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+This is a dump from Google's source control system of the change
+that removed UCS-2 support from RE2. As the explanation below
+says, UCS-2 mode is fundamentally at odds with things like ^ and $,
+so it never really worked very well. But if you are interested in using
+it without those operators, it did work for that. It assumed that the
+UCS-2 data was in the native host byte order.
+
+If you are interested in adding UCS-2 mode back, this patch might
+be a good starting point.
+
+
+Change 12780686 by rsc@rsc-re2 on 2009/09/16 15:30:15
+
+ Retire UCS-2 mode.
+
+ I added it as an experiment for V8, but it
+ requires 2-byte lookahead to do completely,
+ and RE2 has 1-byte lookahead (enough for UTF-8)
+ as a fairly deep fundamental assumption,
+ so it did not support ^ or $.
+
+==== re2/bitstate.cc#2 - re2/bitstate.cc#3 ====
+re2/bitstate.cc#2:314,321 - re2/bitstate.cc#3:314,319
+ cap_[0] = p;
+ if (TrySearch(prog_->start(), p)) // Match must be leftmost; done.
+ return true;
+- if (prog_->flags() & Regexp::UCS2)
+- p++;
+ }
+ return false;
+ }
+==== re2/compile.cc#17 - re2/compile.cc#18 ====
+re2/compile.cc#17:95,101 - re2/compile.cc#18:95,100
+ // Input encodings.
+ enum Encoding {
+ kEncodingUTF8 = 1, // UTF-8 (0-10FFFF)
+- kEncodingUCS2, // UCS-2 (0-FFFF), native byte order
+ kEncodingLatin1, // Latin1 (0-FF)
+ };
+
+re2/compile.cc#17:168,176 - re2/compile.cc#18:167,172
+ void AddRuneRangeLatin1(Rune lo, Rune hi, bool foldcase);
+ void AddRuneRangeUTF8(Rune lo, Rune hi, bool foldcase);
+ void Add_80_10ffff();
+- void AddRuneRangeUCS2(Rune lo, Rune hi, bool foldcase);
+- void AddUCS2Pair(uint8 lo1, uint8 hi1, bool fold1,
+- uint8 lo2, uint8 hi2, bool fold2);
+
+ // New suffix that matches the byte range lo-hi, then goes to next.
+ Inst* RuneByteSuffix(uint8 lo, uint8 hi, bool foldcase, Inst* next);
+re2/compile.cc#17:475,481 - re2/compile.cc#18:471,477
+
+ // Converts rune range lo-hi into a fragment that recognizes
+ // the bytes that would make up those runes in the current
+- // encoding (Latin 1, UTF-8, or UCS-2).
++ // encoding (Latin 1 or UTF-8).
+ // This lets the machine work byte-by-byte even when
+ // using multibyte encodings.
+
+re2/compile.cc#17:488,496 - re2/compile.cc#18:484,489
+ case kEncodingLatin1:
+ AddRuneRangeLatin1(lo, hi, foldcase);
+ break;
+- case kEncodingUCS2:
+- AddRuneRangeUCS2(lo, hi, foldcase);
+- break;
+ }
+ }
+
+re2/compile.cc#17:503,581 - re2/compile.cc#18:496,501
+ AddSuffix(RuneByteSuffix(lo, hi, foldcase, NULL));
+ }
+
+- // Test whether 16-bit values are big or little endian.
+- static bool BigEndian() {
+- union {
+- char byte[2];
+- int16 endian;
+- } u;
+-
+- u.byte[0] = 1;
+- u.byte[1] = 2;
+- return u.endian == 0x0102;
+- }
+-
+- void Compiler::AddUCS2Pair(uint8 lo1, uint8 hi1, bool fold1,
+- uint8 lo2, uint8 hi2, bool fold2) {
+- Inst* ip;
+- if (reversed_) {
+- ip = RuneByteSuffix(lo1, hi1, fold1, NULL);
+- ip = RuneByteSuffix(lo2, hi2, fold2, ip);
+- } else {
+- ip = RuneByteSuffix(lo2, hi2, fold2, NULL);
+- ip = RuneByteSuffix(lo1, hi1, fold1, ip);
+- }
+- AddSuffix(ip);
+- }
+-
+- void Compiler::AddRuneRangeUCS2(Rune lo, Rune hi, bool foldcase) {
+- if (lo > hi || lo > 0xFFFF)
+- return;
+- if (hi > 0xFFFF)
+- hi = 0xFFFF;
+-
+- // We'll assemble a pattern assuming big endian.
+- // If the machine isn't, tell Cat to reverse its arguments.
+- bool oldreversed = reversed_;
+- if (!BigEndian()) {
+- reversed_ = !oldreversed;
+- }
+-
+- // Split into bytes.
+- int lo1 = lo >> 8;
+- int lo2 = lo & 0xFF;
+- int hi1 = hi >> 8;
+- int hi2 = hi & 0xFF;
+-
+- if (lo1 == hi1) {
+- // Easy case: high bits are same in both.
+- // Only do ASCII case folding on the second byte if the top byte is 00.
+- AddUCS2Pair(lo1, lo1, false, lo2, hi2, lo1==0 && foldcase);
+- } else {
+- // Harder case: different second byte ranges depending on first byte.
+-
+- // Initial fragment.
+- if (lo2 > 0) {
+- AddUCS2Pair(lo1, lo1, false, lo2, 0xFF, lo1==0 && foldcase);
+- lo1++;
+- }
+-
+- // Trailing fragment.
+- if (hi2 < 0xFF) {
+- AddUCS2Pair(hi1, hi1, false, 0, hi2, false);
+- hi1--;
+- }
+-
+- // Inner ranges.
+- if (lo1 <= hi1) {
+- AddUCS2Pair(lo1, hi1, false, 0, 0xFF, false);
+- }
+- }
+-
+- // Restore reverse setting.
+- reversed_ = oldreversed;
+- }
+-
+ // Table describing how to make a UTF-8 matching machine
+ // for the rune range 80-10FFFF (Runeself-Runemax).
+ // This range happens frequently enough (for example /./ and /[^a-z]/)
+re2/compile.cc#17:707,716 - re2/compile.cc#18:627,634
+
+ Frag Compiler::Literal(Rune r, bool foldcase) {
+ switch (encoding_) {
+- default: // UCS-2 or something new
+- BeginRange();
+- AddRuneRange(r, r, foldcase);
+- return EndRange();
++ default:
++ return kNullFrag;
+
+ case kEncodingLatin1:
+ return ByteRange(r, r, foldcase);
+re2/compile.cc#17:927,934 - re2/compile.cc#18:845,850
+
+ if (re->parse_flags() & Regexp::Latin1)
+ c.encoding_ = kEncodingLatin1;
+- else if (re->parse_flags() & Regexp::UCS2)
+- c.encoding_ = kEncodingUCS2;
+ c.reversed_ = reversed;
+ if (max_mem <= 0) {
+ c.max_inst_ = 100000; // more than enough
+re2/compile.cc#17:983,993 - re2/compile.cc#18:899,905
+ c.prog_->set_start_unanchored(c.prog_->start());
+ } else {
+ Frag dot;
+- if (c.encoding_ == kEncodingUCS2) {
+- dot = c.Cat(c.ByteRange(0x00, 0xFF, false), c.ByteRange(0x00, 0xFF, false));
+- } else {
+- dot = c.ByteRange(0x00, 0xFF, false);
+- }
++ dot = c.ByteRange(0x00, 0xFF, false);
+ Frag dotloop = c.Star(dot, true);
+ Frag unanchored = c.Cat(dotloop, all);
+ c.prog_->set_start_unanchored(unanchored.begin);
+==== re2/nfa.cc#8 - re2/nfa.cc#9 ====
+re2/nfa.cc#8:426,432 - re2/nfa.cc#9:426,431
+ const char* bp = context.begin();
+ int c = -1;
+ int wasword = 0;
+- bool ucs2 = prog_->flags() & Regexp::UCS2;
+
+ if (text.begin() > context.begin()) {
+ c = text.begin()[-1] & 0xFF;
+re2/nfa.cc#8:492,498 - re2/nfa.cc#9:491,497
+ // If there's a required first byte for an unanchored search
+ // and we're not in the middle of any possible matches,
+ // use memchr to search for the byte quickly.
+- if (!ucs2 && !anchored && first_byte_ >= 0 && runq->size() == 0 &&
++ if (!anchored && first_byte_ >= 0 && runq->size() == 0 &&
+ p < text.end() && (p[0] & 0xFF) != first_byte_) {
+ p = reinterpret_cast<const char*>(memchr(p, first_byte_,
+ text.end() - p));
+re2/nfa.cc#8:505,526 - re2/nfa.cc#9:504,514
+ flag = Prog::EmptyFlags(context, p);
+ }
+
+- // In UCS-2 mode, if we need to start a new thread,
+- // make sure to do it on an even boundary.
+- if(ucs2 && runq->size() == 0 &&
+- (p - context.begin()) % 2 && p < text.end()) {
+- p++;
+- flag = Prog::EmptyFlags(context, p);
+- }
+-
+ // Steal match storage (cleared but unused as of yet)
+ // temporarily to hold match boundaries for new thread.
+- // In UCS-2 mode, only start the thread on a 2-byte boundary.
+- if(!ucs2 || (p - context.begin()) % 2 == 0) {
+- match_[0] = p;
+- AddToThreadq(runq, start_, flag, p, match_);
+- match_[0] = NULL;
+- }
++ match_[0] = p;
++ AddToThreadq(runq, start_, flag, p, match_);
++ match_[0] = NULL;
+ }
+
+ // If all the threads have died, stop early.
+==== re2/parse.cc#22 - re2/parse.cc#23 ====
+re2/parse.cc#22:160,167 - re2/parse.cc#23:160,165
+ status_(status), stacktop_(NULL), ncap_(0) {
+ if (flags_ & Latin1)
+ rune_max_ = 0xFF;
+- else if (flags & UCS2)
+- rune_max_ = 0xFFFF;
+ else
+ rune_max_ = Runemax;
+ }
+re2/parse.cc#22:365,387 - re2/parse.cc#23:363,374
+ bool Regexp::ParseState::PushCarat() {
+ if (flags_ & OneLine) {
+ return PushSimpleOp(kRegexpBeginText);
+- } else {
+- if (flags_ & UCS2) {
+- status_->set_code(kRegexpUnsupported);
+- status_->set_error_arg("multiline ^ in UCS-2 mode");
+- return false;
+- }
+- return PushSimpleOp(kRegexpBeginLine);
+ }
++ return PushSimpleOp(kRegexpBeginLine);
+ }
+
+ // Pushes a \b or \B onto the stack.
+ bool Regexp::ParseState::PushWordBoundary(bool word) {
+- if (flags_ & UCS2) {
+- status_->set_code(kRegexpUnsupported);
+- status_->set_error_arg("\\b or \\B in UCS-2 mode");
+- return false;
+- }
+ if (word)
+ return PushSimpleOp(kRegexpWordBoundary);
+ return PushSimpleOp(kRegexpNoWordBoundary);
+re2/parse.cc#22:397,407 - re2/parse.cc#23:384,389
+ bool ret = PushSimpleOp(kRegexpEndText);
+ flags_ = oflags;
+ return ret;
+- }
+- if (flags_ & UCS2) {
+- status_->set_code(kRegexpUnsupported);
+- status_->set_error_arg("multiline $ in UCS-2 mode");
+- return false;
+ }
+ return PushSimpleOp(kRegexpEndLine);
+ }
+==== re2/re2.cc#34 - re2/re2.cc#35 ====
+re2/re2.cc#34:79,86 - re2/re2.cc#35:79,84
+ return RE2::ErrorBadUTF8;
+ case re2::kRegexpBadNamedCapture:
+ return RE2::ErrorBadNamedCapture;
+- case re2::kRegexpUnsupported:
+- return RE2::ErrorUnsupported;
+ }
+ return RE2::ErrorInternal;
+ }
+re2/re2.cc#34:122,130 - re2/re2.cc#35:120,125
+ break;
+ case RE2::Options::EncodingLatin1:
+ flags |= Regexp::Latin1;
+- break;
+- case RE2::Options::EncodingUCS2:
+- flags |= Regexp::UCS2;
+ break;
+ }
+
+==== re2/re2.h#36 - re2/re2.h#37 ====
+re2/re2.h#36:246,252 - re2/re2.h#37:246,251
+ ErrorBadUTF8, // invalid UTF-8 in regexp
+ ErrorBadNamedCapture, // bad named capture group
+ ErrorPatternTooLarge, // pattern too large (compile failed)
+- ErrorUnsupported, // unsupported feature (in UCS-2 mode)
+ };
+
+ // Predefined common options.
+re2/re2.h#36:570,576 - re2/re2.h#37:569,574
+
+ enum Encoding {
+ EncodingUTF8 = 1,
+- EncodingUCS2, // 16-bit Unicode 0-FFFF only
+ EncodingLatin1
+ };
+
+==== re2/regexp.cc#15 - re2/regexp.cc#16 ====
+re2/regexp.cc#15:324,333 - re2/regexp.cc#16:324,329
+ // the regexp that remains after the prefix. The prefix might
+ // be ASCII case-insensitive.
+ bool Regexp::RequiredPrefix(string *prefix, bool *foldcase, Regexp** suffix) {
+- // Don't even bother for UCS-2; it's time to throw that code away.
+- if (parse_flags_ & UCS2)
+- return false;
+-
+ // No need for a walker: the regexp must be of the form
+ // 1. some number of ^ anchors
+ // 2. a literal char or string
+==== re2/regexp.h#20 - re2/regexp.h#21 ====
+re2/regexp.h#20:187,193 - re2/regexp.h#21:187,192
+ kRegexpBadPerlOp, // bad perl operator
+ kRegexpBadUTF8, // invalid UTF-8 in regexp
+ kRegexpBadNamedCapture, // bad named capture
+- kRegexpUnsupported, // unsupported operator
+ };
+
+ // Error status for certain operations.
+re2/regexp.h#20:307,316 - re2/regexp.h#21:306,314
+ // \Q and \E to disable/enable metacharacters
+ // (?P<name>expr) for named captures
+ // \C to match any single byte
+- UCS2 = 1<<10, // Text is in UCS-2, regexp is in UTF-8.
+- UnicodeGroups = 1<<11, // Allow \p{Han} for Unicode Han group
++ UnicodeGroups = 1<<10, // Allow \p{Han} for Unicode Han group
+ // and \P{Han} for its negation.
+- NeverNL = 1<<12, // Never match NL, even if the regexp mentions
++ NeverNL = 1<<11, // Never match NL, even if the regexp mentions
+ // it explicitly.
+
+ // As close to Perl as we can get.
+==== re2/testing/backtrack.cc#4 - re2/testing/backtrack.cc#5 ====
+re2/testing/backtrack.cc#4:134,141 - re2/testing/backtrack.cc#5:134,139
+ cap_[0] = p;
+ if (Visit(prog_->start(), p)) // Match must be leftmost; done.
+ return true;
+- if (prog_->flags() & Regexp::UCS2)
+- p++;
+ }
+ return false;
+ }
+==== re2/testing/tester.cc#12 - re2/testing/tester.cc#13 ====
+re2/testing/tester.cc#12:144,154 - re2/testing/tester.cc#13:144,152
+ static ParseMode parse_modes[] = {
+ { single_line, "single-line" },
+ { single_line|Regexp::Latin1, "single-line, latin1" },
+- { single_line|Regexp::UCS2, "single-line, ucs2" },
+ { multi_line, "multiline" },
+ { multi_line|Regexp::NonGreedy, "multiline, nongreedy" },
+ { multi_line|Regexp::Latin1, "multiline, latin1" },
+- { multi_line|Regexp::UCS2, "multiline, ucs2" },
+ };
+
+ static string FormatMode(Regexp::ParseFlags flags) {
+re2/testing/tester.cc#12:179,189 - re2/testing/tester.cc#13:177,185
+ RegexpStatus status;
+ regexp_ = Regexp::Parse(regexp_str, flags, &status);
+ if (regexp_ == NULL) {
+- if (status.code() != kRegexpUnsupported) {
+- LOG(INFO) << "Cannot parse: " << CEscape(regexp_str_)
+- << " mode: " << FormatMode(flags);
+- error_ = true;
+- }
++ LOG(INFO) << "Cannot parse: " << CEscape(regexp_str_)
++ << " mode: " << FormatMode(flags);
++ error_ = true;
+ return;
+ }
+ prog_ = regexp_->CompileToProg(0);
+re2/testing/tester.cc#12:230,237 - re2/testing/tester.cc#13:226,231
+ RE2::Options options;
+ if (flags & Regexp::Latin1)
+ options.set_encoding(RE2::Options::EncodingLatin1);
+- else if (flags & Regexp::UCS2)
+- options.set_encoding(RE2::Options::EncodingUCS2);
+ if (kind_ == Prog::kLongestMatch)
+ options.set_longest_match(true);
+ re2_ = new RE2(re, options);
+re2/testing/tester.cc#12:281,379 - re2/testing/tester.cc#13:275,280
+ delete re2_;
+ }
+
+- // Converts UTF-8 string in text into UCS-2 string in new_text.
+- static bool ConvertUTF8ToUCS2(const StringPiece& text, StringPiece* new_text) {
+- const char* p = text.begin();
+- const char* ep = text.end();
+- uint16* q = new uint16[ep - p];
+- uint16* q0 = q;
+-
+- int n;
+- Rune r;
+- for (; p < ep; p += n) {
+- if (!fullrune(p, ep - p)) {
+- delete[] q0;
+- return false;
+- }
+- n = chartorune(&r, p);
+- if (r > 0xFFFF) {
+- delete[] q0;
+- return false;
+- }
+- *q++ = r;
+- }
+- *new_text = StringPiece(reinterpret_cast<char*>(q0), 2*(q - q0));
+- return true;
+- }
+-
+- // Rewrites *sp from being a pointer into text8 (UTF-8)
+- // to being a pointer into text16 (equivalent text but in UCS-2).
+- static void AdjustUTF8ToUCS2(const StringPiece& text8, const StringPiece& text16,
+- StringPiece *sp) {
+- if (sp->begin() == NULL && text8.begin() != NULL)
+- return;
+-
+- int nrune = 0;
+- int n;
+- Rune r;
+- const char* p = text8.begin();
+- const char* ep = text8.end();
+- const char* spbegin = NULL;
+- const char* spend = NULL;
+- for (;;) {
+- if (p == sp->begin())
+- spbegin = text16.begin() + sizeof(uint16)*nrune;
+- if (p == sp->end())
+- spend = text16.begin() + sizeof(uint16)*nrune;
+- if (p >= ep)
+- break;
+- n = chartorune(&r, p);
+- p += n;
+- nrune++;
+- }
+- if (spbegin == NULL || spend == NULL) {
+- LOG(FATAL) << "Error in AdjustUTF8ToUCS2 "
+- << CEscape(text8) << " "
+- << (int)(sp->begin() - text8.begin()) << " "
+- << (int)(sp->end() - text8.begin());
+- }
+- *sp = StringPiece(spbegin, spend - spbegin);
+- }
+-
+- // Rewrites *sp from begin a pointer into text16 (UCS-2)
+- // to being a pointer into text8 (equivalent text but in UTF-8).
+- static void AdjustUCS2ToUTF8(const StringPiece& text16, const StringPiece& text8,
+- StringPiece* sp) {
+- if (sp->begin() == NULL)
+- return;
+-
+- int nrune = 0;
+- int n;
+- Rune r;
+- const char* p = text8.begin();
+- const char* ep = text8.end();
+- const char* spbegin = NULL;
+- const char* spend = NULL;
+- for (;;) {
+- if (nrune == (sp->begin() - text16.begin())/2)
+- spbegin = p;
+- if (nrune == (sp->end() - text16.begin())/2)
+- spend = p;
+- if (p >= ep)
+- break;
+- n = chartorune(&r, p);
+- p += n;
+- nrune++;
+- }
+- if (text8.begin() != NULL && (spbegin == NULL || spend == NULL)) {
+- LOG(FATAL) << "Error in AdjustUCS2ToUTF8 "
+- << CEscape(text16) << " "
+- << (int)(sp->begin() - text16.begin()) << " "
+- << (int)(sp->end() - text16.begin());
+- }
+- *sp = StringPiece(spbegin, spend - spbegin);
+- }
+-
+ // Runs a single search using the named engine type.
+ // This interface hides all the irregularities of the various
+ // engine interfaces from the rest of this file.
+re2/testing/tester.cc#12:393,411 - re2/testing/tester.cc#13:294,300
+
+ StringPiece text = orig_text;
+ StringPiece context = orig_context;
+- bool ucs2 = false;
+
+- if ((flags() & Regexp::UCS2) && type != kEnginePCRE) {
+- if (!ConvertUTF8ToUCS2(orig_context, &context)) {
+- result->skipped = true;
+- return;
+- }
+-
+- // Rewrite context to refer to new text.
+- AdjustUTF8ToUCS2(orig_context, context, &text);
+- ucs2 = true;
+- }
+-
+ switch (type) {
+ default:
+ LOG(FATAL) << "Bad RunSearch type: " << (int)type;
+re2/testing/tester.cc#12:557,577 - re2/testing/tester.cc#13:446,451
+ }
+ }
+
+- // If we did UCS-2 matching, rewrite the matches to refer
+- // to the original UTF-8 text.
+- if (ucs2) {
+- if (result->matched) {
+- if (result->have_submatch0) {
+- AdjustUCS2ToUTF8(context, orig_context, &result->submatch[0]);
+- } else if (result->have_submatch) {
+- for (int i = 0; i < nsubmatch; i++) {
+- AdjustUCS2ToUTF8(context, orig_context, &result->submatch[i]);
+- }
+- }
+- }
+- delete[] context.begin();
+- }
+-
+ if (!result->matched)
+ memset(result->submatch, 0, sizeof result->submatch);
+ }
+re2/testing/tester.cc#12:596,617 - re2/testing/tester.cc#13:470,475
+ return true;
+ }
+
+- // Check whether text uses only Unicode points <= 0xFFFF
+- // (in the BMP).
+- static bool IsBMP(const StringPiece& text) {
+- const char* p = text.begin();
+- const char* ep = text.end();
+- while (p < ep) {
+- if (!fullrune(p, ep - p))
+- return false;
+- Rune r;
+- p += chartorune(&r, p);
+- if (r > 0xFFFF)
+- return false;
+- }
+- return true;
+- }
+-
+ // Runs a single test.
+ bool TestInstance::RunCase(const StringPiece& text, const StringPiece& context,
+ Prog::Anchor anchor) {
+re2/testing/tester.cc#12:619,625 - re2/testing/tester.cc#13:477,483
+ Result correct;
+ RunSearch(kEngineBacktrack, text, context, anchor, &correct);
+ if (correct.skipped) {
+- if (regexp_ == NULL || !IsBMP(context)) // okay to skip in UCS-2 mode
++ if (regexp_ == NULL)
+ return true;
+ LOG(ERROR) << "Skipped backtracking! " << CEscape(regexp_str_)
+ << " " << FormatMode(flags_);
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