internal static ValueObject GetInitExpr(InitExpr init, List <GlobalInstance> initialized_globals)
{
if (init.expr.Length < 3)
{
throw new Exception("Unexpected init expression.");
}
uint pc = 0;
ValueObject ret = null;
switch (init.expr[0])
{
case (byte)WebAssemblyOpcode.I32_CONST:
ret = new ValueObject(LEB128.ReadUInt32(init.expr, ref pc));
break;
case (byte)WebAssemblyOpcode.I64_CONST:
ret = new ValueObject(LEB128.ReadUInt64(init.expr, ref pc));
break;
case (byte)WebAssemblyOpcode.F32_CONST:
ret = new ValueObject(BitConverter.ToSingle(init.expr, (int)pc));
break;
case (byte)WebAssemblyOpcode.F64_CONST:
ret = new ValueObject(BitConverter.ToDouble(init.expr, (int)pc));
break;
case (byte)WebAssemblyOpcode.GLOBAL_GET:
GlobalInstance gi = initialized_globals[LEB128.ReadInt32(init.expr, ref pc)];
if (!gi.is_mutable)
{
throw new Exception("Unexpected init expression.");
}
ret = gi.value;
break;
default:
throw new Exception("Invalid init expression. Expected only simple constant load instruction or global get.");
}
pc++;
if (init.expr[pc] != (byte)WebAssemblyOpcode.END || init.expr.Length > pc)
{
throw new Exception("Invalid init expression.");
}
return(ret);
}
private void InitGlobal(WebAssemblyFile file)
{
logger.Debug("Instanciating Globals.");
List <GlobalInstance> finalized_globals = new List <GlobalInstance>();
for (uint i = 0; i < (uint)file.global.globals.Length; i++)
{
var global = file.global.globals[i];
var value = WebAssemblyHelper.GetInitExpr(global.init, finalized_globals);
logger.ConditionalTrace($"Instanciating GlobalInstance({global.type.mutability}, {global.type.content_type}, {value}).");
globals[i] = new GlobalInstance(global.type.mutability, global.type.content_type, value);
finalized_globals.Add(globals[i]);
}
logger.Debug("Done instanciating Globals.");
}