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annotate system.c @ 1117:928a65750345

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Initial support for Genesis/Megadrive PBC mode. VDP still needs Mode 4 to be useful.
author Michael Pavone <pavone@retrodev.com>
date Thu, 22 Dec 2016 19:51:25 -0800
parents 2eb54e24914e
children 4490c9c12272
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1 #include <string.h>
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2 #include "system.h"
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3 #include "genesis.h"
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4 #include "sms.h"
928a65750345 Initial support for Genesis/Megadrive PBC mode. VDP still needs Mode 4 to be useful.
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5
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6 uint8_t safe_cmp(char *str, long offset, uint8_t *buffer, long filesize)
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parents: 1111
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7 {
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8 long len = strlen(str);
928a65750345 Initial support for Genesis/Megadrive PBC mode. VDP still needs Mode 4 to be useful.
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9 return filesize >= offset+len && !memcmp(str, buffer + offset, len);
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10 }
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11
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12 system_type detect_system_type(uint8_t *rom, long filesize)
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13 {
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14 if (safe_cmp("SEGA", 0x100, rom, filesize)) {
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15 //TODO: Differentiate between vanilla Genesis and Sega CD/32X games
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16 return SYSTEM_GENESIS;
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17 }
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18 if (safe_cmp("TMR SEGA", 0x1FF0, rom, filesize)
928a65750345 Initial support for Genesis/Megadrive PBC mode. VDP still needs Mode 4 to be useful.
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19 || safe_cmp("TMR SEGA", 0x3FF0, rom, filesize)
928a65750345 Initial support for Genesis/Megadrive PBC mode. VDP still needs Mode 4 to be useful.
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parents: 1111
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20 || safe_cmp("TMR SEGA", 0x7FF0, rom, filesize)
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21 ) {
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22 return SYSTEM_SMS;
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23 }
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24 //TODO: Detect Jaguar ROMs here
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25
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26 //More certain checks failed, look for a valid 68K reset vector
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27 if (filesize >= 8) {
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28 uint32_t reset = rom[4] << 24 | rom[5] << 16 | rom[6] << 8 | rom[7];
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29 if (!(reset & 1) && reset < filesize) {
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30 //we have a valid looking reset vector, assume it's a Genesis ROM
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31 return SYSTEM_GENESIS;
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32 }
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33 }
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34 return SYSTEM_UNKNOWN;
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35 }
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36
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37 system_header *alloc_config_system(system_type stype, void *rom, uint32_t rom_size, void *lock_on, uint32_t lock_on_size, uint32_t opts, uint8_t force_region, rom_info *info_out)
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38 {
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39 switch (stype)
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40 {
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41 case SYSTEM_GENESIS:
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42 return &(alloc_config_genesis(rom, rom_size, lock_on, lock_on_size, opts, force_region, info_out))->header;
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parents: 1111
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43 #ifndef NO_Z80
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44 case SYSTEM_SMS:
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parents: 1111
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45 return &(alloc_configure_sms(rom, rom_size, lock_on, lock_on_size, opts, force_region, info_out))->header;
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parents: 1111
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46 #endif
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47 default:
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48 return NULL;
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49 }
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50 }