131 lines
4.5 KiB
C++
131 lines
4.5 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is mozilla.org code.
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*
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* The Initial Developer of the Original Code is
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* Netscape Communications Corporation.
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* Portions created by the Initial Developer are Copyright (C) 2001
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* L. David Baron <dbaron@dbaron.org> (original author)
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* Kai Engert <kaie@netscape.com>
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#include "prlog.h"
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#include "nsEntropyCollector.h"
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#include "nsMemory.h"
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nsEntropyCollector::nsEntropyCollector()
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:mBytesCollected(0), mWritePointer(mEntropyCache)
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{
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}
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nsEntropyCollector::~nsEntropyCollector()
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{
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}
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NS_IMPL_THREADSAFE_ISUPPORTS2(nsEntropyCollector,
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nsIEntropyCollector,
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nsIBufEntropyCollector)
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NS_IMETHODIMP
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nsEntropyCollector::RandomUpdate(void *new_entropy, PRInt32 bufLen)
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{
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if (bufLen > 0) {
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if (mForwardTarget) {
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return mForwardTarget->RandomUpdate(new_entropy, bufLen);
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}
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else {
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const unsigned char *InputPointer = (const unsigned char *)new_entropy;
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const unsigned char *PastEndPointer = mEntropyCache + entropy_buffer_size;
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// if the input is large, we only take as much as we can store
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PRInt32 bytes_wanted = PR_MIN(bufLen, entropy_buffer_size);
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// remember the number of bytes we will have after storing new_entropy
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mBytesCollected = PR_MIN(entropy_buffer_size, mBytesCollected + bytes_wanted);
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// as the above statements limit bytes_wanted to the entropy_buffer_size,
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// this loop will iterate at most twice.
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while (bytes_wanted > 0) {
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// how many bytes to end of cyclic buffer?
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const PRInt32 space_to_end = PastEndPointer - mWritePointer;
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// how many bytes can we copy, not reaching the end of the buffer?
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const PRInt32 this_time = PR_MIN(space_to_end, bytes_wanted);
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// copy at most to the end of the cyclic buffer
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for (PRInt32 i = 0; i < this_time; ++i) {
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// accept the fact that we use our buffer's random uninitialized content
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unsigned int old = *mWritePointer;
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// combine new and old value already stored in buffer
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// this logic comes from PSM 1
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*mWritePointer++ = ((old << 1) | (old >> 7)) ^ *InputPointer++;
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}
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PR_ASSERT(mWritePointer <= PastEndPointer);
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PR_ASSERT(mWritePointer >= mEntropyCache);
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// have we arrived at the end of the buffer?
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if (PastEndPointer == mWritePointer) {
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// reset write pointer back to begining of our buffer
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mWritePointer = mEntropyCache;
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}
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// subtract the number of bytes we have already copied
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bytes_wanted -= this_time;
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}
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}
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}
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return NS_OK;
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}
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NS_IMETHODIMP
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nsEntropyCollector::ForwardTo(nsIEntropyCollector *aCollector)
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{
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NS_PRECONDITION(!mForwardTarget, "|ForwardTo| should only be called once.");
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mForwardTarget = aCollector;
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mForwardTarget->RandomUpdate(mEntropyCache, mBytesCollected);
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mBytesCollected = 0;
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return NS_OK;
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}
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NS_IMETHODIMP
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nsEntropyCollector::DontForward()
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{
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mForwardTarget = nsnull;
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return NS_OK;
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}
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