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/*

 * shpart.c -- show partitions on a disk

 */

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <stdarg.h>

#define SECTOR_SIZE     512

#define NPE             (SECTOR_SIZE / sizeof(PartEntry))

#define DESCR_SIZE      20

typedef struct {

  unsigned long type;

  unsigned long start;

  unsigned long size;

  char descr[DESCR_SIZE];

} PartEntry;

PartEntry ptr[NPE];

/**************************************************************/

void error(char *fmt, ...) {

  va_list ap;

  va_start(ap, fmt);

  printf("Error: ");

  vprintf(fmt, ap);

  printf("\n");

  va_end(ap);

  exit(1);

}

/**************************************************************/

unsigned long getNumber(unsigned char *p) {

  return (unsigned long) *(p + 0) << 24 |

         (unsigned long) *(p + 1) << 16 |

         (unsigned long) *(p + 2) <<  8 |

         (unsigned long) *(p + 3) <<  0;

}

void convertPartitionTable(PartEntry *e, int n) {

  int i;

  unsigned char *p;

  for (i = 0; i < n; i++) {

    p = (unsigned char *) &e[i];

    e[i].type = getNumber(p + 0);

    e[i].start = getNumber(p + 4);

    e[i].size = getNumber(p + 8);

  }

}

/**************************************************************/

int main(int argc, char *argv[]) {

  char *diskName;

  FILE *disk;

  unsigned long diskSize;

  unsigned long numSectors;

  unsigned long partLast;

  int i, j;

  char c;

  /* check command line arguments */

  if (argc != 2) {

    printf("Usage: %s <disk image file>\n", argv[0]);

    exit(1);

  }

  diskName = argv[1];

  /* determine disk size */

  disk = fopen(diskName, "rb");

  if (disk == NULL) {

    error("cannot open disk image '%s'", diskName);

  }

  fseek(disk, 0, SEEK_END);

  diskSize = ftell(disk);

  numSectors = diskSize / SECTOR_SIZE;

  fclose(disk);

  printf("Disk '%s' has %lu (0x%lX) sectors.\n",

         diskName, numSectors, numSectors);

  if (numSectors < 32) {

    error("disk is too small");

  }

  if (diskSize % SECTOR_SIZE != 0) {

    printf("Warning: disk size is not a multiple of sector size!\n");

  }

  /* read partition table record */

  disk = fopen(diskName, "rb");

  if (disk == NULL) {

    error("cannot open disk image '%s'", diskName);

  }

  fseek(disk, 1 * SECTOR_SIZE, SEEK_SET);

  if (fread(ptr, 1, SECTOR_SIZE, disk) != SECTOR_SIZE) {

    error("cannot read partition table from disk image '%s'", diskName);

  }

  fclose(disk);

  convertPartitionTable(ptr, NPE);

  /* show partition table */

  printf("Partitions:\n");

  printf(" # b type       start      last       size       description\n");

  for (i = 0; i < NPE; i++) {

    if (ptr[i].type != 0) {

      partLast = ptr[i].start + ptr[i].size - 1;

    } else {

      partLast = 0;

    }

    printf("%2d %s 0x%08lX 0x%08lX 0x%08lX 0x%08lX ",

           i,

           ptr[i].type & 0x80000000 ? "*" : " ",

           ptr[i].type & 0x7FFFFFFF,

           ptr[i].start,

           partLast,

           ptr[i].size);

    for (j = 0; j < DESCR_SIZE; j++) {

      c = ptr[i].descr[j];

      if (c == '\0') {

        break;

      }

      if (c >= 0x20 && c < 0x7F) {

        printf("%c", c);

      } else {

        printf(".");

      }

    }

    printf("\n");

  }

  /* done */

  return 0;

}