text.

How can I convert a binary file to the text for the C/C++ declaration of an array which is initialized to the contents of the file?

Answer 1

On Debian and other Linux distros is installed by default (along with vim) the xxd tool, which, given the -i option, can do what you want:

matteo@teodeb:~/Desktop$ echo Hello World\! > temp
matteo@teodeb:~/Desktop$ xxd -i temp 
unsigned char temp[] = {
  0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x20, 0x57, 0x6f, 0x72, 0x6c, 0x64, 0x21,
  0x0a
};
unsigned int temp_len = 13;

Answer 2

The accepted answer using xxd tool is nice if you are on a *nix-like system. Here is a "one-liner" for any system that has python executable on the path:

python -c "import sys;a=sys.argv;open(a[2],'wb').write(('const unsigned char '+a[3]+'[] = {'+','.join([hex(b) for b in open(a[1],'rb').read()])+'};').encode('utf-8'))" <binary file> <header file> <array name>

< binary file > is the name of the file you want to turn into a C header, < header file > is the name of the header file, and < array name > is the name you want the array to have.

The above one-line Python command does approximately the same as the following (much more readable) Python program:

import sys

with open(sys.argv[2],'wb') as result_file:
  result_file.write(b'const char %s[] = {' % sys.argv[3].encode('utf-8'))
  for b in open(sys.argv[1], 'rb').read():
    result_file.write(b'0x%02X,' % b)
  result_file.write(b'};')

Answer 3

One simple tool can be found here:

#include <stdio.h>
#include <assert.h>

int main(int argc, char** argv) {
    assert(argc == 2);
    char* fn = argv[1];
    FILE* f = fopen(fn, "rb");
    printf("char a[] = {\n");
    unsigned long n = 0;
    while(!feof(f)) {
        unsigned char c;
        if(fread(&c, 1, 1, f) == 0) break;
        printf("0x%.2X,", (int)c);
        ++n;
        if(n % 10 == 0) printf("\n");
    }
    fclose(f);
    printf("};\n");
}

Answer 4

I checked all available options and decided to make my own little program to do the conversion:

https://github.com/TheLivingOne/bin2array/blob/master/bin2array.c

It works much faster than bin2c and even xxd which is important for larger files, especially if you want to embed the conversion into your build system. E.g. for 50 Mb file on my machine:

bin2c.py > 20 sec

Simple Python scripts - about 10 sec

xxd - about 3 sec

bin2array - about 0.4 sec

Also, it produces much more compact output and adds alignment to the array, in case you want to put 32 or 64 bit values there.

Answer 5

There are a few apps now that perhaps at the time this question was posed were not available. So I would like to list the ones that I know of here as current potential solutions.

Executables & libraries:

• Binary to Header (Native & Python command line executables)
• File To C Array (GUI tool but does include a library)
• Bin2C (Windows only, GUI interface works but I couldn't convert from command line)
• file2c (BSD & ported to some Linux distros)

Online tools (not relevant to question but may be useful to others):

• FileToCArry
• image2cpp (image file types only)

Answer 6

This tool compiles in the developer command prompt in C. It produces output to the terminal displaying the contents in the "array_name.c" file that is created. Note that some terminals may display the "\b" character.

    #include <stdio.h>
    #include <assert.h>

    int main(int argc, char** argv) {
    assert(argc == 2);
    char* fn = argv[1];

    // Open file passed by reference
    FILE* f = fopen(fn, "rb");
    // Opens a new file in the programs location
    FILE* fw = fopen("array_name.c","w");

    // Next two lines write the strings to the console and .c file
    printf("char array_name[] = {\n");
    fprintf(fw,"char hex_array[] = {\n");

    // Declare long integer for number of columns in the array being made
    unsigned long n = 0;

    // Loop until end of file
    while((!feof(f))){
        // Declare character that stores the bytes from hex file
        unsigned char c;

        // Ignore failed elements read
        if(fread(&c, 1, 1, f) == 0) break;
        // Prints to console and file, "0x%.2X" ensures format for all
        // read bytes is like "0x00"
        printf("0x%.2X,", (int)c);
        fprintf(fw,"0x%.2X,", (int)c);

        // Increment counter, if 20 columns have been made, begin new line
        ++n;
        if(n % 20 == 0){
            printf("\n");
            fprintf(fw,"\n");
        }
    }

    // fseek places cursor to overwrite extra "," made from previous loop
    // this is for the new .c file. Since "\b" is technically a character
    // to remove the extra "," requires overwriting it.
    fseek(fw, -1, SEEK_CUR);

    // "\b" moves cursor back one in the terminal
    printf("\b};\n");
    fprintf(fw,"};\n");
    fclose(f);
    fclose(fw);
}

Answer 7

This is a binary file to C array generator python source code which is identical program in Albert's answer.

import sys
from functools import partial

if len(sys.argv) < 2:
  sys.exit('Usage: %s file' % sys.argv[0])
print("char a[] = {")
n = 0
with open(sys.argv[1], "rb") as in_file:
  for c in iter(partial(in_file.read, 1), b''):
    print("0x%02X," % ord(c), end='')
    n += 1
    if n % 16 == 0:
      print("")
print("};")

Answer 8

The question is old but let me suggest simple tool which can be used as alternative...

You can use GUI based tool called Fluid. It is actually used for designing interface for FLTK toolkit but can also generate unsigned char array for C++ from binary file. Download it from muquit.

Answer 9

You can use ld. Refer https://github.com/termux/termux-packages/issues/16429#issuecomment-1541466535. I reorganize it in an article.