/// <summary>
/// Tries to consume a token of the given type
/// </summary>
/// <param name="val">The value of the token, can be null to ignore</param>
/// <param name="type">The type of the token, can be null to ignore</param>
/// <returns>A bool signifying if the symbol could be matched or not</returns>
protected bool Match(int p, string val, Lexer.Token.TokenType? type)
{
bool ok = true;
if (val != null && lookahead.Value != val)
ok = false;
else if (type.HasValue && lookahead.Type != type.Value)
ok = false;
if (!ok && p == 1)
SyntaxError(string.Format("{0}: expected '{1}', got instead '{2}', a {3}",
lookahead.Line, val ?? type.Value.ToString(), lookahead.Value, lookahead.Type.ToString()));
if (lookahead.Type != Lexer.Token.TokenType.EndOfFile)
lookahead = lexer.GetNextToken();
return ok;
}
/// <summary>
/// The main function. Runs the parser over the stream and
/// returns whether or not the stream is valid.
/// </summary>
/// <returns>A bool indicating whether or not the stream is valid syntactically</returns>
public bool Parse()
{
// first parse the program
// phase 1
CompilerStack.Clear();
CompilerStack.Push(new StackFrame(this));
lexer.Reset();
lookahead = lexer.GetNextToken();
SemanticInfo si = new SemanticInfo();
bool ok1 = NTF_Prog(1, si) && Match(1, Lexer.Token.TokenType.EndOfFile);
ComputeClassSizes();
// phase 2
CompilerStack.Clear();
CompilerStack.Push(new StackFrame(this));
si = new SemanticInfo();
lexer.Reset();
lookahead = lexer.GetNextToken();
bool ok2 = NTF_Prog(2, si) && Match(2, Lexer.Token.TokenType.EndOfFile);
si.Code.Insert(0, "stack res 5000\nalign\n");
si.Code.Append(
@"
putint align
add r2,r0,r0 % Initialize buffer's index i
cge r3,r1,r0 % True if N >= 0
bnz r3,putint1 % Branch if True (N >= 0)
sub r1,r0,r1 % N = -N
putint1 modi r4,r1,10 % Rightmost digit
addi r4,r4,48 % Convert to ch
divi r1,r1,10 % Truncate rightmost digit
sb putint9(r2),r4 % Store ch in buffer
addi r2,r2,1 % i++
bnz r1,putint1 % Loop if not finished
bnz r3,putint2 % Branch if True (N >= 0)
addi r3,r0,45
sb putint9(r2),r3 % Store '-' in buffer
addi r2,r2,1 % i++
add r1,r0,r0 % Initialize output register (r1 = 0)
putint2 subi r2,r2,1 % i--
lb r1,putint9(r2) % Load ch from buffer
putc r1 % Output ch
bnz r2,putint2 % Loop if not finished
addi r1,r0,13 % load new line
putc r1 % print it
addi r1,r0,10 % new feed thingie
putc r1
jr r15 % return to the caller
putint9 res 12 % loacl buffer (12 bytes)
align
getint add r1,r0,r0 % n := 0 (result)
add r2,r0,r0 % c := 0 (character)
add r3,r0,r0 % s := 0 (sign)
getint1 getc r2 % read c
ceqi r4,r2,32
bnz r4,getint1 % skip blanks
ceqi r4,r2,43
bnz r4,getint2 % branch if c is '+'
ceqi r4,r2,45
bz r4,getint3 % branch if c is not '-'
addi r3,r0,1 % s := 1 (number is negative)
getint2 getc r2 % read c
getint3 ceqi r4,r2,10
bnz r4,getint5 % branch if c is \n
cgei r4,r2,48
bz r4,getint4 % c < 0
clei r4,r2,57
bz r4,getint4 % c > 9
muli r1,r1,10 % n := 10 * n
add r1,r1,r2 % n := n + c
subi r1,r1,48 % n := n - '0'
j getint2
getint4 addi r2,r0,63 % c := '?'
putc r2 % write c
j getint % Try again
getint5 bz r3,getint6 % branch if s = 0 (number is positive)
sub r1,r0,r1 % n := -n
getint6 jr r15 % return
");
Log(LogType.Code, si.Code.ToString());
// then write out the debug information
Log(LogType.SymbolTable, Global.ToString());
foreach (string error in Errors)
Log(LogType.Error, error);
foreach (string warning in Warnings)
Log(LogType.Warning, warning);
// and flush the streams
foreach (TextWriter tw in Output.Values)
tw.Flush();
return ok1 && ok2;
}
/// <summary>
/// Skips all the errors until the next (maybe valid) token
/// </summary>
/// <param name="tokens">The list of "valid" tokens</param>
/// <returns>true if there has been an error that was skipped, false otherwise</returns>
protected bool SkipErrors(int p, params object[] tokens)
{
if (ValidLookAhead(tokens))
return false;
if (p == 1)
SyntaxError(string.Format("{0}:unexpected token '{1}' of type '{2}'",
lookahead.Line, lookahead.Value, lookahead.Type));
do
{
if (lookahead.Type == Lexer.Token.TokenType.EndOfFile)
break;
lookahead = lexer.GetNextToken();
} while (!ValidLookAhead(tokens));
if (p == 1)
Warning(string.Format("{0}:Resuming parsing near the token '{1}' of type '{2}'",
lookahead.Line, lookahead.Value, lookahead.Type));
return true;
}
