/*
 * read_data v1.3   (c) 1998,2004 by van Hauser / THC <vh@thc.org>
 * http://www.thc.org
 *
 * reads data from a blockdevice into a file.
 */
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>

#define MAX_SIZE 100000    /* max bytes to read */

int main (int argc, char *argv[]) {
    char dev[100];
    unsigned long bytes, reat;
    off_t start;
    struct stat st;
    int f;
    char buf[MAX_SIZE];
    char filename[50];

    if (argc!=4) {
        printf("Syntax: %s blockdevice start_address no_of_bytes\n",argv[0]);
        printf("Output is saved to start_address_no_of_bytes\n");
        exit(1);
    }
    strncpy(dev, argv[1], sizeof(dev)-1);
    if (sizeof(start) < 8)
      start = atol(argv[2]);
    else
      start = strtoll(argv[2], (char **)NULL, 10);
    bytes = atol(argv[3]);

    if ((bytes < 1) || (bytes > MAX_SIZE)) {
	printf("Error: number of bytes to read must be between 1 and %d\n", MAX_SIZE);
	exit (1);
    }
    if (lstat(dev, &st) != 0) {
	perror("Can't access blockdevice");
	exit(1);
    }
    if ((st.st_mode & S_IFBLK) != S_IFBLK) {
    	printf("Warning: %s is not a block device\n", dev);
    }
    sync();
    if ((f = open(dev, O_RDONLY)) < 0) {
	perror("Can't open blockdevice for reading");
	exit(1);
    }
    if (lseek(f, start, SEEK_SET) < 0) {
        if (sizeof(start) < 8)
  	  printf("Can't seek to offset %lu\n", (unsigned long) start);
  	else
  	  printf("Can't seek to offset %llu\n", (unsigned long long) start);
	exit(1);
    }
    reat = read(f, buf, bytes);
    if (reat <= 0) {
        printf("Couldn't read data from device\n");
        exit(1);
    }
    if (reat != bytes) {
	printf("Warning: I could only read %lu bytes\n", reat);
    }
    close(f);
    if (sizeof(start) < 8)
      sprintf(filename, "%lu.%lu", (unsigned long) start, reat);
    else
      sprintf(filename, "%llu.%lu", (unsigned long long) start, reat);
    if ((f = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0600)) < 0) {
        perror("Could not create outputfile");
        exit(1);
    }
    if (write(f, buf, reat) != reat) {
	printf("Could not write all data to file %s\n", filename);
	exit(1);
    }
    close(f);
    printf("Output successfully written into the file %s\n", filename);
    exit(0);
}