* BBufferIO did not implement Seek() and Position() correctly; it just passed

it to the stream. This caused Read()/Write() to need two syscalls for nothing
  (this only caused the actual stream to share the same position with the
  BBufferIO, something you just cannot rely on when using buffered I/O).
* Anyway, this reduces the time VirtualBox needs to open some RAW test images
  from over 4 minutes to less than 15 seconds...


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@28662 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/os/support/BufferIO.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2007, Haiku, Inc. All Rights Reserved.
+ * Copyright 2007-2008, Haiku, Inc. All Rights Reserved.
  * Distributed under the terms of the MIT License.
  */
 #ifndef _BUFFER_IO_H
@@ -40,7 +40,8 @@ class BBufferIO : public BPositionIO {
 		char* fBuffer;
 		size_t fBufferSize;
 		size_t fBufferUsed;
-		uint32 _reserved_ints[6];
+		off_t fPosition;
+		uint32 _reserved_ints[4];
 		bool fBufferIsDirty;
 		bool fOwnsStream;
 		bool _reserved_bools[6];

src/kits/support/BufferIO.cpp

@@ -1,5 +1,5 @@
 /*
- *	Copyright (c) 2001-2007, Haiku
+ *	Copyright (c) 2001-2008, Haiku
  *	Distributed under the terms of the MIT license
  *
  *	Authors:
@@ -24,10 +24,8 @@ BBufferIO::BBufferIO(BPositionIO *stream, size_t bufferSize, bool ownsStream)
 	fOwnsStream(ownsStream)
 
 {
-	if (bufferSize < 512)
-		bufferSize = 512;
-	
-	fBufferSize = bufferSize;
+	fBufferSize = max_c(bufferSize, 512);
+	fPosition = stream->Position();
 
 	// What can we do if this malloc fails ?
 	// I think R5 uses new, but doesn't catch the thrown exception
@@ -59,13 +57,12 @@ BBufferIO::ReadAt(off_t pos, void *buffer, size_t size)
 	// stream on construction.
 	if (fStream == NULL)
 		return B_NO_INIT;
-
 	if (buffer == NULL)
 		return B_BAD_VALUE;
 
 	// If the amount of data we want doesn't fit in the buffer, just
 	// read it directly from the disk (and don't touch the buffer).
-	if (size > fBufferSize) {
+	if (size > fBufferSize || fBuffer == NULL) {
 		if (fBufferIsDirty)
 			Flush();
 		return fStream->ReadAt(pos, buffer, size);
@@ -100,12 +97,11 @@ BBufferIO::WriteAt(off_t pos, const void *buffer, size_t size)
 {
 	if (fStream == NULL)
 		return B_NO_INIT;
-
 	if (buffer == NULL)
 		return B_BAD_VALUE;
 
 	// If data doesn't fit into the buffer, write it directly to the stream
-	if (size > fBufferSize)
+	if (size > fBufferSize || fBuffer == NULL)
 		return fStream->WriteAt(pos, buffer, size);
 
 	// If we have cached data in the buffer, whose offset into the stream
@@ -147,17 +143,40 @@ BBufferIO::Seek(off_t position, uint32 seekMode)
 	if (fStream == NULL)
 		return B_NO_INIT;
 
-	return fStream->Seek(position, seekMode);
+	switch (seekMode) {
+		case SEEK_CUR:
+			fPosition += position;
+			if (fPosition < 0)
+				fPosition = 0;
+			break;
+		case SEEK_SET:
+			if (position < 0)
+				return B_BAD_VALUE;
+
+			fPosition = position;
+			break;
+		case SEEK_END:
+		{
+			off_t size;
+			status_t status = fStream->GetSize(&size);
+			if (status != B_OK)
+				return status;
+
+			fPosition = size - position;
+			if (fPosition < 0)
+				fPosition = 0;
+			break;
+		}
+	}
+
+	return fPosition;
 }
 
 
 off_t
 BBufferIO::Position() const
 {
-	if (fStream == NULL)
-		return B_NO_INIT;
-
-	return fStream->Position();
+	return fPosition;
 }
 
 
@@ -208,9 +227,9 @@ BBufferIO::OwnsStream() const
 
 
 void
-BBufferIO::SetOwnsStream(bool owns_stream)
+BBufferIO::SetOwnsStream(bool ownsStream)
 {
-	fOwnsStream = owns_stream;
+	fOwnsStream = ownsStream;
 }