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/*
loadramdisk.c
Copy a device or file specified as argument to /dev/ram
*/
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/ioctl.h>
#define RAM "/dev/ram"
char buf[10240];
static unsigned long size_device(int fd);
int main(int argc, char *argv[])
{
unsigned long off, size;
int r, s, fd, ramfd;
char *src;
if (argc != 2)
{
fprintf(stderr, "Usage: loadramdisk <file>\n");
exit(1);
}
src= argv[1];
fd= open(src, O_RDONLY);
if (fd < 0)
{
fprintf(stderr, "Unable to open '%s': %s\n",
src, strerror(errno));
exit(1);
}
/* Get the size of the device */
errno= 0;
size= size_device(fd);
if (errno != 0)
{
fprintf(stderr, "Lseek(end) failed on '%s': %s\n",
src, strerror(errno));
exit(1);
}
if (lseek(fd, 0, SEEK_SET) != 0)
{
fprintf(stderr, "Lseek(0) failed on '%s': %s\n",
src, strerror(errno));
exit(1);
}
ramfd= open(RAM, O_RDWR);
if (ramfd < 0)
{
fprintf(stderr, "Unable to open '%s': %s\n",
RAM, strerror(errno));
exit(1);
}
r= ioctl(ramfd, MIOCRAMSIZE, &size);
if (r != 0)
{
fprintf(stderr, "MIOCRAMSIZE %lu failed on '%s': %s\n",
size, RAM, strerror(errno));
exit(1);
}
off= 0;
while (off < size)
{
r= read(fd, buf, sizeof(buf));
if (r <= 0)
{
fprintf(stderr, "error reading '%s': %s\n",
src, r == 0 ? "unexpected EOF" :
strerror(errno));
exit(1);
}
s= write(ramfd, buf, r);
if (s != r)
{
fprintf(stderr, "error writing to '%s': %s\n", RAM,
s >= 0 ? "short write" : strerror(errno));
exit(1);
}
off += r;
}
exit(0);
}
static unsigned long size_device(int fd)
{
char b;
int r;
unsigned long low, mid, high;
/* Try to find the size of a device using binary search */
low= 0;
high= -1;
while (mid= low+(high-low)/2, mid > low)
{
if (lseek(fd, mid, SEEK_SET) != mid)
{
fprintf(stderr, "lseek to %lu failed: %s\n",
mid, strerror(errno));
exit(1);
}
r= read(fd, &b, 1);
if (r < 0)
{
fprintf(stderr, "read failed at position %lu: %s\n",
mid, strerror(errno));
exit(1);
}
if (r > 0)
low= mid;
else
high= mid;
}
return high;
}
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