icuSources/common/unicode/stringpiece.h

   1 // © 2016 and later: Unicode, Inc. and others.
   2 // License & terms of use: http://www.unicode.org/copyright.html
   3 // Copyright (C) 2009-2013, International Business Machines
   4 // Corporation and others. All Rights Reserved.
   5 //
   6 // Copyright 2001 and onwards Google Inc.
   7 // Author: Sanjay Ghemawat
   8
   9 // This code is a contribution of Google code, and the style used here is
  10 // a compromise between the original Google code and the ICU coding guidelines.
  11 // For example, data types are ICU-ified (size_t,int->int32_t),
  12 // and API comments doxygen-ified, but function names and behavior are
  13 // as in the original, if possible.
  14 // Assertion-style error handling, not available in ICU, was changed to
  15 // parameter "pinning" similar to UnicodeString.
  16 //
  17 // In addition, this is only a partial port of the original Google code,
  18 // limited to what was needed so far. The (nearly) complete original code
  19 // is in the ICU svn repository at icuhtml/trunk/design/strings/contrib
  20 // (see ICU ticket 6765, r25517).
  21
  22 #ifndef __STRINGPIECE_H__
  23 #define __STRINGPIECE_H__
  24
  25 /**
  26  * \file
  27  * \brief C++ API: StringPiece: Read-only byte string wrapper class.
  28  */
  29
  30 #include "unicode/utypes.h"
  31 #include "unicode/uobject.h"
  32 #include "unicode/std_string.h"
  33
  34 // Arghh!  I wish C++ literals were "string".
  35
  36 #if U_SHOW_CPLUSPLUS_API
  37 U_NAMESPACE_BEGIN
  38
  39 /**
  40  * A string-like object that points to a sized piece of memory.
  41  *
  42  * We provide non-explicit singleton constructors so users can pass
  43  * in a "const char*" or a "string" wherever a "StringPiece" is
  44  * expected.
  45  *
  46  * Functions or methods may use StringPiece parameters to accept either a
  47  * "const char*" or a "string" value that will be implicitly converted to a
  48  * StringPiece.
  49  *
  50  * Systematic usage of StringPiece is encouraged as it will reduce unnecessary
  51  * conversions from "const char*" to "string" and back again.
  52  *
  53  * @stable ICU 4.2
  54  */
  55 class U_COMMON_API StringPiece : public UMemory {
  56  private:
  57   const char*   ptr_;
  58   int32_t       length_;
  59
  60  public:
  61   /**
  62    * Default constructor, creates an empty StringPiece.
  63    * @stable ICU 4.2
  64    */
  65   StringPiece() : ptr_(NULL), length_(0) { }
  66   /**
  67    * Constructs from a NUL-terminated const char * pointer.
  68    * @param str a NUL-terminated const char * pointer
  69    * @stable ICU 4.2
  70    */
  71   StringPiece(const char* str);
  72   /**
  73    * Constructs from a std::string.
  74    * @stable ICU 4.2
  75    */
  76   StringPiece(const std::string& str)
  77     : ptr_(str.data()), length_(static_cast<int32_t>(str.size())) { }
  78   /**
  79    * Constructs from a const char * pointer and a specified length.
  80    * @param offset a const char * pointer (need not be terminated)
  81    * @param len the length of the string; must be non-negative
  82    * @stable ICU 4.2
  83    */
  84   StringPiece(const char* offset, int32_t len) : ptr_(offset), length_(len) { }
  85   /**
  86    * Substring of another StringPiece.
  87    * @param x the other StringPiece
  88    * @param pos start position in x; must be non-negative and <= x.length().
  89    * @stable ICU 4.2
  90    */
  91   StringPiece(const StringPiece& x, int32_t pos);
  92   /**
  93    * Substring of another StringPiece.
  94    * @param x the other StringPiece
  95    * @param pos start position in x; must be non-negative and <= x.length().
  96    * @param len length of the substring;
  97    *            must be non-negative and will be pinned to at most x.length() - pos.
  98    * @stable ICU 4.2
  99    */
 100   StringPiece(const StringPiece& x, int32_t pos, int32_t len);
 101
 102   /**
 103    * Returns the string pointer. May be NULL if it is empty.
 104    *
 105    * data() may return a pointer to a buffer with embedded NULs, and the
 106    * returned buffer may or may not be null terminated.  Therefore it is
 107    * typically a mistake to pass data() to a routine that expects a NUL
 108    * terminated string.
 109    * @return the string pointer
 110    * @stable ICU 4.2
 111    */
 112   const char* data() const { return ptr_; }
 113   /**
 114    * Returns the string length. Same as length().
 115    * @return the string length
 116    * @stable ICU 4.2
 117    */
 118   int32_t size() const { return length_; }
 119   /**
 120    * Returns the string length. Same as size().
 121    * @return the string length
 122    * @stable ICU 4.2
 123    */
 124   int32_t length() const { return length_; }
 125   /**
 126    * Returns whether the string is empty.
 127    * @return TRUE if the string is empty
 128    * @stable ICU 4.2
 129    */
 130   UBool empty() const { return length_ == 0; }
 131
 132   /**
 133    * Sets to an empty string.
 134    * @stable ICU 4.2
 135    */
 136   void clear() { ptr_ = NULL; length_ = 0; }
 137
 138   /**
 139    * Reset the stringpiece to refer to new data.
 140    * @param xdata pointer the new string data.  Need not be nul terminated.
 141    * @param len the length of the new data
 142    * @stable ICU 4.8
 143    */
 144   void set(const char* xdata, int32_t len) { ptr_ = xdata; length_ = len; }
 145
 146   /**
 147    * Reset the stringpiece to refer to new data.
 148    * @param str a pointer to a NUL-terminated string.
 149    * @stable ICU 4.8
 150    */
 151   void set(const char* str);
 152
 153   /**
 154    * Removes the first n string units.
 155    * @param n prefix length, must be non-negative and <=length()
 156    * @stable ICU 4.2
 157    */
 158   void remove_prefix(int32_t n) {
 159     if (n >= 0) {
 160       if (n > length_) {
 161         n = length_;
 162       }
 163       ptr_ += n;
 164       length_ -= n;
 165     }
 166   }
 167
 168   /**
 169    * Removes the last n string units.
 170    * @param n suffix length, must be non-negative and <=length()
 171    * @stable ICU 4.2
 172    */
 173   void remove_suffix(int32_t n) {
 174     if (n >= 0) {
 175       if (n <= length_) {
 176         length_ -= n;
 177       } else {
 178         length_ = 0;
 179       }
 180     }
 181   }
 182
 183   /**
 184    * Maximum integer, used as a default value for substring methods.
 185    * @stable ICU 4.2
 186    */
 187   static const int32_t npos; // = 0x7fffffff;
 188
 189   /**
 190    * Returns a substring of this StringPiece.
 191    * @param pos start position; must be non-negative and <= length().
 192    * @param len length of the substring;
 193    *            must be non-negative and will be pinned to at most length() - pos.
 194    * @return the substring StringPiece
 195    * @stable ICU 4.2
 196    */
 197   StringPiece substr(int32_t pos, int32_t len = npos) const {
 198     return StringPiece(*this, pos, len);
 199   }
 200 };
 201
 202 /**
 203  * Global operator == for StringPiece
 204  * @param x The first StringPiece to compare.
 205  * @param y The second StringPiece to compare.
 206  * @return TRUE if the string data is equal
 207  * @stable ICU 4.8
 208  */
 209 U_EXPORT UBool U_EXPORT2
 210 operator==(const StringPiece& x, const StringPiece& y);
 211
 212 /**
 213  * Global operator != for StringPiece
 214  * @param x The first StringPiece to compare.
 215  * @param y The second StringPiece to compare.
 216  * @return TRUE if the string data is not equal
 217  * @stable ICU 4.8
 218  */
 219 inline UBool operator!=(const StringPiece& x, const StringPiece& y) {
 220   return !(x == y);
 221 }
 222
 223 U_NAMESPACE_END
 224 #endif // U_SHOW_CPLUSPLUS_API
 225
 226 #endif  // __STRINGPIECE_H__