namespace std {
class strstreambuf : public basic_streambuf<char> {
public:
strstreambuf() : strstreambuf(0) {}
explicit strstreambuf(streamsize alsize_arg);
strstreambuf(void* (*palloc_arg)(size_t), void (*pfree_arg)(void*));
strstreambuf(char* gnext_arg, streamsize n, char* pbeg_arg = nullptr);
strstreambuf(const char* gnext_arg, streamsize n);
strstreambuf(signed char* gnext_arg, streamsize n,
signed char* pbeg_arg = nullptr);
strstreambuf(const signed char* gnext_arg, streamsize n);
strstreambuf(unsigned char* gnext_arg, streamsize n,
unsigned char* pbeg_arg = nullptr);
strstreambuf(const unsigned char* gnext_arg, streamsize n);
virtual ~strstreambuf();
void freeze(bool freezefl = true);
char* str();
int pcount();
protected:
int_type overflow (int_type c = EOF) override;
int_type pbackfail(int_type c = EOF) override;
int_type underflow() override;
pos_type seekoff(off_type off, ios_base::seekdir way,
ios_base::openmode which = ios_base::in | ios_base::out) override;
pos_type seekpos(pos_type sp,
ios_base::openmode which = ios_base::in | ios_base::out) override;
streambuf* setbuf(char* s, streamsize n) override;
private:
using strstate = T1;
static const strstate allocated;
static const strstate constant;
static const strstate dynamic;
static const strstate frozen;
strstate strmode;
streamsize alsize;
void* (*palloc)(size_t);
void (*pfree)(void*);
};
}
The class
strstreambuf
associates the input sequence, and possibly the output sequence, with an object of some
character
array type, whose elements store arbitrary values
.The array object has several attributes
.[
Note 1:
For the sake of exposition, these are represented as elements of a bitmask type
(indicated here as
T1) called
strstate.The elements are:
- allocated, set when a dynamic array object has been
allocated, and hence will be freed by the destructor for the
strstreambuf object;
- constant, set when the array object 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 object not be altered, reallocated, or freed.
—
end note]
[
Note 2:
For the sake of exposition, the maintained data is presented here as:
- strstate strmode, the attributes of the array object
associated with the strstreambuf object;
- int alsize, the suggested minimum size for a
dynamic array object;
- void* (*palloc)(size_t), points to the function
to call to allocate a dynamic array object;
- void (*pfree)(void*), points to the function to
call to free a dynamic array object.
—
end note]
Each object of class
strstreambuf
has a
seekable area,
delimited by the pointers
seeklow and
seekhigh.If
gnext is a null pointer, the seekable area is undefined
.Otherwise,
seeklow equals
gbeg and
seekhigh is either
pend,
if
pend is not a null pointer, or
gend.