1 頭文件
#include <iostream>
#include <fstream>
#include <string>
2 讀取一行
void UsingifstreamReadLineMethod()
{
char szBuf[256] = { 0 };
std::ifstream fileHandle("E:/thriftserver/output/facealarmnew.txt");
fileHandle.getline(szBuf, 100);
size_t nLen = strlen(szBuf);
}
3 讀取整個文本
void UsingifstreamReadMethod1()
{
std::ifstream fileHandle;
int nFileLen = 0;
fileHandle.open("E:/thriftserver/output/facealarmnew.txt");
fileHandle.seekg(0, std::ios::end);
nFileLen = fileHandle.tellg();
fileHandle.seekg(0, std::ios::beg);
char szFileBuf[4096] = { 0 };
fileHandle.read(szFileBuf, nFileLen);
std::cout << nFileLen << std::endl;
fileHandle.close();
}
void UsingifStreamReadMethod2()
{
std::ifstream fileHandle;
fileHandle.open("E:/thriftserver/output/facealarmnew.txt");
std::string strFileBuf;
fileHandle >> strFileBuf;
std::cout << strFileBuf.length() << std::endl;
}
上述的兩個方法,都嘗試讀取整個文本的數據,但是第二個方法在讀取Json格式的數據情況下,會出現讀取不完整的情況,文本長度是2876,但是第二個方法讀取到的字符串長度是871,所以在使用的過程中,一定要謹慎小心,目前懷疑是在讀取到空字符的時候,就直接返回了,導致數據讀取出錯
4直接將ifstream文件句柄傳遞給Jsoncpp解析器,進行文本的解析
void UsingifstreamReadJson()
{
std::ifstream fileHandle;
fileHandle.open("E:/thriftserver/output/facealarmnew.txt");
Json::Reader reader;
Json::Value root;
if (NULL == reader.parse(fileHandle, root))
{
fileHandle.close();
return;
}
fileHandle.close();
std::string strName = root["name"].asString();
}
參考文章備忘
c++中一次讀取整個文件的內容的方法:
讀取至char*的情況
std::ifstream t;
int length;
t.open("file.txt"); // open input file
t.seekg(0, std::ios::end); // go to the end
length = t.tellg(); // report location (this is the length)
t.seekg(0, std::ios::beg); // go back to the beginning
buffer = new char[length]; // allocate memory for a buffer of appropriate dimension
t.read(buffer, length); // read the whole file into the buffer
t.close(); // close file handle
// ... do stuff with buffer here ...
讀取至std::string的情況:
第一種方法:
#include <string>
#include <fstream>
#include <streambuf>
std::ifstream t("file.txt");
std::string str((std::istreambuf_iterator<char>(t)),
std::istreambuf_iterator<char>());
第二種方法:
#include <string>
#include <fstream>
#include <sstream>
std::ifstream t("file.txt");
std::stringstream buffer;
buffer << t.rdbuf();
std::string contents(buffer.str());
reference
http://stackoverflow.com/questions/2602013/read-whole-ascii-file-into-c-stdstring
摘自:http://www.cnblogs.com/kex1n/p/4028428.html