std::basic_istream::putback
basic_istream& putback( char_type ch ); | ? | ? |
|---|
把字符ch返回到输入流，因此下一个提取的字符将是ch...
先清eofbit，则表现为UnformattedInputFunction在构造和检查哨兵对象之后，如果rdbuf()不为空，调用rdbuf()->sputbackc(ch)，这就叫rdbuf()->pbackfail(ch)如果ch不等于最近提取的字符。
如果rdbuf()为空或如果rdbuf->sputbackc(ch)回报Traits::eof()，电话setstate(badbit)...
在任何情况下，设置gcount()对零。
参数
ch | - | character to put into input stream |
|---|
返回值
*this...
例外
failure如果发生错误%28，则错误状态标志不是goodbit29%和exceptions()将被抛向那个州。
如果内部操作抛出异常，则会捕获该操作，并且badbit已经设定好了。如果exceptions()设置为badbit，异常将被重新抛出。
例
演示修改和不修改的腐返回%28%29之间的区别.
二次
#include <sstream>
#include <iostream>
int main()
{
std::stringstream s1("Hello, world"); // IO stream
s1.get();
if (s1.putback('Y')) // modifies the buffer
std::cout << s1.rdbuf() << '\n';
else
std::cout << "putback failed\n";
std::istringstream s2("Hello, world"); // input-only stream
s2.get();
if (s2.putback('Y')) // cannot modify input-only buffer
std::cout << s2.rdbuf() << '\n';
else
std::cout << "putback failed\n";
s2.clear();
if (s2.putback('H')) // non-modifying putback
std::cout << s2.rdbuf() << '\n';
else
std::cout << "putback failed\n";
}二次
产出：
二次
Yello, world
putback failed
Hello, world二次
另见
sputbackc | puts one character back in the input sequence (public member function of std::basic_streambuf) |
|---|---|
unget | unextracts a character (public member function) |
peek | reads the next character without extracting it (public member function) |
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