std::basic_istream::seekg
basic_istream& seekg( pos_type pos ); | ? | ? |
|---|---|---|
basic_istream& seekg( off_type off, std::ios_base::seekdir dir); | ? | ? |
设置当前关联的输入位置指示符。streambuf对象。如果失败，呼叫setstate(std::ios_base::failbit)...
Before doing anything else, seekg clears eofbit. | (since C++11) |
|---|
seekg表现为UnformattedInputFunction，除了gcount()不受影响。在构造和检查哨兵对象之后，
1%29将输入位置指示符设置为相对于文件%29值开头的绝对%28。pos.具体而言，执行rdbuf()->pubseekpos(pos,std::ios_base::in)...
2%29将输入位置指示器设置为位置。off相对于位置，由dir.具体而言，执行rdbuf()->pubseekoff(off, dir,std::ios_base::in)...
参数
pos | - | absolute position to set the input position indicator to. | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
off | - | relative position to set the input position indicator to. | ||||||||
dir | - | defines base position to apply the relative offset to. It can be one of the following constants: Constant Explanation beg the beginning of a stream end the ending of a stream cur the current position of stream position indicator | Constant | Explanation | beg | the beginning of a stream | end | the ending of a stream | cur | the current position of stream position indicator |
Constant | Explanation | |||||||||
beg | the beginning of a stream | |||||||||
end | the ending of a stream | |||||||||
cur | the current position of stream position indicator |
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
二次
#include <iostream>
#include <string>
#include <sstream>
int main()
{
std::string str = "Hello, world";
std::istringstream in(str);
std::string word1, word2;
in >> word1;
in.seekg(0); // rewind
in >> word2;
std::cout << "word1 = " << word1 << '\n'
<< "word2 = " << word2 << '\n';
}二次
产出：
二次
word1 = Hello,
word2 = Hello,二次
另见
tellg | returns the input position indicator (public member function) |
|---|---|
tellp | returns the output position indicator (public member function of std::basic_ostream) |
seekp | sets the output position indicator (public member function of std::basic_ostream) |
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