import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

xpcom/io/nsStorageStream.h

@@ -0,0 +1,73 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * The storage stream provides an internal buffer that can be filled by a
+ * client using a single output stream.  One or more independent input streams
+ * can be created to read the data out non-destructively.  The implementation
+ * uses a segmented buffer internally to avoid realloc'ing of large buffers,
+ * with the attendant performance loss and heap fragmentation.
+ */
+
+#ifndef _nsStorageStream_h_
+#define _nsStorageStream_h_
+
+#include "nsIStorageStream.h"
+#include "nsIOutputStream.h"
+#include "nsMemory.h"
+#include "mozilla/Attributes.h"
+
+#define NS_STORAGESTREAM_CID                       \
+{ /* 669a9795-6ff7-4ed4-9150-c34ce2971b63 */       \
+  0x669a9795,                                      \
+  0x6ff7,                                          \
+  0x4ed4,                                          \
+  {0x91, 0x50, 0xc3, 0x4c, 0xe2, 0x97, 0x1b, 0x63} \
+}
+
+#define NS_STORAGESTREAM_CONTRACTID "@mozilla.org/storagestream;1"
+
+class nsSegmentedBuffer;
+
+class nsStorageStream final
+  : public nsIStorageStream
+  , public nsIOutputStream
+{
+public:
+  nsStorageStream();
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSISTORAGESTREAM
+  NS_DECL_NSIOUTPUTSTREAM
+
+  friend class nsStorageInputStream;
+
+private:
+  ~nsStorageStream();
+
+  nsSegmentedBuffer* mSegmentedBuffer;
+  uint32_t           mSegmentSize;       // All segments, except possibly the last, are of this size
+                                         //   Must be power-of-2
+  uint32_t           mSegmentSizeLog2;   // log2(mSegmentSize)
+  bool               mWriteInProgress;   // true, if an un-Close'ed output stream exists
+  int32_t            mLastSegmentNum;    // Last segment # in use, -1 initially
+  char*              mWriteCursor;       // Pointer to next byte to be written
+  char*              mSegmentEnd;        // Pointer to one byte after end of segment
+                                         //   containing the write cursor
+  uint32_t           mLogicalLength;     // Number of bytes written to stream
+
+  nsresult Seek(int32_t aPosition);
+  uint32_t SegNum(uint32_t aPosition)
+  {
+    return aPosition >> mSegmentSizeLog2;
+  }
+  uint32_t SegOffset(uint32_t aPosition)
+  {
+    return aPosition & (mSegmentSize - 1);
+  }
+};
+
+#endif //  _nsStorageStream_h_