1，类型转换
#include<iostream>
#include<sstream>
#include<string>
using namespace std;
int main()
{
stringstream stream;
//类型转换
int i=1000;
string result;
stream<<1000;
stream>>result;
//给数组赋值
stream.clear();
char result1[8];
stream<<8888;
stream>>result1;
return 0;
}
2 内存文件读取
fstream中处理文件非常方便，但当仅适用于将硬盘与内存的交互，当内存中有一个文件（场景：从数据库中读取到一个二进制文件存取到一个buffer），它就无法直接处理，那么有没有一个类可以像fstream直接处理内存的中的buffer，有，没错就是stringstream
unsigned char str[]=
{
0x00,0x00,0x00,0x03,0xBE,0x19,0x33,0x15,0x41,0x43,
0x43,0x45,0x50,0x54,0x32,0x30,0x31,0x32,0x2D,0x30,
0x35,0x2D,0x33,0x30,0x20,0x31,0x35,0x3A,0x30,0x35,
0x3A,0x30,0x32,0xCD,0xCB,0xB3,0xF6,0x00,0x00,0x03,
0x9A,0x19,0x33,0x15,0x41,0x43,0x43,0x45,0x50,0x54,
0x32,0x30,0x31,0x32,0x2D,0x30,0x35,0x2D,0x33,0x30,
0x20,0x31,0x35,0x3A,0x30,0x38,0x3A,0x32,0x34,0xCD,
0xCB,0xB3,0xF6,0x00,0x00,0x03,0x76,0x19,0x33,0x15,
0x41,0x43,0x43,0x45,0x50,0x54,0x32,0x30,0x31,0x32,
0x2D,0x30,0x35,0x2D,0x33,0x30,0x20,0x31,0x35,0x3A,
0x30,0x39,0x3A,0x35,0x30,0xCD,0xCB,0xB3,0xF6,0x00,
0x00,0x03,0x52,0x19,0x33,0x15,0x41,0x43,0x43,0x45,
0x50,0x54,0x32,0x30,0x31,0x32,0x2D,0x30,0x35,0x2D,
0x33,0x30,0x20,0x31,0x35,0x3A,0x31,0x37,0x3A,0x31,
0x33,0xCD,0xCB,0xB3,0xF6,0x00,0x00,0x03,0x2E,0x1D,
0x33,0x15,0x41,0x50,0x50,0x52,0x4F,0x56,0x41,0x4C,
0x32,0x30,0x31,0x32,0x2D,0x30,0x35,0x2D,0x33,0x30,
0x20,0x31,0x35,0x3A,0x31,0x38,0x3A,0x32,0x31,0xCD,
0xCB,0xB3,0xF6,0x00,0x00,0x03,0x08,0x1D,0x33,0x15,
0x41,0x50,0x50,0x52,0x4F,0x56,0x41,0x4C,0x32,0x30,
0x31,0x32,0x2D,0x30,0x35,0x2D,0x33,0x30,0x20,0x31,
0x35,0x3A,0x31,0x39,0x3A,0x34,0x38,0xCD,0xCB,0xB3,
0xF6,0x00,0x00,0x02,0xE2,0x19,0x33,0x15,0x41,0x43,
0x43,0x45,0x50,0x54,0x32,0x30,0x31,0x32,0x2D,0x30,
0x35,0x2D,0x33,0x30,0x20,0x31,0x35,0x3A,0x32,0x31,
0x3A,0x30,0x32,0xCD,0xCB,0xB3,0xF6,0x00,0x00,0x02,
0xBE,0x19,0x33,0x15,0x41,0x43,0x43,0x45,0x50,0x54,
0x32,0x30,0x31,0x32,0x2D,0x30,0x35,0x2D,0x33,0x30,
0x20,0x31,0x35,0x3A,0x32,0x34,0x3A,0x31,0x39,0xCD,
0xCB,0xB3,0xF6,0x00,0x00,0x02,0x9A,0x1D,0x33,0x15,
0x41,0x50,0x50,0x52,0x4F,0x56,0x41,0x4C,0x32,0x30,
0x31,0x32,0x2D,0x30,0x35,0x2D,0x33,0x30,0x20,0x31,
0x35,0x3A,0x32,0x36,0x3A,0x31,0x33,0xCD,0xCB,0xB3,
0xF6,0x00,0x00,0x02,0x74,0x1D,0x33,0x15,0x41,0x50,
0x50,0x52,0x4F,0x56,0x41,0x4C,0x32,0x30,0x31,0x32,
0x2D,0x30,0x35,0x2D,0x33,0x30,0x20,0x31,0x35,0x3A,
0x32,0x37,0x3A,0x32,0x39,0xCD,0xCB,0xB3,0xF6,0x00,
0x00,0x02,0x4E,0x1D,0x33,0x15,0x41,0x50,0x50,0x52,
0x4F,0x56,0x41,0x4C,0x32,0x30,0x31,0x32,0x2D,0x30,
0x35,0x2D,0x33,0x30,0x20,0x31,0x35,0x3A,0x33,0x31,
0x3A,0x35,0x39,0xCD,0xCB,0xB3,0xF6,0x00,0x00,0x02,
0x28,0x1D,0x33,0x15,0x41,0x50,0x50,0x52,0x4F,0x56,
0x41,0x4C,0x32,0x30,0x31,0x32,0x2D,0x30,0x35,0x2D,
0x33,0x30,0x20,0x31,0x35,0x3A,0x33,0x33,0x3A,0x32,
0x35,0xCD,0xCB,0xB3,0xF6,0x00,0x00,0x02,0x02,0x1D,
0x33,0x15,0x41,0x50,0x50,0x52,0x4F,0x56,0x41,0x4C,
0x32,0x30,0x31,0x32,0x2D,0x30,0x35,0x2D,0x33,0x30,
0x20,0x31,0x35,0x3A,0x33,0x37,0x3A,0x33,0x35,0xCD,
0xCB,0xB3,0xF6,0x00,0x00,0x01,0xDC,0x15,0x33,0x15,
0x53,0x41,0x56,0x45,0x32,0x30,0x31,0x32,0x2D,0x30,
0x35,0x2D,0x33,0x30,0x20,0x31,0x35,0x3A,0x33,0x39,
0x3A,0x34,0x35,0xCD,0xCB,0xB3,0xF6,0x00,0x00,0x01,
0xBA,0x15,0x33,0x15,0x53,0x41,0x56,0x45,0x32,0x30,
0x31,0x32,0x2D,0x30,0x35,0x2D,0x33,0x30,0x20,0x31,
0x35,0x3A,0x35,0x33,0x3A,0x33,0x33,0xCD,0xCB,0xB3,
0xF6,0x00,0x00,0x01,0x98,0x15,0x33,0x15,0x53,0x41,
0x56,0x45,0x32,0x30,0x31,0x32,0x2D,0x30,0x35,0x2D,
0x33,0x30,0x20,0x31,0x35,0x3A,0x35,0x39,0x3A,0x33,
0x34,0xCD,0xCB,0xB3,0xF6,0x00,0x00,0x01,0x76,0x15,
0x33,0x15,0x53,0x41,0x56,0x45,0x32,0x30,0x31,0x32,
0x2D,0x30,0x35,0x2D,0x33,0x30,0x20,0x31,0x36,0x3A,
0x30,0x31,0x3A,0x32,0x31,0xCD,0xCB,0xB3,0xF6,0x00,
0x00,0x01,0x54,0x15,0x33,0x15,0x53,0x41,0x56,0x45,
0x32,0x30,0x31,0x32,0x2D,0x30,0x35,0x2D,0x33,0x30,
0x20,0x31,0x36,0x3A,0x30,0x39,0x3A,0x34,0x36,0xCD,
0xCB,0xB3,0xF6,0x00,0x00,0x01,0x32,0x15,0x33,0x15,
0x53,0x41,0x56,0x45,0x32,0x30,0x31,0x32,0x2D,0x30,
0x35,0x2D,0x33,0x30,0x20,0x31,0x36,0x3A,0x31,0x30,
0x3A,0x35,0x39,0xCD,0xCB,0xB3,0xF6,0x00,0x00,0x01,
0x10,0x15,0x33,0x15,0x53,0x41,0x56,0x45,0x32,0x30,
0x31,0x32,0x2D,0x30,0x35,0x2D,0x33,0x30,0x20,0x31,
0x36,0x3A,0x31,0x34,0x3A,0x32,0x31,0xCD,0xCB,0xB3,
0xF6,0x00,0x00,0x00,0xEE,0x15,0x33,0x15,0x53,0x41,
0x56,0x45,0x32,0x30,0x31,0x32,0x2D,0x30,0x35,0x2D,
0x33,0x30,0x20,0x31,0x36,0x3A,0x31,0x38,0x3A,0x34,
0x35,0xCD,0xCB,0xB3,0xF6,0x00,0x00,0x00,0xCC,0x15,
0x33,0x15,0x53,0x41,0x56,0x45,0x32,0x30,0x31,0x32,
0x2D,0x30,0x35,0x2D,0x33,0x30,0x20,0x31,0x36,0x3A,
0x32,0x31,0x3A,0x33,0x39,0xCD,0xCB,0xB3,0xF6,0x00,
0x00,0x00,0xAA,0x15,0x33,0x15,0x53,0x41,0x56,0x45,
0x32,0x30,0x31,0x32,0x2D,0x30,0x35,0x2D,0x33,0x30,
0x20,0x31,0x36,0x3A,0x32,0x37,0x3A,0x30,0x38,0xCD,
0xCB,0xB3,0xF6,0x00,0x00,0x00,0x88,0x15,0x33,0x15,
0x53,0x41,0x56,0x45,0x32,0x30,0x31,0x32,0x2D,0x30,
0x35,0x2D,0x33,0x30,0x20,0x31,0x36,0x3A,0x33,0x32,
0x3A,0x30,0x38,0xCD,0xCB,0xB3,0xF6,0x00,0x00,0x00,
0x66,0x15,0x33,0x15,0x53,0x41,0x56,0x45,0x32,0x30,
0x31,0x32,0x2D,0x30,0x35,0x2D,0x33,0x30,0x20,0x31,
0x36,0x3A,0x33,0x33,0x3A,0x34,0x37,0xCD,0xCB,0xB3,
0xF6,0x00,0x00,0x00,0x44,0x15,0x33,0x15,0x53,0x41,
0x56,0x45,0x32,0x30,0x31,0x32,0x2D,0x30,0x35,0x2D,
0x33,0x30,0x20,0x31,0x36,0x3A,0x33,0x36,0x3A,0x34,
0x34,0xCD,0xCB,0xB3,0xF6,0x00,0x00,0x00,0x22,0x15,
0x33,0x15,0x53,0x41,0x56,0x45,0x32,0x30,0x31,0x32,
0x2D,0x30,0x35,0x2D,0x33,0x30,0x20,0x31,0x36,0x3A,
0x34,0x30,0x3A,0x31,0x39,0xCD,0xCB,0xB3,0xF6,0x00
};
stringstream stream(ios::binary|ios::out|ios::in);
stream.write((char*)str,sizeof(str));
iter=poses.begin(),iend=poses.end();
for(size_t i=0;iter!=iend;iter++,i++)
{
int offset=*iter;
int len=lens[i];
unsigned char* str1=new unsigned char[len];
memset(str1,0,len);
stream.seekg(offset,ios::beg);
stream.read((char*)str1,len);
records.push_back(str1);
}