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https://github.com/FDOS/kernel.git
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Optimized initdisk.c by using constants instead of variables where possible.
git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@1450 6ac86273-5f31-0410-b378-82cca8765d1b
This commit is contained in:
Bart Oldeman
parent
a93b71a18b
commit
9e0b5e5bf6
@ -394,25 +394,24 @@ void printCHS(char *title, struct CHS *chs)
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Portions copyright 1992, 1993 Remy Card
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and 1991 Linus Torvalds
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*/
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/* defaults: */
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#define MAXCLUSTSIZE 128
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#define NSECTORFAT12 8
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#define NFAT 2
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VOID CalculateFATData(ddt * pddt, ULONG NumSectors, UBYTE FileSystem)
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{
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UBYTE maxclustsize;
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ULONG fatdata;
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bpb *defbpb = &pddt->ddt_defbpb;
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/* FAT related items */
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defbpb->bpb_nfat = 2;
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defbpb->bpb_ndirent = (FileSystem == FAT32
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|| FileSystem == FAT32_LBA) ? 0 : 512;
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defbpb->bpb_nfat = NFAT;
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/* normal value of number of entries in root dir */
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defbpb->bpb_nreserved = (FileSystem == FAT32
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|| FileSystem == FAT32_LBA) ? 0x20 : 1;
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fatdata =
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NumSectors - cdiv(defbpb->bpb_ndirent * DIRENT_SIZE,
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defbpb->bpb_nbyte) - defbpb->bpb_nreserved;
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maxclustsize = 128;
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defbpb->bpb_ndirent = 512;
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defbpb->bpb_nreserved = 1;
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/* SEC_SIZE * DIRENT_SIZE / defbpb->bpb_ndirent + defbpb->bpb_nreserved */
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fatdata = NumSectors - (DIRENT_SIZE + 1);
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#ifdef DEBUG
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if (FileSystem != FAT12)
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DebugPrintf(("%ld sectors for FAT+data, starting with %d sectors/cluster\n", fatdata, defbpb->bpb_nsector));
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@ -423,9 +422,9 @@ VOID CalculateFATData(ddt * pddt, ULONG NumSectors, UBYTE FileSystem)
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case FAT12:
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case FAT12_LBA:
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{
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unsigned fatdat, fatlength, clust, maxclust;
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unsigned fatdat;
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/* in DOS, FAT12 defaults to 4096kb (8 sector) - clusters. */
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defbpb->bpb_nsector = 8;
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defbpb->bpb_nsector = NSECTORFAT12;
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/* Force maximal fatdata=32696 sectors since with our only possible sector
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size (512 bytes) this is the maximum for 4k clusters.
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#clus*secperclus+#fats*fatlength= 4077 * 8 + 2 * 12 = 32640.
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@ -433,26 +432,28 @@ VOID CalculateFATData(ddt * pddt, ULONG NumSectors, UBYTE FileSystem)
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fatdat = (unsigned)fatdata;
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if (fatdata > 32640)
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fatdat = 32640;
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/* The "+2*defbpb->bpb_nsector" is for the reserved first two FAT entries */
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fatlength = cdiv(fatdat + 2 * defbpb->bpb_nsector,
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defbpb->bpb_nbyte * 2 * defbpb->bpb_nsector / 3 +
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defbpb->bpb_nfat);
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/* The "+2*NSECTOR" is for the reserved first two FAT entries */
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defbpb->bpb_nfsect = cdiv(fatdat + 2 * NSECTORFAT12,
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SEC_SIZE * 2 * NSECTORFAT12 / 3 + NFAT);
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#if DEBUG
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/* Need to calculate number of clusters, since the unused parts of the
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* FATS and data area together could make up space for an additional,
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* not really present cluster. */
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clust =
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(fatdat - defbpb->bpb_nfat * fatlength) / defbpb->bpb_nsector;
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maxclust = (fatlength * 2 * defbpb->bpb_nbyte) / 3;
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if (maxclust > FAT12MAX)
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maxclust = FAT12MAX;
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DebugPrintf(("FAT12: #clu=%u, fatlength=%u, maxclu=%u, limit=%u\n",
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clust, fatlength, maxclust, FAT12MAX));
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if (clust > maxclust - 2)
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* not really present cluster.
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* (This is really done in fatfs.c, bpbtodpb) */
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{
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clust = maxclust - 2;
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DebugPrintf(("FAT12: too many clusters: setting to maxclu-2\n"));
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unsigned clust = (fatdat - 2 * defbpb->bpb_nfsect) / NSECTORFAT12;
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unsigned maxclust = (defbpb->bpb_nfsect * 2 * SEC_SIZE) / 3;
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if (maxclust > FAT12MAX)
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maxclust = FAT12MAX;
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printf(("FAT12: #clu=%u, fatlength=%u, maxclu=%u, limit=%u\n",
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clust, defbpb->bpb_nfsect, maxclust, FAT12MAX));
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if (clust > maxclust - 2)
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{
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clust = maxclust - 2;
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printf(("FAT12: too many clusters: setting to maxclu-2\n"));
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}
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}
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defbpb->bpb_nfsect = fatlength;
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#endif
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memcpy(pddt->ddt_fstype, MSDOS_FAT12_SIGN, 8);
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break;
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}
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@ -477,14 +478,12 @@ VOID CalculateFATData(ddt * pddt, ULONG NumSectors, UBYTE FileSystem)
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defbpb->bpb_nsector));
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fatlength = (unsigned)cdiv(fatdata + 2 * defbpb->bpb_nsector,
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(ULONG)defbpb->bpb_nbyte * defbpb->bpb_nsector / 2 +
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defbpb->bpb_nfat);
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(SEC_SIZE/2) * defbpb->bpb_nsector + NFAT);
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/* Need to calculate number of clusters, since the unused parts of the
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* FATS and data area together could make up space for an additional,
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* not really present cluster. */
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clust =
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(fatdata - defbpb->bpb_nfat * fatlength) / defbpb->bpb_nsector;
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maxclust = ((unsigned long)fatlength * defbpb->bpb_nbyte) / 2;
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clust = (fatdata - NFAT * fatlength) / defbpb->bpb_nsector;
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maxclust = (unsigned long)fatlength * (SEC_SIZE/2);
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if (maxclust > FAT16MAX)
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maxclust = FAT16MAX;
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DebugPrintf(("FAT16: #clu=%lu, fatlen=%u, maxclu=%lu, limit=%u\n",
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@ -505,7 +504,7 @@ VOID CalculateFATData(ddt * pddt, ULONG NumSectors, UBYTE FileSystem)
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break;
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defbpb->bpb_nsector <<= 1;
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}
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while (defbpb->bpb_nsector && defbpb->bpb_nsector <= maxclustsize);
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while (defbpb->bpb_nsector && defbpb->bpb_nsector <= MAXCLUSTSIZE);
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defbpb->bpb_nfsect = fatlength;
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memcpy(pddt->ddt_fstype, MSDOS_FAT16_SIGN, 8);
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break;
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@ -530,17 +529,18 @@ VOID CalculateFATData(ddt * pddt, ULONG NumSectors, UBYTE FileSystem)
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if (NumSectors <= 532480UL) /* disks up to 260 MB, 0.5K cluster */
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nsector = 1;
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defbpb->bpb_nsector = nsector;
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defbpb->bpb_ndirent = 0;
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defbpb->bpb_nreserved = 0x20;
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fatdata = NumSectors - 0x20;
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do
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{
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fatlength = cdiv(fatdata + 2 * defbpb->bpb_nsector,
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(ULONG)defbpb->bpb_nbyte * defbpb->bpb_nsector / 4 +
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defbpb->bpb_nfat);
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(SEC_SIZE/4) * defbpb->bpb_nsector + NFAT);
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/* Need to calculate number of clusters, since the unused parts of the
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* FATS and data area together could make up space for an additional,
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* not really present cluster. */
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clust =
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(fatdata - defbpb->bpb_nfat * fatlength) / defbpb->bpb_nsector;
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maxclust = (fatlength * defbpb->bpb_nbyte) / 4;
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clust = (fatdata - NFAT * fatlength) / defbpb->bpb_nsector;
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maxclust = fatlength * (SEC_SIZE/4);
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if (maxclust > FAT32MAX)
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maxclust = FAT32MAX;
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DebugPrintf(("FAT32: #clu=%u, fatlen=%u, maxclu=%u, limit=%u\n",
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@ -554,7 +554,7 @@ VOID CalculateFATData(ddt * pddt, ULONG NumSectors, UBYTE FileSystem)
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break;
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defbpb->bpb_nsector <<= 1;
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}
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while (defbpb->bpb_nsector && defbpb->bpb_nsector <= maxclustsize);
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while (defbpb->bpb_nsector && defbpb->bpb_nsector <= MAXCLUSTSIZE);
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defbpb->bpb_nfsect = 0;
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defbpb->bpb_xnfsect = fatlength;
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/* set up additional FAT32 fields */
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