#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <string.h>
#include <openssl/sha.h>
#include <unistd.h>
#include <errno.h>

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

    int fd, length=4*1024;
    void * memptr;
    long * long_array;
    int i;
    SHA_CTX context;
    char md[20];

    if (argc != 3){
        printf("USAGE: dump <filename> <size>\n");
        exit(-1);
    }

    printf("[DUMP] opening file %s\n", argv[1]);
    length=atoi(argv[2])*1024*1024;
//    length=atoi(argv[2]);
    printf("[DUMP] size is %d\n", length);

    fd=open(argv[1], O_RDWR);

    if ((memptr = mmap(NULL, length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)) == (caddr_t)-1){
        printf("mmap failed (0x%x)\n", memptr);
        close (fd);
        exit (-1);
    }

    srand(time());
    long_array=(long *)memptr;
    for (i=0; i < length/sizeof(long); i++){
        long_array[i]=rand();
    }

    memset(md,0,20);

    SHA1_Init(&context);
    SHA1_Update(&context,memptr,length);
    SHA1_Final(md,&context);

    printf("[DUMP] ");
    for(i = 0; i < SHA_DIGEST_LENGTH; ++i )
    {
        unsigned char c = md[i];
        printf("%2.2x",c);
    }
    printf("\n");

    printf("munmap is unmapping %x\n", memptr);
    munmap(memptr, length);

    close(fd);

}