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[英]What is the best way to convert a 2D string vector to a 2D int vector c++?
[英]Best way to convert 2D vector to C type (for SGX enclave)
std::vector
有一个data()
方法,它将为您提供一个指向其数据的普通指针。 但是,您需要对第二层向量执行某些操作,因此您需要创建一个临时数组,该数组将存储内部向量中的普通指针列表。
#include <algorithm>
#include <iostream>
#include <vector>
extern "C" int my_c_function(int **double_pointer, int rows, int cols) {
for (int i = 0; i < rows; ++i) {
for (int j = 0; j < cols; ++j) {
printf("%d ", double_pointer[i][j]);
}
printf("\n");
}
}
int main() {
std::vector<std::vector<int>> ImagePixels{{1, 2, 3}, {4, 5, 6}};
// transform a vector of vectors into a vector of pointers
std::vector<int*> ptrs(ImagePixels.size());
std::transform(begin(ImagePixels), end(ImagePixels), begin(ptrs),
[](std::vector<int> &inner_vec) {
return inner_vec.data();
});
my_c_function(ptrs.data(), ImagePixels.size(), ImagePixels[0].size());
}
实例: https : //onlinegdb.com/BJvb3yG3f
但是,如果您可以控制整个代码,我建议使用平面结构,您只需将整个图片存储到falt std::vector<int>
。 你甚至可以在std :: vector周围做一个简单的包装,以便更容易操作这样的结构:
class image {
public:
image(int rows = 0; int cols = 0)
: rows_{rows}, cols_{cols}, data_(rows * cols) {}
int &operator ()(int row, int col) {
return data_[row * cols_ + col];
}
int *data() { return data_.data(); };
// needs a few more utilities and constant versions of the methods
private:
std::vector<int> data_;
int rows_;
int cols_;
};
然后你可以这样做:
image im(3, 2);
// set pixels
im(0, 0) = 1;
im(0, 1) = 2;
int *d = im.data(); // a plain pointer to an array of data
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