SSBUF(3C++) SSBUF(3C++)
NAMEstrstreambuf - 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
sbuf.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.
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SSBUF(3C++) SSBUF(3C++)
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.
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.
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SSBUF(3C++) SSBUF(3C++)
SEE ALSO
sbuf.pub(3C++), strstream(3C++)
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