C ++从ifstream读取一块并写入ofstream

Question

I want to read a chunk of bytes from one ifstream then write to another ofstream .

here is my code:

size_t chunk_size = ...;
std::ifstream ifs(in_file_name);
std::ofstream ofs(out_file_name);

char * buffer = new char[chunk_size];
ifs.read(buffer, chunk_size);
ofs << buffer;
delete[] buffer;

is it the right way to do this?

According to CPP document, std::ostream::operator<< accept a streambuffer * as argument. I'm not sure whether a char array can be treated as a bufferstream.

(I can compile and run the code, but there is some problem in my program, I'm not sure if it's caused by this, still trying to figure it out...)

Answer 1

is it the right way to do this?

Not quite so. If you use std::istream::read() then most probably you should pair it with std::ostream::write() and it is better to use std::vector<char> for memory management (or at least smart pointer):

size_t chunk_size = ...;
std::ifstream ifs(in_file_name);
std::ofstream ofs(out_file_name);

{ // you can use block to limit lifetime of the vector
    std::vector<char> buffer( chunk_size );
    ifs.read( buffer.data(), buffer.size() );
    ofs.write( buffer.data(), buffer.size() ); 
} 

problem with your code std::ostream::operator<< overload for const char * expects null terminated string, not binary data of fixed size