ForInStatement ParseForInStatement()
{
var statement = new ForInStatement(_current.m_line);
statement.name_list = ParseNameList();
if (NextToken().m_type != (int)TokenType.IN)
{
throw NewParserException("expect 'in' in for-in-statement", _current);
}
// 这个结构特殊，返回的是迭代器，
statement.exp_list = ParseExpList();
if (NextToken().m_type != (int)TokenType.DO)
{
throw NewParserException("expect 'do' to start for-in-body", _current);
}
statement.block = ParseBlock();
if (NextToken().m_type != (int)TokenType.END)
{
throw NewParserException("expect 'end' to complete for-in-body", _current);
}
return(statement);
}
void HandleForInStatement(ForInStatement tree)
{
EnterBlock();
var f = GetCurrentFunction();
Instruction code;
// init iterator function
HandleExpList(tree.exp_list, 3);
var func_register = GenerateRegisterId();
var table_register = GenerateRegisterId();
var index_register = GenerateRegisterId();
EnterLoop();
{
EnterBlock();
// alloca registers for names
int name_start = GetNextRegisterId();
HandleNameList(tree.name_list);
int name_end = GetNextRegisterId();
// allocate temp registers for call iterator function
int temp_func = name_start;
int temp_table = name_start + 1;
int temp_index = name_start + 2;
// call iterate function
Action <int, int> move = (int dst, int src) =>
{
var l_code = Instruction.AB(OpType.OpType_Move, dst, src);
f.AddInstruction(l_code, tree.name_list.line);
};
move(temp_func, func_register);
move(temp_table, table_register);
move(temp_index, index_register);
code = Instruction.ABC(OpType.OpType_Call, temp_func, 2, 0);
f.AddInstruction(code, tree.exp_list.line);
code = Instruction.A(OpType.OpType_FillNilFromTopToA, name_end);
f.AddInstruction(code, tree.exp_list.line);
// jump to loop tail when the first name value is nil
code = Instruction.ABx(OpType.OpType_JmpNil, name_start, 0);
int index = f.AddInstruction(code, tree.exp_list.line);
AddLoopJumpInfo(JumpType.JumpTail, index);
// index = name1
move(index_register, name_start);
HandleBlock(tree.block);
LeaveBlock();
// jump to loop head
code = Instruction.Bx(OpType.OpType_Jmp, 0);
index = f.AddInstruction(code, -1);
AddLoopJumpInfo(JumpType.JumpHead, index);
}
LeaveLoop();
LeaveBlock();
}
