__stdio_read.c raw

   1  #include "stdio_impl.h"
   2  #include <sys/uio.h>
   3  
   4  size_t __stdio_read(FILE *f, unsigned char *buf, size_t len)
   5  {
   6  	struct iovec iov[2] = {
   7  		{ .iov_base = buf, .iov_len = len - !!f->buf_size },
   8  		{ .iov_base = f->buf, .iov_len = f->buf_size }
   9  	};
  10  	ssize_t cnt;
  11  
  12  	cnt = iov[0].iov_len ? syscall(SYS_readv, f->fd, iov, 2)
  13  		: syscall(SYS_read, f->fd, iov[1].iov_base, iov[1].iov_len);
  14  	if (cnt <= 0) {
  15  		f->flags |= cnt ? F_ERR : F_EOF;
  16  		return 0;
  17  	}
  18  	if (cnt <= iov[0].iov_len) return cnt;
  19  	cnt -= iov[0].iov_len;
  20  	f->rpos = f->buf;
  21  	f->rend = f->buf + cnt;
  22  	if (f->buf_size) buf[len-1] = *f->rpos++;
  23  	return len;
  24  }
  25