Library: Strings
Does not inherit
|
assign() char_type compare() copy() eof() |
eq() eq_int_type() find() int_type length() |
lt() move() not_eof() off_type pos_type |
state_type to_char_type() to_int_type() |
A traits class with types and operations for the basic_string container and iostream classes
#include <string>
namespace std {
template<class charT>
struct char_traits;
}
namespace std {
template<> struct char_traits<char>;
template<> struct char_traits<wchar_t>;
}
The structure template char_traits defines the types and functions necessary to implement the iostreams and string class templates. It is templatized on charT, which represents the character container type. Each specialized version of char_traits includes the default definitions corresponding to the specialized character container type.
Users have to provide specialization for char_traits if they use character types other than char and wchar_t.
namespace std {
template<class charT>
struct char_traits {
typedef charT char_type;
typedef INT_T int_type;
typedef POS_T pos_type;
typedef OFF_T off_type;
typedef STATE_T state_type;
static char_type to_char_type(const int_type&);
static int_type to_int_type(const char_type&);
static bool eq(const char_type&,const char_type&);
static bool eq_int_type(const int_type&,
const int_type&);
static int_type eof();
static int_type not_eof(const int_type&);
static void assign(char_type&,
const char_type&);
static bool lt(const char_type&,
const char_type&);
static int compare(const char_type*,
const char_type*,size_t);
static size_t length(const char_type*);
static const char_type* find(const char_type*,int n,
const char_type&);
static char_type* move(char_type*,
const char_type*,size_t);
static char_type* copy(char_type*,const char_type*,
size_t);
static char_type* assign(char_type*,size_t,
char_type);
};
}
char_type
The type char_type represents the character container type. It must be convertible to int_type.
int_type
The type int_type is another character container type that can also hold an end-of-file value. It is used as the return type of some of the iostream class member functions. If char_type is either char or wchar_t, int_type is int or wint_t, respectively.
off_type
The type off_type represents offsets to positional information. It is used to represent:
A signed displacement, measured in characters, from a specified position within a sequence.
An absolute position within a sequence.
The value off_type(-1) can be used as an error indicator. Value of type off_type can be converted to type pos_type, but no validity of the resulting pos_type value is ensured.
If char_type is either char or wchar_t, off_type is streamoff.
pos_type
The type pos_type describes an object that can store all the information necessary to restore an arbitrary sequence to a previous stream position and conversion state. The conversion pos_type(off_type(-1)) constructs the invalid pos_type value to signal error.
If char_type is either char or wchar_t, pos_type is streampos or wstreampos, respectively.
state_type
The type state_type holds the conversion state, and is compatible with the function locale::codecvt().
If char_type is either char or wchar_t, state_type is mbstate_t.
Table 12 lists the default specialization types and their values on char and wchar_t.
| specialization type | on char | on wchar_t |
char_type |
char |
wchar_t |
int_type |
int |
wint_t |
off_type |
streamoff |
streamoff |
pos_type |
streampos |
wstreampos |
state_type |
mbstate_t |
mbstate_t |
void assign(char_type& c1, const char_type& c2);
Assigns one character value to another. The value of c2 is assigned to c1.
char_type* assign(char_type* s, size_t n, char_type a);
Assigns one character value to n elements of a character array. The value of a is assigned to n elements of s.
char_type* copy(char_type* s1, const char_type* s2, size_t n);
Copies n characters from the object pointed to by s1 into the object pointed to by s2. The ranges of (s1,s1+n) and (s2,s2+n) may not overlap.
int_type eof();
Returns an int_type value that represents the end-of-file. It is returned by several functions to indicate end-of-file state, or to indicate an invalid return value.
const char_type* find(const char_type* s, int n, const char_type& a);
Looks for the value of a in s. Only n elements of s are examined. Returns a pointer to the matched element if one is found. Otherwise returns 0.
size_t length(const char_type* s);
Returns the length of a null terminated character string pointed to by s.
char_type* move(char_type* s1, const char_type* s2, size_t n);
Moves n characters from the object pointed to by s1 into the object pointed to by s2. The ranges of (s1,s1+n) and (s2,s2+n) may overlap.
int_type not_eof(const int_type& c);
Returns c if c is not equal to the end-of-file value. Otherwise returns 0.
int compare(const char_type* s1,const char_type* s2,size_t n);
Compares n values from s1 with n values from s2. Returns 1 if s1 is greater than s2, -1 if s1 is less than s2, or 0 if they are equal.
bool eq(const char_type& c1, const char_type& c2);
Returns true if c1 and c2 represent the same character.
bool eq_int_type(const int_type& c1, const int_type& c2);
Returns true if c1 and c2 are equal.
bool lt(const char_type& c1,const char_type& c2);
Returns true if c1 is less than c2.
char_type to_char_type(const int_type& c);
Converts a valid character represented by a value of type int_type to the corresponding char_type value.
int_type to_int_type(const char_type& c);
Converts a valid character represented by a value of type char_type to the corresponding int_type value.
iosfwd, fpos
ISO/IEC 14882:1998 -- International Standard for Information Systems --Programming Language C++, Section 21.1