icuSources/common/unicode/stringpiece.h

   1 // Copyright (C) 2009-2012, International Business Machines
   2 // Corporation and others. All Rights Reserved.
   3 //
   4 // Copyright 2001 and onwards Google Inc.
   5 // Author: Sanjay Ghemawat
   6
   7 // This code is a contribution of Google code, and the style used here is
   8 // a compromise between the original Google code and the ICU coding guidelines.
   9 // For example, data types are ICU-ified (size_t,int->int32_t),
  10 // and API comments doxygen-ified, but function names and behavior are
  11 // as in the original, if possible.
  12 // Assertion-style error handling, not available in ICU, was changed to
  13 // parameter "pinning" similar to UnicodeString.
  14 //
  15 // In addition, this is only a partial port of the original Google code,
  16 // limited to what was needed so far. The (nearly) complete original code
  17 // is in the ICU svn repository at icuhtml/trunk/design/strings/contrib
  18 // (see ICU ticket 6765, r25517).
  19
  20 #ifndef __STRINGPIECE_H__
  21 #define __STRINGPIECE_H__
  22
  23 /**
  24  * \file
  25  * \brief C++ API: StringPiece: Read-only byte string wrapper class.
  26  */
  27
  28 #include "unicode/utypes.h"
  29 #include "unicode/uobject.h"
  30 #include "unicode/std_string.h"
  31
  32 // Arghh!  I wish C++ literals were "string".
  33
  34 U_NAMESPACE_BEGIN
  35
  36 /**
  37  * A string-like object that points to a sized piece of memory.
  38  *
  39  * We provide non-explicit singleton constructors so users can pass
  40  * in a "const char*" or a "string" wherever a "StringPiece" is
  41  * expected.
  42  *
  43  * Functions or methods may use const StringPiece& parameters to accept either
  44  * a "const char*" or a "string" value that will be implicitly converted to
  45  * a StringPiece.
  46  *
  47  * Systematic usage of StringPiece is encouraged as it will reduce unnecessary
  48  * conversions from "const char*" to "string" and back again.
  49  *
  50  * @stable ICU 4.2
  51  */
  52 class U_COMMON_API StringPiece : public UMemory {
  53  private:
  54   const char*   ptr_;
  55   int32_t       length_;
  56
  57  public:
  58   /**
  59    * Default constructor, creates an empty StringPiece.
  60    * @stable ICU 4.2
  61    */
  62   StringPiece() : ptr_(NULL), length_(0) { }
  63   /**
  64    * Constructs from a NUL-terminated const char * pointer.
  65    * @param str a NUL-terminated const char * pointer
  66    * @stable ICU 4.2
  67    */
  68   StringPiece(const char* str);
  69 #if U_HAVE_STD_STRING
  70   /**
  71    * Constructs from a std::string.
  72    * @stable ICU 4.2
  73    */
  74   StringPiece(const std::string& str)
  75     : ptr_(str.data()), length_(static_cast<int32_t>(str.size())) { }
  76 #endif
  77   /**
  78    * Constructs from a const char * pointer and a specified length.
  79    * @param offset a const char * pointer (need not be terminated)
  80    * @param len the length of the string; must be non-negative
  81    * @stable ICU 4.2
  82    */
  83   StringPiece(const char* offset, int32_t len) : ptr_(offset), length_(len) { }
  84   /**
  85    * Substring of another StringPiece.
  86    * @param x the other StringPiece
  87    * @param pos start position in x; must be non-negative and <= x.length().
  88    * @stable ICU 4.2
  89    */
  90   StringPiece(const StringPiece& x, int32_t pos);
  91   /**
  92    * Substring of another StringPiece.
  93    * @param x the other StringPiece
  94    * @param pos start position in x; must be non-negative and <= x.length().
  95    * @param len length of the substring;
  96    *            must be non-negative and will be pinned to at most x.length() - pos.
  97    * @stable ICU 4.2
  98    */
  99   StringPiece(const StringPiece& x, int32_t pos, int32_t len);
 100
 101   /**
 102    * Returns the string pointer. May be NULL if it is empty.
 103    *
 104    * data() may return a pointer to a buffer with embedded NULs, and the
 105    * returned buffer may or may not be null terminated.  Therefore it is
 106    * typically a mistake to pass data() to a routine that expects a NUL
 107    * terminated string.
 108    * @return the string pointer
 109    * @stable ICU 4.2
 110    */
 111   const char* data() const { return ptr_; }
 112   /**
 113    * Returns the string length. Same as length().
 114    * @return the string length
 115    * @stable ICU 4.2
 116    */
 117   int32_t size() const { return length_; }
 118   /**
 119    * Returns the string length. Same as size().
 120    * @return the string length
 121    * @stable ICU 4.2
 122    */
 123   int32_t length() const { return length_; }
 124   /**
 125    * Returns whether the string is empty.
 126    * @return TRUE if the string is empty
 127    * @stable ICU 4.2
 128    */
 129   UBool empty() const { return length_ == 0; }
 130
 131   /**
 132    * Sets to an empty string.
 133    * @stable ICU 4.2
 134    */
 135   void clear() { ptr_ = NULL; length_ = 0; }
 136
 137   /**
 138    * Reset the stringpiece to refer to new data.
 139    * @param xdata pointer the new string data.  Need not be nul terminated.
 140    * @param len the length of the new data
 141    * @stable ICU 4.8
 142    */
 143   void set(const char* xdata, int32_t len) { ptr_ = xdata; length_ = len; }
 144
 145   /**
 146    * Reset the stringpiece to refer to new data.
 147    * @param str a pointer to a NUL-terminated string.
 148    * @stable ICU 4.8
 149    */
 150   void set(const char* str);
 151
 152   /**
 153    * Removes the first n string units.
 154    * @param n prefix length, must be non-negative and <=length()
 155    * @stable ICU 4.2
 156    */
 157   void remove_prefix(int32_t n) {
 158     if (n >= 0) {
 159       if (n > length_) {
 160         n = length_;
 161       }
 162       ptr_ += n;
 163       length_ -= n;
 164     }
 165   }
 166
 167   /**
 168    * Removes the last n string units.
 169    * @param n suffix length, must be non-negative and <=length()
 170    * @stable ICU 4.2
 171    */
 172   void remove_suffix(int32_t n) {
 173     if (n >= 0) {
 174       if (n <= length_) {
 175         length_ -= n;
 176       } else {
 177         length_ = 0;
 178       }
 179     }
 180   }
 181
 182   /**
 183    * Maximum integer, used as a default value for substring methods.
 184    * @stable ICU 4.2
 185    */
 186   static const int32_t npos = 0x7fffffff;
 187
 188   /**
 189    * Returns a substring of this StringPiece.
 190    * @param pos start position; must be non-negative and <= length().
 191    * @param len length of the substring;
 192    *            must be non-negative and will be pinned to at most length() - pos.
 193    * @return the substring StringPiece
 194    * @stable ICU 4.2
 195    */
 196   StringPiece substr(int32_t pos, int32_t len = npos) const {
 197     return StringPiece(*this, pos, len);
 198   }
 199 };
 200
 201 /**
 202  * Global operator == for StringPiece
 203  * @param x The first StringPiece to compare.
 204  * @param y The second StringPiece to compare.
 205  * @return TRUE if the string data is equal
 206  * @stable ICU 4.8
 207  */
 208 U_EXPORT UBool U_EXPORT2
 209 operator==(const StringPiece& x, const StringPiece& y);
 210
 211 /**
 212  * Global operator != for StringPiece
 213  * @param x The first StringPiece to compare.
 214  * @param y The second StringPiece to compare.
 215  * @return TRUE if the string data is not equal
 216  * @stable ICU 4.8
 217  */
 218 inline UBool operator!=(const StringPiece& x, const StringPiece& y) {
 219   return !(x == y);
 220 }
 221
 222 U_NAMESPACE_END
 223
 224 #endif  // __STRINGPIECE_H__