Virtual Machine + Assembler/Showcase (SoCoder)

Created 29 June 2010 | Last Edited 30 June 2010)

Virtual Machine + Assembler - Created by HoboBen (No Votes)

An open source Virtual Machine and Assembler for the Cobra programming language.

Created using Cobra > Windows

View Worklog (0 entries)

1.6mb zip

VM Updates

The imaginatively named "vm" Virtual Machine is a typeless, procedural VM, with native support for functions and strings. Use the "vmAsm" assembler to assemble programs into a vmx (VM eXecutable) binary file that vm can run.

This program is open source - see license-vm.txt and license-vmAsm.txt for licensing details.

Contains an example front-end with an example script ready-to-run!

Latest Comments

Posted : Friday, 02 July 2010, 09:11

HoboBen

Bugs & fixes:

Fixed a bug where global arrays were accessed in the wrong direction (local ones were working). Here's the fix - replace the Vm_ResolveOpStackIndex function in vm.cps (line 300) with the following:

Function Vm_ResolveOpStackIndex(index: Integer) : Integer
Var
    vmValue: ^vmValues
    stackValue: ^vmValues
    base, offset: Integer
Begin
    vmValue = IndexedItem(vmActiveScript.instrStreamCurrInstr.opList, index)
    
    Case vmValue.opType of
        (OP_TYPE_ABS_STACK_INDEX):
            result = vmValue.iValue 
        
        (OP_TYPE_REL_STACK_INDEX):
            base = vmValue.iValue
            offset = vmValue.iOffsetIndex
            stackValue = Vm_GetStackValue(offset)
            
            If base < 0 then
                result = base - stackValue.iValue
            Else
                result = base + stackValue.iValue
            Endif
        
        Default:
            result = 0
            MessageBox("ResolveOpStackIndex - case shouldn't happen")  
    
    EndCase
End

-->

Additionally, HAPI funcs were buggy. Fix Vm_GetHapiFunc in vm.cps (line 456):

Function Vm_GetHapiFunc(index: Integer): ^vmHapiFuncs
Var
    vmHapiFunc: ^vmHapiFuncs
Begin
    result = IndexedItem(vmActiveScript.hapiFuncsList, index)
End

-->

At approx line 1200, these instructions also need fixing:

            (INSTR_FLOAT):
                dest = Vm_ResolveOpValue(0)
                dest.rValue = Vm_CoerceValueToFloat(dest)
                dest.opType = OP_TYPE_FLOAT
                incStream = TRUE

            (INSTR_INT):
                dest = Vm_ResolveOpValue(0)
                dest.iValue = Vm_CoerceValueToInt(dest)
                dest.opType = OP_TYPE_INT
                incStream = TRUE
                
            (INSTR_STRING):
                dest = Vm_ResolveOpValue(0)
                dest.sValue.sString = Vm_CoerceValueToString(dest)
                dest.opType = OP_TYPE_STRING_INDEX
                incStream = TRUE

-->

Unfixed: Assembly scripts will not work properly if a function has both local variables (var) AND parameters (param). Either on its own will work. Workaround: use global variables for some function vars or params.

Posted : Monday, 05 July 2010, 16:32

HoboBen

Working pacman example:

Download (ready-to-run!) ~1.5 MB

The example is over 1000 lines of assembly and took four days. You'd be mad to actually use the VM this way, but as a "proof of concept" it's pretty good.

Host API functions:

; HapiDrawCell (x, y, cellState)
; HapiCreateSprite(), returns index
; HapiPositionSprite(index, x, y)
; HapiSetSpriteFrame(index, frame)
; HapiFreeSprite(index)
; HapiGetDelta(), returns delta as real
; HapiRnd(), returns random number between 0 and 1
; HapiGetTicks(), returns ticks as integer
; HapiKeyDown(key), returns 0 (false) or 1 (true)
; HapiDisplayStats(score, eaten)