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/*
* Copyright (C) 2011 Daniel Bates (dbates@intudata.com). All Rights Reserved.
* Copyright (c) 2012 Google, inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef DecodeEscapeSequences_h
#define DecodeEscapeSequences_h
#include "TextEncoding.h"
#include <wtf/ASCIICType.h>
#include <wtf/Assertions.h>
#include <wtf/text/StringBuilder.h>
namespace WebCore {
// See <http://en.wikipedia.org/wiki/Percent-encoding#Non-standard_implementations>.
struct Unicode16BitEscapeSequence {
enum { sequenceSize = 6 }; // e.g. %u26C4
static size_t findInString(StringView string, size_t startPosition) { return string.find(StringView("%u"), startPosition); }
static size_t findEndOfRun(StringView string, size_t startPosition, size_t endPosition)
{
size_t runEnd = startPosition;
while (endPosition - runEnd >= sequenceSize && string[runEnd] == '%' && string[runEnd + 1] == 'u'
&& isASCIIHexDigit(string[runEnd + 2]) && isASCIIHexDigit(string[runEnd + 3])
&& isASCIIHexDigit(string[runEnd + 4]) && isASCIIHexDigit(string[runEnd + 5])) {
runEnd += sequenceSize;
}
return runEnd;
}
static String decodeRun(StringView run, const TextEncoding&)
{
// Each %u-escape sequence represents a UTF-16 code unit.
// See <http://www.w3.org/International/iri-edit/draft-duerst-iri.html#anchor29>.
// For 16-bit escape sequences, we know that findEndOfRun() has given us a contiguous run of sequences
// without any intervening characters, so decode the run without additional checks.
auto numberOfSequences = run.length() / sequenceSize;
StringBuilder builder;
builder.reserveCapacity(numberOfSequences);
while (numberOfSequences--) {
UChar codeUnit = (toASCIIHexValue(run[2]) << 12) | (toASCIIHexValue(run[3]) << 8) | (toASCIIHexValue(run[4]) << 4) | toASCIIHexValue(run[5]);
builder.append(codeUnit);
run = run.substring(sequenceSize);
}
return builder.toString();
}
};
struct URLEscapeSequence {
enum { sequenceSize = 3 }; // e.g. %41
static size_t findInString(StringView string, size_t startPosition) { return string.find('%', startPosition); }
static size_t findEndOfRun(StringView string, size_t startPosition, size_t endPosition)
{
// Make the simplifying assumption that supported encodings may have up to two unescaped characters
// in the range 0x40 - 0x7F as the trailing bytes of their sequences which need to be passed into the
// decoder as part of the run. In other words, we end the run at the first value outside of the
// 0x40 - 0x7F range, after two values in this range, or at a %-sign that does not introduce a valid
// escape sequence.
size_t runEnd = startPosition;
int numberOfTrailingCharacters = 0;
while (runEnd < endPosition) {
if (string[runEnd] == '%') {
if (endPosition - runEnd >= sequenceSize && isASCIIHexDigit(string[runEnd + 1]) && isASCIIHexDigit(string[runEnd + 2])) {
runEnd += sequenceSize;
numberOfTrailingCharacters = 0;
} else
break;
} else if (string[runEnd] >= 0x40 && string[runEnd] <= 0x7F && numberOfTrailingCharacters < 2) {
runEnd += 1;
numberOfTrailingCharacters += 1;
} else
break;
}
return runEnd;
}
static Vector<char, 512> decodeRun(StringView run)
{
// For URL escape sequences, we know that findEndOfRun() has given us a run where every %-sign introduces
// a valid escape sequence, but there may be characters between the sequences.
Vector<char, 512> buffer;
buffer.resize(run.length()); // Unescaping hex sequences only makes the length smaller.
char* p = buffer.data();
while (!run.isEmpty()) {
if (run[0] == '%') {
*p++ = (toASCIIHexValue(run[1]) << 4) | toASCIIHexValue(run[2]);
run = run.substring(sequenceSize);
} else {
*p++ = run[0];
run = run.substring(1);
}
}
ASSERT(buffer.size() >= static_cast<size_t>(p - buffer.data())); // Prove buffer not overrun.
buffer.shrink(p - buffer.data());
return buffer;
}
static String decodeRun(StringView run, const TextEncoding& encoding)
{
auto buffer = decodeRun(run);
if (!encoding.isValid())
return UTF8Encoding().decode(buffer.data(), buffer.size());
return encoding.decode(buffer.data(), buffer.size());
}
};
template<typename EscapeSequence>
String decodeEscapeSequences(StringView string, const TextEncoding& encoding)
{
StringBuilder result;
size_t length = string.length();
size_t decodedPosition = 0;
size_t searchPosition = 0;
size_t encodedRunPosition;
while ((encodedRunPosition = EscapeSequence::findInString(string, searchPosition)) != notFound) {
size_t encodedRunEnd = EscapeSequence::findEndOfRun(string, encodedRunPosition, length);
searchPosition = encodedRunEnd;
if (encodedRunEnd == encodedRunPosition) {
++searchPosition;
continue;
}
String decoded = EscapeSequence::decodeRun(string.substring(encodedRunPosition, encodedRunEnd - encodedRunPosition), encoding);
if (decoded.isEmpty())
continue;
result.append(string.substring(decodedPosition, encodedRunPosition - decodedPosition));
result.append(decoded);
decodedPosition = encodedRunEnd;
}
result.append(string.substring(decodedPosition, length - decodedPosition));
return result.toString();
}
inline Vector<char> decodeURLEscapeSequencesAsData(StringView string, const TextEncoding& encoding)
{
ASSERT(encoding.isValid());
Vector<char> result;
size_t decodedPosition = 0;
size_t searchPosition = 0;
while (true) {
size_t encodedRunPosition = URLEscapeSequence::findInString(string, searchPosition);
size_t encodedRunEnd = 0;
if (encodedRunPosition != notFound) {
encodedRunEnd = URLEscapeSequence::findEndOfRun(string, encodedRunPosition, string.length());
searchPosition = encodedRunEnd;
if (encodedRunEnd == encodedRunPosition) {
++searchPosition;
continue;
}
}
// Strings are encoded as requested.
auto stringFragment = string.substring(decodedPosition, encodedRunPosition - decodedPosition);
auto encodedStringFragment = encoding.encode(stringFragment, URLEncodedEntitiesForUnencodables);
result.append(encodedStringFragment.data(), encodedStringFragment.length());
if (encodedRunPosition == notFound)
return result;
// Bytes go through as-is.
auto decodedEscapeSequence = URLEscapeSequence::decodeRun(string.substring(encodedRunPosition, encodedRunEnd - encodedRunPosition));
ASSERT(!decodedEscapeSequence.isEmpty());
result.appendVector(decodedEscapeSequence);
decodedPosition = encodedRunEnd;
}
}
} // namespace WebCore
#endif // DecodeEscapeSequences_h
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