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1. Compiling

This file should compile in most C compilers. By way of example in one of the most common compilers, the command to compile in gcc is: gcc -o rompad rompad.c

2. Preamble

3. Main Function

rompad.c

1	#include <stdio.h>
2	#include <stdlib.h>
3	#include <string.h>
4	int main( int argc, char* argv ) {
5	int retval = 0;
6	FILE* bios_in = NULL;
7	FILE* bios_out = NULL;
8	size_t pg_sz = 0;
9	size_t rom_sz = 0;
10	size_t in_sz = 0;
11	size_t pg_writ_sz = 0;
12	size_t iter_r_sz = 0;
13	size_t iter_w_sz = 0;
14	size_t file_writ_sz = 0;
15	char* bios_in_c = argv1;
16	char buffer1024;

Make sure command line makes sense.

rompad.c

17	if( 5 != argc ) {
18	printf( "usage: pad <bios_in> <bios_out> <pg_sz_kb> <rom_sz_kb>\n" );
19	retval = 1;
20	goto cleanup;
21	}

Open input and output ROM files.

rompad.c

22	bios_in = fopen( bios_in_c, "rb" );
23	bios_out = fopen( argv2, "wb" );

Get page and output ROM size from the command line, converting from KB to bytes.

rompad.c

24	pg_sz = atoi( argv3 ) * 1024;
25	rom_sz = atoi( argv4 ) * 1024;

Get the input ROM size from the input ROM file, in bytes.

rompad.c

26	fseek( bios_in, 0, SEEK_END );
27	in_sz = ftell( bios_in );
28	fseek( bios_in, 0, SEEK_SET );

Status update.

rompad.c

29	printf( "bios_in \"%s\" sz: %lu\n", bios_in_c, in_sz );
30	if( in_sz < pg_sz ) {
31	printf( "pages will be padded to %lu\n", pg_sz );
32	}

Iterate pages until the output ROM file matches the size specified on the command line.

rompad.c

33	while( file_writ_sz < rom_sz ) {

Iterate bytes from the input ROM and then zero-padding until the current position in the output ROM matches a page size.

rompad.c

34	pg_writ_sz = 0;
35	while( pg_writ_sz < pg_sz ) {

Determine if there are still bytes to read from the input ROM, or if we should switch to zero-padding.

rompad.c

36	if( pg_writ_sz < in_sz ) {
37	iter_r_sz = fread( buffer, 1, 1024, bios_in );
38	printf( "copying %lu bytes to page...\n", iter_r_sz );
39	} else {
40	iter_r_sz = 1024;
41	printf( "padding %lu bytes to page...\n", iter_r_sz );
42	memset( buffer, '\0', iter_r_sz );
43	}

Write read bytes or zero padding to output ROM file.

rompad.c

44	iter_w_sz = fwrite( buffer, 1, iter_r_sz, bios_out );
45	if( iter_w_sz < iter_r_sz ) {
46	printf( "could not write buffer!\n" );
47	retval = 2;
48	goto cleanup;
49	}
50	pg_writ_sz += iter_w_sz;
51	}

Bump up file written size by this page's written size.

rompad.c

52	file_writ_sz += pg_writ_sz;
53	fseek( bios_in, 0, SEEK_SET );
54	printf( "wrote %lu bytes to file...\n", file_writ_sz );
55	}

Close remaining open ROM files.

rompad.c

56	cleanup:
57	if( NULL != bios_in ) {
58	fclose( bios_in );
59	}
60	if( NULL != bios_out ) {
61	fclose( bios_out );
62	}
63	return retval;
64	}