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1 : //===- Twine.h - Fast Temporary String Concatenation ------------*- C++ -*-===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 :
10 : #ifndef LLVM_ADT_TWINE_H
11 : #define LLVM_ADT_TWINE_H
12 :
13 : #include "llvm/ADT/SmallVector.h"
14 : #include "llvm/ADT/StringRef.h"
15 : #include "llvm/Support/ErrorHandling.h"
16 : #include <cassert>
17 : #include <cstdint>
18 : #include <string>
19 :
20 : namespace llvm {
21 :
22 : class formatv_object_base;
23 : class raw_ostream;
24 :
25 : /// Twine - A lightweight data structure for efficiently representing the
26 : /// concatenation of temporary values as strings.
27 : ///
28 : /// A Twine is a kind of rope, it represents a concatenated string using a
29 : /// binary-tree, where the string is the preorder of the nodes. Since the
30 : /// Twine can be efficiently rendered into a buffer when its result is used,
31 : /// it avoids the cost of generating temporary values for intermediate string
32 : /// results -- particularly in cases when the Twine result is never
33 : /// required. By explicitly tracking the type of leaf nodes, we can also avoid
34 : /// the creation of temporary strings for conversions operations (such as
35 : /// appending an integer to a string).
36 : ///
37 : /// A Twine is not intended for use directly and should not be stored, its
38 : /// implementation relies on the ability to store pointers to temporary stack
39 : /// objects which may be deallocated at the end of a statement. Twines should
40 : /// only be used accepted as const references in arguments, when an API wishes
41 : /// to accept possibly-concatenated strings.
42 : ///
43 : /// Twines support a special 'null' value, which always concatenates to form
44 : /// itself, and renders as an empty string. This can be returned from APIs to
45 : /// effectively nullify any concatenations performed on the result.
46 : ///
47 : /// \b Implementation
48 : ///
49 : /// Given the nature of a Twine, it is not possible for the Twine's
50 : /// concatenation method to construct interior nodes; the result must be
51 : /// represented inside the returned value. For this reason a Twine object
52 : /// actually holds two values, the left- and right-hand sides of a
53 : /// concatenation. We also have nullary Twine objects, which are effectively
54 : /// sentinel values that represent empty strings.
55 : ///
56 : /// Thus, a Twine can effectively have zero, one, or two children. The \see
57 : /// isNullary(), \see isUnary(), and \see isBinary() predicates exist for
58 : /// testing the number of children.
59 : ///
60 : /// We maintain a number of invariants on Twine objects (FIXME: Why):
61 : /// - Nullary twines are always represented with their Kind on the left-hand
62 : /// side, and the Empty kind on the right-hand side.
63 : /// - Unary twines are always represented with the value on the left-hand
64 : /// side, and the Empty kind on the right-hand side.
65 : /// - If a Twine has another Twine as a child, that child should always be
66 : /// binary (otherwise it could have been folded into the parent).
67 : ///
68 : /// These invariants are check by \see isValid().
69 : ///
70 : /// \b Efficiency Considerations
71 : ///
72 : /// The Twine is designed to yield efficient and small code for common
73 : /// situations. For this reason, the concat() method is inlined so that
74 : /// concatenations of leaf nodes can be optimized into stores directly into a
75 : /// single stack allocated object.
76 : ///
77 : /// In practice, not all compilers can be trusted to optimize concat() fully,
78 : /// so we provide two additional methods (and accompanying operator+
79 : /// overloads) to guarantee that particularly important cases (cstring plus
80 : /// StringRef) codegen as desired.
81 : class Twine {
82 : /// NodeKind - Represent the type of an argument.
83 : enum NodeKind : unsigned char {
84 : /// An empty string; the result of concatenating anything with it is also
85 : /// empty.
86 : NullKind,
87 :
88 : /// The empty string.
89 : EmptyKind,
90 :
91 : /// A pointer to a Twine instance.
92 : TwineKind,
93 :
94 : /// A pointer to a C string instance.
95 : CStringKind,
96 :
97 : /// A pointer to an std::string instance.
98 : StdStringKind,
99 :
100 : /// A pointer to a StringRef instance.
101 : StringRefKind,
102 :
103 : /// A pointer to a SmallString instance.
104 : SmallStringKind,
105 :
106 : /// A pointer to a formatv_object_base instance.
107 : FormatvObjectKind,
108 :
109 : /// A char value, to render as a character.
110 : CharKind,
111 :
112 : /// An unsigned int value, to render as an unsigned decimal integer.
113 : DecUIKind,
114 :
115 : /// An int value, to render as a signed decimal integer.
116 : DecIKind,
117 :
118 : /// A pointer to an unsigned long value, to render as an unsigned decimal
119 : /// integer.
120 : DecULKind,
121 :
122 : /// A pointer to a long value, to render as a signed decimal integer.
123 : DecLKind,
124 :
125 : /// A pointer to an unsigned long long value, to render as an unsigned
126 : /// decimal integer.
127 : DecULLKind,
128 :
129 : /// A pointer to a long long value, to render as a signed decimal integer.
130 : DecLLKind,
131 :
132 : /// A pointer to a uint64_t value, to render as an unsigned hexadecimal
133 : /// integer.
134 : UHexKind
135 : };
136 :
137 : union Child
138 : {
139 : const Twine *twine;
140 : const char *cString;
141 : const std::string *stdString;
142 : const StringRef *stringRef;
143 : const SmallVectorImpl<char> *smallString;
144 : const formatv_object_base *formatvObject;
145 : char character;
146 : unsigned int decUI;
147 : int decI;
148 : const unsigned long *decUL;
149 : const long *decL;
150 : const unsigned long long *decULL;
151 : const long long *decLL;
152 : const uint64_t *uHex;
153 : };
154 :
155 : /// LHS - The prefix in the concatenation, which may be uninitialized for
156 : /// Null or Empty kinds.
157 : Child LHS;
158 :
159 : /// RHS - The suffix in the concatenation, which may be uninitialized for
160 : /// Null or Empty kinds.
161 : Child RHS;
162 :
163 : /// LHSKind - The NodeKind of the left hand side, \see getLHSKind().
164 : NodeKind LHSKind = EmptyKind;
165 :
166 : /// RHSKind - The NodeKind of the right hand side, \see getRHSKind().
167 : NodeKind RHSKind = EmptyKind;
168 :
169 : /// Construct a nullary twine; the kind must be NullKind or EmptyKind.
170 2 : explicit Twine(NodeKind Kind) : LHSKind(Kind) {
171 : assert(isNullary() && "Invalid kind!");
172 : }
173 :
174 : /// Construct a binary twine.
175 : explicit Twine(const Twine &LHS, const Twine &RHS)
176 : : LHSKind(TwineKind), RHSKind(TwineKind) {
177 : this->LHS.twine = &LHS;
178 : this->RHS.twine = &RHS;
179 : assert(isValid() && "Invalid twine!");
180 : }
181 :
182 : /// Construct a twine from explicit values.
183 : explicit Twine(Child LHS, NodeKind LHSKind, Child RHS, NodeKind RHSKind)
184 55721048 : : LHS(LHS), RHS(RHS), LHSKind(LHSKind), RHSKind(RHSKind) {
185 : assert(isValid() && "Invalid twine!");
186 : }
187 :
188 : /// Check for the null twine.
189 : bool isNull() const {
190 191867201 : return getLHSKind() == NullKind;
191 : }
192 :
193 : /// Check for the empty twine.
194 : bool isEmpty() const {
195 : return getLHSKind() == EmptyKind;
196 : }
197 :
198 : /// Check if this is a nullary twine (null or empty).
199 : bool isNullary() const {
200 50844805 : return isNull() || isEmpty();
201 : }
202 :
203 : /// Check if this is a unary twine.
204 : bool isUnary() const {
205 82694254 : return getRHSKind() == EmptyKind && !isNullary();
206 : }
207 :
208 : /// Check if this is a binary twine.
209 : bool isBinary() const {
210 : return getLHSKind() != NullKind && getRHSKind() != EmptyKind;
211 : }
212 :
213 : /// Check if this is a valid twine (satisfying the invariants on
214 : /// order and number of arguments).
215 : bool isValid() const {
216 : // Nullary twines always have Empty on the RHS.
217 : if (isNullary() && getRHSKind() != EmptyKind)
218 : return false;
219 :
220 : // Null should never appear on the RHS.
221 : if (getRHSKind() == NullKind)
222 : return false;
223 :
224 : // The RHS cannot be non-empty if the LHS is empty.
225 : if (getRHSKind() != EmptyKind && getLHSKind() == EmptyKind)
226 : return false;
227 :
228 : // A twine child should always be binary.
229 : if (getLHSKind() == TwineKind &&
230 : !LHS.twine->isBinary())
231 : return false;
232 : if (getRHSKind() == TwineKind &&
233 : !RHS.twine->isBinary())
234 : return false;
235 :
236 : return true;
237 : }
238 :
239 : /// Get the NodeKind of the left-hand side.
240 0 : NodeKind getLHSKind() const { return LHSKind; }
241 :
242 : /// Get the NodeKind of the right-hand side.
243 0 : NodeKind getRHSKind() const { return RHSKind; }
244 :
245 : /// Print one child from a twine.
246 : void printOneChild(raw_ostream &OS, Child Ptr, NodeKind Kind) const;
247 :
248 : /// Print the representation of one child from a twine.
249 : void printOneChildRepr(raw_ostream &OS, Child Ptr,
250 : NodeKind Kind) const;
251 :
252 : public:
253 : /// @name Constructors
254 : /// @{
255 :
256 : /// Construct from an empty string.
257 14869667 : /*implicit*/ Twine() {
258 : assert(isValid() && "Invalid twine!");
259 : }
260 :
261 : Twine(const Twine &) = default;
262 :
263 : /// Construct from a C string.
264 : ///
265 : /// We take care here to optimize "" into the empty twine -- this will be
266 : /// optimized out for string constants. This allows Twine arguments have
267 : /// default "" values, without introducing unnecessary string constants.
268 85881452 : /*implicit*/ Twine(const char *Str) {
269 3696466 : if (Str[0] != '\0') {
270 52596510 : LHS.cString = Str;
271 41106237 : LHSKind = CStringKind;
272 : } else
273 : LHSKind = EmptyKind;
274 :
275 : assert(isValid() && "Invalid twine!");
276 : }
277 :
278 : /// Construct from an std::string.
279 15177572 : /*implicit*/ Twine(const std::string &Str) : LHSKind(StdStringKind) {
280 9025218 : LHS.stdString = &Str;
281 : assert(isValid() && "Invalid twine!");
282 : }
283 :
284 : /// Construct from a StringRef.
285 70271717 : /*implicit*/ Twine(const StringRef &Str) : LHSKind(StringRefKind) {
286 66924259 : LHS.stringRef = &Str;
287 : assert(isValid() && "Invalid twine!");
288 : }
289 :
290 : /// Construct from a SmallString.
291 : /*implicit*/ Twine(const SmallVectorImpl<char> &Str)
292 8147902 : : LHSKind(SmallStringKind) {
293 7974592 : LHS.smallString = &Str;
294 : assert(isValid() && "Invalid twine!");
295 : }
296 :
297 : /// Construct from a formatv_object_base.
298 : /*implicit*/ Twine(const formatv_object_base &Fmt)
299 36742 : : LHSKind(FormatvObjectKind) {
300 36742 : LHS.formatvObject = &Fmt;
301 : assert(isValid() && "Invalid twine!");
302 : }
303 :
304 : /// Construct from a char.
305 1299746 : explicit Twine(char Val) : LHSKind(CharKind) {
306 1096638 : LHS.character = Val;
307 : }
308 :
309 : /// Construct from a signed char.
310 1 : explicit Twine(signed char Val) : LHSKind(CharKind) {
311 1 : LHS.character = static_cast<char>(Val);
312 : }
313 :
314 : /// Construct from an unsigned char.
315 1 : explicit Twine(unsigned char Val) : LHSKind(CharKind) {
316 1 : LHS.character = static_cast<char>(Val);
317 : }
318 :
319 : /// Construct a twine to print \p Val as an unsigned decimal integer.
320 5384476 : explicit Twine(unsigned Val) : LHSKind(DecUIKind) {
321 5287102 : LHS.decUI = Val;
322 : }
323 :
324 : /// Construct a twine to print \p Val as a signed decimal integer.
325 5051367 : explicit Twine(int Val) : LHSKind(DecIKind) {
326 4041320 : LHS.decI = Val;
327 : }
328 :
329 : /// Construct a twine to print \p Val as an unsigned decimal integer.
330 543091 : explicit Twine(const unsigned long &Val) : LHSKind(DecULKind) {
331 541841 : LHS.decUL = &Val;
332 : }
333 :
334 : /// Construct a twine to print \p Val as a signed decimal integer.
335 42895 : explicit Twine(const long &Val) : LHSKind(DecLKind) {
336 42895 : LHS.decL = &Val;
337 : }
338 :
339 : /// Construct a twine to print \p Val as an unsigned decimal integer.
340 : explicit Twine(const unsigned long long &Val) : LHSKind(DecULLKind) {
341 : LHS.decULL = &Val;
342 : }
343 :
344 : /// Construct a twine to print \p Val as a signed decimal integer.
345 : explicit Twine(const long long &Val) : LHSKind(DecLLKind) {
346 : LHS.decLL = &Val;
347 : }
348 :
349 : // FIXME: Unfortunately, to make sure this is as efficient as possible we
350 : // need extra binary constructors from particular types. We can't rely on
351 : // the compiler to be smart enough to fold operator+()/concat() down to the
352 : // right thing. Yet.
353 :
354 : /// Construct as the concatenation of a C string and a StringRef.
355 : /*implicit*/ Twine(const char *LHS, const StringRef &RHS)
356 1513510 : : LHSKind(CStringKind), RHSKind(StringRefKind) {
357 1519884 : this->LHS.cString = LHS;
358 1400193 : this->RHS.stringRef = &RHS;
359 : assert(isValid() && "Invalid twine!");
360 : }
361 :
362 : /// Construct as the concatenation of a StringRef and a C string.
363 : /*implicit*/ Twine(const StringRef &LHS, const char *RHS)
364 4607193 : : LHSKind(StringRefKind), RHSKind(CStringKind) {
365 4607193 : this->LHS.stringRef = &LHS;
366 3318636 : this->RHS.cString = RHS;
367 : assert(isValid() && "Invalid twine!");
368 : }
369 :
370 : /// Since the intended use of twines is as temporary objects, assignments
371 : /// when concatenating might cause undefined behavior or stack corruptions
372 : Twine &operator=(const Twine &) = delete;
373 :
374 : /// Create a 'null' string, which is an empty string that always
375 : /// concatenates to form another empty string.
376 : static Twine createNull() {
377 : return Twine(NullKind);
378 : }
379 :
380 : /// @}
381 : /// @name Numeric Conversions
382 : /// @{
383 :
384 : // Construct a twine to print \p Val as an unsigned hexadecimal integer.
385 : static Twine utohexstr(const uint64_t &Val) {
386 : Child LHS, RHS;
387 : LHS.uHex = &Val;
388 : RHS.twine = nullptr;
389 : return Twine(LHS, UHexKind, RHS, EmptyKind);
390 : }
391 :
392 : /// @}
393 : /// @name Predicate Operations
394 : /// @{
395 :
396 : /// Check if this twine is trivially empty; a false return value does not
397 : /// necessarily mean the twine is empty.
398 : bool isTriviallyEmpty() const {
399 : return isNullary();
400 : }
401 :
402 : /// Return true if this twine can be dynamically accessed as a single
403 : /// StringRef value with getSingleStringRef().
404 : bool isSingleStringRef() const {
405 87492175 : if (getRHSKind() != EmptyKind) return false;
406 :
407 75401364 : switch (getLHSKind()) {
408 : case EmptyKind:
409 : case CStringKind:
410 : case StdStringKind:
411 : case StringRefKind:
412 : case SmallStringKind:
413 : return true;
414 : default:
415 : return false;
416 : }
417 : }
418 :
419 : /// @}
420 : /// @name String Operations
421 : /// @{
422 :
423 : Twine concat(const Twine &Suffix) const;
424 :
425 : /// @}
426 : /// @name Output & Conversion.
427 : /// @{
428 :
429 : /// Return the twine contents as a std::string.
430 : std::string str() const;
431 :
432 : /// Append the concatenated string into the given SmallString or SmallVector.
433 : void toVector(SmallVectorImpl<char> &Out) const;
434 :
435 : /// This returns the twine as a single StringRef. This method is only valid
436 : /// if isSingleStringRef() is true.
437 75375705 : StringRef getSingleStringRef() const {
438 : assert(isSingleStringRef() &&"This cannot be had as a single stringref!");
439 75375705 : switch (getLHSKind()) {
440 0 : default: llvm_unreachable("Out of sync with isSingleStringRef");
441 4346862 : case EmptyKind: return StringRef();
442 16143382 : case CStringKind: return StringRef(LHS.cString);
443 8149054 : case StdStringKind: return StringRef(*LHS.stdString);
444 51314869 : case StringRefKind: return *LHS.stringRef;
445 7567756 : case SmallStringKind:
446 15135512 : return StringRef(LHS.smallString->data(), LHS.smallString->size());
447 : }
448 : }
449 :
450 : /// This returns the twine as a single StringRef if it can be
451 : /// represented as such. Otherwise the twine is written into the given
452 : /// SmallVector and a StringRef to the SmallVector's data is returned.
453 87492166 : StringRef toStringRef(SmallVectorImpl<char> &Out) const {
454 : if (isSingleStringRef())
455 75373996 : return getSingleStringRef();
456 12118173 : toVector(Out);
457 24255552 : return StringRef(Out.data(), Out.size());
458 : }
459 :
460 : /// This returns the twine as a single null terminated StringRef if it
461 : /// can be represented as such. Otherwise the twine is written into the
462 : /// given SmallVector and a StringRef to the SmallVector's data is returned.
463 : ///
464 : /// The returned StringRef's size does not include the null terminator.
465 : StringRef toNullTerminatedStringRef(SmallVectorImpl<char> &Out) const;
466 :
467 : /// Write the concatenated string represented by this twine to the
468 : /// stream \p OS.
469 : void print(raw_ostream &OS) const;
470 :
471 : /// Dump the concatenated string represented by this twine to stderr.
472 : void dump() const;
473 :
474 : /// Write the representation of this twine to the stream \p OS.
475 : void printRepr(raw_ostream &OS) const;
476 :
477 : /// Dump the representation of this twine to stderr.
478 : void dumpRepr() const;
479 :
480 : /// @}
481 : };
482 :
483 : /// @name Twine Inline Implementations
484 : /// @{
485 :
486 55751351 : inline Twine Twine::concat(const Twine &Suffix) const {
487 : // Concatenation with null is null.
488 55751351 : if (isNull() || Suffix.isNull())
489 : return Twine(NullKind);
490 :
491 : // Concatenation with empty yields the other side.
492 55751349 : if (isEmpty())
493 54514 : return Suffix;
494 55696835 : if (Suffix.isEmpty())
495 34196 : return *this;
496 :
497 : // Otherwise we need to create a new node, taking care to fold in unary
498 : // twines.
499 : Child NewLHS, NewRHS;
500 : NewLHS.twine = this;
501 : NewRHS.twine = &Suffix;
502 : NodeKind NewLHSKind = TwineKind, NewRHSKind = TwineKind;
503 : if (isUnary()) {
504 22559831 : NewLHS = LHS;
505 : NewLHSKind = getLHSKind();
506 : }
507 : if (Suffix.isUnary()) {
508 55587417 : NewRHS = Suffix.LHS;
509 : NewRHSKind = Suffix.getLHSKind();
510 : }
511 :
512 55662639 : return Twine(NewLHS, NewLHSKind, NewRHS, NewRHSKind);
513 : }
514 :
515 : inline Twine operator+(const Twine &LHS, const Twine &RHS) {
516 18726258 : return LHS.concat(RHS);
517 : }
518 :
519 : /// Additional overload to guarantee simplified codegen; this is equivalent to
520 : /// concat().
521 :
522 : inline Twine operator+(const char *LHS, const StringRef &RHS) {
523 : return Twine(LHS, RHS);
524 : }
525 :
526 : /// Additional overload to guarantee simplified codegen; this is equivalent to
527 : /// concat().
528 :
529 : inline Twine operator+(const StringRef &LHS, const char *RHS) {
530 : return Twine(LHS, RHS);
531 : }
532 :
533 : inline raw_ostream &operator<<(raw_ostream &OS, const Twine &RHS) {
534 35222131 : RHS.print(OS);
535 : return OS;
536 : }
537 :
538 : /// @}
539 :
540 : } // end namespace llvm
541 :
542 : #endif // LLVM_ADT_TWINE_H
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