streabuf.htm

这是关于VC++中的STL容器的资料,包括了STL容器各个类之间关系以及类的说明

<p>
It returns the current character in the input stream or traits::eof().  If the call
to this method is successful it moves the get pointer forward by one value.
</p>
<hr>
<pre>

<a name="seekoff">Method            seekoff()</a>

Access            Protected

Classification    Modifier

Syntax            virtual pos_type seekoff(off_type Off, ios_base::seekdir Way, protected ios_base::openmode which = ios_base::in | ios_base::out)

Parameters        Way is can be

                                      ios_base::beg
                                      ios_base::cur
                                      ios_base::end

                  Off is the number of positions to move relative to Way

                  Which is the open mode of the streambuf object.                    

Return            This method returns an invalid stream position for the streambuf object.
</pre>

<h3>Description</h3>
<p>
The seekoff() method moves to a new position in the stream relative to Way by a value of Off.
This virtual method is designed to be overridden in a derived class.  The seekoff() method
usually returns an invalid stream position for the streambuf object.
</p>
<hr>
<pre>

<a name="seekpos">Method            seekpos()</a>

Access            Protected

Classification    Modifier

Syntax            virtual pos_type seekpos(pos_type Pos, ios_base::openmode Which = ios_base::in | ios_base::out)

Parameters        Pos is the new position in the stream.  Which is the open mode of the
                  stream.

Return            This method returns an invalid stream position for the streambuf object.
</pre>

<h3>Description</h3>
<p>
The seekpos() method moves to a new position in the stream.
This virtual method is designed to be overridden in a derived class.  The seekpos() method
usually returns an invalid stream position for the streambuf object.
</p>
<hr>
<pre>

<a name="setbuf">Method            setbuf()</a>

Access            Public

Classification    Modifier

Syntax            virtual basic_streambuf&lt;char_type,traits&gt;* setbuf(char_type* S, streamsize N)

Parameters        S is a streambuf character. N is a value used to effect the update of
                  the associated buffer object.


Return            This method returns a pointer to this basic_streambuf object.
</pre>

<h3>Description</h3>
<p>
This virtual setbuf() is designed to be overridden in a derived class such as basic_filebuf,
or stringbuf. It serves only as a place holder in the basic_streambuf class.
</p>
<hr>
<pre>

<a name="setg">Method            setg()</a>

Access            Protected

Classification    Modifier

Syntax            void setg(char_type* Gb, char_type* Gnext, char_type* Gend)

Parameters        Gb will be used to update the beginning input area pointer. Gnext
                  will be used to update the next pointer for the input area. Gend
                  will be used to update the pointer that is pointing to the end
                  of the input area.

Return            None
</pre>

<h3>Description</h3>
<p>
The setg() method updates the pointers to the input buffer.  The beginning pointer
is set to Gb.  The next pointer is set to Gnext and the end pointer is set to Gend.
</p>
<hr>
<pre>

<a name="setp">Method            setp()</a>

Access            Protected

Classification    Modifier

Syntax            void setp(char_type* Pb, char_type* Pend); 

Parameters        Pb will be used to update the beginning output area pointer. Pend
                  will be used to update the pointer that is pointing to the end
                  of the output area.

Return            None
</pre>

<h3>Description</h3>
<p>
The setp() method updates the pointers to the output buffer.  The beginning pointer
is set to Pb. The end pointer is set to Pend.
</p>
<hr>
<pre>

<a name="sgetc">Method            sgetc()</a>

Access            Public

Classification    Accessor

Syntax            int_type sgetc();

Parameters        None

Return            This method returns a value not equal to traits::eof() if it
                  was successful otherwise it returns traits::eof().
</pre>               

<h3>Description</h3>
<p>
The sgetc() method returns the next character in the input stream(if there is one)
otherwise it returns traits::eof().
</p>
<hr>
<pre>

<a name="sgetn">Method            sgetn()</a>

Access            Public

Classification    Modifier

Syntax            streamsize sgetn(char_type* Str, streamsize Num)

Parameters        Str is the starting location for a sequence of characters that will
                  be assigned to the streambuf object.  Num is the number of characters
                  that will be assigned to the streambuf object.

Return            This method returns the number of characters inserted into the
                  buffer.

</pre>               

<h3>Description</h3>
<p>
The sgetn() method does its work by calling xsgetn().  The xsgetn() method  inserts Num characters
into the buffer area beginning at the location pointed to by Str.  It will continue to insert
characters until Num characters have been exhausted or until traits::eof() has been reached.
</p>
<hr>
<pre>

<a name="showmanyc">Method            showmanyc()</a>

Access            Protected

Classification    Accessor

Syntax            virtual int showmanyc(); 

Parameters        None

Return            This method will return -1 if there are no characters to extract or
                  an estimation of the least number of characters that can be extracted.
</pre>

<h3>Description</h3>
<p>
The showmanyc() method returns an estimate of the number of characters in the input area
that can be extracted.  However, this method is a virtual method as is designed to be
overridden in a derived class.  The default behavior for this class is for showmanyc() to
return 0.
</p>
<hr>
<pre>


<a name="snextc">Method            snextc()</a>

Access            Public

Classification    Modifier

Syntax            int_type snextc(); 

Parameters        None

Return            This method returns a value not equal to traits::eof() if it
                  was successful otherwise it returns traits::eof().
</pre>               
   
<h3>Description</h3>

<p>
It returns the current character in the input stream or traits::eof().  If the call
to this method is successful it moves the get pointer forward by one value.
</p>
<hr>
<pre>

<a name="sputbackc">Method            sputbackc()</a>

Access            Public

Classification    Modifier

Syntax            int_type sputbackc(char_type CharValue); 

Parameters        CharValue is the character to put back into the input
                  stream.

Return            This method returns pbackfail()
</pre>
   
<h3>Description</h3>
<p>
The sputbackc() method() attempts to place CharValue back into the input stream.
Upon success this method will return gptr() upon failure it returns pbackfail().
</p>
<hr>
<pre>

<a name="sputc">Method            sputc()</a>

Access            Public

Classification    Modifier

Syntax            int_type sputc(char_type CharValue); 

Parameters        CharValue is the character to put into the output
                  stream.

Return            This method returns xsputn()
</pre>
   
<h3>Description</h3>     
<p>
The sputc() method inserts CharValue into the output stream.
</p>
<hr>
<pre>

<a name="sputn">Method            sputn()</a>

Access            Public

Classification    Modifier

Syntax            streamsize sputn(const char_type* Str, streamsize Num) 

Parameters        Str is the beginning of the sequence of elements to be inserted into
                  the output stream.  Num is the number of elements to be inserted into
                  the output stream.

Return            This method returns xsputn()
</pre>
   
<h3>Description</h3>     
<p>
The sputn() method inserts up to Num elements into the output stream.
</p>
<hr>
<pre>


<a name="sungetc">Method            sungetc()</a>

Access            Public

Classification    Modifier

Syntax            int_type sungetc();

Parameters        None      

Return            This method returns either a pointer to the current element or
                  pbackfail()
</pre>
   
<h3>Description</h3>

<p>
The sungetc() method decrements the next pointer for the input buffer if possible.
</p>
<hr>
<pre>

<a name="sync">Method            sync()</a>

Access            Protected

Classification    Accessor

Syntax            virtual int sync()

Parameters        None      

Return            This method will return 0 if successful and -1 on failure.
</pre>

<h3>Description</h3>
<p>
The sync() method synchronizes the controlled sequences with the internal arrays or streams.
In many cases the behavior is to flush the buffer area to the connected output device.
</p>
<hr>
<pre>

<a name="uflow">Method            uflow()</a>

Access            Protected

Classification    Modifier

Syntax            virtual int_type uflow()

Parameters        None      

Return         
</pre>

<h3>Description</h3>
<p>
calls <a = href="streabuf.htm#underflow">underflow()</a>
</p>
<hr>
<pre>

<a name="underflow">Method            underflow()</a>

Access            Protected

Classification    Modifier

Syntax            virtual int_type underflow()

Parameters        None      

Return            This method returns the current element of the input stream on success
                  otherwise traits::eof()
</pre>

<h3>Description</h3>     
<p>
The underflow() method attempts to get more characters from the source or input stream.  This
method is virtual and is designed to be overridden in a derived class.  It will be have
differently based on the type of input stream it is connected to.  The default behavior
of this method is to return traits::eof().
</p>
<hr>
<pre>

<a name="xsgetn">Method            xsgetn()</a>

Access            Protected

Classification    Modifier

Syntax            virtual streamsize xsgetn(char_type* Str, streamsize Num)

Parameters        Str is the starting location for a sequence of characters that will
                  be assigned to the streambuf object.  Num is the number of characters
                  that will be assigned to the streambuf object.
      

Return            This method returns the number of characters inserted into the
                  buffer.

</pre>
<h3>Description</h3>
<p>
The xsgetn() method  inserts Num characters into the buffer area beginning at the location
pointed to by Str.  It will continue to insert characters until Num characters have
been exhausted or until traits::eof() has been reached.
</p>
<hr>
<pre>

<a name="xsputn">Method            xsputn()</a>

Access            Protected

Classification    Modifier

Syntax            virtual streamsize xsgetn(char_type* Str, streamsize Num)

Parameters        Str is the beginning of the sequence of elements to be inserted into
                  the output stream.  Num is the number of elements to be inserted into
                  the output stream.

              

Return            This method returns the number of characters inserted into the
                  output stream.
</pre>
<h3>Description</h3>
<p>
The Xsputn() method inserts up to Num elements into the output stream.
</p>
<hr>
<p>
<a name="diagram"><h2>The Class Relationship Diagram of streambuf</h2></a>
<img src="streambf.gif">
</p>
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