package com.seaofnodes.simple; import com.seaofnodes.graph.GraphObserver; import com.seaofnodes.simple.node.*; import com.seaofnodes.simple.type.*; import java.util.*; /** * The Parser converts a Simple source program to the Sea of Nodes intermediate * representation directly in one pass. There is no intermediate Abstract * Syntax Tree structure. *

* This is a simple recursive descent parser. All lexical analysis is done here as well. */ public class Parser { // Current compilation context; the observer belongs to the parser. public static Parser PARSER; public GraphObserver _obs; public int pos() { return _lexer._position; } /** * A Global Static, unique to each compilation. This is a public, so we * can make constants everywhere without having to thread the StartNode * through the entire parser and optimizer. *

* To make the compiler multithreaded, this field will have to move into a TLS. */ public static StartNode START; public static ConstantNode ZERO; public static XCtrlNode XCTRL; public StopNode STOP; // Field identities are independent of the memory graph and Start's tuple. private final HashMap _aliases = new HashMap<>(); private int _alias = 2; // Debugger Printing. public static boolean SCHEDULED; // True if debug printer can use schedule info // The Lexer. Thin wrapper over a byte[] buffer with a cursor. private final Lexer _lexer; /** * Current ScopeNode - ScopeNodes change as we parse code, but at any point of time * there is one current ScopeNode. The reason the current ScopeNode can change is to do with how * we handle branching. See {@link #parseIf()}. *

* Each ScopeNode contains a stack of lexical scopes, each scope is a symbol table that binds * variable names to Nodes. The top of this stack represents current scope. *

* We keep a list of all ScopeNodes so that we can show them in graphs. * @see #parseIf() * @see #_xScopes */ public ScopeNode _scope; /** * List of keywords disallowed as identifiers */ private static final HashSet KEYWORDS = new HashSet<>(){{ add("bool"); add("break"); add("byte"); add("continue"); add("else"); add("f32"); add("f64"); add("false"); add("flt"); add("i16"); add("i32"); add("i64"); add("i8"); add("if"); add("int"); add("new"); add("null"); add("return"); add("struct"); add("true"); add("u1"); add("u16"); add("u32"); add("u8"); add("while"); }}; /** * We clone ScopeNodes when control flows branch; it is useful to have * a list of all active ScopeNodes for purposes of visualization of the SoN graph */ public final Stack _xScopes = new Stack<>(); ScopeNode _continueScope; ScopeNode _breakScope; // Mapping from a type name to a Type. public static HashMap TYPES = new HashMap<>(); public Parser(String source, TypeInteger arg) { PARSER = this; Node.reset(); IterPeeps.reset(); TYPES.clear(); TYPES.put("bool",TypeInteger.U1 ); TYPES.put("byte",TypeInteger.U8 ); TYPES.put("f32" ,TypeFloat .B32); TYPES.put("f64" ,TypeFloat .BOT); TYPES.put("flt" ,TypeFloat .BOT); TYPES.put("i16" ,TypeInteger.I16); TYPES.put("i32" ,TypeInteger.I32); TYPES.put("i64" ,TypeInteger.BOT); TYPES.put("i8" ,TypeInteger.I8 ); TYPES.put("int" ,TypeInteger.BOT); TYPES.put("u1" ,TypeInteger.U1 ); TYPES.put("u16" ,TypeInteger.U16); TYPES.put("u32" ,TypeInteger.U32); TYPES.put("u8" ,TypeInteger.U8 ); SCHEDULED = false; _lexer = new Lexer(source); _scope = new ScopeNode(); _continueScope = _breakScope = null; START = new StartNode(new Type[]{ Type.CONTROL, TypeMem.BOT, arg }); STOP = new StopNode(source); ZERO = new ConstantNode(TypeInteger.constant(0)).peephole().keep(); XCTRL= new XCtrlNode().peephole().keep(); } public Parser(String source) { this(source, TypeInteger.BOT); } @Override public String toString() { return _lexer.toString(); } String src() { return new String( _lexer._input ); } // Debugging utility to find a Node by index public static Node find(int nid) { return START.find(nid); } private Node ctrl() { return _scope.ctrl(); } private Node ctrl(Node n) { return _scope.ctrl(n); } public StopNode parse() { _xScopes.push(_scope); // Enter a new scope for the initial control and arguments _scope.push(); _scope.define(ScopeNode.CTRL, Type.CONTROL , new CProjNode(START, 0, ScopeNode.CTRL).peephole()); _scope.define(ScopeNode.ARG0, TypeInteger.BOT, new ProjNode(START, 2, ScopeNode.ARG0).peephole()); _scope.define("$mem", TypeMem.BOT, new ProjNode(START, 1, "$mem").peephole()); parseBlock(); if( ctrl()._type==Type.CONTROL ) STOP.addReturn(new ReturnNode(ctrl(), new ConstantNode(TypeInteger.constant(0)).peephole(), _scope).peephole()); _scope.pop(); _xScopes.pop(); if (!_lexer.isEOF()) throw error("Syntax error, unexpected " + _lexer.getAnyNextToken()); STOP.peephole(); return STOP; } /** * Parses a block * * 

     *     '{' statements '}'
     *
* Does not parse the opening or closing '{}' * @return a {@link Node} or {@code null} */ private Node parseBlock() { // Enter a new scope _scope.push(); while (!peek('}') && !_lexer.isEOF()) parseStatement(); // Exit scope _scope.pop(); return null; } /** * Parses a statement * * 
     *     returnStatement | declStatement | blockStatement | ifStatement | expressionStatement
     *
* @return a {@link Node} or {@code null} */ private Node parseStatement() { if( false ) return null; else if (matchx("return") ) return parseReturn(); else if (match ("{") ) return require(parseBlock(),"}"); else if (matchx("if") ) return parseIf(); else if (matchx("while") ) return parseWhile(); else if (matchx("break") ) return parseBreak(); else if (matchx("continue")) return parseContinue(); else if (matchx("struct") ) return parseStruct(); else if (matchx(";") ) return null; // Empty statement // declarations of vars with struct type are handled in parseExpressionStatement due // to ambiguity else return parseExpressionStatement(); } /** * Parse a struct field. * 
     *     type IDENTIFIER ;
     *
*/ private Field parseField() { Type t = type(); if( t==null ) throw errorSyntax("Requires a field type, found '"+_lexer.getAnyNextToken()+"'"); return require(Field.make(requireId().intern(),t),";"); } /** * Parse a struct declaration, and return the following statement. * Only allowed in top level scope. * Structs cannot be redefined. * * @return The statement following the struct */ private Node parseStruct() { if (_xScopes.size() > 1) throw errorSyntax("struct declarations can only appear in top level scope"); String typeName = requireId(); Type t = TYPES.get(typeName); if( t!=null && !(t instanceof TypeStruct ts && ts._fields==null) ) throw errorSyntax("struct '" + typeName + "' cannot be redefined"); ArrayList fields = new ArrayList<>(); require("{"); while (!peek('}') && !_lexer.isEOF()) { Field field = parseField(); if (fields.contains(field)) throw errorSyntax("Field '" + field + "' already defined in struct '" + typeName + "'"); fields.add(field); } require("}"); // Build and install the TypeStruct TypeStruct ts = TypeStruct.make(typeName, fields); TYPES.put(typeName, ts); // Insert the struct name in the collection of all struct names _aliases.put(typeName,_alias); _alias += ts._fields.length; return parseStatement(); } /** * Parses a while statement * * 
     *     while ( expression ) statement
     *
* @return a {@link Node}, never {@code null} */ private Node parseWhile() { var savedContinueScope = _continueScope; var savedBreakScope = _breakScope; require("("); // Loop region has two control inputs, the first is the entry // point, and second is back edge that is set after loop is parsed // (see end_loop() call below). Note that the absence of back edge is // used as an indicator to switch off peepholes of the region and // associated phis; see {@code inProgress()}. ctrl(new LoopNode(ctrl()).peephole()); // Note we set back edge to null here // At loop head, we clone the current Scope (this includes all // names in every nesting level within the Scope). // We create phis eagerly for all the names we find, see dup(). // Save the current scope as the loop head ScopeNode head = _scope.keep(); // Clone the head Scope to create a new Scope for the body. // Create phis eagerly as part of cloning _xScopes.push(_scope = _scope.dup(true)); // The true argument triggers creating phis // Parse predicate var pred = require(parseExpression(), ")"); // IfNode takes current control and predicate Node ifNode = new IfNode(ctrl(), pred).peephole(); // Setup projection nodes Node ifT = new CProjNode(ifNode. keep(), 0, "True" ).peephole().keep(); Node ifF = new CProjNode(ifNode.unkeep(), 1, "False").peephole(); // Clone the body Scope to create the break/exit Scope which accounts for any // side effects in the predicate. The break/exit Scope will be the final // scope after the loop, and its control input is the False branch of // the loop predicate. Note that body Scope is still our current scope. ctrl(ifF); _xScopes.push(_breakScope = _scope.dup()); // No continues yet _continueScope = null; // Parse the true side, which corresponds to loop body // Our current scope is the body Scope ctrl(ifT.unkeep()); // set ctrl token to ifTrue projection parseStatement(); // Parse loop body // Merge the loop bottom into other continue statements if (_continueScope != null) { _continueScope = jumpTo(_continueScope); _scope.kill(); _scope = _continueScope; } // The true branch loops back, so whatever is current _scope.ctrl gets // added to head loop as input. endLoop() updates the head scope, and // goes through all the phis that were created earlier. For each phi, // it sets the second input to the corresponding input from the back // edge. If the phi is redundant, it is replaced by its sole input. var exit = _breakScope; head.endLoop(_scope, exit); head.unkeep().kill(); _xScopes.pop(); // Cleanup _xScopes.pop(); // Cleanup _continueScope = savedContinueScope; _breakScope = savedBreakScope; // At exit the false control is the current control, and // the scope is the exit scope after the exit test. return _scope = exit; } private ScopeNode jumpTo(ScopeNode toScope) { ScopeNode cur = _scope.dup(); ctrl(XCTRL); // Kill current scope // Prune nested lexical scopes that have depth > than the loop head // We use _breakScope as a proxy for the loop head scope to obtain the depth while( cur._scopes.size() > _breakScope._scopes.size() ) cur.pop(); // If this is a continue then first time the target is null // So we just use the pruned current scope as the base for the // "continue" if (toScope == null) return cur; // toScope is either the break scope, or a scope that was created here assert toScope._scopes.size() <= _breakScope._scopes.size(); toScope.ctrl(toScope.mergeScopes(cur)); return toScope; } private void checkLoopActive() { if (_breakScope == null) throw Parser.error("No active loop for a break or continue"); } private Node parseBreak () { checkLoopActive(); return ( _breakScope = require(jumpTo( _breakScope ),";")); } private Node parseContinue() { checkLoopActive(); return (_continueScope = require(jumpTo( _continueScope ),";")); } /** * Parses a statement * * 
     *     if ( expression ) statement [else statement]
     *
* @return a {@link Node}, never {@code null} */ private Node parseIf() { require("("); // Parse predicate var pred = require(parseExpression(), ")").keep(); // IfNode takes current control and predicate Node ifNode = new IfNode(ctrl(), pred).peephole(); // Setup projection nodes Node ifT = new CProjNode(ifNode. keep(), 0, "True" ).peephole().keep(); Node ifF = new CProjNode(ifNode.unkeep(), 1, "False").peephole().keep(); // In if true branch, the ifT proj node becomes the ctrl // But first clone the scope and set it as current int ndefs = _scope.nIns(); ScopeNode fScope = _scope.dup(); // Duplicate current scope fScope.ctrl(ifF); // The pending arm already starts at False _xScopes.push(fScope); // For graph visualization we need all scopes // Parse the true side ctrl(ifT.unkeep()); // set ctrl token to ifTrue projection _scope.upcast(ifT,pred,false); // Up-cast predicate parseStatement(); // Parse true-side ScopeNode tScope = _scope; // Parse the false side _scope = fScope; // Restore scope, then parse else block if any ifF.unkeep(); // fScope already owns the false control _scope.upcast(ifF,pred,true); // Up-cast predicate if (matchx("else")) { parseStatement(); fScope = _scope; } pred.unkeep(); if( tScope.nIns() != ndefs || fScope.nIns() != ndefs ) throw error("Cannot define a new name on one arm of an if"); // Merge results _scope = tScope; _xScopes.pop(); // Discard pushed from graph display return ctrl(tScope.mergeScopes(fScope)); } /** * Parses a return statement; "return" already parsed. * The $ctrl edge is killed. * * 
     *     'return' expr ;
     *
* @return an expression {@link Node}, never {@code null} */ private Node parseReturn() { var expr = require(parseExpression(), ";"); Node ret = STOP.addReturn(new ReturnNode(ctrl(), expr, _scope).peephole()); ctrl(XCTRL); // Kill control return ret; } /** * Parses an expression statement or a declaration statement where type is a struct * * 
     *      name;         // Error
     * type name;         // Define name with default initial value
     * type name = expr;  // Define name with given   initial value
     *      name = expr;  // Reassign existing
     *             expr   // Something else
     *
* @return an expression {@link Node}, never {@code null} */ private Node parseExpressionStatement() { int old = _lexer._position; Type t = type(); String name = requireId(); Node expr; if( match(";") ) { // Assign a default value // No type and no expr is an error if( t==null ) throw errorSyntax("expression"); expr = new ConstantNode(t.makeInit()).peephole(); } else if( match("=") ) { // Assign "= expr;" expr = require(parseExpression(), ";"); } else { // Neither, so just a normal expression parse _lexer._position = old; return require(parseExpression(),";"); } // Defining a new variable vs updating an old one if( t != null ) { if( _scope.define(name,t,expr) == null ) throw error("Redefining name '" + name + "'"); } else { if( _scope.lookup(name)==null ) throw error("Undefined name '" + name + "'"); t = _scope.lookupDeclaredType(name); } // Auto-widen int to float if( expr._type instanceof TypeInteger && t instanceof TypeFloat ) expr = new ToFloatNode(expr).peephole(); // Auto-narrow wide ints to narrow ints expr = zsMask(expr,t); // Auto-deepen forward ref types Type e = expr._type; if( e instanceof TypeMemPtr tmp && tmp._obj._fields==null ) e = tmp.make_from((TypeStruct)TYPES.get(tmp._obj._name)); // Type is sane if( !e.isa(t) ) throw error("Type " + e.str() + " is not of declared type " + t.str()); return _scope.update(name,expr); } // Parse a "type id" and return "type" (and re-parse "id" in caller) or // return null. private Type type() { int old = _lexer._position; String tname = _lexer.matchId(); if( tname==null ) return null; boolean nullable = match("?"); Type t = TYPES.get(tname); // Assume a forward-reference type if( t == null ) { int old2 = _lexer._position; String id = _lexer.matchId(); if( id==null ) { _lexer._position = old; return null; } TYPES.put(tname,t = TypeStruct.make(tname)); _lexer._position = old2; // Reparse ID in caller } return t instanceof TypeStruct obj ? TypeMemPtr.make(obj,nullable) : t; } /** * Parse an expression of the form: * * 
     *     expr : compareExpr
     *
* @return an expression {@link Node}, never {@code null} */ private Node parseExpression() { return parseBitwise(); } /** * Parse an bitwise expression * * 
     *     bitwise : compareExpr (('&' | '|' | '^') compareExpr)*
     *
* @return a bitwise expression {@link Node}, never {@code null} */ private Node parseBitwise() { Node lhs = parseComparison(); while( true ) { if( false ) ; else if( match("&") ) lhs = new AndNode(lhs,null); else if( match("|") ) lhs = new OrNode(lhs,null); else if( match("^") ) lhs = new XorNode(lhs,null); else break; lhs.setDef(2,parseComparison()); lhs = lhs.peephole(); } return lhs; } /** * Parse an expression of the form: * * 
     *     expr : additiveExpr op additiveExpr
     *
* @return an comparator expression {@link Node}, never {@code null} */ private Node parseComparison() { var lhs = parseShift(); while( true ) { int idx=0; boolean negate=false; // Test for any local nodes made, and "keep" lhs during peepholes if( false ) ; else if( match("==") ) { idx=2; lhs = new BoolNode.EQ(lhs, null); } else if( match("!=") ) { idx=2; lhs = new BoolNode.EQ(lhs, null); negate=true; } else if( match("<=") ) { idx=2; lhs = new BoolNode.LE(lhs, null); } else if( match("<" ) ) { idx=2; lhs = new BoolNode.LT(lhs, null); } else if( match(">=") ) { idx=1; lhs = new BoolNode.LE(null, lhs); } else if( match(">" ) ) { idx=1; lhs = new BoolNode.LT(null, lhs); } else break; // Peepholes can fire, but lhs is already "hooked", kept alive lhs.setDef(idx,parseShift()); lhs = lhs.widen().peephole(); if( negate ) // Extra negate for != lhs = new NotNode(lhs).peephole(); } return lhs; } /** * Parse an additive expression * * 
     *     shiftExpr : additiveExpr (('<<' | '>>' | '>>>') additiveExpr)*
     *
* @return a shift expression {@link Node}, never {@code null} */ private Node parseShift() { Node lhs = parseAddition(); while( true ) { if( false ) ; else if( match("<<") ) lhs = new ShlNode(lhs,null); else if( match(">>>")) lhs = new ShrNode(lhs,null); else if( match(">>") ) lhs = new SarNode(lhs,null); else break; lhs.setDef(2,parseAddition()); lhs = lhs.widen().peephole(); } return lhs; } /** * Parse an additive expression * * 
     *     additiveExpr : multiplicativeExpr (('+' | '-') multiplicativeExpr)*
     *
* @return an add expression {@link Node}, never {@code null} */ private Node parseAddition() { Node lhs = parseMultiplication(); while( true ) { if( false ) ; else if( match("+") ) lhs = new AddNode(lhs,null); else if( match("-") ) lhs = new SubNode(lhs,null); else break; lhs.setDef(2,parseMultiplication()); lhs = lhs.widen().peephole(); } return lhs; } /** * Parse an multiplicativeExpr expression * * 
     *     multiplicativeExpr : unaryExpr (('*' | '/') unaryExpr)*
     *
* @return a multiply expression {@link Node}, never {@code null} */ private Node parseMultiplication() { var lhs = parseUnary(); boolean mul; while( true ) { if( false ) ; else if( match("*") ) lhs = new MulNode(lhs,null); else if( match("/") ) lhs = new DivNode(lhs,null); else break; lhs.setDef(2,parseUnary()); lhs = lhs.widen().peephole(); } return lhs; } /** * Parse a unary minus expression. * * 
     *     unaryExpr : ('-') | '!') unaryExpr | postfixExpr | primaryExpr
     *
* @return a unary expression {@link Node}, never {@code null} */ private Node parseUnary() { if (match("-")) return new MinusNode(parseUnary()).widen().peephole(); if (match("!")) return new NotNode(parseUnary()).peephole(); return parsePostfix(parsePrimary()); } /** * Parse a primary expression: * * 
     *     primaryExpr : integerLiteral | Identifier | true | false | null | new Identifier | '(' expression ')'
     *
* @return a primary {@link Node}, never {@code null} */ private Node parsePrimary() { if( _lexer.isNumber(_lexer.peek()) ) return parseLiteral(); if( match("(") ) return require(parseExpression(), ")"); if( matchx("true" ) ) return new ConstantNode(TypeInteger.constant(1)).peephole(); if( matchx("false") ) return ZERO; if( matchx("null" ) ) return new ConstantNode(TypeMemPtr.NULLPTR).peephole(); if( matchx("new") ) { String structName = requireId(); Type t = TYPES.get(structName); if( !(t instanceof TypeStruct obj) || obj._fields==null ) throw error("Unknown struct type '" + structName + "'"); return newStruct(obj); } String name = _lexer.matchId(); if( name == null) throw errorSyntax("an identifier or expression"); Node n = _scope.lookup(name); if( n!=null ) return n; throw error("Undefined name '" + name + "'"); } /** * Return a NewNode but also generate instructions to initialize it. */ private Node newStruct(TypeStruct obj) { Node n = new NewNode(TypeMemPtr.make(obj), ctrl()).peephole().keep(); int alias = _aliases.get(obj._name); for( Field field : obj._fields ) { store(field._fname,alias,field._type,n,new ConstantNode(field._type.makeInit()).peephole(),true); alias++; } return n.unkeep(); } // Memory is one hidden SSA variable, including across branches and loops. private Node mem() { return _scope.lookup("$mem"); } private Node mem(Node n) { return _scope.update("$mem",n); } private void store(String name, int alias, Type glb, Node ptr, Node val, boolean init) { Node prior = mem().keep(); Node st = new StoreNode(name,alias,glb,ctrl(),prior,ptr,val,init).peephole(); mem(new MemMergeNode(prior,alias,st).peephole()); if( prior.unkeep().isUnused() ) prior.kill(); } /** * Parse postfix expression. For now this is just a field * expression, but in future could be array index too. * * 
     *     expr ('.' IDENTIFIER)* [ = expr ]
     *
*/ private Node parsePostfix(Node expr) { if( !match(".") ) return expr; if( !(expr._type instanceof TypeMemPtr ptr) ) throw error("Expected struct reference but got " + expr._type.str()); String name = requireId().intern(); if( expr._type == TypeMemPtr.TOP ) throw error("Accessing field '" + name + "' from null"); if( ptr._obj == null ) throw error("Accessing unknown field '" + name + "' from '" + ptr.str() + "'"); TypeStruct base = (TypeStruct)TYPES.get(ptr._obj._name); int idx = base==null ? -1 : base.find(name); if( idx == -1 ) throw error("Accessing unknown field '" + name + "' from '" + ptr.str() + "'"); int alias = _aliases.get(ptr._obj._name)+idx; if( match("=") ) { // Disambiguate "obj.fld==x" boolean test from "obj.fld=x" field assignment if( peek('=') ) _lexer._position--; else { Node val = parseExpression(); Type glb = base._fields[idx]._type; // Auto-truncate when storing to narrow fields val = zsMask(val,glb); store(name,alias,glb,expr,val,false); return expr; // "obj.a = expr" returns the expression while updating memory } } Type declaredType = base._fields[idx]._type; return parsePostfix(new LoadNode(name, alias, declaredType.glb(), mem(), expr).peephole()); } // zero/sign extend. "i" is limited to either classic unsigned (min==0) or // classic signed (min=minus-power-of-2); max=power-of-2-minus-1. private Node zsMask(Node val, Type t ) { if( !(val._type instanceof TypeInteger tval && t instanceof TypeInteger t0 && !tval.isa(t0)) ) { if( !(val._type instanceof TypeFloat tval && t instanceof TypeFloat t0 && !tval.isa(t0)) ) return val; // Float rounding return new RoundF32Node(val).peephole(); } if( t0._min==0 ) // Unsigned return new AndNode(val,new ConstantNode(TypeInteger.constant(t0._max)).peephole()).peephole(); // Signed extension int shift = Long.numberOfLeadingZeros(t0._max)-1; Node shf = new ConstantNode(TypeInteger.constant(shift)).peephole(); if( shf._type==TypeInteger.ZERO ) return val; return new SarNode(new ShlNode(val,shf.keep()).peephole(),shf.unkeep()).peephole(); } /** * Parse integer literal * * 
     *     integerLiteral: [1-9][0-9]* | [0]
     *     floatLiteral: [digits].[digits]?[e [digits]]?
     *
*/ private ConstantNode parseLiteral() { return (ConstantNode) new ConstantNode(_lexer.parseNumber()).peephole(); } ////////////////////////////////// // Utilities for lexical analysis // Return true and skip if "syntax" is next in the stream. private boolean match (String syntax) { return _lexer.match (syntax); } // Match must be "exact", not be followed by more id letters private boolean matchx(String syntax) { return _lexer.matchx(syntax); } // Return true and do NOT skip if 'ch' is next private boolean peek(char ch) { return _lexer.peek(ch); } private boolean peekIsId() { return _lexer.peekIsId(); } // Require and return an identifier private String requireId() { String id = _lexer.matchId(); if (id != null && !KEYWORDS.contains(id) ) return id; throw error("Expected an identifier, found '"+id+"'"); } // Require an exact match private Parser require(String syntax) { require(null, syntax); return this; } private N require(N n, String syntax) { if (match(syntax)) return n; throw errorSyntax(syntax); } RuntimeException errorSyntax(String syntax) { return error("Syntax error, expected " + syntax + ": " + _lexer.getAnyNextToken()); } public static RuntimeException error( String errorMessage ) { return new RuntimeException(errorMessage); } //////////////////////////////////// // Lexer components private static class Lexer { // Input buffer; an array of text bytes read from a file or a string private final byte[] _input; // Tracks current position in input buffer private int _position = 0; /** * Record the source text for lexing */ public Lexer(String source) { this(source.getBytes()); } /** * Direct from disk file source */ public Lexer(byte[] buf) { _input = buf; } // Very handy in the debugger, shows the unparsed program @Override public String toString() { return new String(_input, _position, _input.length - _position); } // True if at EOF private boolean isEOF() { return _position >= _input.length; } // Peek next character, or report EOF private char peek() { return isEOF() ? Character.MAX_VALUE // Special value that causes parsing to terminate : (char) _input[_position]; } private char nextChar() { char ch = peek(); _position++; return ch; } // True if a white space private boolean isWhiteSpace() { return peek() <= ' '; // Includes all the use space, tab, newline, CR } /** * Return the next non-white-space character */ private void skipWhiteSpace() { while( true ) { if( isWhiteSpace() ) _position++; // Skip // to end of line else if( _position+2 < _input.length && _input[_position ] == '/' && _input[_position+1] == '/') { _position += 2; while( !isEOF() && _input[_position] != '\n' ) _position++; } else break; } } // Return true, if we find "syntax" after skipping white space; also // then advance the cursor past syntax. // Return false otherwise, and do not advance the cursor. boolean match(String syntax) { skipWhiteSpace(); int len = syntax.length(); if (_position + len > _input.length) return false; for (int i = 0; i < len; i++) if ((char) _input[_position + i] != syntax.charAt(i)) return false; _position += len; return true; } // Match must be exact and not followed by more ID characters. // Prevents identifier "ifxy" from matching an "if" statement. boolean matchx(String syntax) { if( !match(syntax) ) return false; if( !isIdLetter(peek()) ) return true; _position -= syntax.length(); return false; } private boolean peek(char ch) { skipWhiteSpace(); return peek()==ch; } boolean peekIsId() { skipWhiteSpace(); return isIdStart(peek()); } // Return an identifier or null String matchId() { return peekIsId() ? parseId() : null; } // Used for errors String getAnyNextToken() { if (isEOF()) return ""; if (isIdStart(peek())) return parseId(); if (isNumber(peek())) return parseNumberString(); if (isPunctuation(peek())) return parsePunctuation(); return String.valueOf(peek()); } boolean isNumber(char ch) {return Character.isDigit(ch);} // Return a constant Type, either TypeInteger or TypeFloat private Type parseNumber() { int old = _position; int len = isLongOrDouble(); if( len > 0 ) { if( len > 1 && _input[old]=='0' ) throw error("Syntax error: integer values cannot start with '0'"); return TypeInteger.constant(Long.parseLong(new String(_input,old,len))); } return TypeFloat.constant(Double.parseDouble(new String(_input,old,-len))); } private String parseNumberString() { int old = _position; int len = Math.abs(isLongOrDouble()); _position += len; return new String(_input,old,len); } // Return +len that ends a long // Return -len that ends a double private int isLongOrDouble() { int old = _position; char c; while( Character.isDigit(c=nextChar()) ) ; if( !(c=='e' || c=='.') ) return --_position - old; while( Character.isDigit(c=nextChar()) || c=='e' || c=='.' ) ; return -(--_position - old); } // First letter of an identifier private boolean isIdStart(char ch) { return Character.isAlphabetic(ch) || ch == '_'; } // All characters of an identifier, e.g. "_x123" private boolean isIdLetter(char ch) { return Character.isLetterOrDigit(ch) || ch == '_'; } private String parseId() { int start = _position; while (isIdLetter(nextChar())) ; return new String(_input, start, --_position - start); } // private boolean isPunctuation(char ch) { return "=;[]<>()+-/*".indexOf(ch) != -1; } private String parsePunctuation() { int start = _position; return new String(_input, start, 1); } } }