CODEWITHSUNDEEP
c++pointersmemory-addresspointer-to-pointer
Alejandro
Alejandro

Reputation: 31

How to obtain data from a memory address pointed by another pointer?

I am working with GenICam library, one of the methods is described as follows: enter image description here

I am using this method to get camera frames. We must provide to pBuffer a pointer, the method will return to our pointer, the memory address where data is stored.

So, I want to obtain the data stored in that memory address, but doing it in this way:

char* image_data = nullptr; 
image_data = new char[1024];
status = gentl->DSGetBufferInfo(datastream_module_handle, new_buffer_event_data.BufferHandle, GenTL::BUFFER_INFO_BASE, &info_datatype, image_data, &info_datasize);
std::cout << **image_data << std::endl;

I am getting this error: error c2100 illegal indirection c++.

I tried to use an auxiliar pointer:

char* image_data = nullptr;
image_data = new char[1024];
char* p_image_data = nullptr;
p_image_data = new char[1024];
status = gentl ... (same method)
p_image_data = *image_data;
std::cout << *p_image_data << std::endl;

but i obtained the following error: error C2440: '=' : cannot convert from char to char *.

How can I obtain the data stored in that memory address ?

Upvotes: 1

Views: 93

Answers (1)

Blaze
Blaze

Reputation: 16876

p_image_data = *image_data;

Should be 

p_image_data = image_data;

They both have the same type (char*), so there's no need to dereference. By dereferencing image_data, you get a char again, and that can't be assigned to p_image_data (which is char*), hence the error.

Of course, now you're not copying the data, just setting the pointer. What you probably want instead is:

memcpy(p_image_data, image_data, 1024);

This copies the 1024 chars that image_data points to (after being modified by DSGetBufferInfo) to the 1024 bytes pointed to by p_image_data.

Upvotes: 3

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