Question

Alright, so here is a really weird one. I am reading raw data into a buffer, nothing fancy, my code went like so:

typedef unsigned char Byte;
/* ... */
static Byte SerializeBuffer[2048];
/* ... */
std::streamsize readInBuffer = 
                data.read((char*)SerializeBuffer, sizeof(SerializeBuffer));

But I would keep getting the compile error message 'error: invalid cast from type ‘void *’ to type ‘std::streamsize’', No idea why the compiler thought that sizeof was a void pointer. Well I tried casting it in several ways, but the same error kept happening. I ended up with this:

std::streamsize dummy = sizeof(SerializeBuffer);
std::streamsize readInBuffer = 
                data.read((char*)SerializeBuffer, reinterpret_cast<std::streamsize>(dummy));

Which pops up the following: error: invalid cast from type ‘std::streamsize’ to type ‘std::streamsize’

I am at a complete loss. Any other Ideas?

Compiler: gcc 4.4.5
OS: Linux 2.6.35

edit:
Same thing on Visual Studio 2010

Answer 1

If data is an istream, keep in mind that the member read returns a reference to data (the stream itself), not the number of characters read.

The void * stuff is probably because the compiler, to assign it to the std::streamsize member, tries to use the implicit conversion to void * (the one that is used when you do if(data) ...), but still void * is not a good match for std::streamsize.

By the way, the information about the number of characters read can be obtained, after the call to read, using the gcount method.