These are commonly asked questions.  I mean no disrespect to the poster.  Maybe there ought to be more documentation in the source code?
 
> mem->memory[mem->size] = 0;
> what does this line do?

It puts a zero at the end of the data that has been copied into the buffer.  That zero will be overwritten if and when there is a subsequent data-write, or it will function to mark the end of the buffer if it is the final data-write.

> chunk.memory = malloc(1);

> Why do I need this malloc(1)? Why can't realloc do the rest? If I omit
> this line, the program crashes.

You need malloc(1) to create a buffer that can subsequently be passed to realloc().  malloc(0) might make more sense, but some implementations won't allocate a buffer of 0 size and pass a useful pointer to it in response to malloc(0).

What I did in my code was to have a pointer to buffer, and a size_t that identified the buffer size.  They are both initialized to zero.  When the callback function executes, if there is a pointer, it calls realloc().  If there is no valid pointer, it calls malloc().  I've just shifted the malloc() into the callback.  No biggie.

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Received on 2011-06-18