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0d172cc2c4
Running a ROM on an everdrive is one thing, but running a ROM directly is another: my hacked up sega.bin didn't have a proper checksum, so the ROM didn't run. This new tool transforms a binary into a properly-headered ROM. Has been tested on an actual SMS.
54 lines
1.3 KiB
C
54 lines
1.3 KiB
C
/* ./smsrom fname
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Transforms binary at fname into an 8K, 16K or 32K Sega Master System ROM with
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a header fit for an Export SMS. The resulting ROM is spit to stdout.
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Whether the ROM is 8, 16 or 32K depends on the size of binary at fname.
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*/
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#include <stdio.h>
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#include <inttypes.h>
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int main(int argc, char **argv)
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{
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if (argc != 2) {
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fprintf(stderr, "Usage: ./smsrom fname\n");
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return 1;
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}
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FILE *fp = fopen(argv[1], "r");
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if (!fp) {
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fprintf(stderr, "Can't open %s.\n", argv[1]);
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return 1;
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}
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fseek(fp, 0, SEEK_END);
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long fsize = ftell(fp);
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fseek(fp, 0, SEEK_SET);
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uint8_t hdsz = 0x4a; // size flag in header. either 4a, 4b or 4c.
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int romsize = 0x2000;
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while (romsize-16 < fsize) {
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romsize *= 2;
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hdsz++;
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if (romsize > 0x8000) {
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fprintf(stderr, "binary too big\n");
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return 1;
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}
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}
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uint16_t chksum = 0;
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for (int i=0; i<romsize-16; i++) {
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int c = getc(fp);
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if (c == EOF) c = 0;
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putchar(c);
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chksum += c;
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}
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// and now, the header
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printf("TMR SEGA");
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putchar(0);
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putchar(0);
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putchar(chksum & 0xff);
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putchar(chksum >> 8);
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putchar(0);
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putchar(0);
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putchar(0);
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putchar(hdsz);
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return 0;
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}
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