c++ std::ifstream 读取文件不完整？ 是不是忘记了ios_base::binary

一次浪费时间又把你折磨的无以复加的小问题。

读取图片本应该读取20000字节的，为何只读取了300字节？原来少了ios_base::binary!!!

如果读取的非字符串形式的文本，注意应该要加上ios_base::binary，否则可能遇到0就提前返回了EOF。

下面直接上我出过问题的代码，当然现在是正确的...

	//发送图片的图片数据缓冲区
	boost::shared_ptr _img_buffer;
	unsigned int _img_buffer_size;

{
#define IMG_RES "../Debug/767011.jpg"

		using namespace std;

		std::ifstream* tmpImg = new std::ifstream(IMG_RES, ios_base::in | ios_base::_Nocreate | ios_base::binary);

		if(tmpImg == NULL || !tmpImg->is_open()){
			ASSERT_THROW;
		}

		tmpImg->seekg(0, ios::end);
		_img_buffer_size = (int)tmpImg->tellg();

		if(_img_buffer_size == -1){
			ASSERT_THROW;
		}

		if(_img_buffer != NULL){
			ASSERT_THROW;
		}

		_img_buffer = boost::shared_ptr(new char[_img_buffer_size], [](char* p){delete [] p; p=NULL;});

		if(_img_buffer == NULL){
			ASSERT_THROW;
		}

		memset(_img_buffer.get(), 0, _img_buffer_size);
		tmpImg->seekg(0, ios::beg);

		unsigned int tmpCount = 0;

		do 
		{
			std::istream& tmpIs = tmpImg->read(_img_buffer.get()+tmpCount, _img_buffer_size-tmpCount);

			if(tmpIs.eof()){
				break;
			}

			if(tmpIs.rdstate() != std::ios_base::goodbit){
				ASSERT_THROW;
			}

			tmpCount += (unsigned int)tmpIs.gcount();
		} while (tmpCount < _img_buffer_size);

		tmpImg->close();
		SAFE_DELETE(tmpImg);
	}