mirror of
https://github.com/rvtr/unlaunch-installer_dev.git
synced 2026-01-26 13:43:08 -05:00
93 lines
2.4 KiB
C
93 lines
2.4 KiB
C
#include "sav.h"
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#include <string.h>
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#include <malloc.h>
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#define align(v, a) (((v) % (a)) ? ((v) + (a) - ((v) % (a))) : (v))
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bool initFatHeader(FILE* f)
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{
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if (!f)
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return false;
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//get size
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fseek(f, 0, SEEK_END);
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u32 size = ftell(f);
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//based on GodMode9
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//https://github.com/d0k3/GodMode9/blob/d8d43c14f3317423c677b1c7e0987bcb9bbd7299/arm9/source/game/nds.c#L47-L105
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const u16 sectorSize = 0x200;
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//fit maximum sectors for the size
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const u16 maxSectors = size / sectorSize;
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u16 sectorCount = 1;
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u16 secPerTrk = 1;
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u16 numHeads = 1;
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u16 sectorCountNext = 0;
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while (sectorCountNext <= maxSectors)
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{
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sectorCountNext = secPerTrk * (numHeads + 1) * (numHeads + 1);
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if (sectorCountNext <= maxSectors)
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{
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numHeads++;
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sectorCount = sectorCountNext;
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secPerTrk++;
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sectorCountNext = secPerTrk * numHeads * numHeads;
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if (sectorCountNext <= maxSectors)
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{
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sectorCount = sectorCountNext;
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}
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}
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}
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sectorCountNext = (secPerTrk + 1) * numHeads * numHeads;
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if (sectorCountNext <= maxSectors)
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{
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secPerTrk++;
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sectorCount = sectorCountNext;
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}
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u8 secPerCluster = (sectorCount > (8 << 10)) ? 8 : (sectorCount > (1 << 10) ? 4 : 1);
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u16 rootEntryCount = size < 0x8C000 ? 0x20 : 0x200;
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u16 totalClusters = align(sectorCount, secPerCluster) / secPerCluster;
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u32 fatBytes = (align(totalClusters, 2) / 2) * 3; // 2 sectors -> 3 byte
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u16 fatSize = align(fatBytes, sectorSize) / sectorSize;
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FATHeader* h = (FATHeader*)malloc(sizeof(FATHeader));
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h->BS_JmpBoot[0] = 0xE9;
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h->BS_JmpBoot[1] = 0;
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h->BS_JmpBoot[2] = 0;
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memcpy(h->BS_OEMName, "MSWIN4.1", 8);
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h->BPB_BytesPerSec = sectorSize;
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h->BPB_SecPerClus = secPerCluster;
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h->BPB_RsvdSecCnt = 0x0001;
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h->BPB_NumFATs = 0x02;
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h->BPB_RootEntCnt = rootEntryCount;
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h->BPB_TotSec16 = sectorCount;
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h->BPB_Media = 0xF8; // "hard drive"
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h->BPB_FATSz16 = fatSize;
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h->BPB_SecPerTrk = secPerTrk;
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h->BPB_NumHeads = numHeads;
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h->BPB_HiddSec = 0x00000000;
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h->BPB_TotSec32 = 0x00000000;
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h->BS_DrvNum = 0x05;
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h->BS_Reserved1 = 0x00;
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h->BS_BootSig = 0x29;
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h->BS_VolID = 0x12345678;
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memcpy(h->BS_VolLab, "VOLUMELABEL", 11);
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memcpy(h->BS_FilSysType,"FAT12 ", 8);
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memset(h->BS_BootCode, 0, sizeof(h->BS_BootCode));
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h->BS_BootSign = 0xAA55;
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fseek(f, 0, SEEK_SET);
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fwrite(h, sizeof(FATHeader), 1, f);
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free(h);
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return true;
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} |