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30 #ifndef DecodeEscapeSequences_h
31 #define DecodeEscapeSequences_h
33 #include "wtf/ASCIICType.h"
34 #include "wtf/Assertions.h"
35 #include "wtf/text/StringBuilder.h"
36 #include "wtf/text/TextEncoding.h"
40 // See <http://en.wikipedia.org/wiki/Percent-encoding#Non-standard_implementations>.
41 struct Unicode16BitEscapeSequence {
42 enum { sequenceSize = 6 }; // e.g. %u26C4
43 static size_t findInString(const String& string, size_t startPosition) { return string.find("%u", startPosition); }
44 static size_t findEndOfRun(const String& string, size_t startPosition, size_t endPosition)
46 size_t runEnd = startPosition;
47 while (endPosition - runEnd >= sequenceSize && string[runEnd] == '%' && string[runEnd + 1] == 'u'
48 && isASCIIHexDigit(string[runEnd + 2]) && isASCIIHexDigit(string[runEnd + 3])
49 && isASCIIHexDigit(string[runEnd + 4]) && isASCIIHexDigit(string[runEnd + 5])) {
50 runEnd += sequenceSize;
55 template<typename CharType>
56 static String decodeRun(const CharType* run, size_t runLength, const WTF::TextEncoding&)
58 // Each %u-escape sequence represents a UTF-16 code unit.
59 // See <http://www.w3.org/International/iri-edit/draft-duerst-iri.html#anchor29>.
60 // For 16-bit escape sequences, we know that findEndOfRun() has given us a contiguous run of sequences
61 // without any intervening characters, so decode the run without additional checks.
62 size_t numberOfSequences = runLength / sequenceSize;
63 StringBuilder builder;
64 builder.reserveCapacity(numberOfSequences);
65 while (numberOfSequences--) {
66 UChar codeUnit = (toASCIIHexValue(run[2]) << 12) | (toASCIIHexValue(run[3]) << 8) | (toASCIIHexValue(run[4]) << 4) | toASCIIHexValue(run[5]);
67 builder.append(codeUnit);
70 return builder.toString();
74 struct URLEscapeSequence {
75 enum { sequenceSize = 3 }; // e.g. %41
76 static size_t findInString(const String& string, size_t startPosition) { return string.find('%', startPosition); }
77 static size_t findEndOfRun(const String& string, size_t startPosition, size_t endPosition)
79 // Make the simplifying assumption that supported encodings may have up to two unescaped characters
80 // in the range 0x40 - 0x7F as the trailing bytes of their sequences which need to be passed into the
81 // decoder as part of the run. In other words, we end the run at the first value outside of the
82 // 0x40 - 0x7F range, after two values in this range, or at a %-sign that does not introduce a valid
84 size_t runEnd = startPosition;
85 int numberOfTrailingCharacters = 0;
86 while (runEnd < endPosition) {
87 if (string[runEnd] == '%') {
88 if (endPosition - runEnd >= sequenceSize && isASCIIHexDigit(string[runEnd + 1]) && isASCIIHexDigit(string[runEnd + 2])) {
89 runEnd += sequenceSize;
90 numberOfTrailingCharacters = 0;
93 } else if (string[runEnd] >= 0x40 && string[runEnd] <= 0x7F && numberOfTrailingCharacters < 2) {
95 numberOfTrailingCharacters += 1;
102 template<typename CharType>
103 static String decodeRun(const CharType* run, size_t runLength, const WTF::TextEncoding& encoding)
105 // For URL escape sequences, we know that findEndOfRun() has given us a run where every %-sign introduces
106 // a valid escape sequence, but there may be characters between the sequences.
107 Vector<char, 512> buffer;
108 buffer.resize(runLength); // Unescaping hex sequences only makes the length smaller.
109 char* p = buffer.data();
110 const CharType* runEnd = run + runLength;
111 while (run < runEnd) {
113 *p++ = (toASCIIHexValue(run[1]) << 4) | toASCIIHexValue(run[2]);
120 ASSERT(buffer.size() >= static_cast<size_t>(p - buffer.data())); // Prove buffer not overrun.
121 return (encoding.isValid() ? encoding : UTF8Encoding()).decode(buffer.data(), p - buffer.data());
125 template<typename EscapeSequence>
126 String decodeEscapeSequences(const String& string, const WTF::TextEncoding& encoding)
128 StringBuilder result;
129 size_t length = string.length();
130 size_t decodedPosition = 0;
131 size_t searchPosition = 0;
132 size_t encodedRunPosition;
133 while ((encodedRunPosition = EscapeSequence::findInString(string, searchPosition)) != kNotFound) {
134 size_t encodedRunEnd = EscapeSequence::findEndOfRun(string, encodedRunPosition, length);
135 searchPosition = encodedRunEnd;
136 if (encodedRunEnd == encodedRunPosition) {
141 String decoded = string.is8Bit() ?
142 EscapeSequence::decodeRun(string.characters8() + encodedRunPosition, encodedRunEnd - encodedRunPosition, encoding) :
143 EscapeSequence::decodeRun(string.characters16() + encodedRunPosition, encodedRunEnd - encodedRunPosition, encoding);
145 if (decoded.isEmpty())
148 result.append(string, decodedPosition, encodedRunPosition - decodedPosition);
149 result.append(decoded);
150 decodedPosition = encodedRunEnd;
152 result.append(string, decodedPosition, length - decodedPosition);
153 return result.toString();
158 #endif // DecodeEscapeSequences_h