lib/Support/StringRef.cpp

   1 //===-- StringRef.cpp - Lightweight String References ---------------------===//
   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 #include "llvm/ADT/StringRef.h"
  11 #include "llvm/ADT/APInt.h"
  12 #include <bitset>
  13
  14 using namespace llvm;
  15
  16 // MSVC emits references to this into the translation units which reference it.
  17 #ifndef _MSC_VER
  18 const size_t StringRef::npos;
  19 #endif
  20
  21 static char ascii_tolower(char x) {
  22   if (x >= 'A' && x <= 'Z')
  23     return x - 'A' + 'a';
  24   return x;
  25 }
  26
  27 static bool ascii_isdigit(char x) {
  28   return x >= '0' && x <= '9';
  29 }
  30
  31 /// compare_lower - Compare strings, ignoring case.
  32 int StringRef::compare_lower(StringRef RHS) const {
  33   for (size_t I = 0, E = min(Length, RHS.Length); I != E; ++I) {
  34     unsigned char LHC = ascii_tolower(Data[I]);
  35     unsigned char RHC = ascii_tolower(RHS.Data[I]);
  36     if (LHC != RHC)
  37       return LHC < RHC ? -1 : 1;
  38   }
  39
  40   if (Length == RHS.Length)
  41     return 0;
  42   return Length < RHS.Length ? -1 : 1;
  43 }
  44
  45 /// compare_numeric - Compare strings, handle embedded numbers.
  46 int StringRef::compare_numeric(StringRef RHS) const {
  47   for (size_t I = 0, E = min(Length, RHS.Length); I != E; ++I) {
  48     if (Data[I] == RHS.Data[I])
  49       continue;
  50     if (ascii_isdigit(Data[I]) && ascii_isdigit(RHS.Data[I])) {
  51       // The longer sequence of numbers is larger. This doesn't really handle
  52       // prefixed zeros well.
  53       for (size_t J = I+1; J != E+1; ++J) {
  54         bool ld = J < Length && ascii_isdigit(Data[J]);
  55         bool rd = J < RHS.Length && ascii_isdigit(RHS.Data[J]);
  56         if (ld != rd)
  57           return rd ? -1 : 1;
  58         if (!rd)
  59           break;
  60       }
  61     }
  62     return (unsigned char)Data[I] < (unsigned char)RHS.Data[I] ? -1 : 1;
  63   }
  64   if (Length == RHS.Length)
  65     return 0;
  66   return Length < RHS.Length ? -1 : 1;
  67 }
  68
  69 // Compute the edit distance between the two given strings.
  70 unsigned StringRef::edit_distance(llvm::StringRef Other,
  71                                   bool AllowReplacements,
  72                                   unsigned MaxEditDistance) {
  73   // The algorithm implemented below is the "classic"
  74   // dynamic-programming algorithm for computing the Levenshtein
  75   // distance, which is described here:
  76   //
  77   //   http://en.wikipedia.org/wiki/Levenshtein_distance
  78   //
  79   // Although the algorithm is typically described using an m x n
  80   // array, only two rows are used at a time, so this implemenation
  81   // just keeps two separate vectors for those two rows.
  82   size_type m = size();
  83   size_type n = Other.size();
  84
  85   const unsigned SmallBufferSize = 64;
  86   unsigned SmallBuffer[SmallBufferSize];
  87   unsigned *Allocated = 0;
  88   unsigned *previous = SmallBuffer;
  89   if (2*(n + 1) > SmallBufferSize)
  90     Allocated = previous = new unsigned [2*(n+1)];
  91   unsigned *current = previous + (n + 1);
  92
  93   for (unsigned i = 0; i <= n; ++i)
  94     previous[i] = i;
  95
  96   for (size_type y = 1; y <= m; ++y) {
  97     current[0] = y;
  98     unsigned BestThisRow = current[0];
  99
 100     for (size_type x = 1; x <= n; ++x) {
 101       if (AllowReplacements) {
 102         current[x] = min(previous[x-1] + ((*this)[y-1] == Other[x-1]? 0u:1u),
 103                          min(current[x-1], previous[x])+1);
 104       }
 105       else {
 106         if ((*this)[y-1] == Other[x-1]) current[x] = previous[x-1];
 107         else current[x] = min(current[x-1], previous[x]) + 1;
 108       }
 109       BestThisRow = min(BestThisRow, current[x]);
 110     }
 111
 112     if (MaxEditDistance && BestThisRow > MaxEditDistance)
 113       return MaxEditDistance + 1;
 114
 115     unsigned *tmp = current;
 116     current = previous;
 117     previous = tmp;
 118   }
 119
 120   unsigned Result = previous[n];
 121   delete [] Allocated;
 122
 123   return Result;
 124 }
 125
 126 //===----------------------------------------------------------------------===//
 127 // String Searching
 128 //===----------------------------------------------------------------------===//
 129
 130
 131 /// find - Search for the first string \arg Str in the string.
 132 ///
 133 /// \return - The index of the first occurence of \arg Str, or npos if not
 134 /// found.
 135 size_t StringRef::find(StringRef Str, size_t From) const {
 136   size_t N = Str.size();
 137   if (N > Length)
 138     return npos;
 139   for (size_t e = Length - N + 1, i = min(From, e); i != e; ++i)
 140     if (substr(i, N).equals(Str))
 141       return i;
 142   return npos;
 143 }
 144
 145 /// rfind - Search for the last string \arg Str in the string.
 146 ///
 147 /// \return - The index of the last occurence of \arg Str, or npos if not
 148 /// found.
 149 size_t StringRef::rfind(StringRef Str) const {
 150   size_t N = Str.size();
 151   if (N > Length)
 152     return npos;
 153   for (size_t i = Length - N + 1, e = 0; i != e;) {
 154     --i;
 155     if (substr(i, N).equals(Str))
 156       return i;
 157   }
 158   return npos;
 159 }
 160
 161 /// find_first_of - Find the first character in the string that is in \arg
 162 /// Chars, or npos if not found.
 163 ///
 164 /// Note: O(size() + Chars.size())
 165 StringRef::size_type StringRef::find_first_of(StringRef Chars,
 166                                               size_t From) const {
 167   std::bitset<1 << CHAR_BIT> CharBits;
 168   for (size_type i = 0; i != Chars.size(); ++i)
 169     CharBits.set((unsigned char)Chars[i]);
 170
 171   for (size_type i = min(From, Length), e = Length; i != e; ++i)
 172     if (CharBits.test((unsigned char)Data[i]))
 173       return i;
 174   return npos;
 175 }
 176
 177 /// find_first_not_of - Find the first character in the string that is not
 178 /// \arg C or npos if not found.
 179 StringRef::size_type StringRef::find_first_not_of(char C, size_t From) const {
 180   for (size_type i = min(From, Length), e = Length; i != e; ++i)
 181     if (Data[i] != C)
 182       return i;
 183   return npos;
 184 }
 185
 186 /// find_first_not_of - Find the first character in the string that is not
 187 /// in the string \arg Chars, or npos if not found.
 188 ///
 189 /// Note: O(size() + Chars.size())
 190 StringRef::size_type StringRef::find_first_not_of(StringRef Chars,
 191                                                   size_t From) const {
 192   std::bitset<1 << CHAR_BIT> CharBits;
 193   for (size_type i = 0; i != Chars.size(); ++i)
 194     CharBits.set((unsigned char)Chars[i]);
 195
 196   for (size_type i = min(From, Length), e = Length; i != e; ++i)
 197     if (!CharBits.test((unsigned char)Data[i]))
 198       return i;
 199   return npos;
 200 }
 201
 202
 203 //===----------------------------------------------------------------------===//
 204 // Helpful Algorithms
 205 //===----------------------------------------------------------------------===//
 206
 207 /// count - Return the number of non-overlapped occurrences of \arg Str in
 208 /// the string.
 209 size_t StringRef::count(StringRef Str) const {
 210   size_t Count = 0;
 211   size_t N = Str.size();
 212   if (N > Length)
 213     return 0;
 214   for (size_t i = 0, e = Length - N + 1; i != e; ++i)
 215     if (substr(i, N).equals(Str))
 216       ++Count;
 217   return Count;
 218 }
 219
 220 static unsigned GetAutoSenseRadix(StringRef &Str) {
 221   if (Str.startswith("0x")) {
 222     Str = Str.substr(2);
 223     return 16;
 224   } else if (Str.startswith("0b")) {
 225     Str = Str.substr(2);
 226     return 2;
 227   } else if (Str.startswith("0")) {
 228     return 8;
 229   } else {
 230     return 10;
 231   }
 232 }
 233
 234
 235 /// GetAsUnsignedInteger - Workhorse method that converts a integer character
 236 /// sequence of radix up to 36 to an unsigned long long value.
 237 static bool GetAsUnsignedInteger(StringRef Str, unsigned Radix,
 238                                  unsigned long long &Result) {
 239   // Autosense radix if not specified.
 240   if (Radix == 0)
 241     Radix = GetAutoSenseRadix(Str);
 242
 243   // Empty strings (after the radix autosense) are invalid.
 244   if (Str.empty()) return true;
 245
 246   // Parse all the bytes of the string given this radix.  Watch for overflow.
 247   Result = 0;
 248   while (!Str.empty()) {
 249     unsigned CharVal;
 250     if (Str[0] >= '0' && Str[0] <= '9')
 251       CharVal = Str[0]-'0';
 252     else if (Str[0] >= 'a' && Str[0] <= 'z')
 253       CharVal = Str[0]-'a'+10;
 254     else if (Str[0] >= 'A' && Str[0] <= 'Z')
 255       CharVal = Str[0]-'A'+10;
 256     else
 257       return true;
 258
 259     // If the parsed value is larger than the integer radix, the string is
 260     // invalid.
 261     if (CharVal >= Radix)
 262       return true;
 263
 264     // Add in this character.
 265     unsigned long long PrevResult = Result;
 266     Result = Result*Radix+CharVal;
 267
 268     // Check for overflow.
 269     if (Result < PrevResult)
 270       return true;
 271
 272     Str = Str.substr(1);
 273   }
 274
 275   return false;
 276 }
 277
 278 bool StringRef::getAsInteger(unsigned Radix, unsigned long long &Result) const {
 279   return GetAsUnsignedInteger(*this, Radix, Result);
 280 }
 281
 282
 283 bool StringRef::getAsInteger(unsigned Radix, long long &Result) const {
 284   unsigned long long ULLVal;
 285
 286   // Handle positive strings first.
 287   if (empty() || front() != '-') {
 288     if (GetAsUnsignedInteger(*this, Radix, ULLVal) ||
 289         // Check for value so large it overflows a signed value.
 290         (long long)ULLVal < 0)
 291       return true;
 292     Result = ULLVal;
 293     return false;
 294   }
 295
 296   // Get the positive part of the value.
 297   if (GetAsUnsignedInteger(substr(1), Radix, ULLVal) ||
 298       // Reject values so large they'd overflow as negative signed, but allow
 299       // "-0".  This negates the unsigned so that the negative isn't undefined
 300       // on signed overflow.
 301       (long long)-ULLVal > 0)
 302     return true;
 303
 304   Result = -ULLVal;
 305   return false;
 306 }
 307
 308 bool StringRef::getAsInteger(unsigned Radix, int &Result) const {
 309   long long Val;
 310   if (getAsInteger(Radix, Val) ||
 311       (int)Val != Val)
 312     return true;
 313   Result = Val;
 314   return false;
 315 }
 316
 317 bool StringRef::getAsInteger(unsigned Radix, unsigned &Result) const {
 318   unsigned long long Val;
 319   if (getAsInteger(Radix, Val) ||
 320       (unsigned)Val != Val)
 321     return true;
 322   Result = Val;
 323   return false;
 324 }
 325
 326 bool StringRef::getAsInteger(unsigned Radix, APInt &Result) const {
 327   StringRef Str = *this;
 328
 329   // Autosense radix if not specified.
 330   if (Radix == 0)
 331     Radix = GetAutoSenseRadix(Str);
 332
 333   assert(Radix > 1 && Radix <= 36);
 334
 335   // Empty strings (after the radix autosense) are invalid.
 336   if (Str.empty()) return true;
 337
 338   // Skip leading zeroes.  This can be a significant improvement if
 339   // it means we don't need > 64 bits.
 340   while (!Str.empty() && Str.front() == '0')
 341     Str = Str.substr(1);
 342
 343   // If it was nothing but zeroes....
 344   if (Str.empty()) {
 345     Result = APInt(64, 0);
 346     return false;
 347   }
 348
 349   // (Over-)estimate the required number of bits.
 350   unsigned Log2Radix = 0;
 351   while ((1U << Log2Radix) < Radix) Log2Radix++;
 352   bool IsPowerOf2Radix = ((1U << Log2Radix) == Radix);
 353
 354   unsigned BitWidth = Log2Radix * Str.size();
 355   if (BitWidth < Result.getBitWidth())
 356     BitWidth = Result.getBitWidth(); // don't shrink the result
 357   else
 358     Result.zext(BitWidth);
 359
 360   APInt RadixAP, CharAP; // unused unless !IsPowerOf2Radix
 361   if (!IsPowerOf2Radix) {
 362     // These must have the same bit-width as Result.
 363     RadixAP = APInt(BitWidth, Radix);
 364     CharAP = APInt(BitWidth, 0);
 365   }
 366
 367   // Parse all the bytes of the string given this radix.
 368   Result = 0;
 369   while (!Str.empty()) {
 370     unsigned CharVal;
 371     if (Str[0] >= '0' && Str[0] <= '9')
 372       CharVal = Str[0]-'0';
 373     else if (Str[0] >= 'a' && Str[0] <= 'z')
 374       CharVal = Str[0]-'a'+10;
 375     else if (Str[0] >= 'A' && Str[0] <= 'Z')
 376       CharVal = Str[0]-'A'+10;
 377     else
 378       return true;
 379
 380     // If the parsed value is larger than the integer radix, the string is
 381     // invalid.
 382     if (CharVal >= Radix)
 383       return true;
 384
 385     // Add in this character.
 386     if (IsPowerOf2Radix) {
 387       Result <<= Log2Radix;
 388       Result |= CharVal;
 389     } else {
 390       Result *= RadixAP;
 391       CharAP = CharVal;
 392       Result += CharAP;
 393     }
 394
 395     Str = Str.substr(1);
 396   }
 397
 398   return false;
 399 }