strstreambuf(3C++) - strstreambuf(3C++)
Standard C++ Library Copyright 1998, Rogue Wave Software, Inc.
NAMEstrstreambuf
- Associates either the input sequence or the output sequence with a
tiny character array whose elements store arbitrary values.
SYNOPSIS
#include <strstream>
class strstreambuf
: public basic_streambuf<char>
DESCRIPTION
The class strstreambuf is derived from basic_streambuf specialized on
type char to associate either the input sequence or the output sequence
with a tiny character array whose elements store arbitrary values.
Each object of type strstreambuf controls two character sequences:
· A character input sequence
· A character output sequence
Note: see basic_streambuf.
The two sequences are related to each other, but are manipulated sepa‐
rately. This means that you can read and write characters at different
positions in objects of type strstreambuf without any conflict (in
opposition to the basic_filebuf objects).
The underlying array has several attributes:
· allocated, set when a dynamic array has been allocated, and hence
should be freed by the destructor of the strstreambuf object.
· constant, set when the array has const elements, so the output
sequence cannot be written.
· dynamic, set when the array object is allocated (or reallocated)
as necessary to hold a character sequence that can change in
length.
· frozen, set when the program has requested that the array not be
altered, reallocated, or freed.
This is a deprecated feature and might not be available in future ver‐
sions.
INTERFACE
class strstreambuf
: public basic_streambuf<char> {
public:
typedef char_traits<char> traits;
typedef basic_ios<char, traits> ios_type;
typedef char char_type;
typedef typename traits::int_type int_type;
typedef typename traits::pos_type pos_type;
typedef typename traits::off_type off_type;
explicit strstreambuf(streamsize alsize = 0);
strstreambuf(void *(*palloc)(size_t),
void (*pfree)(void *));
strstreambuf(char *gnext, streamsize n, char *pbeg = 0);
strstreambuf(unsigned char *gnext, streamsize n,
unsigned char *pbeg = 0);
strstreambuf(signed char *gnext, streamsize n,
signed char *pbeg = 0);
strstreambuf(const char *gnext, streamsize n);
strstreambuf(const unsigned char *gnext, streamsize n);
strstreambuf(const signed char *gnext, streamsize n);
virtual ~strstreambuf();
void freeze(bool f = 1);
char *str();
int pcount() const;
protected:
virtual int_type overflow(int_type c = traits::eof());
virtual int_type pbackfail(int_type c = traits::eof());
virtual int_type underflow();
virtual pos_type seekoff(off_type, ios_type::seekdir way,
ios_type::openmode which =
ios_type::in | ios_type::out);
virtual pos_type seekpos(pos_type sp,
ios_type::openmode which =
ios_type::in | ios_type::out);
virtual streambuf* setbuf(char *s, streamsize n);
virtual streamsize xsputn(const char_type* s,
streamsize n);
};
TYPES
char_type
The type char_type is a synonym of type char.
int_type
The type int_type is a synonym of type traits::in_type.
ios_type
The type ios_type is an instantiation of class basic_ios on type char.
off_type
The type off_type is a synonym of type traits::off_type.
pos_type
The type pos_type is a synonym of type traits::pos_type.
traits
The type traits is a synonym of type char_traits<char>.
CONSTRUCTORS
explicit strstreambuf(streamsize alsize = 0);
Constructs an object of class strstreambuf, initializing the base class
with streambuf(). After initialization the strstreambuf object is in
dynamic mode and its array object has a size of alsize.
strstreambuf(void* (*palloc)(size_t),
void (*pfree)(void*));
Constructs an object of class strstreambuf, initializing the base class
with streambuf(). After initialization the strstreambuf object is in
dynamic mode. The function used to allocate memory is pointed to by void*
(*palloc)(size_t) and the one used to free memory is pointed to by void
(*pfree)(void*).
strstreambuf(char* gnext, streamsize n,
char* pbeg = 0);
strstreambuf(signed char* gnext, streamsize n,
signed char* pbeg = 0);
strstreambuf(unsigned char* gnext, streamsize n,
unsigned char* pbeg = 0);
Constructs an object of class strstreambuf, initializing the base class
with streambuf(). The argument gnext points to the first element of an
array object whose number of elements is:
n, if n > 0
::strlen(gnext), if n == 0
INT_MAX, if n < 0
If pbeg is a null pointer, sets only the input sequence to gnext. Otherwise,
also sets the output sequence to pbeg.
strstreambuf(const char* gnext, streamsize n);
strstreambuf(const signed char* gnext, streamsize n);
strstreambuf(const unsigned char* gnext, streamsize n);
Constructs an object of class strstreambuf, initializing the base class
with streambuf(). The argument gnext points to the first element of an
array object whose number of elements is:
n, if n > 0
::strlen(gnext), if n == 0
INT_MAX, if n < 0
Sets the input sequence to gnext and the mode to constant.
DESTRUCTORSvirtual ~strstreambuf();
Destroys an object of class strstreambuf. The function frees the dynami‐
cally allocated array object only if allocated is set and frozen is not
set.
MEMBER FUNCTIONS
void
freeze(bool freezefl = 1);
If the mode is dynamic, alters the freeze status of the dynamic array as
follows:
- If freezefl is false, the function sets the freeze status to
frozen.
- Otherwise, it clears the freeze status..RE
int_typeoverflow( int_type c = traits::eof() );
If the output sequence has a put position available, and c is not
traits::eof(), then writes c into it. If there is no position available,
the function increases the size of the array object by allocating more mem‐
ory, and then writes c at the new current put position. If dynamic is not
set or if frozen is set, the operation fails. The function returns
traits::not_eof(c), except if it fails, in which case it returns
traits::eof().
int_typepbackfail( int_type c = traits::eof() );
Puts back the character designated by c into the input sequence. If
traits::eq_int_type(c,traits::eof()) returns true, move the input sequence
one position backward. If the operation fails, the function returns
traits::eof(). Otherwise it returns traits::not_eof(c).
intpcount() const;
Returns the size of the output sequence.
pos_typeseekoff(off_type off, ios_base::seekdir way,
ios_base::openmode which =
ios_base::in | ios_base::out);
If the open mode is in | out, alters the stream position of both the input
and the output sequence. If the open mode is in, alters the stream position
of only the input sequence. If the open mode is out, alters the stream
position of only the output sequence. The new position is calculated by
combining the two parameters off (displacement) and way (reference point).
If the current position of the sequence is invalid before repositioning,
the operation fails and the return value is pos_type(off_type(-1)). Other‐
wise the function returns the current new position.
pos_typeseekpos(pos_type sp, ios_base::openmode which =
ios_base::in | ios_base::out);
If the open mode is in | out, alters the stream position of both the input
and the output sequence. If the open mode is in, alters the stream position
of only the input sequence. If the open mode is out, alters the stream
position of only the output sequence. If the current position of the
sequence is invalid before repositioning, the operation fails and the
return value is pos_type(off_type(-1)). Otherwise the function returns the
current new position.
strstreambuf*setbuf(char* s, streamsize n);
If dynamic is set and freeze is not, proceed as follows:
If s is not a null pointer and n is greater than the number of characters
already in the current array, replaces it (copy its contents) by the array
of size n pointed to by s.
char*str();
Calls freeze(), then returns the beginning pointer for the input sequence.
int_typeunderflow();
If the input sequence has a read position available, returns the content of
this position. Otherwise tries to expand the input sequence to match the
output sequence and if possible returns the content of the new current
position. The function returns traits::eof() to indicate failure.
In the case where s is a null pointer and n is greater than the number of
characters already in the current array, resizes it to size n.
If the function fails, it returns a null pointer.
streamsizexsputn(const char_type* s, streamsize n);
Writes up to n characters to the output sequence. The characters written
are obtained from successive elements of the array whose first element is
designated by s. The function returns the number of characters written.
EXAMPLE
//
// stdlib/examples/manual/strstreambuf.cpp
//
#include<iostream>
#include<strstream>
#include<iomanip>
void main ( )
{
using namespace std;
// create a read/write strstream object
// and attach it to an ostrstream object
ostrstream out;
// tie the istream object to the ostrstream object
istream in(out.rdbuf());
// output to out
out << "anticonstitutionellement is a big word !!!";
// create a NTBS
const char *p ="Le rat des villes et le rat des champs";
// output the NTBS
out << p << endl;
// resize the buffer
if ( out.rdbuf()->pubsetbuf(0,5000) )
cout << endl << "Success in allocating the buffer"
<< endl;
// output the all buffer to stdout
cout << in.rdbuf( );
// output the decimal conversion of 100 in hex
// with right padding and a width field of 200
out << dec << setfill('!') << setw(200) << 0x100 << endl;
// output the content of the input sequence to stdout
cout << in.rdbuf( ) << endl;
// number of elements in the output sequence
cout << out.rdbuf()->pcount() << endl;
// resize the buffer to a minimum size
if ( out.rdbuf()->pubsetbuf(0,out.rdbuf()->pcount()) )
cout << endl << "Success in resizing the buffer" << endl;
// output the content of the all array object
cout << out.rdbuf()->str() << endl;
}
SEE ALSO
char_traits(3C++), ios_base(3C++), basic_ios(3C++), basic_stream‐
buf(3C++), istrstream(3c++), ostrstream(3C++), strstream(3c++)
Working Paper for Draft Proposed International Standard for Information
Systems--Programming Language C++, Annex D Compatibility features Sec‐
tion D.5
STANDARDS CONFORMANCE
ANSI X3J16/ISO WG21 Joint C++ Committee
Rogue Wave Software 02 Apr 1998 strstreambuf(3C++)
