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/*

 * wrpart.c -- write a binary image to a partition 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 int type;

  unsigned int start;

  unsigned int 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 int getNumber(unsigned char *p) {

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

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

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

         (unsigned int) *(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;

  char *partNmbr;

  char *partName;

  FILE *disk;

  unsigned int diskSize;

  char *endp;

  int partno;

  unsigned int partStart;

  unsigned int partSize;

  FILE *image;

  unsigned int imageSize;

  unsigned int i;

  unsigned char sectBuf[SECTOR_SIZE];

  int n;

  /* check command line arguments */

  if (argc != 4) {

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

    printf("<partition number> <partition image>\n");

    exit(1);

  }

  diskName = argv[1];

  partNmbr = argv[2];

  partName = argv[3];

  /* read partition table record */

  disk = fopen(diskName, "r+b");

  if (disk == NULL) {

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

  }

  fseek(disk, 0, SEEK_END);

  diskSize = ftell(disk) / SECTOR_SIZE;

  printf("disk '%s' has %u (0x%X) sectors\n",

         diskName, diskSize, diskSize);

  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);

  }

  convertPartitionTable(ptr, NPE);

  /* get partition number, determine start and size of partition */

  partno = strtol(partNmbr, &endp, 10);

  if (*endp != '\0') {

    error("cannot read partition number");

  }

  if (partno < 0 || partno > 15) {

    error("illegal partition number %d", partno);

  }

  if ((ptr[partno].type & 0x7FFFFFFF) == 0) {

    error("partition %d is not allocated in partition table", partno);

  }

  partStart = ptr[partno].start;

  partSize = ptr[partno].size;

  printf("partition %d: start sector %u (0x%X), size is %u (0x%X) sectors\n",

         partno, partStart, partStart, partSize, partSize);

  if (partStart >= diskSize || partStart + partSize > diskSize) {

    error("partition %d is larger than the disk", partno);

  }

  fseek(disk, partStart * SECTOR_SIZE, SEEK_SET);

  /* open partition image, check size (rounded up to whole sectors) */

  image = fopen(partName, "rb");

  if (image == NULL) {

    error("cannot open partition image '%s'", partName);

  }

  fseek(image, 0, SEEK_END);

  imageSize = (ftell(image) + SECTOR_SIZE - 1) / SECTOR_SIZE;

  printf("partition image '%s' occupies %d (0x%X) sectors\n",

         partName, imageSize, imageSize);

  if (imageSize > partSize) {

    error("partition image (%d sectors) too big for partition (%d sectors)",

          imageSize, partSize);

  }

  fseek(image, 0, SEEK_SET);

  /* copy partition image to partition on disk */

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

    n = fread(sectBuf, 1, SECTOR_SIZE, image);

    if (n != SECTOR_SIZE) {

      if (i != imageSize - 1) {

        error("cannot read partition image '%s'", partName);

      } else {

        while (n < SECTOR_SIZE) {

          sectBuf[n++] = 0;

        }

      }

    }

    n = fwrite(sectBuf, 1, SECTOR_SIZE, disk);

    if (n != SECTOR_SIZE) {

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

    }

  }

  printf("partition image '%s' (%d sectors) copied to partition %d\n",

         partName, imageSize, partno);

  fclose(image);

  fclose(disk);

  return 0;

}