src/stdio/__stdio_write.c

   1 #include "stdio_impl.h"
   2 #include <sys/uio.h>
   3
   4 size_t __stdio_write(FILE *f, const unsigned char *buf, size_t len)
   5 {
   6         struct iovec iovs[2] = {
   7                 { .iov_base = f->wbase, .iov_len = f->wpos-f->wbase },
   8                 { .iov_base = (void *)buf, .iov_len = len }
   9         };
  10         struct iovec *iov = iovs;
  11         size_t rem = iov[0].iov_len + iov[1].iov_len;
  12         int iovcnt = 2;
  13         ssize_t cnt;
  14         for (;;) {
  15                 cnt = syscall(SYS_writev, f->fd, iov, iovcnt);
  16                 if (cnt == rem) {
  17                         f->wend = f->buf + f->buf_size;
  18                         f->wpos = f->wbase = f->buf;
  19                         return len;
  20                 }
  21                 if (cnt < 0) {
  22                         f->wpos = f->wbase = f->wend = 0;
  23                         f->flags |= F_ERR;
  24                         return iovcnt == 2 ? 0 : len-iov[0].iov_len;
  25                 }
  26                 rem -= cnt;
  27                 if (cnt > iov[0].iov_len) {
  28                         cnt -= iov[0].iov_len;
  29                         iov++; iovcnt--;
  30                 }
  31                 iov[0].iov_base = (char *)iov[0].iov_base + cnt;
  32                 iov[0].iov_len -= cnt;
  33         }
  34 }