C++ 在单次调用c++;
我试图将一个二进制文件读入一个结构数组C++ 在单次调用c++;,c++,binaryfiles,ifstream,C++,Binaryfiles,Ifstream,我试图将一个二进制文件读入一个结构数组 struct FeaturePoint { FeaturePoint (const int & _cluster_id, const float _x, const float _y, const float _a, const float _b ) : cluster_id (_cluster_id), x(_x
struct FeaturePoint
{
FeaturePoint (const int & _cluster_id,
const float _x,
const float _y,
const float _a,
const float _b
) : cluster_id (_cluster_id), x(_x), y(_y), a(_a), b(_b) {}
FeaturePoint (){}
int cluster_id;
float x;
float y;
float a;
float b;
};
下面的代码可以工作,但一次只执行一个元素,方法是将每个新元素推送到一个数组中
void LoadImageFeaturesFromBinaryFile(const char * FileName, std::vector<FeaturePoint>& features )
{
char strInputPath[200];
strcpy (strInputPath,"/mnt/imagesearch/tests/");
strcat (strInputPath,FileName);
strcat (strInputPath,".bin");
features.clear();
ifstream::pos_type size;
ifstream file (strInputPath, ios::in|ios::binary|ios::ate);
if (file.is_open())
{
size = file.tellg();
cout<< "this file size is : "<<size<<" for "<<strInputPath<<" " <<sizeof( FeaturePoint )<<endl;
file.seekg (0, ios::beg);
while (!file.eof())
{
try
{
FeaturePoint fp;
file.read( reinterpret_cast<char*>(&fp), sizeof( FeaturePoint ) );
features.push_back(fp);
}
catch (int e)
{ cout << "An exception occurred. Exception Nr. " << e << endl; }
}
sort (features.begin(), features.begin()+features.size(),CompareClusterIndexes);
file.close();
}
}
void LoadImageFeaturesFromBinaryFile(const char*FileName,std::vector&features)
{
字符strInputPath[200];
strcpy(strInputPath,“/mnt/imagesearch/tests/”;
strcat(strInputPath,文件名);
strcat(strInputPath,“.bin”);
特征。清除();
ifstream::pos_类型大小;
ifstream文件(strInputPath,ios::in | ios::binary | ios::ate);
if(file.is_open())
{
size=file.tellg();
cout您的特性
的类型是一个std::vector,您将其大小写为char。类型vector不是数组。这是错误的:
features.reserve( size/sizeof( FeaturePoint ));
file.read( reinterpret_cast<char*>(&features), size );
要将数据读入向量,应调整其大小,而不仅仅是保留,如下所示:
features.resize( size/sizeof( FeaturePoint ));
这也是错误的:
features.reserve( size/sizeof( FeaturePoint ));
file.read( reinterpret_cast<char*>(&features), size );
file.read(重新解释铸件和特征),尺寸;
你不是在矢量数据上写,你是在覆盖结构本身,还有谁知道还有什么。应该是这样的:
file.read( reinterpret_cast<char*>(&features[0]), size );
file.read(重新解释强制转换(&features[0]),大小);
正如尼莫所说,这不太可能提高你的表现。我想你想要的
file.read( reinterpret_cast<char*>(&features[0]), size );
file.read(重新解释强制转换(&features[0]),大小);
您还需要确保size
是sizeof(FeaturePoint)的倍数
。否则,你会读得有点太多。我预测,一旦你开始使用它,你会惊讶于它对性能的改善是多么的少。帮你自己一个忙,使用std::string
而不是strcat
。对,这会初始化整个(大于缓存)因此,即使磁盘不是瓶颈,这也不会比原始代码快。“保留”加上“推回”通常更快…如果您读取的速度不是内存磁盘的百万倍。