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Annotation of hatari/tools/hmsa/floppy.c, revision 1.1.1.2

1.1       root        1: /*
                      2:   Hatari tool: Magic Shadow Archiver - floppy.c
                      3: 
1.1.1.2 ! root        4:   This file is distributed under the GNU General Public License, version 2
        !             5:   or at your option any later version. Read the file gpl.txt for details.
1.1       root        6: 
                      7:   Check for valid floppy disk geometry.
                      8: */
                      9: 
                     10: #include <stdio.h>
                     11: #include <SDL_endian.h>
                     12: 
                     13: #include "hmsa.h"
                     14: #include "floppy.h"
                     15: 
                     16: 
                     17: /**
                     18:  * Double-check information read from boot-sector as this is sometimes found to
                     19:  * be incorrect. The .ST image file should be divisible by the sector size and
                     20:  * sectors per track.
                     21:  * NOTE - Pass information from boot-sector to this function (if we can't
                     22:  * decide we leave it alone).
                     23:  */
                     24: static void Floppy_DoubleCheckFormat(long nDiskSize, Uint16 *pnSides, Uint16 *pnSectorsPerTrack)
                     25: {
                     26:        int nSectorsPerTrack;
                     27:        long TotalSectors;
                     28: 
                     29:        /* Now guess at number of sides */
                     30:        if (nDiskSize < (500*1024))                    /* Is size is >500k assume 2 sides to disk! */
                     31:                *pnSides = 1;
                     32:        else
                     33:                *pnSides = 2;
                     34: 
                     35:        /* And Sectors Per Track(always 512 bytes per sector) */
                     36:        TotalSectors = nDiskSize/512;                 /* # Sectors on disk image */
                     37:        /* Does this match up with what we've read from boot-sector? */
                     38:        nSectorsPerTrack = *pnSectorsPerTrack;
                     39:        if (nSectorsPerTrack==0)                      /* Check valid, default to 9 */
                     40:                nSectorsPerTrack = 9;
                     41:        if ((TotalSectors%nSectorsPerTrack)!=0)
                     42:        {
                     43:                /* No, we have an invalid boot-sector - re-calculate from disk size */
                     44:                if ((TotalSectors%9)==0)                    /* Work in this order.... */
                     45:                        *pnSectorsPerTrack = 9;
                     46:                else if ((TotalSectors%10)==0)
                     47:                        *pnSectorsPerTrack = 10;
                     48:                else if ((TotalSectors%11)==0)
                     49:                        *pnSectorsPerTrack = 11;
                     50:                else if ((TotalSectors%12)==0)
                     51:                        *pnSectorsPerTrack = 12;
                     52:        }
                     53:        /* else unknown, assume boot-sector is correct!!! */
                     54: }
                     55: 
                     56: 
                     57: /**
                     58:  * Find details of disk image. We need to do this via a function as sometimes the boot-block
                     59:  * is not actually correct with the image - some demos/game disks have incorrect bytes in the
                     60:  * boot sector and this attempts to find the correct values.
                     61:  */
                     62: void Floppy_FindDiskDetails(const Uint8 *pBuffer, int nImageBytes,
                     63:                             unsigned short *pnSectorsPerTrack, unsigned short *pnSides)
                     64: {
                     65:        Uint16 nSectorsPerTrack, nSides, nSectors;
                     66: 
                     67:        /* First do check to find number of sectors and bytes per sector */
                     68:        nSectorsPerTrack = SDL_SwapLE16(*(const Uint16 *)(pBuffer+24));   /* SPT */
                     69:        nSides = SDL_SwapLE16(*(const Uint16 *)(pBuffer+26));             /* SIDE */
                     70:        nSectors = pBuffer[19] | (pBuffer[20] << 8);                      /* total sectors */
                     71: 
                     72:        /* If the number of sectors announced is incorrect, the boot-sector may
                     73:         * contain incorrect information, eg the 'Eat.st' demo, or wrongly imaged
                     74:         * single/double sided floppies... */
                     75:        if (nSectors != nImageBytes/512)
                     76:                Floppy_DoubleCheckFormat(nImageBytes, &nSides, &nSectorsPerTrack);
                     77: 
                     78:        /* And set values */
                     79:        if (pnSectorsPerTrack)
                     80:                *pnSectorsPerTrack = nSectorsPerTrack;
                     81:        if (pnSides)
                     82:                *pnSides = nSides;
                     83: }

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