fstream和stringstream之间的转换

#include <fstream>
#include <sstream>

const char* filepath = "C:/test.txt";
ifstream in(filepath);
if(in.bad())
{
printf("open file '%d' failed!", filepath);
return;
}
stringstream ss;

ss << in.rdbuf();
string str(ss.str());
printf(str.c_str());

in.close();

void RegexSearch::LoadStreamFromFile( char** buffer,const char* filepath )
{
FILE* pFile = NULL;
int err = ::fopen_s(&pFile, filepath, "rb");
if(0 != err)
{
printf("open file '%s' failed!", filepath);
return;
}
unsigned int length = 0;
int growSize = 512;
while(!feof(pFile))
{
char* temp = (char*)calloc(length + growSize, sizeof(char));
//将之前已读取的字节流拷贝到新的已扩容的动态数组中
memcpy( temp, *buffer, length );
if(*buffer)
free(*buffer);
*buffer = temp;
//每次读取固定大小growSize长度个字符，并拼接到*buffer指向的字符串尾部
fread((*buffer) + length, sizeof(char), growSize, pFile);
length += growSize;
}
fclose(pFile);
}