xpcom/string/nsTSubstring.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "double-conversion/double-conversion.h"
   8 #include "mozilla/CheckedInt.h"
   9 #include "mozilla/MathAlgorithms.h"
  10 #include "mozilla/MemoryReporting.h"
  11 #include "mozilla/Printf.h"
  12 #include "mozilla/ResultExtensions.h"
  13
  14 #include "nsASCIIMask.h"
  15 #include "nsCharTraits.h"
  16 #include "nsISupports.h"
  17 #include "nsString.h"
  18 #include "nsTArray.h"
  19
  20 #ifdef DEBUG
  21 #  include "nsStringStats.h"
  22 #else
  23 #  define STRING_STAT_INCREMENT(_s)
  24 #endif
  25
  26 // It's not worthwhile to reallocate the buffer and memcpy the
  27 // contents over when the size difference isn't large. With
  28 // power-of-two allocation buckets and 64 as the typical inline
  29 // capacity, considering that above 1000 there performance aspects
  30 // of realloc and memcpy seem to be absorbed, relative to the old
  31 // code, by the performance benefits of the new code being exact,
  32 // we need to choose which transitions of 256 to 128, 512 to 256
  33 // and 1024 to 512 to allow. As a guess, let's pick the middle
  34 // one as the the largest potential transition that we forgo. So
  35 // we'll shrink from 1024 bucket to 512 bucket but not from 512
  36 // bucket to 256 bucket. We'll decide by comparing the difference
  37 // of capacities. As bucket differences, the differences are 256
  38 // and 512. Since the capacities have various overheads, we
  39 // can't compare with 256 or 512 exactly but it's easier to
  40 // compare to some number that's between the two, so it's
  41 // far away from either to ignore the overheads.
  42 const uint32_t kNsStringBufferShrinkingThreshold = 384;
  43
  44 using double_conversion::DoubleToStringConverter;
  45
  46 // ---------------------------------------------------------------------------
  47
  48 static const char16_t gNullChar = 0;
  49
  50 char* const nsCharTraits<char>::sEmptyBuffer =
  51     (char*)const_cast<char16_t*>(&gNullChar);
  52 char16_t* const nsCharTraits<char16_t>::sEmptyBuffer =
  53     const_cast<char16_t*>(&gNullChar);
  54
  55 // ---------------------------------------------------------------------------
  56
  57 static void ReleaseData(void* aData, nsAString::DataFlags aFlags) {
  58   if (aFlags & nsAString::DataFlags::REFCOUNTED) {
  59     nsStringBuffer::FromData(aData)->Release();
  60   } else if (aFlags & nsAString::DataFlags::OWNED) {
  61     // Treat this as destruction of a "StringAdopt" object for leak
  62     // tracking purposes.
  63     MOZ_LOG_DTOR(aData, "StringAdopt", 1);
  64
  65     free(aData);
  66     STRING_STAT_INCREMENT(AdoptFree);
  67   }
  68   // otherwise, nothing to do.
  69 }
  70
  71 // ---------------------------------------------------------------------------
  72
  73 #ifdef XPCOM_STRING_CONSTRUCTOR_OUT_OF_LINE
  74 template <typename T>
  75 nsTSubstring<T>::nsTSubstring(char_type* aData, size_type aLength,
  76                               DataFlags aDataFlags, ClassFlags aClassFlags)
  77     : ::mozilla::detail::nsTStringRepr<T>(aData, aLength, aDataFlags,
  78                                           aClassFlags) {
  79   AssertValid();
  80
  81   if (aDataFlags & DataFlags::OWNED) {
  82     STRING_STAT_INCREMENT(Adopt);
  83     MOZ_LOG_CTOR(this->mData, "StringAdopt", 1);
  84   }
  85 }
  86 #endif /* XPCOM_STRING_CONSTRUCTOR_OUT_OF_LINE */
  87
  88 /**
  89  * helper function for down-casting a nsTSubstring to an nsTAutoString.
  90  */
  91 template <typename T>
  92 inline const nsTAutoString<T>* AsAutoString(const nsTSubstring<T>* aStr) {
  93   return static_cast<const nsTAutoString<T>*>(aStr);
  94 }
  95
  96 template <typename T>
  97 mozilla::Result<mozilla::BulkWriteHandle<T>, nsresult>
  98 nsTSubstring<T>::BulkWrite(size_type aCapacity, size_type aPrefixToPreserve,
  99                            bool aAllowShrinking) {
 100   auto r = StartBulkWriteImpl(aCapacity, aPrefixToPreserve, aAllowShrinking);
 101   if (MOZ_UNLIKELY(r.isErr())) {
 102     return r.propagateErr();
 103   }
 104   return mozilla::BulkWriteHandle<T>(this, r.unwrap());
 105 }
 106
 107 template <typename T>
 108 auto nsTSubstring<T>::StartBulkWriteImpl(size_type aCapacity,
 109                                          size_type aPrefixToPreserve,
 110                                          bool aAllowShrinking,
 111                                          size_type aSuffixLength,
 112                                          size_type aOldSuffixStart,
 113                                          size_type aNewSuffixStart)
 114     -> mozilla::Result<size_type, nsresult> {
 115   // Note! Capacity does not include room for the terminating null char.
 116
 117   MOZ_ASSERT(aPrefixToPreserve <= aCapacity,
 118              "Requested preservation of an overlong prefix.");
 119   MOZ_ASSERT(aNewSuffixStart + aSuffixLength <= aCapacity,
 120              "Requesed move of suffix to out-of-bounds location.");
 121   // Can't assert aOldSuffixStart, because mLength may not be valid anymore,
 122   // since this method allows itself to be called more than once.
 123
 124   // If zero capacity is requested, set the string to the special empty
 125   // string.
 126   if (MOZ_UNLIKELY(!aCapacity)) {
 127     ReleaseData(this->mData, this->mDataFlags);
 128     SetToEmptyBuffer();
 129     return 0;
 130   }
 131
 132   // Note! Capacity() returns 0 when the string is immutable.
 133   const size_type curCapacity = Capacity();
 134
 135   bool shrinking = false;
 136
 137   // We've established that aCapacity > 0.
 138   // |curCapacity == 0| means that the buffer is immutable or 0-sized, so we
 139   // need to allocate a new buffer. We cannot use the existing buffer even
 140   // though it might be large enough.
 141
 142   if (aCapacity <= curCapacity) {
 143     if (aAllowShrinking) {
 144       shrinking = true;
 145     } else {
 146       char_traits::move(this->mData + aNewSuffixStart,
 147                         this->mData + aOldSuffixStart, aSuffixLength);
 148       if (aSuffixLength) {
 149         char_traits::uninitialize(this->mData + aPrefixToPreserve,
 150                                   XPCOM_MIN(aNewSuffixStart - aPrefixToPreserve,
 151                                             kNsStringBufferMaxPoison));
 152         char_traits::uninitialize(
 153             this->mData + aNewSuffixStart + aSuffixLength,
 154             XPCOM_MIN(curCapacity + 1 - aNewSuffixStart - aSuffixLength,
 155                       kNsStringBufferMaxPoison));
 156       } else {
 157         char_traits::uninitialize(this->mData + aPrefixToPreserve,
 158                                   XPCOM_MIN(curCapacity + 1 - aPrefixToPreserve,
 159                                             kNsStringBufferMaxPoison));
 160       }
 161       return curCapacity;
 162     }
 163   }
 164
 165   char_type* oldData = this->mData;
 166   DataFlags oldFlags = this->mDataFlags;
 167
 168   char_type* newData;
 169   DataFlags newDataFlags;
 170   size_type newCapacity;
 171
 172   // If this is an nsTAutoStringN, it's possible that we can use the inline
 173   // buffer.
 174   if ((this->mClassFlags & ClassFlags::INLINE) &&
 175       (aCapacity <= AsAutoString(this)->mInlineCapacity)) {
 176     newCapacity = AsAutoString(this)->mInlineCapacity;
 177     newData = (char_type*)AsAutoString(this)->mStorage;
 178     newDataFlags = DataFlags::TERMINATED | DataFlags::INLINE;
 179   } else {
 180     // If |aCapacity > kMaxCapacity|, then our doubling algorithm may not be
 181     // able to allocate it.  Just bail out in cases like that.  We don't want
 182     // to be allocating 2GB+ strings anyway.
 183     static_assert((sizeof(nsStringBuffer) & 0x1) == 0,
 184                   "bad size for nsStringBuffer");
 185     if (MOZ_UNLIKELY(!this->CheckCapacity(aCapacity))) {
 186       return mozilla::Err(NS_ERROR_OUT_OF_MEMORY);
 187     }
 188
 189     // We increase our capacity so that the allocated buffer grows
 190     // exponentially, which gives us amortized O(1) appending. Below the
 191     // threshold, we use powers-of-two. Above the threshold, we grow by at
 192     // least 1.125, rounding up to the nearest MiB.
 193     const size_type slowGrowthThreshold = 8 * 1024 * 1024;
 194
 195     // nsStringBuffer allocates sizeof(nsStringBuffer) + passed size, and
 196     // storageSize below wants extra 1 * sizeof(char_type).
 197     const size_type neededExtraSpace =
 198         sizeof(nsStringBuffer) / sizeof(char_type) + 1;
 199
 200     size_type temp;
 201     if (aCapacity >= slowGrowthThreshold) {
 202       size_type minNewCapacity =
 203           curCapacity + (curCapacity >> 3);  // multiply by 1.125
 204       temp = XPCOM_MAX(aCapacity, minNewCapacity) + neededExtraSpace;
 205
 206       // Round up to the next multiple of MiB, but ensure the expected
 207       // capacity doesn't include the extra space required by nsStringBuffer
 208       // and null-termination.
 209       const size_t MiB = 1 << 20;
 210       temp = (MiB * ((temp + MiB - 1) / MiB)) - neededExtraSpace;
 211     } else {
 212       // Round up to the next power of two.
 213       temp =
 214           mozilla::RoundUpPow2(aCapacity + neededExtraSpace) - neededExtraSpace;
 215     }
 216
 217     newCapacity = XPCOM_MIN(temp, base_string_type::kMaxCapacity);
 218     MOZ_ASSERT(newCapacity >= aCapacity,
 219                "should have hit the early return at the top");
 220     // Avoid shrinking if the new buffer size is close to the old. Note that
 221     // unsigned underflow is defined behavior.
 222     if ((curCapacity - newCapacity) <= kNsStringBufferShrinkingThreshold &&
 223         (this->mDataFlags & DataFlags::REFCOUNTED)) {
 224       MOZ_ASSERT(aAllowShrinking, "How come we didn't return earlier?");
 225       // We're already close enough to the right size.
 226       newData = oldData;
 227       newCapacity = curCapacity;
 228     } else {
 229       size_type storageSize = (newCapacity + 1) * sizeof(char_type);
 230       // Since we allocate only by powers of 2 we always fit into a full
 231       // mozjemalloc bucket, it's not useful to use realloc, which may spend
 232       // time uselessly copying too much.
 233       nsStringBuffer* newHdr = nsStringBuffer::Alloc(storageSize).take();
 234       if (newHdr) {
 235         newData = (char_type*)newHdr->Data();
 236       } else if (shrinking) {
 237         // We're still in a consistent state.
 238         //
 239         // Since shrinking is just a memory footprint optimization, we
 240         // don't propagate OOM if we tried to shrink in order to avoid
 241         // OOM crashes from infallible callers. If we're lucky, soon enough
 242         // a fallible caller reaches OOM and is able to deal or we end up
 243         // disposing of this string before reaching OOM again.
 244         newData = oldData;
 245         newCapacity = curCapacity;
 246       } else {
 247         return mozilla::Err(NS_ERROR_OUT_OF_MEMORY);
 248       }
 249     }
 250     newDataFlags = DataFlags::TERMINATED | DataFlags::REFCOUNTED;
 251   }
 252
 253   this->mData = newData;
 254   this->mDataFlags = newDataFlags;
 255
 256   if (oldData == newData) {
 257     char_traits::move(newData + aNewSuffixStart, oldData + aOldSuffixStart,
 258                       aSuffixLength);
 259     if (aSuffixLength) {
 260       char_traits::uninitialize(this->mData + aPrefixToPreserve,
 261                                 XPCOM_MIN(aNewSuffixStart - aPrefixToPreserve,
 262                                           kNsStringBufferMaxPoison));
 263       char_traits::uninitialize(
 264           this->mData + aNewSuffixStart + aSuffixLength,
 265           XPCOM_MIN(newCapacity + 1 - aNewSuffixStart - aSuffixLength,
 266                     kNsStringBufferMaxPoison));
 267     } else {
 268       char_traits::uninitialize(this->mData + aPrefixToPreserve,
 269                                 XPCOM_MIN(newCapacity + 1 - aPrefixToPreserve,
 270                                           kNsStringBufferMaxPoison));
 271     }
 272   } else {
 273     char_traits::copy(newData, oldData, aPrefixToPreserve);
 274     char_traits::copy(newData + aNewSuffixStart, oldData + aOldSuffixStart,
 275                       aSuffixLength);
 276     ReleaseData(oldData, oldFlags);
 277   }
 278
 279   return newCapacity;
 280 }
 281
 282 template <typename T>
 283 void nsTSubstring<T>::FinishBulkWriteImpl(size_type aLength) {
 284   if (aLength) {
 285     FinishBulkWriteImplImpl(aLength);
 286   } else {
 287     ReleaseData(this->mData, this->mDataFlags);
 288     SetToEmptyBuffer();
 289   }
 290   AssertValid();
 291 }
 292
 293 template <typename T>
 294 void nsTSubstring<T>::Finalize() {
 295   ReleaseData(this->mData, this->mDataFlags);
 296   // this->mData, this->mLength, and this->mDataFlags are purposefully left
 297   // dangling
 298 }
 299
 300 template <typename T>
 301 bool nsTSubstring<T>::ReplacePrep(index_type aCutStart, size_type aCutLength,
 302                                   size_type aNewLength) {
 303   aCutLength = XPCOM_MIN(aCutLength, this->mLength - aCutStart);
 304
 305   mozilla::CheckedInt<size_type> newTotalLen = this->Length();
 306   newTotalLen += aNewLength;
 307   newTotalLen -= aCutLength;
 308   if (!newTotalLen.isValid()) {
 309     return false;
 310   }
 311
 312   if (aCutStart == this->mLength && Capacity() > newTotalLen.value()) {
 313     this->mDataFlags &= ~DataFlags::VOIDED;
 314     this->mData[newTotalLen.value()] = char_type(0);
 315     this->mLength = newTotalLen.value();
 316     return true;
 317   }
 318
 319   return ReplacePrepInternal(aCutStart, aCutLength, aNewLength,
 320                              newTotalLen.value());
 321 }
 322
 323 template <typename T>
 324 bool nsTSubstring<T>::ReplacePrepInternal(index_type aCutStart,
 325                                           size_type aCutLen, size_type aFragLen,
 326                                           size_type aNewLen) {
 327   size_type newSuffixStart = aCutStart + aFragLen;
 328   size_type oldSuffixStart = aCutStart + aCutLen;
 329   size_type suffixLength = this->mLength - oldSuffixStart;
 330
 331   mozilla::Result<size_type, nsresult> r = StartBulkWriteImpl(
 332       aNewLen, aCutStart, false, suffixLength, oldSuffixStart, newSuffixStart);
 333   if (r.isErr()) {
 334     return false;
 335   }
 336   FinishBulkWriteImpl(aNewLen);
 337   return true;
 338 }
 339
 340 template <typename T>
 341 typename nsTSubstring<T>::size_type nsTSubstring<T>::Capacity() const {
 342   // return 0 to indicate an immutable or 0-sized buffer
 343
 344   size_type capacity;
 345   if (this->mDataFlags & DataFlags::REFCOUNTED) {
 346     // if the string is readonly, then we pretend that it has no capacity.
 347     nsStringBuffer* hdr = nsStringBuffer::FromData(this->mData);
 348     if (hdr->IsReadonly()) {
 349       capacity = 0;
 350     } else {
 351       capacity = (size_t(hdr->StorageSize()) / sizeof(char_type)) - 1;
 352     }
 353   } else if (this->mDataFlags & DataFlags::INLINE) {
 354     MOZ_ASSERT(this->mClassFlags & ClassFlags::INLINE);
 355     capacity = AsAutoString(this)->mInlineCapacity;
 356   } else if (this->mDataFlags & DataFlags::OWNED) {
 357     // we don't store the capacity of an adopted buffer because that would
 358     // require an additional member field.  the best we can do is base the
 359     // capacity on our length.  remains to be seen if this is the right
 360     // trade-off.
 361     capacity = this->mLength;
 362   } else {
 363     capacity = 0;
 364   }
 365
 366   return capacity;
 367 }
 368
 369 template <typename T>
 370 bool nsTSubstring<T>::EnsureMutable(size_type aNewLen) {
 371   if (aNewLen == size_type(-1) || aNewLen == this->mLength) {
 372     if (this->mDataFlags & (DataFlags::INLINE | DataFlags::OWNED)) {
 373       return true;
 374     }
 375     if ((this->mDataFlags & DataFlags::REFCOUNTED) &&
 376         !nsStringBuffer::FromData(this->mData)->IsReadonly()) {
 377       return true;
 378     }
 379
 380     aNewLen = this->mLength;
 381   }
 382   return SetLength(aNewLen, mozilla::fallible);
 383 }
 384
 385 // ---------------------------------------------------------------------------
 386
 387 // This version of Assign is optimized for single-character assignment.
 388 template <typename T>
 389 void nsTSubstring<T>::Assign(char_type aChar) {
 390   if (MOZ_UNLIKELY(!Assign(aChar, mozilla::fallible))) {
 391     AllocFailed(1);
 392   }
 393 }
 394
 395 template <typename T>
 396 bool nsTSubstring<T>::Assign(char_type aChar, const fallible_t&) {
 397   auto r = StartBulkWriteImpl(1, 0, true);
 398   if (MOZ_UNLIKELY(r.isErr())) {
 399     return false;
 400   }
 401   *this->mData = aChar;
 402   FinishBulkWriteImpl(1);
 403   return true;
 404 }
 405
 406 template <typename T>
 407 void nsTSubstring<T>::Assign(const char_type* aData, size_type aLength) {
 408   if (MOZ_UNLIKELY(!Assign(aData, aLength, mozilla::fallible))) {
 409     AllocFailed(aLength == size_type(-1) ? char_traits::length(aData)
 410                                          : aLength);
 411   }
 412 }
 413
 414 template <typename T>
 415 bool nsTSubstring<T>::Assign(const char_type* aData,
 416                              const fallible_t& aFallible) {
 417   return Assign(aData, size_type(-1), aFallible);
 418 }
 419
 420 template <typename T>
 421 bool nsTSubstring<T>::Assign(const char_type* aData, size_type aLength,
 422                              const fallible_t& aFallible) {
 423   if (!aData || aLength == 0) {
 424     Truncate();
 425     return true;
 426   }
 427
 428   if (MOZ_UNLIKELY(aLength == size_type(-1))) {
 429     aLength = char_traits::length(aData);
 430   }
 431
 432   if (MOZ_UNLIKELY(this->IsDependentOn(aData, aData + aLength))) {
 433     return Assign(string_type(aData, aLength), aFallible);
 434   }
 435
 436   auto r = StartBulkWriteImpl(aLength, 0, true);
 437   if (MOZ_UNLIKELY(r.isErr())) {
 438     return false;
 439   }
 440   char_traits::copy(this->mData, aData, aLength);
 441   FinishBulkWriteImpl(aLength);
 442   return true;
 443 }
 444
 445 template <typename T>
 446 void nsTSubstring<T>::AssignASCII(const char* aData, size_type aLength) {
 447   if (MOZ_UNLIKELY(!AssignASCII(aData, aLength, mozilla::fallible))) {
 448     AllocFailed(aLength);
 449   }
 450 }
 451
 452 template <typename T>
 453 bool nsTSubstring<T>::AssignASCII(const char* aData, size_type aLength,
 454                                   const fallible_t& aFallible) {
 455   MOZ_ASSERT(aLength != size_type(-1));
 456
 457   // A Unicode string can't depend on an ASCII string buffer,
 458   // so this dependence check only applies to CStrings.
 459   if constexpr (std::is_same_v<T, char>) {
 460     if (this->IsDependentOn(aData, aData + aLength)) {
 461       return Assign(string_type(aData, aLength), aFallible);
 462     }
 463   }
 464
 465   auto r = StartBulkWriteImpl(aLength, 0, true);
 466   if (MOZ_UNLIKELY(r.isErr())) {
 467     return false;
 468   }
 469   char_traits::copyASCII(this->mData, aData, aLength);
 470   FinishBulkWriteImpl(aLength);
 471   return true;
 472 }
 473
 474 template <typename T>
 475 void nsTSubstring<T>::AssignLiteral(const char_type* aData, size_type aLength) {
 476   ReleaseData(this->mData, this->mDataFlags);
 477   SetData(const_cast<char_type*>(aData), aLength,
 478           DataFlags::TERMINATED | DataFlags::LITERAL);
 479 }
 480
 481 template <typename T>
 482 void nsTSubstring<T>::Assign(const self_type& aStr) {
 483   if (!Assign(aStr, mozilla::fallible)) {
 484     AllocFailed(aStr.Length());
 485   }
 486 }
 487
 488 template <typename T>
 489 bool nsTSubstring<T>::Assign(const self_type& aStr,
 490                              const fallible_t& aFallible) {
 491   // |aStr| could be sharable. We need to check its flags to know how to
 492   // deal with it.
 493
 494   if (&aStr == this) {
 495     return true;
 496   }
 497
 498   if (!aStr.mLength) {
 499     Truncate();
 500     this->mDataFlags |= aStr.mDataFlags & DataFlags::VOIDED;
 501     return true;
 502   }
 503
 504   if (aStr.mDataFlags & DataFlags::REFCOUNTED) {
 505     // nice! we can avoid a string copy :-)
 506
 507     // |aStr| should be null-terminated
 508     NS_ASSERTION(aStr.mDataFlags & DataFlags::TERMINATED,
 509                  "shared, but not terminated");
 510
 511     ReleaseData(this->mData, this->mDataFlags);
 512
 513     SetData(aStr.mData, aStr.mLength,
 514             DataFlags::TERMINATED | DataFlags::REFCOUNTED);
 515
 516     // get an owning reference to the this->mData
 517     nsStringBuffer::FromData(this->mData)->AddRef();
 518     return true;
 519   }
 520   if (aStr.mDataFlags & DataFlags::LITERAL) {
 521     MOZ_ASSERT(aStr.mDataFlags & DataFlags::TERMINATED, "Unterminated literal");
 522
 523     AssignLiteral(aStr.mData, aStr.mLength);
 524     return true;
 525   }
 526
 527   // else, treat this like an ordinary assignment.
 528   return Assign(aStr.Data(), aStr.Length(), aFallible);
 529 }
 530
 531 template <typename T>
 532 void nsTSubstring<T>::Assign(self_type&& aStr) {
 533   if (!Assign(std::move(aStr), mozilla::fallible)) {
 534     AllocFailed(aStr.Length());
 535   }
 536 }
 537
 538 template <typename T>
 539 void nsTSubstring<T>::AssignOwned(self_type&& aStr) {
 540   MOZ_ASSERT(aStr.mDataFlags & (DataFlags::REFCOUNTED | DataFlags::OWNED),
 541              "neither shared nor owned");
 542
 543   // If they have a REFCOUNTED or OWNED buffer, we can avoid a copy - so steal
 544   // their buffer and reset them to the empty string.
 545
 546   // |aStr| should be null-terminated
 547   MOZ_ASSERT(aStr.mDataFlags & DataFlags::TERMINATED,
 548              "shared or owned, but not terminated");
 549
 550   ReleaseData(this->mData, this->mDataFlags);
 551
 552   SetData(aStr.mData, aStr.mLength, aStr.mDataFlags);
 553   aStr.SetToEmptyBuffer();
 554 }
 555
 556 template <typename T>
 557 bool nsTSubstring<T>::Assign(self_type&& aStr, const fallible_t& aFallible) {
 558   // We're moving |aStr| in this method, so we need to try to steal the data,
 559   // and in the fallback perform a copy-assignment followed by a truncation of
 560   // the original string.
 561
 562   if (&aStr == this) {
 563     NS_WARNING("Move assigning a string to itself?");
 564     return true;
 565   }
 566
 567   if (aStr.mDataFlags & (DataFlags::REFCOUNTED | DataFlags::OWNED)) {
 568     AssignOwned(std::move(aStr));
 569     return true;
 570   }
 571
 572   // Otherwise treat this as a normal assignment, and truncate the moved string.
 573   // We don't truncate the source string if the allocation failed.
 574   if (!Assign(aStr, aFallible)) {
 575     return false;
 576   }
 577   aStr.Truncate();
 578   return true;
 579 }
 580
 581 template <typename T>
 582 void nsTSubstring<T>::Assign(const substring_tuple_type& aTuple) {
 583   if (!Assign(aTuple, mozilla::fallible)) {
 584     AllocFailed(aTuple.Length());
 585   }
 586 }
 587
 588 template <typename T>
 589 bool nsTSubstring<T>::AssignNonDependent(const substring_tuple_type& aTuple,
 590                                          size_type aTupleLength,
 591                                          const mozilla::fallible_t& aFallible) {
 592   NS_ASSERTION(aTuple.Length() == aTupleLength, "wrong length passed");
 593
 594   auto r = StartBulkWriteImpl(aTupleLength);
 595   if (r.isErr()) {
 596     return false;
 597   }
 598
 599   aTuple.WriteTo(this->mData, aTupleLength);
 600
 601   FinishBulkWriteImpl(aTupleLength);
 602   return true;
 603 }
 604
 605 template <typename T>
 606 bool nsTSubstring<T>::Assign(const substring_tuple_type& aTuple,
 607                              const fallible_t& aFallible) {
 608   const auto [isDependentOnThis, tupleLength] =
 609       aTuple.IsDependentOnWithLength(this->mData, this->mData + this->mLength);
 610   if (isDependentOnThis) {
 611     string_type temp;
 612     self_type& tempSubstring = temp;
 613     if (!tempSubstring.AssignNonDependent(aTuple, tupleLength, aFallible)) {
 614       return false;
 615     }
 616     AssignOwned(std::move(temp));
 617     return true;
 618   }
 619
 620   return AssignNonDependent(aTuple, tupleLength, aFallible);
 621 }
 622
 623 template <typename T>
 624 void nsTSubstring<T>::Adopt(char_type* aData, size_type aLength) {
 625   if (aData) {
 626     ReleaseData(this->mData, this->mDataFlags);
 627
 628     if (aLength == size_type(-1)) {
 629       aLength = char_traits::length(aData);
 630     }
 631
 632     SetData(aData, aLength, DataFlags::TERMINATED | DataFlags::OWNED);
 633
 634     STRING_STAT_INCREMENT(Adopt);
 635     // Treat this as construction of a "StringAdopt" object for leak
 636     // tracking purposes.
 637     MOZ_LOG_CTOR(this->mData, "StringAdopt", 1);
 638   } else {
 639     SetIsVoid(true);
 640   }
 641 }
 642
 643 // This version of Replace is optimized for single-character replacement.
 644 template <typename T>
 645 void nsTSubstring<T>::Replace(index_type aCutStart, size_type aCutLength,
 646                               char_type aChar) {
 647   aCutStart = XPCOM_MIN(aCutStart, this->Length());
 648
 649   if (ReplacePrep(aCutStart, aCutLength, 1)) {
 650     this->mData[aCutStart] = aChar;
 651   }
 652 }
 653
 654 template <typename T>
 655 bool nsTSubstring<T>::Replace(index_type aCutStart, size_type aCutLength,
 656                               char_type aChar, const fallible_t&) {
 657   aCutStart = XPCOM_MIN(aCutStart, this->Length());
 658
 659   if (!ReplacePrep(aCutStart, aCutLength, 1)) {
 660     return false;
 661   }
 662
 663   this->mData[aCutStart] = aChar;
 664
 665   return true;
 666 }
 667
 668 template <typename T>
 669 void nsTSubstring<T>::Replace(index_type aCutStart, size_type aCutLength,
 670                               const char_type* aData, size_type aLength) {
 671   if (!Replace(aCutStart, aCutLength, aData, aLength, mozilla::fallible)) {
 672     AllocFailed(this->Length() - aCutLength + 1);
 673   }
 674 }
 675
 676 template <typename T>
 677 bool nsTSubstring<T>::Replace(index_type aCutStart, size_type aCutLength,
 678                               const char_type* aData, size_type aLength,
 679                               const fallible_t& aFallible) {
 680   // unfortunately, some callers pass null :-(
 681   if (!aData) {
 682     aLength = 0;
 683   } else {
 684     if (aLength == size_type(-1)) {
 685       aLength = char_traits::length(aData);
 686     }
 687
 688     if (this->IsDependentOn(aData, aData + aLength)) {
 689       nsTAutoString<T> temp(aData, aLength);
 690       return Replace(aCutStart, aCutLength, temp, aFallible);
 691     }
 692   }
 693
 694   aCutStart = XPCOM_MIN(aCutStart, this->Length());
 695
 696   bool ok = ReplacePrep(aCutStart, aCutLength, aLength);
 697   if (!ok) {
 698     return false;
 699   }
 700
 701   if (aLength > 0) {
 702     char_traits::copy(this->mData + aCutStart, aData, aLength);
 703   }
 704
 705   return true;
 706 }
 707
 708 template <typename T>
 709 void nsTSubstring<T>::Replace(index_type aCutStart, size_type aCutLength,
 710                               const substring_tuple_type& aTuple) {
 711   const auto [isDependentOnThis, tupleLength] =
 712       aTuple.IsDependentOnWithLength(this->mData, this->mData + this->mLength);
 713
 714   if (isDependentOnThis) {
 715     nsTAutoString<T> temp;
 716     if (!temp.AssignNonDependent(aTuple, tupleLength, mozilla::fallible)) {
 717       AllocFailed(tupleLength);
 718     }
 719     Replace(aCutStart, aCutLength, temp);
 720     return;
 721   }
 722
 723   aCutStart = XPCOM_MIN(aCutStart, this->Length());
 724
 725   if (ReplacePrep(aCutStart, aCutLength, tupleLength) && tupleLength > 0) {
 726     aTuple.WriteTo(this->mData + aCutStart, tupleLength);
 727   }
 728 }
 729
 730 template <typename T>
 731 void nsTSubstring<T>::ReplaceLiteral(index_type aCutStart, size_type aCutLength,
 732                                      const char_type* aData,
 733                                      size_type aLength) {
 734   aCutStart = XPCOM_MIN(aCutStart, this->Length());
 735
 736   if (!aCutStart && aCutLength == this->Length() &&
 737       !(this->mDataFlags & DataFlags::REFCOUNTED)) {
 738     // Check for REFCOUNTED above to avoid undoing the effect of
 739     // SetCapacity().
 740     AssignLiteral(aData, aLength);
 741   } else if (ReplacePrep(aCutStart, aCutLength, aLength) && aLength > 0) {
 742     char_traits::copy(this->mData + aCutStart, aData, aLength);
 743   }
 744 }
 745
 746 template <typename T>
 747 void nsTSubstring<T>::Append(char_type aChar) {
 748   if (MOZ_UNLIKELY(!Append(aChar, mozilla::fallible))) {
 749     AllocFailed(this->mLength + 1);
 750   }
 751 }
 752
 753 template <typename T>
 754 bool nsTSubstring<T>::Append(char_type aChar, const fallible_t& aFallible) {
 755   size_type oldLen = this->mLength;
 756   size_type newLen = oldLen + 1;  // Can't overflow
 757   auto r = StartBulkWriteImpl(newLen, oldLen, false);
 758   if (MOZ_UNLIKELY(r.isErr())) {
 759     return false;
 760   }
 761   this->mData[oldLen] = aChar;
 762   FinishBulkWriteImpl(newLen);
 763   return true;
 764 }
 765
 766 template <typename T>
 767 void nsTSubstring<T>::Append(const char_type* aData, size_type aLength) {
 768   if (MOZ_UNLIKELY(!Append(aData, aLength, mozilla::fallible))) {
 769     AllocFailed(this->mLength + (aLength == size_type(-1)
 770                                      ? char_traits::length(aData)
 771                                      : aLength));
 772   }
 773 }
 774
 775 template <typename T>
 776 bool nsTSubstring<T>::Append(const char_type* aData, size_type aLength,
 777                              const fallible_t& aFallible) {
 778   if (MOZ_UNLIKELY(aLength == size_type(-1))) {
 779     aLength = char_traits::length(aData);
 780   }
 781
 782   if (MOZ_UNLIKELY(!aLength)) {
 783     // Avoid undoing the effect of SetCapacity() if both
 784     // mLength and aLength are zero.
 785     return true;
 786   }
 787
 788   if (MOZ_UNLIKELY(this->IsDependentOn(aData, aData + aLength))) {
 789     return Append(string_type(aData, aLength), mozilla::fallible);
 790   }
 791   size_type oldLen = this->mLength;
 792   mozilla::CheckedInt<size_type> newLen(oldLen);
 793   newLen += aLength;
 794   if (MOZ_UNLIKELY(!newLen.isValid())) {
 795     return false;
 796   }
 797   auto r = StartBulkWriteImpl(newLen.value(), oldLen, false);
 798   if (MOZ_UNLIKELY(r.isErr())) {
 799     return false;
 800   }
 801   char_traits::copy(this->mData + oldLen, aData, aLength);
 802   FinishBulkWriteImpl(newLen.value());
 803   return true;
 804 }
 805
 806 template <typename T>
 807 void nsTSubstring<T>::AppendASCII(const char* aData, size_type aLength) {
 808   if (MOZ_UNLIKELY(!AppendASCII(aData, aLength, mozilla::fallible))) {
 809     AllocFailed(this->mLength +
 810                 (aLength == size_type(-1) ? strlen(aData) : aLength));
 811   }
 812 }
 813
 814 template <typename T>
 815 bool nsTSubstring<T>::AppendASCII(const char* aData,
 816                                   const fallible_t& aFallible) {
 817   return AppendASCII(aData, size_type(-1), aFallible);
 818 }
 819
 820 template <typename T>
 821 bool nsTSubstring<T>::AppendASCII(const char* aData, size_type aLength,
 822                                   const fallible_t& aFallible) {
 823   if (MOZ_UNLIKELY(aLength == size_type(-1))) {
 824     aLength = strlen(aData);
 825   }
 826
 827   if (MOZ_UNLIKELY(!aLength)) {
 828     // Avoid undoing the effect of SetCapacity() if both
 829     // mLength and aLength are zero.
 830     return true;
 831   }
 832
 833   if constexpr (std::is_same_v<T, char>) {
 834     // 16-bit string can't depend on an 8-bit buffer
 835     if (MOZ_UNLIKELY(this->IsDependentOn(aData, aData + aLength))) {
 836       return Append(string_type(aData, aLength), mozilla::fallible);
 837     }
 838   }
 839
 840   size_type oldLen = this->mLength;
 841   mozilla::CheckedInt<size_type> newLen(oldLen);
 842   newLen += aLength;
 843   if (MOZ_UNLIKELY(!newLen.isValid())) {
 844     return false;
 845   }
 846   auto r = StartBulkWriteImpl(newLen.value(), oldLen, false);
 847   if (MOZ_UNLIKELY(r.isErr())) {
 848     return false;
 849   }
 850   char_traits::copyASCII(this->mData + oldLen, aData, aLength);
 851   FinishBulkWriteImpl(newLen.value());
 852   return true;
 853 }
 854
 855 template <typename T>
 856 void nsTSubstring<T>::Append(const self_type& aStr) {
 857   if (MOZ_UNLIKELY(!Append(aStr, mozilla::fallible))) {
 858     AllocFailed(this->mLength + aStr.Length());
 859   }
 860 }
 861
 862 template <typename T>
 863 bool nsTSubstring<T>::Append(const self_type& aStr,
 864                              const fallible_t& aFallible) {
 865   // Check refcounted to avoid undoing the effects of SetCapacity().
 866   if (MOZ_UNLIKELY(!this->mLength &&
 867                    !(this->mDataFlags & DataFlags::REFCOUNTED))) {
 868     return Assign(aStr, mozilla::fallible);
 869   }
 870   return Append(aStr.BeginReading(), aStr.Length(), mozilla::fallible);
 871 }
 872
 873 template <typename T>
 874 void nsTSubstring<T>::Append(const substring_tuple_type& aTuple) {
 875   if (MOZ_UNLIKELY(!Append(aTuple, mozilla::fallible))) {
 876     AllocFailed(this->mLength + aTuple.Length());
 877   }
 878 }
 879
 880 template <typename T>
 881 bool nsTSubstring<T>::Append(const substring_tuple_type& aTuple,
 882                              const fallible_t& aFallible) {
 883   const auto [isDependentOnThis, tupleLength] =
 884       aTuple.IsDependentOnWithLength(this->mData, this->mData + this->mLength);
 885
 886   if (MOZ_UNLIKELY(!tupleLength)) {
 887     // Avoid undoing the effect of SetCapacity() if both
 888     // mLength and tupleLength are zero.
 889     return true;
 890   }
 891
 892   if (MOZ_UNLIKELY(isDependentOnThis)) {
 893     return Append(string_type(aTuple), aFallible);
 894   }
 895
 896   size_type oldLen = this->mLength;
 897   mozilla::CheckedInt<size_type> newLen(oldLen);
 898   newLen += tupleLength;
 899   if (MOZ_UNLIKELY(!newLen.isValid())) {
 900     return false;
 901   }
 902   auto r = StartBulkWriteImpl(newLen.value(), oldLen, false);
 903   if (MOZ_UNLIKELY(r.isErr())) {
 904     return false;
 905   }
 906   aTuple.WriteTo(this->mData + oldLen, tupleLength);
 907   FinishBulkWriteImpl(newLen.value());
 908   return true;
 909 }
 910
 911 template <typename T>
 912 void nsTSubstring<T>::SetCapacity(size_type aCapacity) {
 913   if (!SetCapacity(aCapacity, mozilla::fallible)) {
 914     AllocFailed(aCapacity);
 915   }
 916 }
 917
 918 template <typename T>
 919 bool nsTSubstring<T>::SetCapacity(size_type aCapacity, const fallible_t&) {
 920   size_type length = this->mLength;
 921   // This method can no longer be used to shorten the
 922   // logical length.
 923   size_type capacity = XPCOM_MAX(aCapacity, length);
 924
 925   auto r = StartBulkWriteImpl(capacity, length, true);
 926   if (r.isErr()) {
 927     return false;
 928   }
 929
 930   if (MOZ_UNLIKELY(!capacity)) {
 931     // Zero capacity was requested on a zero-length
 932     // string. In this special case, we are pointing
 933     // to the special empty buffer, which is already
 934     // zero-terminated and not writable, so we must
 935     // not attempt to zero-terminate it.
 936     AssertValid();
 937     return true;
 938   }
 939
 940   // FinishBulkWriteImpl with argument zero releases
 941   // the heap-allocated buffer. However, SetCapacity()
 942   // is a special case that allows mLength to be zero
 943   // while a heap-allocated buffer exists.
 944   // By calling FinishBulkWriteImplImpl, we skip the
 945   // zero case handling that's inappropriate in the
 946   // SetCapacity() case.
 947   FinishBulkWriteImplImpl(length);
 948   return true;
 949 }
 950
 951 template <typename T>
 952 void nsTSubstring<T>::SetLength(size_type aLength) {
 953   if (!SetLength(aLength, mozilla::fallible)) {
 954     AllocFailed(aLength);
 955   }
 956 }
 957
 958 template <typename T>
 959 bool nsTSubstring<T>::SetLength(size_type aLength,
 960                                 const fallible_t& aFallible) {
 961   size_type preserve = XPCOM_MIN(aLength, this->Length());
 962   auto r = StartBulkWriteImpl(aLength, preserve, true);
 963   if (r.isErr()) {
 964     return false;
 965   }
 966
 967   FinishBulkWriteImpl(aLength);
 968
 969   return true;
 970 }
 971
 972 template <typename T>
 973 void nsTSubstring<T>::Truncate() {
 974   ReleaseData(this->mData, this->mDataFlags);
 975   SetToEmptyBuffer();
 976   AssertValid();
 977 }
 978
 979 template <typename T>
 980 void nsTSubstring<T>::SetIsVoid(bool aVal) {
 981   if (aVal) {
 982     Truncate();
 983     this->mDataFlags |= DataFlags::VOIDED;
 984   } else {
 985     this->mDataFlags &= ~DataFlags::VOIDED;
 986   }
 987 }
 988
 989 template <typename T>
 990 void nsTSubstring<T>::StripChar(char_type aChar) {
 991   if (this->mLength == 0) {
 992     return;
 993   }
 994
 995   if (!EnsureMutable()) {  // XXX do this lazily?
 996     AllocFailed(this->mLength);
 997   }
 998
 999   // XXX(darin): this code should defer writing until necessary.
1000
1001   char_type* to = this->mData;
1002   char_type* from = this->mData;
1003   char_type* end = this->mData + this->mLength;
1004
1005   while (from < end) {
1006     char_type theChar = *from++;
1007     if (aChar != theChar) {
1008       *to++ = theChar;
1009     }
1010   }
1011   *to = char_type(0);  // add the null
1012   this->mLength = to - this->mData;
1013 }
1014
1015 template <typename T>
1016 void nsTSubstring<T>::StripChars(const char_type* aChars) {
1017   if (this->mLength == 0) {
1018     return;
1019   }
1020
1021   if (!EnsureMutable()) {  // XXX do this lazily?
1022     AllocFailed(this->mLength);
1023   }
1024
1025   // XXX(darin): this code should defer writing until necessary.
1026
1027   char_type* to = this->mData;
1028   char_type* from = this->mData;
1029   char_type* end = this->mData + this->mLength;
1030
1031   while (from < end) {
1032     char_type theChar = *from++;
1033     const char_type* test = aChars;
1034
1035     for (; *test && *test != theChar; ++test)
1036       ;
1037
1038     if (!*test) {
1039       // Not stripped, copy this char.
1040       *to++ = theChar;
1041     }
1042   }
1043   *to = char_type(0);  // add the null
1044   this->mLength = to - this->mData;
1045 }
1046
1047 template <typename T>
1048 void nsTSubstring<T>::StripTaggedASCII(const ASCIIMaskArray& aToStrip) {
1049   if (this->mLength == 0) {
1050     return;
1051   }
1052
1053   size_t untaggedPrefixLength = 0;
1054   for (; untaggedPrefixLength < this->mLength; ++untaggedPrefixLength) {
1055     uint32_t theChar = (uint32_t)this->mData[untaggedPrefixLength];
1056     if (mozilla::ASCIIMask::IsMasked(aToStrip, theChar)) {
1057       break;
1058     }
1059   }
1060
1061   if (untaggedPrefixLength == this->mLength) {
1062     return;
1063   }
1064
1065   if (!EnsureMutable()) {
1066     AllocFailed(this->mLength);
1067   }
1068
1069   char_type* to = this->mData + untaggedPrefixLength;
1070   char_type* from = to;
1071   char_type* end = this->mData + this->mLength;
1072
1073   while (from < end) {
1074     uint32_t theChar = (uint32_t)*from++;
1075     // Replacing this with a call to ASCIIMask::IsMasked
1076     // regresses performance somewhat, so leaving it inlined.
1077     if (!mozilla::ASCIIMask::IsMasked(aToStrip, theChar)) {
1078       // Not stripped, copy this char.
1079       *to++ = (char_type)theChar;
1080     }
1081   }
1082   *to = char_type(0);  // add the null
1083   this->mLength = to - this->mData;
1084 }
1085
1086 template <typename T>
1087 void nsTSubstring<T>::StripCRLF() {
1088   // Expanding this call to copy the code from StripTaggedASCII
1089   // instead of just calling it does somewhat help with performance
1090   // but it is not worth it given the duplicated code.
1091   StripTaggedASCII(mozilla::ASCIIMask::MaskCRLF());
1092 }
1093
1094 template <typename T>
1095 struct MOZ_STACK_CLASS PrintfAppend : public mozilla::PrintfTarget {
1096   explicit PrintfAppend(nsTSubstring<T>* aString) : mString(aString) {}
1097
1098   bool append(const char* aStr, size_t aLen) override {
1099     if (aLen == 0) {
1100       return true;
1101     }
1102
1103     mString->AppendASCII(aStr, aLen);
1104     return true;
1105   }
1106
1107  private:
1108   nsTSubstring<T>* mString;
1109 };
1110
1111 template <typename T>
1112 void nsTSubstring<T>::AppendPrintf(const char* aFormat, ...) {
1113   PrintfAppend<T> appender(this);
1114   va_list ap;
1115   va_start(ap, aFormat);
1116   bool r = appender.vprint(aFormat, ap);
1117   if (!r) {
1118     MOZ_CRASH("Allocation or other failure in PrintfTarget::print");
1119   }
1120   va_end(ap);
1121 }
1122
1123 template <typename T>
1124 void nsTSubstring<T>::AppendVprintf(const char* aFormat, va_list aAp) {
1125   PrintfAppend<T> appender(this);
1126   bool r = appender.vprint(aFormat, aAp);
1127   if (!r) {
1128     MOZ_CRASH("Allocation or other failure in PrintfTarget::print");
1129   }
1130 }
1131
1132 template <typename T>
1133 void nsTSubstring<T>::AppendIntDec(int32_t aInteger) {
1134   PrintfAppend<T> appender(this);
1135   bool r = appender.appendIntDec(aInteger);
1136   if (MOZ_UNLIKELY(!r)) {
1137     MOZ_CRASH("Allocation or other failure while appending integers");
1138   }
1139 }
1140
1141 template <typename T>
1142 void nsTSubstring<T>::AppendIntDec(uint32_t aInteger) {
1143   PrintfAppend<T> appender(this);
1144   bool r = appender.appendIntDec(aInteger);
1145   if (MOZ_UNLIKELY(!r)) {
1146     MOZ_CRASH("Allocation or other failure while appending integers");
1147   }
1148 }
1149
1150 template <typename T>
1151 void nsTSubstring<T>::AppendIntOct(uint32_t aInteger) {
1152   PrintfAppend<T> appender(this);
1153   bool r = appender.appendIntOct(aInteger);
1154   if (MOZ_UNLIKELY(!r)) {
1155     MOZ_CRASH("Allocation or other failure while appending integers");
1156   }
1157 }
1158
1159 template <typename T>
1160 void nsTSubstring<T>::AppendIntHex(uint32_t aInteger) {
1161   PrintfAppend<T> appender(this);
1162   bool r = appender.appendIntHex(aInteger);
1163   if (MOZ_UNLIKELY(!r)) {
1164     MOZ_CRASH("Allocation or other failure while appending integers");
1165   }
1166 }
1167
1168 template <typename T>
1169 void nsTSubstring<T>::AppendIntDec(int64_t aInteger) {
1170   PrintfAppend<T> appender(this);
1171   bool r = appender.appendIntDec(aInteger);
1172   if (MOZ_UNLIKELY(!r)) {
1173     MOZ_CRASH("Allocation or other failure while appending integers");
1174   }
1175 }
1176
1177 template <typename T>
1178 void nsTSubstring<T>::AppendIntDec(uint64_t aInteger) {
1179   PrintfAppend<T> appender(this);
1180   bool r = appender.appendIntDec(aInteger);
1181   if (MOZ_UNLIKELY(!r)) {
1182     MOZ_CRASH("Allocation or other failure while appending integers");
1183   }
1184 }
1185
1186 template <typename T>
1187 void nsTSubstring<T>::AppendIntOct(uint64_t aInteger) {
1188   PrintfAppend<T> appender(this);
1189   bool r = appender.appendIntOct(aInteger);
1190   if (MOZ_UNLIKELY(!r)) {
1191     MOZ_CRASH("Allocation or other failure while appending integers");
1192   }
1193 }
1194
1195 template <typename T>
1196 void nsTSubstring<T>::AppendIntHex(uint64_t aInteger) {
1197   PrintfAppend<T> appender(this);
1198   bool r = appender.appendIntHex(aInteger);
1199   if (MOZ_UNLIKELY(!r)) {
1200     MOZ_CRASH("Allocation or other failure while appending integers");
1201   }
1202 }
1203
1204 // Returns the length of the formatted aDouble in aBuf.
1205 static int FormatWithoutTrailingZeros(char (&aBuf)[40], double aDouble,
1206                                       int aPrecision) {
1207   static const DoubleToStringConverter converter(
1208       DoubleToStringConverter::UNIQUE_ZERO |
1209           DoubleToStringConverter::NO_TRAILING_ZERO |
1210           DoubleToStringConverter::EMIT_POSITIVE_EXPONENT_SIGN,
1211       "Infinity", "NaN", 'e', -6, 21, 6, 1);
1212   double_conversion::StringBuilder builder(aBuf, sizeof(aBuf));
1213   converter.ToPrecision(aDouble, aPrecision, &builder);
1214   int length = builder.position();
1215   builder.Finalize();
1216   return length;
1217 }
1218
1219 template <typename T>
1220 void nsTSubstring<T>::AppendFloat(float aFloat) {
1221   char buf[40];
1222   int length = FormatWithoutTrailingZeros(buf, aFloat, 6);
1223   AppendASCII(buf, length);
1224 }
1225
1226 template <typename T>
1227 void nsTSubstring<T>::AppendFloat(double aFloat) {
1228   char buf[40];
1229   int length = FormatWithoutTrailingZeros(buf, aFloat, 15);
1230   AppendASCII(buf, length);
1231 }
1232
1233 template <typename T>
1234 size_t nsTSubstring<T>::SizeOfExcludingThisIfUnshared(
1235     mozilla::MallocSizeOf aMallocSizeOf) const {
1236   if (this->mDataFlags & DataFlags::REFCOUNTED) {
1237     return nsStringBuffer::FromData(this->mData)
1238         ->SizeOfIncludingThisIfUnshared(aMallocSizeOf);
1239   }
1240   if (this->mDataFlags & DataFlags::OWNED) {
1241     return aMallocSizeOf(this->mData);
1242   }
1243
1244   // If we reach here, exactly one of the following must be true:
1245   // - DataFlags::VOIDED is set, and this->mData points to sEmptyBuffer;
1246   // - DataFlags::INLINE is set, and this->mData points to a buffer within a
1247   //   string object (e.g. nsAutoString);
1248   // - None of DataFlags::REFCOUNTED, DataFlags::OWNED, DataFlags::INLINE is
1249   //   set, and this->mData points to a buffer owned by something else.
1250   //
1251   // In all three cases, we don't measure it.
1252   return 0;
1253 }
1254
1255 template <typename T>
1256 size_t nsTSubstring<T>::SizeOfExcludingThisEvenIfShared(
1257     mozilla::MallocSizeOf aMallocSizeOf) const {
1258   // This is identical to SizeOfExcludingThisIfUnshared except for the
1259   // DataFlags::REFCOUNTED case.
1260   if (this->mDataFlags & DataFlags::REFCOUNTED) {
1261     return nsStringBuffer::FromData(this->mData)
1262         ->SizeOfIncludingThisEvenIfShared(aMallocSizeOf);
1263   }
1264   if (this->mDataFlags & DataFlags::OWNED) {
1265     return aMallocSizeOf(this->mData);
1266   }
1267   return 0;
1268 }
1269
1270 template <typename T>
1271 size_t nsTSubstring<T>::SizeOfIncludingThisIfUnshared(
1272     mozilla::MallocSizeOf aMallocSizeOf) const {
1273   return aMallocSizeOf(this) + SizeOfExcludingThisIfUnshared(aMallocSizeOf);
1274 }
1275
1276 template <typename T>
1277 size_t nsTSubstring<T>::SizeOfIncludingThisEvenIfShared(
1278     mozilla::MallocSizeOf aMallocSizeOf) const {
1279   return aMallocSizeOf(this) + SizeOfExcludingThisEvenIfShared(aMallocSizeOf);
1280 }
1281
1282 template <typename T>
1283 nsTSubstringSplitter<T> nsTSubstring<T>::Split(const char_type aChar) const {
1284   return nsTSubstringSplitter<T>(
1285       nsTCharSeparatedTokenizerTemplate<
1286           NS_TokenizerIgnoreNothing, T,
1287           nsTokenizerFlags::IncludeEmptyTokenAtEnd>(*this, aChar));
1288 }
1289
1290 // Common logic for nsTSubstring<T>::ToInteger and nsTSubstring<T>::ToInteger64.
1291 template <typename T, typename int_type>
1292 int_type ToIntegerCommon(const nsTSubstring<T>& aSrc, nsresult* aErrorCode,
1293                          uint32_t aRadix) {
1294   MOZ_ASSERT(aRadix == 10 || aRadix == 16);
1295
1296   // Initial value, override if we find an integer.
1297   *aErrorCode = NS_ERROR_ILLEGAL_VALUE;
1298
1299   // Begin by skipping over leading chars that shouldn't be part of the number.
1300   auto cp = aSrc.BeginReading();
1301   auto endcp = aSrc.EndReading();
1302   bool negate = false;
1303   bool done = false;
1304
1305   // NB: For backwards compatibility I'm not going to change this logic but
1306   //     it seems really odd. Previously there was logic to auto-detect the
1307   //     radix if kAutoDetect was passed in. In practice this value was never
1308   //     used, so it pretended to auto detect and skipped some preceding
1309   //     letters (excluding valid hex digits) but never used the result.
1310   //
1311   //     For example if you pass in "Get the number: 10", aRadix = 10 we'd
1312   //     skip the 'G', and then fail to parse "et the number: 10". If aRadix =
1313   //     16 we'd skip the 'G', and parse just 'e' returning 14.
1314   while ((cp < endcp) && (!done)) {
1315     switch (*cp++) {
1316         // clang-format off
1317       case 'a': case 'b': case 'c': case 'd': case 'e': case 'f':
1318       case 'A': case 'B': case 'C': case 'D': case 'E': case 'F':
1319       case '0': case '1': case '2': case '3': case '4':
1320       case '5': case '6': case '7': case '8': case '9':
1321         done = true;
1322         break;
1323       // clang-format on
1324       case '-':
1325         negate = true;
1326         break;
1327       default:
1328         break;
1329     }
1330   }
1331
1332   if (!done) {
1333     // No base 16 or base 10 digits were found.
1334     return 0;
1335   }
1336
1337   // Step back.
1338   cp--;
1339
1340   mozilla::CheckedInt<int_type> result;
1341
1342   // Now iterate the numeric chars and build our result.
1343   while (cp < endcp) {
1344     auto theChar = *cp++;
1345     if (('0' <= theChar) && (theChar <= '9')) {
1346       result = (aRadix * result) + (theChar - '0');
1347     } else if ((theChar >= 'A') && (theChar <= 'F')) {
1348       if (10 == aRadix) {
1349         // Invalid base 10 digit, error out.
1350         return 0;
1351       }
1352       result = (aRadix * result) + ((theChar - 'A') + 10);
1353     } else if ((theChar >= 'a') && (theChar <= 'f')) {
1354       if (10 == aRadix) {
1355         // Invalid base 10 digit, error out.
1356         return 0;
1357       }
1358       result = (aRadix * result) + ((theChar - 'a') + 10);
1359     } else if ((('X' == theChar) || ('x' == theChar)) && result == 0) {
1360       // For some reason we support a leading 'x' regardless of radix. For
1361       // example: "000000x500", aRadix = 10 would be parsed as 500 rather
1362       // than 0.
1363       continue;
1364     } else {
1365       // We've encountered a char that's not a legal number or sign and we can
1366       // terminate processing.
1367       break;
1368     }
1369
1370     if (!result.isValid()) {
1371       // Overflow!
1372       return 0;
1373     }
1374   }
1375
1376   // Integer found.
1377   *aErrorCode = NS_OK;
1378
1379   if (negate) {
1380     result = -result;
1381   }
1382
1383   return result.value();
1384 }
1385
1386 template <typename T>
1387 int32_t nsTSubstring<T>::ToInteger(nsresult* aErrorCode,
1388                                    uint32_t aRadix) const {
1389   return ToIntegerCommon<T, int32_t>(*this, aErrorCode, aRadix);
1390 }
1391
1392 /**
1393  * nsTSubstring::ToInteger64
1394  */
1395 template <typename T>
1396 int64_t nsTSubstring<T>::ToInteger64(nsresult* aErrorCode,
1397                                      uint32_t aRadix) const {
1398   return ToIntegerCommon<T, int64_t>(*this, aErrorCode, aRadix);
1399 }
1400
1401 /**
1402  * nsTSubstring::Mid
1403  */
1404 template <typename T>
1405 typename nsTSubstring<T>::size_type nsTSubstring<T>::Mid(
1406     self_type& aResult, index_type aStartPos, size_type aLengthToCopy) const {
1407   if (aStartPos == 0 && aLengthToCopy >= this->mLength) {
1408     aResult = *this;
1409   } else {
1410     aResult = Substring(*this, aStartPos, aLengthToCopy);
1411   }
1412
1413   return aResult.mLength;
1414 }
1415
1416 /**
1417  * nsTSubstring::StripWhitespace
1418  */
1419
1420 template <typename T>
1421 void nsTSubstring<T>::StripWhitespace() {
1422   if (!StripWhitespace(mozilla::fallible)) {
1423     this->AllocFailed(this->mLength);
1424   }
1425 }
1426
1427 template <typename T>
1428 bool nsTSubstring<T>::StripWhitespace(const fallible_t&) {
1429   if (!this->EnsureMutable()) {
1430     return false;
1431   }
1432
1433   this->StripTaggedASCII(mozilla::ASCIIMask::MaskWhitespace());
1434   return true;
1435 }
1436
1437 /**
1438  * nsTSubstring::ReplaceChar,ReplaceSubstring
1439  */
1440
1441 template <typename T>
1442 void nsTSubstring<T>::ReplaceChar(char_type aOldChar, char_type aNewChar) {
1443   int32_t i = this->FindChar(aOldChar);
1444   if (i == kNotFound) {
1445     return;
1446   }
1447
1448   if (!this->EnsureMutable()) {
1449     this->AllocFailed(this->mLength);
1450   }
1451   for (; i != kNotFound; i = this->FindChar(aOldChar, i + 1)) {
1452     this->mData[i] = aNewChar;
1453   }
1454 }
1455
1456 template <typename T>
1457 void nsTSubstring<T>::ReplaceChar(const string_view& aSet, char_type aNewChar) {
1458   int32_t i = this->FindCharInSet(aSet);
1459   if (i == kNotFound) {
1460     return;
1461   }
1462
1463   if (!this->EnsureMutable()) {
1464     this->AllocFailed(this->mLength);
1465   }
1466   for (; i != kNotFound; i = this->FindCharInSet(aSet, i + 1)) {
1467     this->mData[i] = aNewChar;
1468   }
1469 }
1470
1471 template <typename T>
1472 void nsTSubstring<T>::ReplaceSubstring(const char_type* aTarget,
1473                                        const char_type* aNewValue) {
1474   ReplaceSubstring(nsTDependentString<T>(aTarget),
1475                    nsTDependentString<T>(aNewValue));
1476 }
1477
1478 template <typename T>
1479 bool nsTSubstring<T>::ReplaceSubstring(const char_type* aTarget,
1480                                        const char_type* aNewValue,
1481                                        const fallible_t& aFallible) {
1482   return ReplaceSubstring(nsTDependentString<T>(aTarget),
1483                           nsTDependentString<T>(aNewValue), aFallible);
1484 }
1485
1486 template <typename T>
1487 void nsTSubstring<T>::ReplaceSubstring(const self_type& aTarget,
1488                                        const self_type& aNewValue) {
1489   if (!ReplaceSubstring(aTarget, aNewValue, mozilla::fallible)) {
1490     // Note that this may wildly underestimate the allocation that failed, as
1491     // we could have been replacing multiple copies of aTarget.
1492     this->AllocFailed(this->mLength + (aNewValue.Length() - aTarget.Length()));
1493   }
1494 }
1495
1496 template <typename T>
1497 bool nsTSubstring<T>::ReplaceSubstring(const self_type& aTarget,
1498                                        const self_type& aNewValue,
1499                                        const fallible_t&) {
1500   struct Segment {
1501     uint32_t mBegin, mLength;
1502     Segment(uint32_t aBegin, uint32_t aLength)
1503         : mBegin(aBegin), mLength(aLength) {}
1504   };
1505
1506   if (aTarget.Length() == 0) {
1507     return true;
1508   }
1509
1510   // Remember all of the non-matching parts.
1511   AutoTArray<Segment, 16> nonMatching;
1512   uint32_t i = 0;
1513   mozilla::CheckedUint32 newLength;
1514   while (true) {
1515     int32_t r = this->Find(aTarget, i);
1516     int32_t until = (r == kNotFound) ? this->Length() - i : r - i;
1517     nonMatching.AppendElement(Segment(i, until));
1518     newLength += until;
1519     if (r == kNotFound) {
1520       break;
1521     }
1522
1523     newLength += aNewValue.Length();
1524     i = r + aTarget.Length();
1525     if (i >= this->Length()) {
1526       // Add an auxiliary entry at the end of the list to help as an edge case
1527       // for the algorithms below.
1528       nonMatching.AppendElement(Segment(this->Length(), 0));
1529       break;
1530     }
1531   }
1532
1533   if (!newLength.isValid()) {
1534     return false;
1535   }
1536
1537   // If there's only one non-matching segment, then the target string was not
1538   // found, and there's nothing to do.
1539   if (nonMatching.Length() == 1) {
1540     MOZ_ASSERT(
1541         nonMatching[0].mBegin == 0 && nonMatching[0].mLength == this->Length(),
1542         "We should have the correct non-matching segment.");
1543     return true;
1544   }
1545
1546   // Make sure that we can mutate our buffer.
1547   // Note that we always allocate at least an this->mLength sized buffer,
1548   // because the rest of the algorithm relies on having access to all of the
1549   // original string.  In other words, we over-allocate in the shrinking case.
1550   uint32_t oldLen = this->Length();
1551   auto r =
1552       this->StartBulkWriteImpl(XPCOM_MAX(oldLen, newLength.value()), oldLen);
1553   if (r.isErr()) {
1554     return false;
1555   }
1556
1557   if (aTarget.Length() >= aNewValue.Length()) {
1558     // In the shrinking case, start filling the buffer from the beginning.
1559     const uint32_t delta = (aTarget.Length() - aNewValue.Length());
1560     for (i = 1; i < nonMatching.Length(); ++i) {
1561       // When we move the i'th non-matching segment into position, we need to
1562       // account for the characters deleted by the previous |i| replacements by
1563       // subtracting |i * delta|.
1564       const char_type* sourceSegmentPtr = this->mData + nonMatching[i].mBegin;
1565       char_type* destinationSegmentPtr =
1566           this->mData + nonMatching[i].mBegin - i * delta;
1567       // Write the i'th replacement immediately before the new i'th non-matching
1568       // segment.
1569       char_traits::copy(destinationSegmentPtr - aNewValue.Length(),
1570                         aNewValue.Data(), aNewValue.Length());
1571       char_traits::move(destinationSegmentPtr, sourceSegmentPtr,
1572                         nonMatching[i].mLength);
1573     }
1574   } else {
1575     // In the growing case, start filling the buffer from the end.
1576     const uint32_t delta = (aNewValue.Length() - aTarget.Length());
1577     for (i = nonMatching.Length() - 1; i > 0; --i) {
1578       // When we move the i'th non-matching segment into position, we need to
1579       // account for the characters added by the previous |i| replacements by
1580       // adding |i * delta|.
1581       const char_type* sourceSegmentPtr = this->mData + nonMatching[i].mBegin;
1582       char_type* destinationSegmentPtr =
1583           this->mData + nonMatching[i].mBegin + i * delta;
1584       char_traits::move(destinationSegmentPtr, sourceSegmentPtr,
1585                         nonMatching[i].mLength);
1586       // Write the i'th replacement immediately before the new i'th non-matching
1587       // segment.
1588       char_traits::copy(destinationSegmentPtr - aNewValue.Length(),
1589                         aNewValue.Data(), aNewValue.Length());
1590     }
1591   }
1592
1593   // Adjust the length and make sure the string is null terminated.
1594   this->FinishBulkWriteImpl(newLength.value());
1595
1596   return true;
1597 }
1598
1599 /**
1600  * nsTSubstring::Trim
1601  */
1602
1603 template <typename T>
1604 void nsTSubstring<T>::Trim(const std::string_view& aSet, bool aTrimLeading,
1605                            bool aTrimTrailing, bool aIgnoreQuotes) {
1606   char_type* start = this->mData;
1607   char_type* end = this->mData + this->mLength;
1608
1609   // skip over quotes if requested
1610   if (aIgnoreQuotes && this->mLength > 2 &&
1611       this->mData[0] == this->mData[this->mLength - 1] &&
1612       (this->mData[0] == '\'' || this->mData[0] == '"')) {
1613     ++start;
1614     --end;
1615   }
1616
1617   if (aTrimLeading) {
1618     uint32_t cutStart = start - this->mData;
1619     uint32_t cutLength = 0;
1620
1621     // walk forward from start to end
1622     for (; start != end; ++start, ++cutLength) {
1623       if ((*start & ~0x7F) ||  // non-ascii
1624           aSet.find(char(*start)) == std::string_view::npos) {
1625         break;
1626       }
1627     }
1628
1629     if (cutLength) {
1630       this->Cut(cutStart, cutLength);
1631
1632       // reset iterators
1633       start = this->mData + cutStart;
1634       end = this->mData + this->mLength - cutStart;
1635     }
1636   }
1637
1638   if (aTrimTrailing) {
1639     uint32_t cutEnd = end - this->mData;
1640     uint32_t cutLength = 0;
1641
1642     // walk backward from end to start
1643     --end;
1644     for (; end >= start; --end, ++cutLength) {
1645       if ((*end & ~0x7F) ||  // non-ascii
1646           aSet.find(char(*end)) == std::string_view::npos) {
1647         break;
1648       }
1649     }
1650
1651     if (cutLength) {
1652       this->Cut(cutEnd - cutLength, cutLength);
1653     }
1654   }
1655 }
1656
1657 /**
1658  * nsTSubstring::CompressWhitespace.
1659  */
1660
1661 template <typename T>
1662 void nsTSubstring<T>::CompressWhitespace(bool aTrimLeading,
1663                                          bool aTrimTrailing) {
1664   // Quick exit
1665   if (this->mLength == 0) {
1666     return;
1667   }
1668
1669   if (!this->EnsureMutable()) {
1670     this->AllocFailed(this->mLength);
1671   }
1672
1673   const ASCIIMaskArray& mask = mozilla::ASCIIMask::MaskWhitespace();
1674
1675   char_type* to = this->mData;
1676   char_type* from = this->mData;
1677   char_type* end = this->mData + this->mLength;
1678
1679   // Compresses runs of whitespace down to a normal space ' ' and convert
1680   // any whitespace to a normal space.  This assumes that whitespace is
1681   // all standard 7-bit ASCII.
1682   bool skipWS = aTrimLeading;
1683   while (from < end) {
1684     uint32_t theChar = *from++;
1685     if (mozilla::ASCIIMask::IsMasked(mask, theChar)) {
1686       if (!skipWS) {
1687         *to++ = ' ';
1688         skipWS = true;
1689       }
1690     } else {
1691       *to++ = theChar;
1692       skipWS = false;
1693     }
1694   }
1695
1696   // If we need to trim the trailing whitespace, back up one character.
1697   if (aTrimTrailing && skipWS && to > this->mData) {
1698     to--;
1699   }
1700
1701   *to = char_type(0);  // add the null
1702   this->mLength = to - this->mData;
1703 }
1704
1705 template class nsTSubstring<char>;
1706 template class nsTSubstring<char16_t>;