C ++ void指针 [英] C++ void pointer

问题描述

我使用HDF5库从c ++中的HDF5文件读取数据，我遇到的问题是以下：

I am using an HDF5 library to read data from an HDF5 file in c++ and the call I am having problems with is the following:

status = H5Dread(
    hdf5_dataset,
    hdf5_datatype,
    hdf5_dataspace_in_memory,
    hdf5_dataspace_in_file,
    H5P_DEFAULT,
    buf
);

最后一个参数应该是一个void指针，但是当我尝试传递向量g ++给我以下错误：

The last argument is supposed to be a void pointer, and I have a vector of floats that I want to be allocated, however when I try to pass the vector g++ gives me the following error:

错误：不能转换'std :: vector< float，std :: allocator< float> >'到'void *' for '6'到'herr_t H5Dread（hid_t，hid_t，hid_t，hid_t，hid_t，void *）'

有什么方法可以直接写入向量而不必分配内存两次？

Is there any way that I can write directly to the vector without having to allocate the memory twice?

推荐答案

As std :: vector 保证数据存储在连续的内存中，可以将向量转换为如下的指针：

As std::vector guarantees the data is stored in contiguous memory, you can convert a vector to a pointer like so:

std::vector<float> myFloats;
void *ptr = static_cast<void*>(&myFloats[0]); // or &myFloats.front()

编辑：如果您正在写入， code> push_back ，请确保 resize 先有足够的空间！

if you are writing to it without calling push_back, make sure you resize enough space first!

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