1 files changed, 77 insertions, 0 deletions
diff --git a/xpcom/io/nsStorageStream.h b/xpcom/io/nsStorageStream.h
new file mode 100644
index 0000000000..67caea2e59
--- /dev/null
+++ b/xpcom/io/nsStorageStream.h
@@ -0,0 +1,77 @@
+/* -*- 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 "mozilla/Attributes.h"
+#include "mozilla/Mutex.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();
+
+  mozilla::Mutex mMutex{"nsStorageStream"};
+  nsSegmentedBuffer* mSegmentedBuffer MOZ_GUARDED_BY(mMutex) = nullptr;
+  // All segments, except possibly the last, are of this size.  Must be
+  // power-of-2
+  uint32_t mSegmentSize MOZ_GUARDED_BY(mMutex) = 0;
+  // log2(mSegmentSize)
+  uint32_t mSegmentSizeLog2 MOZ_GUARDED_BY(mMutex) = 0;
+  // true, if an un-Close'ed output stream exists
+  bool mWriteInProgress MOZ_GUARDED_BY(mMutex) = false;
+  // Last segment # in use, -1 initially
+  int32_t mLastSegmentNum MOZ_GUARDED_BY(mMutex) = -1;
+  // Pointer to next byte to be written
+  char* mWriteCursor MOZ_GUARDED_BY(mMutex) = nullptr;
+  // Pointer to one byte after end of segment containing the write cursor
+  char* mSegmentEnd MOZ_GUARDED_BY(mMutex) = nullptr;
+  // Number of bytes written to stream
+  uint32_t mLogicalLength MOZ_GUARDED_BY(mMutex) = 0;
+  // number of input streams actively reading a segment.
+  uint32_t mActiveSegmentBorrows MOZ_GUARDED_BY(mMutex) = 0;
+
+  nsresult SetLengthLocked(uint32_t aLength) MOZ_REQUIRES(mMutex);
+  nsresult Seek(int32_t aPosition) MOZ_REQUIRES(mMutex);
+  uint32_t SegNum(uint32_t aPosition) MOZ_REQUIRES(mMutex) {
+    return aPosition >> mSegmentSizeLog2;
+  }
+  uint32_t SegOffset(uint32_t aPosition) MOZ_REQUIRES(mMutex) {
+    return aPosition & (mSegmentSize - 1);
+  }
+};
+
+#endif  //  _nsStorageStream_h_