Various fixes for buffered R/W I/O and seeking

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@630 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 60 insertions, 46 deletions

diff --git a/nuttx/lib/lib_libfwrite.c b/nuttx/lib/lib_libfwrite.c
index 361d88127..01bc3c285 100644
--- a/nuttx/lib/lib_libfwrite.c
+++ b/nuttx/lib/lib_libfwrite.c
@@ -83,7 +83,7 @@
  ****************************************************************************/
 
 /****************************************************************************
- * lib_fwrite
+ * Name: lib_fwrite
  ****************************************************************************/
 
 ssize_t lib_fwrite(const void *ptr, size_t count, FILE *stream)
@@ -91,73 +91,87 @@ ssize_t lib_fwrite(const void *ptr, size_t count, FILE *stream)
 {
   const unsigned char *start = ptr;
   const unsigned char *src   = ptr;
-  ssize_t bytes_written;
+  ssize_t ret = ERROR;
   unsigned char *dest;
 
   /* Make sure that writing to this stream is allowed */
 
-  if ((!stream) || ((stream->fs_oflags & O_WROK) == 0))
+  if (!stream || (stream->fs_oflags & O_WROK) == 0)
     {
       *get_errno_ptr() = EBADF;
-      bytes_written = -1;
+      goto errout;
     }
-  else
+
+  /* Get exclusive access to the stream */
+
+  lib_take_semaphore(stream);
+
+  /* If the buffer is currently being used for read access, then
+   * discard all of the read-ahead data.  We do not support concurrent
+   * buffered read/write access.
+   */
+
+  if (lib_rdflush(stream) < 0)
     {
-      /* Loop until all of the bytes have been buffered */
+      goto errout_with_semaphore;
+    }
 
-      lib_take_semaphore(stream);
-      while (count > 0)
-	{
-	  /* Determine the number of bytes left in the buffer */
+  /* Loop until all of the bytes have been buffered */
 
-	  size_t gulp_size = stream->fs_bufend - stream->fs_bufpos;
+  while (count > 0)
+    {
+      /* Determine the number of bytes left in the buffer */
 
-	  /* Will the user data fit into the amount of buffer space
-	   * that we have left?
-	   */
+      size_t gulp_size = stream->fs_bufend - stream->fs_bufpos;
 
-	  if (gulp_size > count)
-	    {
-	      /* Yes, clip the gulp to the size of the user data */
+      /* Will the user data fit into the amount of buffer space
+       * that we have left?
+       */
 
-	      gulp_size = count;
-	    }
+      if (gulp_size > count)
+        {
+          /* Yes, clip the gulp to the size of the user data */
 
-	  /* Adjust the number of bytes remaining to be transferred
-	   * on the next pass through the loop (might be zero).
-	   */
+          gulp_size = count;
+        }
 
-	  count -= gulp_size;
+      /* Adjust the number of bytes remaining to be transferred
+       * on the next pass through the loop (might be zero).
+       */
 
-	  /* Transfer the data into the buffer */
+      count -= gulp_size;
 
-	  for (dest = stream->fs_bufpos; gulp_size > 0; gulp_size--)
-	    {
-	      *dest++ = *src++;
-	    }
-	  stream->fs_bufpos = dest;
+      /* Transfer the data into the buffer */
 
-	  /* Is the buffer full? */
+      for (dest = stream->fs_bufpos; gulp_size > 0; gulp_size--)
+        {
+          *dest++ = *src++;
+        }
+      stream->fs_bufpos = dest;
 
-	  if (dest >= stream->fs_bufend)
-	    {
-	      /* flush the buffered data to the IO stream */
+      /* Is the buffer full? */
 
-	      int bytes_buffered = fflush(stream);
-	      if (bytes_buffered < 0)
-		{
-		  bytes_written = bytes_buffered;
-		  goto err_out;
-		}
-	    }
-	}
-  
-      bytes_written = src - start;
+      if (dest >= stream->fs_bufend)
+        {
+          /* Flush the buffered data to the IO stream */
 
-    err_out:
-      lib_give_semaphore(stream);
+          int bytes_buffered = fflush_internal(stream, FALSE);
+          if (bytes_buffered < 0)
+            {
+              goto errout_with_semaphore;
+            }
+        }
     }
-  return bytes_written;
+
+  /* Return the number of bytes written */
+
+  ret = src - start;
+
+errout_with_semaphore:
+  lib_give_semaphore(stream);
+
+errout:
+  return ret;
 }
 #else
 {