problem with fwrite

[Lei Yang]

Hi all,

This is not really a kernel issue, apologize if anyone thinks that this 
is not the right place to post it. But I am writing a kernel module and 
got stuck on fwrite, really hope someone could point out what stupid 
mistake I've made. I wrote a very simple code to test the idea, what I 
really want to do in fred() is to read from 'dest' and write to 'src'. 
It seems that upon running , fgetc doesn't get anything from in_stream, 
so the first char it gets is an EOF and it breaks. Just why fwrite 
didn't write anything to in_stream?

If this is not the right way to do it, what is ?

Appreciate any comments, even harsh ones.

TIA
Lei

// in test.c

#include <stdio.h>

fred(char *dest, size_t *destlen, char *src, size_t size)
{
    FILE *in_stream = tmpfile();
    FILE *out_stream = tmpfile();
    fwrite(src, 1, size, in_stream);

    int c, i;
    for(i = 0;;i++)
    {
  	c = fgetc(in_stream);
  	fprintf(stderr, "get char %c\n", c);
	if ( c == EOF) break;
  	fputc(c, out_stream);
     }

    *destlen = i;
	
    fseek(out_stream, 0, SEEK_SET); //rewind
    fread(dest, 1, *destlen, out_stream);
    fclose(in_stream);
    fclose(out_stream);
    fprintf(stderr, "buf = `%s', size = %d\n", dest, *destlen);
}

int main(void)
{
  static char source[] = "really hope this works ";

  char *bp = malloc (2048);
  size_t destlen;

  fred(bp, &destlen, source, strlen(source));

  fprintf(stderr, "buf = `%s', size = %d\n", bp, destlen);
  return 0;
}
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