std::strstreambuf::strstreambuf
From cppreference.com
< cpplrm; | iolrm; | strstreambuf
| (1) | ||
| explicit strstreambuf( std::streamsize alsize = 0 ); |
(until C++11) | |
| strstreambuf() : strstreambuf(0) {} explicit strstreambuf( std::streamsize alsize ); |
(since C++11) | |
| strstreambuf( void* (*palloc)(std::size_t), void (*pfree)(void*) ); |
(2) | |
| strstreambuf( char* gnext, std::streamsize n, char* pbeg = 0 ); |
(3) | |
| strstreambuf( signed char* gnext, std::streamsize n, signed char* pbeg = 0 ); |
(4) | |
| strstreambuf( unsigned char* gnext, std::streamsize n, unsigned char* pbeg = 0 ); |
(5) | |
| strstreambuf( const char* gnext, std::streamsize n ); |
(6) | |
| strstreambuf( const signed char* gnext, std::streamsize n); |
(7) | |
| strstreambuf( const unsigned char* gnext, std::streamsize n ); |
(8) | |
1) Constructs a
std::strstreambuf object: initializes the base class by calling the default constructor of std::streambuf, initializes the buffer state to "dynamic" (the buffer will be allocated as needed), initializes allocated size to the provided alsize, initializes the allocation and the deallocation functions to null (will use new[] and delete[])2) Constructs a
std::strstreambuf object: initializes the base class by calling the default constructor of std::streambuf, initializes the buffer state to "dynamic" (the buffer will be allocated as needed), initializes allocated size to unspecified value, initializes the allocation function to palloc and the deallocation function to pfree3-5) Constructs a
std::strstreambuf object in following steps:a) Initializes the base class by calling the default constructor of std::streambuf
b) Initializes the buffer state to "constant" (the buffer is a user-provided fixed-size buffer)
c) Determines the number of elements in the user-provided array as follows: if
n is greater than zero, n is used. If n is zero, std::strlen(gnext) is executed to determine the buffer size. If n is negative, INT_MAX is used.d) Configures the std::basic_streambuf pointers as follows: If
pbeg is a null pointer, calls setg(gnext, gnext, gnext + N). If pbeg is not a null pointer, executes setg(gnext, gnext, pbeg) and setp(pbeg, pbeg+N), where N is the number of elements in the array as determined earlier.6-8) Same as strstreambuf((char*)gnext, n), except the "constant" bit is set in the buffer state bitmask (output to this buffer is not allowed)
Parameters
| alsize | - | the initial size of the dynamically allocated buffer |
| palloc | - | pointer to user-provided allocation function |
| pfree | - | pointer to user-provided deallocation function |
| gnext | - | pointer to the start of the get area in the user-provided array |
| pbeg | - | pointer to the start of the put area in the user-provided array |
| n | - | the number of bytes in the get area (if pbeg is null) or in the put area (if pbeg is not null) of the user-provided array |
Notes
These constructors are typically called by the constructors of std::strstream
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| P0935R0 | C++11 | default constructor was explicit | made implicit |
Example
Run this code
#include <strstream> #include <iostream> int main() { std::strstreambuf dyn; // dynamic std::strstream dyn_s; // equivalent stream dyn_s << 1.23 << std::ends; std::cout << dyn_s.str() << '\n'; dyn_s.freeze(false); char buf[10]; std::strstreambuf user(buf, 10, buf); // user-provided output buffer std::ostrstream user_s(buf, 10); // equivalent stream user_s << 1.23 << std::ends; std::cout << buf << '\n'; std::strstreambuf lit("1 2 3", 5); // constant std::istrstream lit_s("1 2 3"); // equivalent stream int i, j, k; lit_s >> i >> j >> k; std::cout << i << ' ' << j << ' ' << k << '\n'; }
Output:
1.23 1.23 1 2 3
See also
| constructs an strstream, optionally allocating the buffer (public member function of std::strstream) |