Flush buffer after newline in putc, fputc, and puts (but not fputs)

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3607 42af7a65-404d-4744-a932-0658087f49c3

TODO

-NuttX TODO List (Last updated May 6, 2011)
+NuttX TODO List (Last updated May 14, 2011)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 nuttx/
@@ -12,7 +12,7 @@ nuttx/
   (5)  Binary loaders (binfmt/)
  (15)  Network (net/, drivers/net)
   (2)  USB (drivers/usbdev, drivers/usbhost)
-  (5)  Libraries (lib/)
+  (6)  Libraries (lib/)
  (13)  File system/Generic drivers (fs/, drivers/)
   (1)  Graphics subystem (graphics/)
   (1)  Pascal add-on (pcode/)
@@ -371,6 +371,22 @@ o Libraries (lib/)
   Priority:    Low (unless you are using mixed C-buffered I/O with fgets and
                fgetc, for example).
 
+  Description: if CONFIG_STDIO_LINEBUFFER is defined, then fputs() should flush
+               the buffer on each newline encountered in the input stream.  At
+               present, it does not flush at all!  This is because fputs() is
+               based on fwrite() which handles binary data.
+
+               I suppose one could easily check if the last character is '\n'
+               and then flush in fputs() for that case. But that is imperfect
+               logic. It would work for the most frequent cases like puts("abcdef\n")
+               but not in all cases. For example, puts("abc\ndef") should flush
+               "abc\n" to output but keep "def" buffered. I can't get that behavior
+               using lib_fwrite() to implement fputs() (unless lib_fwrite were
+               extended to handle binary or text data with newlines).
+  Status:      Open
+  Priority:    Low (unless you doing lots of puts or fputs output and the
+               current buffer handling does not meet your needs).
+
   Description: Need some minimal termios support... at a minimum, enough to
                switch between raw and "normal" modes to support behavior like
                that needed for readline().

lib/stdio/lib_fputc.c

@@ -89,6 +89,18 @@ int fputc(int c, FAR FILE *stream)
   unsigned char buf = (unsigned char)c;
   if (lib_fwrite(&buf, 1, stream) > 0)
     {
+      /* Flush the buffer if a newline is output */
+
+#ifdef CONFIG_STDIO_LINEBUFFER
+      if (c == '\n')
+        {
+          int ret = lib_fflush(stream, true);
+          if (ret < 0)
+            {
+              return EOF;
+            }
+        }
+#endif
       return c;
     }
   else

lib/stdio/lib_fputs.c

@@ -108,19 +108,20 @@ int fputs(FAR const char *s, FAR FILE *stream)
 
       ntowrite = strlen(s);
       if (ntowrite == 0)
-	{
-	  nput = 0;
-	}
+        {
+          nput = 0;
+        }
       else
-	{
-	  /* Write the string */
-
-	  nwritten = lib_fwrite(s, ntowrite, stream);
-	  if (nwritten > 0)
-	    {
-	      nput = nwritten;
-	    }
-	}
+        {
+          /* Write the string */
+
+          nwritten = lib_fwrite(s, ntowrite, stream);
+          if (nwritten > 0)
+            {
+              nput = nwritten;
+            }
+        }
     }
+
   return nput;
 }

lib/stdio/lib_libvsprintf.c

@@ -1136,6 +1136,8 @@ int lib_vsprintf(FAR struct lib_outstream_s *obj, const char *src, va_list ap)
 #ifdef CONFIG_STDIO_LINEBUFFER
            if (*src == '\n')
              {
+               /* Should return an error on a failure to flush */
+
                (void)obj->flush(obj);
              }
 #endif

lib/stdio/lib_puts.c

@@ -84,31 +84,46 @@
  * Name: puts
  *
  * Description:
- *   puts() writes the string s and a trailing newline to
- *   stdout.
+ *   puts() writes the string s and a trailing newline to stdout.
+ *
  ****************************************************************************/
 
 int puts(FAR const char *s)
 {
+  FILE *stream = stdout;
   int nwritten;
   int nput = EOF;
 
   /* Write the string (the next two steps must be atomic) */
 
-  lib_take_semaphore(stdout);
+  lib_take_semaphore(stream);
 
   /* Write the string without its trailing '\0' */
 
-  nwritten = fputs(s, stdout);
+  nwritten = fputs(s, stream);
   if (nwritten > 0)
     {
       /* Followed by a newline */
+
       char newline = '\n';
-      if (lib_fwrite(&newline, 1, stdout) > 0)
+      if (lib_fwrite(&newline, 1, stream) > 0)
         {
           nput = nwritten + 1;
+
+          /* Flush the buffer after the newline is output */
+
+#ifdef CONFIG_STDIO_LINEBUFFER
+          {
+            int ret = lib_fflush(stream, true);
+            if (ret < 0)
+              {
+                nput = EOF;
+              }
+          }
+#endif
         }
     }
+
   lib_give_semaphore(stdout);
   return nput;
 }