tee: prefer file descriptors over streams

We disable buffering on the streams anyways, so we were effectively
calling the write system call previously despite using streams.

* src/iopoll.h (fclose_wait, fwrite_wait): Remove declarations.
(close_wait, write_wait): Add declarations.
* src/iopoll.c (fwait_for_nonblocking_write, fclose_wait, fwrite_wait):
Remove functions.
(wait_for_nonblocking_write): New function based on
fwait_for_nonblocking_write.
(close_wait): New function based on fclose_wait.
(write_wait): New function based on fwrite_wait.
* src/tee.c: Include fcntl--.h. Don't include stdio--.h.
(get_next_out): Operate on file descriptors instead of streams.
(fail_output): Likewise. Remove clearerr call since we no longer call
fwrite on stdout.
(tee_files): Operate on file descriptors instead of streams. Remove
calls to setvbuf.

src/iopoll.c

@@ -177,62 +177,53 @@ iopoll_output_ok (int fdout)
    Return true, if EAGAIN has been successfully handled. */
 
 static bool
-fwait_for_nonblocking_write (FILE *f)
+wait_for_nonblocking_write (int fd)
 {
   if (! IS_EAGAIN (errno))
     /* non-recoverable write error */
     return false;
 
-  int fd = fileno (f);
-  if (fd == -1)
-    goto fail;
-
   /* wait for the file descriptor to become writable */
   if (iopoll_internal (-1, fd, true, false) != 0)
-    goto fail;
-
-  /* successfully waited for the descriptor to become writable */
-  clearerr (f);
-  return true;
-
-fail:
-  errno = EAGAIN;
-  return false;
-}
-
-
-/* wrapper for fclose() that also waits for F if non blocking.  */
-
-extern bool
-fclose_wait (FILE *f)
-{
-  for (;;)
     {
-      if (fflush (f) == 0)
-        break;
-
-      if (! fwait_for_nonblocking_write (f))
-        break;
+      errno = EAGAIN;
+      return false;
     }
 
-  return fclose (f) == 0;
+  /* successfully waited for the descriptor to become writable */
+  return true;
+}
+
+/* wrapper for close() that also waits for FD if non blocking.  */
+
+extern bool
+close_wait (int fd)
+{
+  while (wait_for_nonblocking_write (fd))
+    ;
+  return close (fd) == 0;
 }
 
 
-/* wrapper for fwrite() that also waits for F if non blocking.  */
+/* wrapper for write() that also waits for FD if non blocking.  */
 
 extern bool
-fwrite_wait (char const *buf, ssize_t size, FILE *f)
+write_wait (int fd, void const *buffer, size_t size)
 {
-  for (;;)
+  unsigned char const *buf = buffer;
+
+  while (true)
     {
-      const size_t written = fwrite (buf, 1, size, f);
+      ssize_t written = write (fd, buf, size);
+      if (written < 0)
+        written = 0;
+
       size -= written;
       affirm (size >= 0);
       if (size <= 0)  /* everything written */
         return true;
 
-      if (! fwait_for_nonblocking_write (f))
+      if (! wait_for_nonblocking_write (fd))
         return false;
 
       buf += written;

src/iopoll.h

@@ -5,5 +5,5 @@ int iopoll (int fdin, int fdout, bool block);
 bool iopoll_input_ok (int fdin);
 bool iopoll_output_ok (int fdout);
 
-bool fclose_wait (FILE *f);
-bool fwrite_wait (char const *buf, ssize_t size, FILE *f);
+bool close_wait (int fd);
+bool write_wait (int fd, void const *buffer, size_t size);

src/tee.c

@@ -24,8 +24,8 @@
 #include "system.h"
 #include "argmatch.h"
 #include "fadvise.h"
+#include "fcntl--.h"
 #include "iopoll.h"
-#include "stdio--.h"
 #include "xbinary-io.h"
 #include "iopoll.h"
 
@@ -194,10 +194,10 @@ main (int argc, char **argv)
 
 ATTRIBUTE_PURE
 static int
-get_next_out (FILE **descriptors, int nfiles, int idx)
+get_next_out (int *descriptors, int nfiles, int idx)
 {
   for (idx++; idx <= nfiles; idx++)
-    if (descriptors[idx])
+    if (0 <= descriptors[idx])
       return idx;
   return -1;  /* no outputs remaining */
 }
@@ -206,21 +206,19 @@ get_next_out (FILE **descriptors, int nfiles, int idx)
    Return true if this indicates a reportable error.  */
 
 static bool
-fail_output (FILE **descriptors, char **files, int i)
+fail_output (int *descriptors, char **files, int i)
 {
   int w_errno = errno;
   bool fail = errno != EPIPE
               || output_error == output_error_exit
               || output_error == output_error_warn;
-  if (descriptors[i] == stdout)
-    clearerr (stdout); /* Avoid redundant close_stdout diagnostic.  */
   if (fail)
     {
       error (output_error == output_error_exit
              || output_error == output_error_exit_nopipe,
              w_errno, "%s", quotef (files[i]));
     }
-  descriptors[i] = NULL;
+  descriptors[i] = -1;
   return fail;
 }
 
@@ -233,16 +231,13 @@ static bool
 tee_files (int nfiles, char **files, bool pipe_check)
 {
   size_t n_outputs = 0;
-  FILE **descriptors;
+  int *descriptors;
   bool *out_pollable IF_LINT ( = NULL);
   char buffer[BUFSIZ];
   ssize_t bytes_read = 0;
   int first_out = 0;  /* idx of first non-null output in descriptors */
   bool ok = true;
-  char const *mode_string =
-    (O_BINARY
-     ? (append ? "ab" : "wb")
-     : (append ? "a" : "w"));
+  int flags = O_WRONLY | O_CREAT | O_BINARY | (append ? O_APPEND : O_TRUNC);
 
   xset_binary_mode (STDIN_FILENO, O_BINARY);
   xset_binary_mode (STDOUT_FILENO, O_BINARY);
@@ -255,18 +250,17 @@ tee_files (int nfiles, char **files, bool pipe_check)
   if (pipe_check)
     out_pollable = xnmalloc (nfiles + 1, sizeof *out_pollable);
   files--;
-  descriptors[0] = stdout;
+  descriptors[0] = STDOUT_FILENO;
   if (pipe_check)
-    out_pollable[0] = iopoll_output_ok (fileno (descriptors[0]));
+    out_pollable[0] = iopoll_output_ok (descriptors[0]);
   files[0] = bad_cast (_("standard output"));
-  setvbuf (stdout, NULL, _IONBF, 0);
   n_outputs++;
 
   for (int i = 1; i <= nfiles; i++)
     {
       /* Do not treat "-" specially - as mandated by POSIX.  */
-       descriptors[i] = fopen (files[i], mode_string);
-      if (descriptors[i] == NULL)
+      descriptors[i] = open (files[i], flags, MODE_RW_UGO);
+      if (descriptors[i] < 0)
         {
           if (pipe_check)
             out_pollable[i] = false;
@@ -278,8 +272,7 @@ tee_files (int nfiles, char **files, bool pipe_check)
       else
         {
           if (pipe_check)
-            out_pollable[i] = iopoll_output_ok (fileno (descriptors[i]));
-          setvbuf (descriptors[i], NULL, _IONBF, 0);
+            out_pollable[i] = iopoll_output_ok (descriptors[i]);
           n_outputs++;
         }
     }
@@ -289,8 +282,7 @@ tee_files (int nfiles, char **files, bool pipe_check)
       if (pipe_check && out_pollable[first_out])
         {
           /* Monitor for input, or errors on first valid output.  */
-          int err = iopoll (STDIN_FILENO, fileno (descriptors[first_out]),
-                            true);
+          int err = iopoll (STDIN_FILENO, descriptors[first_out], true);
 
           /* Close the output if it became a broken pipe.  */
           if (err == IOPOLL_BROKEN_OUTPUT)
@@ -318,8 +310,8 @@ tee_files (int nfiles, char **files, bool pipe_check)
       /* Write to all NFILES + 1 descriptors.
          Standard output is the first one.  */
       for (int i = 0; i <= nfiles; i++)
-        if (descriptors[i]
-            && ! fwrite_wait (buffer, bytes_read, descriptors[i]))
+        if (0 <= descriptors[i]
+            && ! write_wait (descriptors[i], buffer, bytes_read))
           {
             if (fail_output (descriptors, files, i))
               ok = false;
@@ -337,7 +329,7 @@ tee_files (int nfiles, char **files, bool pipe_check)
 
   /* Close the files, but not standard output.  */
   for (int i = 1; i <= nfiles; i++)
-    if (descriptors[i] && ! fclose_wait (descriptors[i]))
+    if (0 <= descriptors[i] && ! close_wait (descriptors[i]))
       {
         error (0, errno, "%s", quotef (files[i]));
         ok = false;