strstreambuf(3C++)

strstreambuf -- streambuf specialized to arrays

Synopsis

   #include <iostream.h>
   #include <strstream.h>
   
   class strstreambuf : public streambuf {
   public:
   		strstreambuf() ;
   		strstreambuf(char*, int, char*);
   		strstreambuf(int);
   		strstreambuf(unsigned char*, int, unsigned char*);
   		strstreambuf(void* (*a)(long), void(*f)(void*));
   

   	void	freeze(int n=1) ;
   	char*	str();
   	virtual streambuf*       setbuf(char*, int)
   };

Description

A strstreambuf is a streambuf that uses an array of bytes (a string) to hold the sequence of characters. Given the convention that a char* should be interpreted as pointing just before the char it really points at, the mapping between the abstract get/put pointers (see streambuf_pub(3C++)) and char* pointers is direct. Moving the pointers corresponds exactly to incrementing and decrementing the char* values.

To accommodate the need for arbitrary length strings strstreambuf supports a dynamic mode. When a strstreambuf is in dynamic mode, space for the character sequence is allocated as needed. When the sequence is extended too far, it will be copied to a new array.

In the following descriptions assume:
-- ssb is a strstreambuf*.
-- n is an int.
-- ptr and pstart are char*s or unsigned char*s.
-- a is a void* (*)(long).
-- f is a void* (*)(void*).

Constructors:

strstreambuf(): Constructs an empty strstreambuf in dynamic mode. This means that space will be automatically allocated to accommodate the characters that are put into the strstreambuf (using operators new and delete). Because this may require copying the original characters, it is recommended that when many characters will be inserted, the program should use setbuf() (described below) to inform the strstreambuf.
strstreambuf(a, f): Constructs an empty strstreambuf in dynamic mode. a is used as the allocator function in dynamic mode. The argument passed to a will be a long denoting the number of bytes to be allocated. If a is null, operator new will be used. f is used to free (or delete) areas returned by a. The argument to f will be a pointer to the array allocated by a. If f is null, operator delete is used.
strstreambuf(n): Constructs an empty strstreambuf in dynamic mode. The initial allocation of space will be at least n bytes.
strstreambuf(ptr, n, pstart): Constructs a strstreambuf to use the bytes starting at ptr. The strstreambuf will be in static mode; it will not grow dynamically. If n is positive, then the n bytes starting at ptr are used as the strstreambuf. If n is zero, ptr is assumed to point to the beginning of a null terminated string and the bytes of that string (not including the terminating null character) will constitute the strstreambuf. If n is negative, the strstreambuf is assumed to continue indefinitely. The get pointer is initialized to ptr. The put pointer is initialized to pstart. If pstart is null, then stores will be treated as errors. If pstart is non-null, then the initial sequence for fetching (the get area) consists of the bytes between ptr and pstart. If pstart is null, then the initial get area consists of the entire array. If pstart is outside the range of a valid stream buffer, the result of a subsequent put or get operation is undefined.

Member functions:

ssb->freeze(n): Inhibits (when n is nonzero) or permits (when n is zero) automatic deletion of the current array. Deletion normally occurs when more space is needed or when ssb is being destroyed. Only space obtained via dynamic allocation is ever freed. It is an error (and the effect is undefined) to store characters into a strstreambuf that was in dynamic allocation mode and is now frozen. It is possible, however, to thaw (unfreeze) such a strstreambuf and resume storing characters.
ptr=ssb->str(): Returns a pointer to the first char of the current array and freezes ssb. If ssb was constructed with an explicit array, ptr will point to that array. If ssb is in dynamic allocation mode, but nothing has yet been stored, ptr may be null.
ssb->setbuf(0,n): ssb remembers n and the next time it does a dynamic mode allocation, it makes sure that at least n bytes are allocated.

References

streambuf_pub(3C++), strstream(3C++)