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263 lines
9.9 KiB
C++
263 lines
9.9 KiB
C++
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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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 Novell code.
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*
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* The Initial Developer of the Original Code is Novell.
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* Portions created by the Initial Developer are Copyright (C) 2006
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Robert O'Callahan <robert@ocallahan.org>
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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 "gfxSkipChars.h"
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#include <stdlib.h>
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#define SHORTCUT_FREQUENCY 256
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// Even numbered list entries are "keep" entries
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static bool
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IsKeepEntry(PRUint32 aEntry)
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{
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return !(aEntry & 1);
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}
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void
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gfxSkipChars::BuildShortcuts()
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{
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if (!mList || mCharCount < SHORTCUT_FREQUENCY)
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return;
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mShortcuts = new Shortcut[mCharCount/SHORTCUT_FREQUENCY];
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if (!mShortcuts)
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return;
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PRUint32 i;
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PRUint32 nextShortcutIndex = 0;
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PRUint32 originalCharOffset = 0;
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PRUint32 skippedCharOffset = 0;
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for (i = 0; i < mListLength; ++i) {
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PRUint8 len = mList[i];
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// We use >= here to ensure that when mCharCount is a multiple of
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// SHORTCUT_FREQUENCY, we fill in the final shortcut with a reference
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// to the last element of mList. This means that in general when a list
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// element ends on an offset that's a multiple of SHORTCUT_FREQUENCY,
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// that list element is the shortcut for that offset, which is
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// slightly suboptimal (the *next* element is the one we really want),
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// but it's all correct and simpler this way.
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while (originalCharOffset + len >= (nextShortcutIndex + 1)*SHORTCUT_FREQUENCY) {
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mShortcuts[nextShortcutIndex] =
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Shortcut(i, originalCharOffset, skippedCharOffset);
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++nextShortcutIndex;
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}
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originalCharOffset += len;
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if (IsKeepEntry(i)) {
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skippedCharOffset += len;
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}
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}
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}
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void
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gfxSkipCharsIterator::SetOffsets(PRUint32 aOffset, bool aInOriginalString)
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{
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NS_ASSERTION(aOffset <= mSkipChars->mCharCount,
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"Invalid offset");
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if (mSkipChars->mListLength == 0) {
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mOriginalStringOffset = mSkippedStringOffset = aOffset;
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return;
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}
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if (aOffset == 0) {
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// Start from the beginning of the string.
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mSkippedStringOffset = 0;
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mOriginalStringOffset = 0;
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mListPrefixLength = 0;
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mListPrefixKeepCharCount = 0;
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mListPrefixCharCount = 0;
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if (aInOriginalString) {
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// Nothing more to do!
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return;
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}
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}
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if (aInOriginalString && mSkipChars->mShortcuts &&
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abs(PRInt32(aOffset) - PRInt32(mListPrefixCharCount)) > SHORTCUT_FREQUENCY) {
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// Take a shortcut. This makes SetOffsets(..., PR_TRUE) O(1) by bounding
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// the iterations in the loop below to at most SHORTCUT_FREQUENCY iterations
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PRUint32 shortcutIndex = aOffset/SHORTCUT_FREQUENCY;
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if (shortcutIndex == 0) {
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mListPrefixLength = 0;
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mListPrefixKeepCharCount = 0;
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mListPrefixCharCount = 0;
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} else {
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const gfxSkipChars::Shortcut& shortcut = mSkipChars->mShortcuts[shortcutIndex - 1];
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mListPrefixLength = shortcut.mListPrefixLength;
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mListPrefixKeepCharCount = shortcut.mListPrefixKeepCharCount;
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mListPrefixCharCount = shortcut.mListPrefixCharCount;
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}
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}
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PRInt32 currentRunLength = mSkipChars->mList[mListPrefixLength];
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for (;;) {
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// See if aOffset is in the string segment described by
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// mSkipChars->mList[mListPrefixLength]
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PRUint32 segmentOffset = aInOriginalString ? mListPrefixCharCount : mListPrefixKeepCharCount;
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if ((aInOriginalString || IsKeepEntry(mListPrefixLength)) &&
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aOffset >= segmentOffset && aOffset < segmentOffset + currentRunLength) {
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PRInt32 offsetInSegment = aOffset - segmentOffset;
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mOriginalStringOffset = mListPrefixCharCount + offsetInSegment;
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mSkippedStringOffset = mListPrefixKeepCharCount;
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if (IsKeepEntry(mListPrefixLength)) {
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mSkippedStringOffset += offsetInSegment;
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}
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return;
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}
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if (aOffset < segmentOffset) {
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// We need to move backwards
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if (mListPrefixLength <= 0) {
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// nowhere to go backwards
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mOriginalStringOffset = mSkippedStringOffset = 0;
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return;
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}
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// Go backwards one segment and restore invariants
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--mListPrefixLength;
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currentRunLength = mSkipChars->mList[mListPrefixLength];
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mListPrefixCharCount -= currentRunLength;
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if (IsKeepEntry(mListPrefixLength)) {
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mListPrefixKeepCharCount -= currentRunLength;
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}
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} else {
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// We need to move forwards
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if (mListPrefixLength >= mSkipChars->mListLength - 1) {
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// nowhere to go forwards
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mOriginalStringOffset = mListPrefixCharCount + currentRunLength;
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mSkippedStringOffset = mListPrefixKeepCharCount;
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if (IsKeepEntry(mListPrefixLength)) {
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mSkippedStringOffset += currentRunLength;
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}
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return;
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}
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// Go forwards one segment and restore invariants
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mListPrefixCharCount += currentRunLength;
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if (IsKeepEntry(mListPrefixLength)) {
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mListPrefixKeepCharCount += currentRunLength;
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}
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++mListPrefixLength;
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currentRunLength = mSkipChars->mList[mListPrefixLength];
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}
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}
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}
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bool
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gfxSkipCharsIterator::IsOriginalCharSkipped(PRInt32* aRunLength) const
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{
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if (mSkipChars->mListLength == 0) {
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if (aRunLength) {
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*aRunLength = mSkipChars->mCharCount - mOriginalStringOffset;
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}
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return mSkipChars->mCharCount == PRUint32(mOriginalStringOffset);
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}
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PRUint32 listPrefixLength = mListPrefixLength;
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// figure out which segment we're in
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PRUint32 currentRunLength = mSkipChars->mList[listPrefixLength];
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// Zero-length list entries are possible. Advance until mListPrefixLength
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// is pointing to a run with real characters (or we're at the end of the
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// string).
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while (currentRunLength == 0 && listPrefixLength < mSkipChars->mListLength - 1) {
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++listPrefixLength;
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// This does not break the iterator's invariant because no skipped
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// or kept characters are being added
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currentRunLength = mSkipChars->mList[listPrefixLength];
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}
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NS_ASSERTION(PRUint32(mOriginalStringOffset) >= mListPrefixCharCount,
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"Invariant violation");
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PRUint32 offsetIntoCurrentRun =
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PRUint32(mOriginalStringOffset) - mListPrefixCharCount;
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if (listPrefixLength >= mSkipChars->mListLength - 1 &&
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offsetIntoCurrentRun >= currentRunLength) {
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NS_ASSERTION(listPrefixLength == mSkipChars->mListLength - 1 &&
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offsetIntoCurrentRun == currentRunLength,
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"Overran end of string");
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// We're at the end of the string
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if (aRunLength) {
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*aRunLength = 0;
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}
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return PR_TRUE;
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}
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bool isSkipped = !IsKeepEntry(listPrefixLength);
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if (aRunLength) {
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// Long runs of all-skipped or all-kept characters will be encoded as
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// sequences of 255, 0, 255, 0 etc. Compute the maximum run length by skipping
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// over zero entries.
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PRUint32 runLength = currentRunLength - offsetIntoCurrentRun;
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for (PRUint32 i = listPrefixLength + 2; i < mSkipChars->mListLength; i += 2) {
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if (mSkipChars->mList[i - 1] != 0)
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break;
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runLength += mSkipChars->mList[i];
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}
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*aRunLength = runLength;
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}
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return isSkipped;
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}
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void
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gfxSkipCharsBuilder::FlushRun()
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{
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NS_ASSERTION((mBuffer.Length() & 1) == mRunSkipped,
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"out of sync?");
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// Fill in buffer entries starting at mBufferLength, as many as necessary
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PRUint32 charCount = mRunCharCount;
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for (;;) {
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PRUint32 chars = NS_MIN<PRUint32>(255, charCount);
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if (!mBuffer.AppendElement(chars)) {
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mInErrorState = PR_TRUE;
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return;
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}
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charCount -= chars;
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if (charCount == 0)
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break;
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if (!mBuffer.AppendElement(0)) {
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mInErrorState = PR_TRUE;
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return;
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}
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}
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NS_ASSERTION(mCharCount + mRunCharCount >= mCharCount,
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"String length overflow");
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mCharCount += mRunCharCount;
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mRunCharCount = 0;
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mRunSkipped = !mRunSkipped;
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}
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