将文件字节写入文件客户端 C++

Question

I have a server (python) that sends bytes from a file to a client in c++. I am using libcurl to make requests to the python server and flask to do all of the "hard" work for me in python. After i get the file bytes from the server, i want to write it to a zip file on the client side. Initially, i was going to use libcurl to do it for me, but i decided i didn't want to do that as it would require an extra function in my wrapper which is not necessary.

FILE* zip_file = fopen(zip_name, "wb");
//make request and store the bytes from the server in a string
fwrite(response_information.first.c_str(), sizeof(char), sizeof(response_information.first.c_str()), zip_file);
//response_information is a pair . First = std::string, Second = curl response code

I do plan on switching to fopen_s (safe version of fopen), but i want to get a working program first. This is part of a bigger project so i can't provide code that can be run. Some things to note that i think can be causing this: storing response as string then attempting to get the c string version and write it to the file. When storing the return value/code of fwrite, i get "8" which means "*" bytes written apparently. Also, when im on windows, it says that the file was modified after i run my program, but nothing is in the zip file itself. How can i write the response bytes to a file?

Answer 1

The third parameter in fwrite is a count of items to write. So sizeof doesn't seem to be the thing you need. response_information.first.c_str() is a pointer, so sizeof(response_information.first.c_str()) returns a pointer size. Here it should be:

fwrite(response_information.first.c_str(), sizeof(char), strlen(response_information.first.c_str()), zip_file);

or

fwrite(response_information.first.c_str(), sizeof(char), response_information.first.length(), zip_file);