Instead of using endian.h that is not portable AND doesn't work with
C++, I'll just write my own using a forced union based type punning
trick.
I've decided to use little endian for the format as well: it seems to
be used by most desktop computers so it should make these functions
faster to run for most CPUs.
Have to define _DEFAULT_SOURCE before you can use the endian
conversion functions. As most standard library headers use
features.h, and _DEFAULT_SOURCE must be defined before features.h is
included, we have to include base.h before other headers.
Essentially a "program header", followed by a count, followed by
instructions.
Provides a stronger format for bytecode files and allows for better
bounds checking on instructions.
Essentially you may "call" an absolute program address, which pushes
the current address onto the call stack. CALL_STACK does the same
thing but the absolute program address is taken from the data stack.
RET pops an address off the call stack then jumps to that address.
Essentially they use the stack for their one and only operand. This
allows user level control, in particular it allows for loops to work
correctly while using these operands.
This will allow for more library level code to be written. For
example, say you wanted to write a generic byte level reversal
algorithm for dynamically sized allocations. Getting the size of the
allocation would be fundamental to this operation.
One may allocate any number of (bytes|hwords|words), set or get some
index from allocated memory, and delete heap memory.
The idea is that all the relevant datums will be on the stack, so no
register usage. This means no instructions should use register space
at all (other than POP, which I'm debating about currently). Register
space is purely for users.
Thankfully multiplication, like addition, is the same under 2s
complement as it is for unsigned numbers. So I just need to implement
those versions to be fine.
A negative number under 2s complement can never be equal to its
positive as the top bit *must* be on. If two numbers are equivalent
bit-by-bit then they are equal for both signed and unsigned numbers.
As it has no dependencies on vm specifically, and it's more necessary
for any vendors who wish to target the virtual machine, it makes more
sense for inst to be a lib module rather than a vm module.
