题
有人可以编写一些示例代码来解释这个概念吗?我知道使用缓冲流的目的,但我也想知道如何实施。
提前致谢!
解决方案
您可以查看平台的实现,C ++标准或 Angelika Langer和Klaus Kreft的“标准C ++ iostreams and Locales”.
为学习曲线做好准备。溪流很古老,而且很复杂。 (弗朗西斯·格拉斯伯洛(Francis Glassborow): “我很少疑问我/O库是任何语言中最困难的方面之一。”)
其他提示
Veeeery在示意性上,用于“输入”流:
class BufferedInputStream
{
public:
BufferedInputStream(SomeExternalDevice d)
: m_Device(d),
m_Current(m_Buffer),
m_End(m_Buffer)
{}
char get(){
if (!IsDataAvailableInBuffer()){
ReadAChunkFromDiskAndPutItInBuffer();
}
return PopByteFromBuffer();
}
private:
bool IsDataAvailableInBuffer()const{
return m_Current != m_End;
}
void ReadAChunkFromDiskAndPutItInBuffer(){
// Buffer must be empty
assert(!IsDataAvailableInBuffer());
// Read bytes from the device
bytes_read = Read(m_Device, m_Buffer, BufferSize);
// Reposition the "begin" and "end" pointers
m_Current = m_Buffer;
m_End = m_Buffer + bytes_read;
}
char PopByteFromBuffer(){
assert(IsDataAvailableInBuffer());
return *m_Current++;
}
// For example, an OS file handle
SomeExternalDevice m_Device;
// The buffer itself
char m_Buffer[BufferSize];
// Begin of buffer contents
char* m_Current;
// End of buffer contents
char* m_End;
};
这样,从磁盘读取数据的数据是缓冲区大小的块,并且大多数调用“ get()”的调用不必最终呼叫到OS,因为它们可以简单地从缓冲区返回字节。
看一下STL实现sstream和sstream.tcc (链接到SGI STL实现)。
基地 stringstream
班级是 basic_stringstream
, ,实现 basic_iostream
界面。
// [27.7.4] Template class basic_stringstream
/**
* @brief Controlling input and output for std::string.
*
* This class supports reading from and writing to objects of type
* std::basic_string, using the inherited functions from
* std::basic_iostream. To control the associated sequence, an instance
* of std::basic_stringbuf is used, which this page refers to as @c sb.
*/
有基类 basic_stringbuf
来自 basic_streambuf
. 。这可以容纳缓冲区。
// [27.7.1] template class basic_stringbuf
/**
* @brief The actual work of input and output (for std::string).
*
* This class associates either or both of its input and output sequences
* with a sequence of characters, which can be initialized from, or made
* available as, a @c std::basic_string. (Paraphrased from [27.7.1]/1.)
*
* For this class, open modes (of type @c ios_base::openmode) have
* @c in set if the input sequence can be read, and @c out set if the
* output sequence can be written.
*/
不隶属于 StackOverflow