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Fix save file FAT header generation

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This commit is contained in:
Pk11 2022-02-21 23:43:50 -06:00
parent baba3783f4
commit db69aca1b4
1 changed files with 62 additions and 92 deletions
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154
arm9/src/sav.c
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@ -2,51 +2,7 @@
#include <string.h>
#include <malloc.h>
static u32 _getClusterSize(u32 sizebytes)
{
if (sizebytes < 573440)
return 512;
else if (sizebytes < 5472256)
return 2048;
else if (sizebytes < 17301504)
return 4096;
else
return 2048;
}
static u16 _getMaxFiles(u32 sizebytes)
{
if (sizebytes < 573440)
return 16;
else
return 256;
}
//wip
static u16 _getFatz(u32 sizebytes)
{
if (sizebytes <= 0x4000) //16 kb
return 1;
else if (sizebytes <= 0x200000) //2 mb
return 3;
else
return 6;
}
//wip
static u16 _getTotSec16(u32 sizebytes, u16 bytesPerSec)
{
if (sizebytes == 0x4000) //16 kb
return 27;
return sizebytes / bytesPerSec;
}
#define align(v, a) (((v) % (a)) ? ((v) + (a) - ((v) % (a))) : (v))
bool initFatHeader(FILE* f)
{
@ -57,61 +13,75 @@ bool initFatHeader(FILE* f)
fseek(f, 0, SEEK_END);
u32 size = ftell(f);
//based on GodMode9
//https://github.com/d0k3/GodMode9/blob/d8d43c14f3317423c677b1c7e0987bcb9bbd7299/arm9/source/game/nds.c#L47-L105
const u16 sectorSize = 0x200;
//fit maximum sectors for the size
const u16 maxSectors = size / sectorSize;
u16 sectorCount = 1;
u16 secPerTrk = 1;
u16 numHeads = 1;
u16 sectorCountNext = 0;
while (sectorCountNext <= maxSectors)
{
sectorCountNext = secPerTrk * (numHeads + 1) * (numHeads + 1);
if (sectorCountNext <= maxSectors)
{
numHeads++;
sectorCount = sectorCountNext;
secPerTrk++;
sectorCountNext = secPerTrk * numHeads * numHeads;
if (sectorCountNext <= maxSectors)
{
sectorCount = sectorCountNext;
}
}
}
sectorCountNext = (secPerTrk + 1) * numHeads * numHeads;
if (sectorCountNext <= maxSectors)
{
secPerTrk++;
sectorCount = sectorCountNext;
}
u8 secPerCluster = (sectorCount > (8 << 10)) ? 8 : (sectorCount > (1 << 10) ? 4 : 1);
u16 rootEntryCount = size < 0x8C000 ? 0x20 : 0x200;
u16 totalClusters = align(sectorCount, secPerCluster) / secPerCluster;
u32 fatBytes = (align(totalClusters, 2) / 2) * 3; // 2 sectors -> 3 byte
u16 fatSize = align(fatBytes, sectorSize) / sectorSize;
FATHeader* h = (FATHeader*)malloc(sizeof(FATHeader));
h->BS_JmpBoot[0] = 0xE9;
h->BS_JmpBoot[1] = 0;
h->BS_JmpBoot[2] = 0;
h->BS_OEMName[0] = 'M';
h->BS_OEMName[1] = 'S';
h->BS_OEMName[2] = 'W';
h->BS_OEMName[3] = 'I';
h->BS_OEMName[4] = 'N';
h->BS_OEMName[5] = '4';
h->BS_OEMName[6] = '.';
h->BS_OEMName[7] = '1';
memcpy(h->BS_OEMName, "MSWIN4.1", 8);
h->BPB_BytesPerSec = 512;
h->BPB_SecPerClus = _getClusterSize(size) / h->BPB_BytesPerSec;
h->BPB_RsvdSecCnt = 1;
h->BPB_NumFATs = 2;
h->BPB_RootEntCnt = _getMaxFiles(size) * 2;
h->BPB_TotSec16 = _getTotSec16(size, h->BPB_BytesPerSec); //
h->BPB_Media = 0xF8;
h->BPB_FATSz16 = _getFatz(size); //
h->BPB_SecPerTrk = 0;
h->BPB_NumHeads = 0;
h->BPB_HiddSec = 0;
h->BPB_TotSec32 = 0;
h->BS_DrvNum = 0x07;
h->BS_Reserved1 = 0;
h->BPB_BytesPerSec = sectorSize;
h->BPB_SecPerClus = secPerCluster;
h->BPB_RsvdSecCnt = 0x0001;
h->BPB_NumFATs = 0x02;
h->BPB_RootEntCnt = rootEntryCount;
h->BPB_TotSec16 = sectorCount;
h->BPB_Media = 0xF8; // "hard drive"
h->BPB_FATSz16 = fatSize;
h->BPB_SecPerTrk = secPerTrk;
h->BPB_NumHeads = numHeads;
h->BPB_HiddSec = 0x00000000;
h->BPB_TotSec32 = 0x00000000;
h->BS_DrvNum = 0x05;
h->BS_Reserved1 = 0x00;
h->BS_BootSig = 0x29;
h->BS_VolID = 305419896;
h->BS_VolLab[0] = 'V';
h->BS_VolLab[1] = 'O';
h->BS_VolLab[2] = 'L';
h->BS_VolLab[3] = 'U';
h->BS_VolLab[4] = 'M';
h->BS_VolLab[5] = 'E';
h->BS_VolLab[6] = 'L';
h->BS_VolLab[7] = 'A';
h->BS_VolLab[8] = 'B';
h->BS_VolLab[9] = 'E';
h->BS_VolLab[10] = 'L';
h->BS_FilSysType[0] = 'F';
h->BS_FilSysType[1] = 'A';
h->BS_FilSysType[2] = 'T';
h->BS_FilSysType[3] = '1';
h->BS_FilSysType[4] = '2';
h->BS_FilSysType[5] = ' ';
h->BS_FilSysType[6] = ' ';
h->BS_FilSysType[7] = ' ';
memset(h->BS_BootCode, 0, 448);
h->BS_VolID = 0x12345678;
memcpy(h->BS_VolLab, "VOLUMELABEL", 11);
memcpy(h->BS_FilSysType,"FAT12 ", 8);
memset(h->BS_BootCode, 0, sizeof(h->BS_BootCode));
h->BS_BootSign = 0xAA55;
fseek(f, 0, SEEK_SET);