It is accomplished ...

git-svn-id: file:///srv/svn/repos/haiku/trunk/current@10 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kits/storage/OffsetFile.cpp

@@ -0,0 +1,171 @@
+//----------------------------------------------------------------------
+//  This software is part of the OpenBeOS distribution and is covered 
+//  by the OpenBeOS license.
+//---------------------------------------------------------------------
+/*!
+	\file OffsetFile.cpp
+	OffsetFile implementation.
+*/
+
+#include <stdio.h>
+
+#include "OffsetFile.h"
+
+namespace StorageKit {
+
+// constructor
+OffsetFile::OffsetFile()
+	: fFile(),
+	  fOffset(0),
+	  fCurrentPosition(0)
+{
+}
+
+// constructor
+OffsetFile::OffsetFile(BFile *file, off_t offset)
+	: fFile(NULL),
+	  fOffset(0),
+	  fCurrentPosition(0)
+{
+	SetTo(file, offset);
+}
+
+// destructor
+OffsetFile::~OffsetFile()
+{
+}
+
+// SetTo
+status_t
+OffsetFile::SetTo(BFile *file, off_t offset)
+{
+	Unset();
+	fFile = file;
+	fOffset = offset;
+	return fFile->InitCheck();
+}
+
+// Unset
+void
+OffsetFile::Unset()
+{
+	fFile = NULL;
+	fOffset = 0;
+	fCurrentPosition = 0;
+}
+
+// InitCheck
+status_t
+OffsetFile::InitCheck() const
+{
+	return (fFile ? fFile->InitCheck() : B_NO_INIT);
+}
+
+// File
+BFile *
+OffsetFile::File() const
+{
+	return fFile;
+}
+
+// ReadAt
+ssize_t
+OffsetFile::ReadAt(off_t pos, void *buffer, size_t size)
+{
+	status_t error = InitCheck();
+	ssize_t result = 0;
+	if (error == B_OK)
+		result = fFile->ReadAt(pos + fOffset, buffer, size);
+	return (error == B_OK ? result : error);
+}
+
+// WriteAt
+ssize_t
+OffsetFile::WriteAt(off_t pos, const void *buffer, size_t size)
+{
+	status_t error = InitCheck();
+	ssize_t result = 0;
+	if (error == B_OK)
+		result = fFile->WriteAt(pos + fOffset, buffer, size);
+	return (error == B_OK ? result : error);
+}
+
+// Seek
+off_t
+OffsetFile::Seek(off_t position, uint32 seekMode)
+{
+	off_t result = B_BAD_VALUE;
+	status_t error = InitCheck();
+	if (error == B_OK) {
+		switch (seekMode) {
+			case SEEK_SET:
+				if (position >= 0)
+					result = fCurrentPosition = position;
+				break;
+			case SEEK_END:
+			{
+				off_t size;
+				error = GetSize(&size);
+				if (error == B_OK) {
+					if (size + position >= 0)
+						result = fCurrentPosition = size + position;
+				}
+				break;
+			}
+			case SEEK_CUR:
+				if (fCurrentPosition + position >= 0)
+					result = fCurrentPosition += position;
+				break;
+			default:
+				break;
+		}
+	}
+	return (error == B_OK ? result : error);
+}
+
+// Position
+off_t
+OffsetFile::Position() const
+{
+	return fCurrentPosition;
+}
+
+// SetSize
+status_t
+OffsetFile::SetSize(off_t size)
+{
+	status_t error = (size >= 0 ? B_OK : B_BAD_VALUE );
+	if (error == B_OK)
+		error = InitCheck();
+	if (error == B_OK)
+		error = fFile->SetSize(size + fOffset);
+	return error;
+}
+
+// GetSize
+status_t
+OffsetFile::GetSize(off_t *size)
+{
+	status_t error = (size ? B_OK : B_BAD_VALUE );
+	if (error == B_OK)
+		error = InitCheck();
+	if (error == B_OK)
+		error = fFile->GetSize(size);
+	if (error == B_OK) {
+		*size -= fOffset;
+		if (*size < 0)
+			*size = 0;
+	}
+	return error;
+}
+
+// Offset
+off_t
+OffsetFile::Offset() const
+{
+	return fOffset;
+}
+
+
+};	// namespace StorageKit
+