strstreambuf

class strstreambuf : public streambuf {
public:
    explicit strstreambuf(streamsize n = 0);
    strstreambuf(void (*palloc)(size_t),
        void (*pfree)(void *));
    strstreambuf(char *gp, streamsize n,
        char *pp = 0);
    strstreambuf(signed char *gp, streamsize n,
        signed char *pp = 0);
    strstreambuf(unsigned char *gp, streamsize n,
        unsigned char *pp = 0);
    strstreambuf(const char *gp, streamsize n);
    strstreambuf(const signed char *gp, streamsize n);
    strstreambuf(const unsigned char *gp, streamsize n);
    void freeze(bool frz = true) const;
    char *str();
    streamsize pcount();
protected:
    virtual streampos seekoff(streamoff off, ios_base::seekdir way,
        ios_base::openmode which = ios_base::in | ios_base::out);
    virtual streampos seekpos(streampos sp,
        ios_base::openmode which = ios_base::in | ios_base::out);
    virtual int underflow();
    virtual int pbackfail(int c = EOF);
    virtual int overflow(int c = EOF);
    };

The class describes a stream buffer that controls the transmission of elements to and from a sequence of elements stored in a char array object. Depending on how it is constructed, the object can be allocated, extended, and freed as necessary to accommodate changes in the sequence.

An object of class strstreambuf stores several bits of mode information as its strstreambuf mode. These bits indicate whether the controlled sequence:

• Has been allocated, and hence needs to be freed eventually.
• Is modifiable.
• Is extendable by reallocating storage.
• Has been frozen and hence needs to be unfrozen before the object is destroyed, or freed (if allocated) by an agency other than the object.

A controlled sequence that is frozen cannot be modified or extended, regardless of the state of these separate mode bits.

The object also stores pointers to two functions that control strstreambuf allocation. If these are null pointers, the object devises its own method of allocating and freeing storage for the controlled sequence.