1 // Copyright 2019 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "src/inspector/v8-string-conversions.h"
6
7 #include <limits>
8 #include <vector>
9
10 #include "src/base/logging.h"
11 #include "src/base/v8-fallthrough.h"
12
13 namespace v8_inspector {
14 namespace {
15 using UChar = uint16_t;
16 using UChar32 = uint32_t;
17
isASCII(UChar c)18 bool isASCII(UChar c) { return !(c & ~0x7F); }
19
20 const UChar replacementCharacter = 0xFFFD;
21
inlineUTF8SequenceLengthNonASCII(char b0)22 inline int inlineUTF8SequenceLengthNonASCII(char b0) {
23 if ((b0 & 0xC0) != 0xC0) return 0;
24 if ((b0 & 0xE0) == 0xC0) return 2;
25 if ((b0 & 0xF0) == 0xE0) return 3;
26 if ((b0 & 0xF8) == 0xF0) return 4;
27 return 0;
28 }
29
inlineUTF8SequenceLength(char b0)30 inline int inlineUTF8SequenceLength(char b0) {
31 return isASCII(b0) ? 1 : inlineUTF8SequenceLengthNonASCII(b0);
32 }
33
34 // Once the bits are split out into bytes of UTF-8, this is a mask OR-ed
35 // into the first byte, depending on how many bytes follow. There are
36 // as many entries in this table as there are UTF-8 sequence types.
37 // (I.e., one byte sequence, two byte... etc.). Remember that sequences
38 // for *legal* UTF-8 will be 4 or fewer bytes total.
39 static const unsigned char firstByteMark[7] = {0x00, 0x00, 0xC0, 0xE0,
40 0xF0, 0xF8, 0xFC};
41
42 enum ConversionResult {
43 conversionOK, // conversion successful
44 sourceExhausted, // partial character in source, but hit end
45 targetExhausted, // insuff. room in target for conversion
46 sourceIllegal // source sequence is illegal/malformed
47 };
48
convertUTF16ToUTF8(const UChar ** sourceStart,const UChar * sourceEnd,char ** targetStart,char * targetEnd,bool strict)49 ConversionResult convertUTF16ToUTF8(const UChar** sourceStart,
50 const UChar* sourceEnd, char** targetStart,
51 char* targetEnd, bool strict) {
52 ConversionResult result = conversionOK;
53 const UChar* source = *sourceStart;
54 char* target = *targetStart;
55 while (source < sourceEnd) {
56 UChar32 ch;
57 uint32_t bytesToWrite = 0;
58 const UChar32 byteMask = 0xBF;
59 const UChar32 byteMark = 0x80;
60 const UChar* oldSource =
61 source; // In case we have to back up because of target overflow.
62 ch = static_cast<uint16_t>(*source++);
63 // If we have a surrogate pair, convert to UChar32 first.
64 if (ch >= 0xD800 && ch <= 0xDBFF) {
65 // If the 16 bits following the high surrogate are in the source buffer...
66 if (source < sourceEnd) {
67 UChar32 ch2 = static_cast<uint16_t>(*source);
68 // If it's a low surrogate, convert to UChar32.
69 if (ch2 >= 0xDC00 && ch2 <= 0xDFFF) {
70 ch = ((ch - 0xD800) << 10) + (ch2 - 0xDC00) + 0x0010000;
71 ++source;
72 } else if (strict) { // it's an unpaired high surrogate
73 --source; // return to the illegal value itself
74 result = sourceIllegal;
75 break;
76 }
77 } else { // We don't have the 16 bits following the high surrogate.
78 --source; // return to the high surrogate
79 result = sourceExhausted;
80 break;
81 }
82 } else if (strict) {
83 // UTF-16 surrogate values are illegal in UTF-32
84 if (ch >= 0xDC00 && ch <= 0xDFFF) {
85 --source; // return to the illegal value itself
86 result = sourceIllegal;
87 break;
88 }
89 }
90 // Figure out how many bytes the result will require
91 if (ch < static_cast<UChar32>(0x80)) {
92 bytesToWrite = 1;
93 } else if (ch < static_cast<UChar32>(0x800)) {
94 bytesToWrite = 2;
95 } else if (ch < static_cast<UChar32>(0x10000)) {
96 bytesToWrite = 3;
97 } else if (ch < static_cast<UChar32>(0x110000)) {
98 bytesToWrite = 4;
99 } else {
100 bytesToWrite = 3;
101 ch = replacementCharacter;
102 }
103
104 target += bytesToWrite;
105 if (target > targetEnd) {
106 source = oldSource; // Back up source pointer!
107 target -= bytesToWrite;
108 result = targetExhausted;
109 break;
110 }
111 switch (bytesToWrite) {
112 case 4:
113 *--target = static_cast<char>((ch | byteMark) & byteMask);
114 ch >>= 6;
115 V8_FALLTHROUGH;
116 case 3:
117 *--target = static_cast<char>((ch | byteMark) & byteMask);
118 ch >>= 6;
119 V8_FALLTHROUGH;
120 case 2:
121 *--target = static_cast<char>((ch | byteMark) & byteMask);
122 ch >>= 6;
123 V8_FALLTHROUGH;
124 case 1:
125 *--target = static_cast<char>(ch | firstByteMark[bytesToWrite]);
126 }
127 target += bytesToWrite;
128 }
129 *sourceStart = source;
130 *targetStart = target;
131 return result;
132 }
133
134 /**
135 * Is this code point a BMP code point (U+0000..U+ffff)?
136 * @param c 32-bit code point
137 * @return TRUE or FALSE
138 * @stable ICU 2.8
139 */
140 #define U_IS_BMP(c) ((uint32_t)(c) <= 0xFFFF)
141
142 /**
143 * Is this code point a supplementary code point (U+010000..U+10FFFF)?
144 * @param c 32-bit code point
145 * @return TRUE or FALSE
146 * @stable ICU 2.8
147 */
148 #define U_IS_SUPPLEMENTARY(c) ((uint32_t)((c)-0x010000) <= 0xFFFFF)
149
150 /**
151 * Is this code point a surrogate (U+d800..U+dfff)?
152 * @param c 32-bit code point
153 * @return TRUE or FALSE
154 * @stable ICU 2.4
155 */
156 #define U_IS_SURROGATE(c) (((c)&0xFFFFF800) == 0xD800)
157
158 /**
159 * Get the lead surrogate (0xD800..0xDBFF) for a
160 * supplementary code point (0x010000..0x10FFFF).
161 * @param supplementary 32-bit code point (U+010000..U+10FFFF)
162 * @return lead surrogate (U+D800..U+DBFF) for supplementary
163 * @stable ICU 2.4
164 */
165 #define U16_LEAD(supplementary) (UChar)(((supplementary) >> 10) + 0xD7C0)
166
167 /**
168 * Get the trail surrogate (0xDC00..0xDFFF) for a
169 * supplementary code point (0x010000..0x10FFFF).
170 * @param supplementary 32-bit code point (U+010000..U+10FFFF)
171 * @return trail surrogate (U+DC00..U+DFFF) for supplementary
172 * @stable ICU 2.4
173 */
174 #define U16_TRAIL(supplementary) (UChar)(((supplementary)&0x3FF) | 0xDC00)
175
176 // This must be called with the length pre-determined by the first byte.
177 // If presented with a length > 4, this returns false. The Unicode
178 // definition of UTF-8 goes up to 4-byte sequences.
isLegalUTF8(const unsigned char * source,int length)179 static bool isLegalUTF8(const unsigned char* source, int length) {
180 unsigned char a;
181 const unsigned char* srcptr = source + length;
182 switch (length) {
183 default:
184 return false;
185 // Everything else falls through when "true"...
186 case 4:
187 if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
188 V8_FALLTHROUGH;
189 case 3:
190 if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
191 V8_FALLTHROUGH;
192 case 2:
193 if ((a = (*--srcptr)) > 0xBF) return false;
194
195 // no fall-through in this inner switch
196 switch (*source) {
197 case 0xE0:
198 if (a < 0xA0) return false;
199 break;
200 case 0xED:
201 if (a > 0x9F) return false;
202 break;
203 case 0xF0:
204 if (a < 0x90) return false;
205 break;
206 case 0xF4:
207 if (a > 0x8F) return false;
208 break;
209 default:
210 if (a < 0x80) return false;
211 }
212 V8_FALLTHROUGH;
213
214 case 1:
215 if (*source >= 0x80 && *source < 0xC2) return false;
216 }
217 if (*source > 0xF4) return false;
218 return true;
219 }
220
221 // Magic values subtracted from a buffer value during UTF8 conversion.
222 // This table contains as many values as there might be trailing bytes
223 // in a UTF-8 sequence.
224 static const UChar32 offsetsFromUTF8[6] = {0x00000000UL,
225 0x00003080UL,
226 0x000E2080UL,
227 0x03C82080UL,
228 static_cast<UChar32>(0xFA082080UL),
229 static_cast<UChar32>(0x82082080UL)};
230
readUTF8Sequence(const char * & sequence,size_t length)231 static inline UChar32 readUTF8Sequence(
232 const char*& sequence, // NOLINT(runtime/references)
233 size_t length) {
234 UChar32 character = 0;
235
236 // The cases all fall through.
237 switch (length) {
238 case 6:
239 character += static_cast<unsigned char>(*sequence++);
240 character <<= 6;
241 V8_FALLTHROUGH;
242 case 5:
243 character += static_cast<unsigned char>(*sequence++);
244 character <<= 6;
245 V8_FALLTHROUGH;
246 case 4:
247 character += static_cast<unsigned char>(*sequence++);
248 character <<= 6;
249 V8_FALLTHROUGH;
250 case 3:
251 character += static_cast<unsigned char>(*sequence++);
252 character <<= 6;
253 V8_FALLTHROUGH;
254 case 2:
255 character += static_cast<unsigned char>(*sequence++);
256 character <<= 6;
257 V8_FALLTHROUGH;
258 case 1:
259 character += static_cast<unsigned char>(*sequence++);
260 }
261
262 return character - offsetsFromUTF8[length - 1];
263 }
264
convertUTF8ToUTF16(const char ** sourceStart,const char * sourceEnd,UChar ** targetStart,UChar * targetEnd,bool * sourceAllASCII,bool strict)265 ConversionResult convertUTF8ToUTF16(const char** sourceStart,
266 const char* sourceEnd, UChar** targetStart,
267 UChar* targetEnd, bool* sourceAllASCII,
268 bool strict) {
269 ConversionResult result = conversionOK;
270 const char* source = *sourceStart;
271 UChar* target = *targetStart;
272 UChar orAllData = 0;
273 while (source < sourceEnd) {
274 int utf8SequenceLength = inlineUTF8SequenceLength(*source);
275 if (sourceEnd - source < utf8SequenceLength) {
276 result = sourceExhausted;
277 break;
278 }
279 // Do this check whether lenient or strict
280 if (!isLegalUTF8(reinterpret_cast<const unsigned char*>(source),
281 utf8SequenceLength)) {
282 result = sourceIllegal;
283 break;
284 }
285
286 UChar32 character = readUTF8Sequence(source, utf8SequenceLength);
287
288 if (target >= targetEnd) {
289 source -= utf8SequenceLength; // Back up source pointer!
290 result = targetExhausted;
291 break;
292 }
293
294 if (U_IS_BMP(character)) {
295 // UTF-16 surrogate values are illegal in UTF-32
296 if (U_IS_SURROGATE(character)) {
297 if (strict) {
298 source -= utf8SequenceLength; // return to the illegal value itself
299 result = sourceIllegal;
300 break;
301 }
302 *target++ = replacementCharacter;
303 orAllData |= replacementCharacter;
304 } else {
305 *target++ = static_cast<UChar>(character); // normal case
306 orAllData |= character;
307 }
308 } else if (U_IS_SUPPLEMENTARY(character)) {
309 // target is a character in range 0xFFFF - 0x10FFFF
310 if (target + 1 >= targetEnd) {
311 source -= utf8SequenceLength; // Back up source pointer!
312 result = targetExhausted;
313 break;
314 }
315 *target++ = U16_LEAD(character);
316 *target++ = U16_TRAIL(character);
317 orAllData = 0xFFFF;
318 } else {
319 if (strict) {
320 source -= utf8SequenceLength; // return to the start
321 result = sourceIllegal;
322 break; // Bail out; shouldn't continue
323 } else {
324 *target++ = replacementCharacter;
325 orAllData |= replacementCharacter;
326 }
327 }
328 }
329 *sourceStart = source;
330 *targetStart = target;
331
332 if (sourceAllASCII) *sourceAllASCII = !(orAllData & ~0x7F);
333
334 return result;
335 }
336
337 // Helper to write a three-byte UTF-8 code point to the buffer, caller must
338 // check room is available.
putUTF8Triple(char * & buffer,UChar ch)339 static inline void putUTF8Triple(char*& buffer, // NOLINT(runtime/references)
340 UChar ch) {
341 *buffer++ = static_cast<char>(((ch >> 12) & 0x0F) | 0xE0);
342 *buffer++ = static_cast<char>(((ch >> 6) & 0x3F) | 0x80);
343 *buffer++ = static_cast<char>((ch & 0x3F) | 0x80);
344 }
345 } // namespace
346
UTF16ToUTF8(const UChar * stringStart,size_t length)347 std::string UTF16ToUTF8(const UChar* stringStart, size_t length) {
348 if (!stringStart || !length) return std::string();
349
350 // Allocate a buffer big enough to hold all the characters
351 // (an individual UTF-16 UChar can only expand to 3 UTF-8 bytes).
352 // Optimization ideas, if we find this function is hot:
353 // * We could speculatively create a CStringBuffer to contain 'length'
354 // characters, and resize if necessary (i.e. if the buffer contains
355 // non-ascii characters). (Alternatively, scan the buffer first for
356 // ascii characters, so we know this will be sufficient).
357 // * We could allocate a CStringBuffer with an appropriate size to
358 // have a good chance of being able to write the string into the
359 // buffer without reallocing (say, 1.5 x length).
360 if (length > std::numeric_limits<unsigned>::max() / 3) return std::string();
361
362 std::string output(length * 3, '\0');
363 const UChar* characters = stringStart;
364 const UChar* characters_end = characters + length;
365 char* buffer = &*output.begin();
366 char* buffer_end = &*output.end();
367 while (characters < characters_end) {
368 // Use strict conversion to detect unpaired surrogates.
369 ConversionResult result = convertUTF16ToUTF8(
370 &characters, characters_end, &buffer, buffer_end, /* strict= */ true);
371 DCHECK_NE(result, targetExhausted);
372 // Conversion fails when there is an unpaired surrogate. Put
373 // replacement character (U+FFFD) instead of the unpaired
374 // surrogate.
375 if (result != conversionOK) {
376 DCHECK_LE(0xD800, *characters);
377 DCHECK_LE(*characters, 0xDFFF);
378 // There should be room left, since one UChar hasn't been
379 // converted.
380 DCHECK_LE(buffer + 3, buffer_end);
381 putUTF8Triple(buffer, replacementCharacter);
382 ++characters;
383 }
384 }
385
386 output.resize(buffer - output.data());
387 return output;
388 }
389
UTF8ToUTF16(const char * stringStart,size_t length)390 std::basic_string<UChar> UTF8ToUTF16(const char* stringStart, size_t length) {
391 if (!stringStart || !length) return std::basic_string<UChar>();
392 std::vector<uint16_t> buffer(length);
393 UChar* bufferStart = buffer.data();
394
395 UChar* bufferCurrent = bufferStart;
396 const char* stringCurrent = reinterpret_cast<const char*>(stringStart);
397 if (convertUTF8ToUTF16(&stringCurrent,
398 reinterpret_cast<const char*>(stringStart + length),
399 &bufferCurrent, bufferCurrent + buffer.size(), nullptr,
400 true) != conversionOK)
401 return std::basic_string<uint16_t>();
402 size_t utf16Length = bufferCurrent - bufferStart;
403 return std::basic_string<UChar>(bufferStart, bufferStart + utf16Length);
404 }
405
406 } // namespace v8_inspector
407