packages/pegjs/lib/compiler/passes/generate-bytecode.js
"use strict";
const util = require( "../../util" );
// Generates bytecode.
//
// Instructions
// ============
//
// Stack Manipulation
// ------------------
//
// [0] PUSH_EMPTY_STRING
//
// stack.push("");
//
// [1] PUSH_UNDEFINED
//
// stack.push(undefined);
//
// [2] PUSH_NULL
//
// stack.push(null);
//
// [3] PUSH_FAILED
//
// stack.push(FAILED);
//
// [4] PUSH_EMPTY_ARRAY
//
// stack.push([]);
//
// [5] PUSH_CURR_POS
//
// stack.push(currPos);
//
// [6] POP
//
// stack.pop();
//
// [7] POP_CURR_POS
//
// currPos = stack.pop();
//
// [8] POP_N n
//
// stack.pop(n);
//
// [9] NIP
//
// value = stack.pop();
// stack.pop();
// stack.push(value);
//
// [10] APPEND
//
// value = stack.pop();
// array = stack.pop();
// array.push(value);
// stack.push(array);
//
// [11] WRAP n
//
// stack.push(stack.pop(n));
//
// [12] TEXT
//
// stack.push(input.substring(stack.pop(), currPos));
//
// Conditions and Loops
// --------------------
//
// [13] IF t, f
//
// if (stack.top()) {
// interpret(ip + 3, ip + 3 + t);
// } else {
// interpret(ip + 3 + t, ip + 3 + t + f);
// }
//
// [14] IF_ERROR t, f
//
// if (stack.top() === FAILED) {
// interpret(ip + 3, ip + 3 + t);
// } else {
// interpret(ip + 3 + t, ip + 3 + t + f);
// }
//
// [15] IF_NOT_ERROR t, f
//
// if (stack.top() !== FAILED) {
// interpret(ip + 3, ip + 3 + t);
// } else {
// interpret(ip + 3 + t, ip + 3 + t + f);
// }
//
// [16] WHILE_NOT_ERROR b
//
// while(stack.top() !== FAILED) {
// interpret(ip + 2, ip + 2 + b);
// }
//
// Matching
// --------
//
// [17] MATCH_ANY a, f, ...
//
// if (input.length > currPos) {
// interpret(ip + 3, ip + 3 + a);
// } else {
// interpret(ip + 3 + a, ip + 3 + a + f);
// }
//
// [18] MATCH_STRING s, a, f, ...
//
// if (input.substr(currPos, literals[s].length) === literals[s]) {
// interpret(ip + 4, ip + 4 + a);
// } else {
// interpret(ip + 4 + a, ip + 4 + a + f);
// }
//
// [19] MATCH_STRING_IC s, a, f, ...
//
// if (input.substr(currPos, literals[s].length).toLowerCase() === literals[s]) {
// interpret(ip + 4, ip + 4 + a);
// } else {
// interpret(ip + 4 + a, ip + 4 + a + f);
// }
//
// [20] MATCH_CLASS c, a, f, ...
//
// if (classes[c].test(input.charAt(currPos))) {
// interpret(ip + 4, ip + 4 + a);
// } else {
// interpret(ip + 4 + a, ip + 4 + a + f);
// }
//
// [21] ACCEPT_N n
//
// stack.push(input.substring(currPos, n));
// currPos += n;
//
// [22] ACCEPT_STRING s
//
// stack.push(literals[s]);
// currPos += literals[s].length;
//
// [23] EXPECT e
//
// expect(expectations[e]);
//
// Calls
// -----
//
// [24] LOAD_SAVED_POS p
//
// savedPos = stack[p];
//
// [25] UPDATE_SAVED_POS
//
// savedPos = currPos;
//
// [26] CALL f, n, pc, p1, p2, ..., pN
//
// value = functions[f](stack[p1], ..., stack[pN]);
// stack.pop(n);
// stack.push(value);
//
// Rules
// -----
//
// [27] RULE r
//
// stack.push(parseRule(r));
//
// Failure Reporting
// -----------------
//
// [28] SILENT_FAILS_ON
//
// silentFails++;
//
// [29] SILENT_FAILS_OFF
//
// silentFails--;
//
// [38] EXPECT_NS_BEGIN
//
// expected.push({ pos: curPos, variants: [] });
//
// [39] EXPECT_NS_END invert
//
// value = expected.pop();
// if (value.pos === expected.top().pos) {
// if (invert) {
// value.variants.forEach(e => { e.not = !e.not; });
// }
// expected.top().variants.pushAll(value.variants);
// }
function generateBytecode( ast, session ) {
const op = session.opcodes;
const literals = [];
const classes = [];
const expectations = [];
const functions = [];
let generate;
function addLiteralConst( value ) {
const index = literals.indexOf( value );
return index === -1 ? literals.push( value ) - 1 : index;
}
function addClassConst( node ) {
const cls = {
value: node.parts,
inverted: node.inverted,
ignoreCase: node.ignoreCase,
};
const pattern = JSON.stringify( cls );
const index = util.findIndex( classes, c => JSON.stringify( c ) === pattern );
return index === -1 ? classes.push( cls ) - 1 : index;
}
function addExpectedConst( expected ) {
const pattern = JSON.stringify( expected );
const index = util.findIndex( expectations, e => JSON.stringify( e ) === pattern );
return index === -1 ? expectations.push( expected ) - 1 : index;
}
function addFunctionConst( predicate, params, code ) {
const func = { predicate: predicate, params: params, body: code };
const pattern = JSON.stringify( func );
const index = util.findIndex( functions, f => JSON.stringify( f ) === pattern );
return index === -1 ? functions.push( func ) - 1 : index;
}
const buildSequence = ( ...parts ) => [].concat( ...parts );
function buildCondition( match, condCode, thenCode, elseCode ) {
if ( match > 0 ) return thenCode;
if ( match < 0 ) return elseCode;
return condCode.concat(
[ thenCode.length, elseCode.length ],
thenCode,
elseCode,
);
}
function buildLoop( condCode, bodyCode ) {
return condCode.concat( [ bodyCode.length ], bodyCode );
}
function buildCall( functionIndex, delta, env, sp ) {
const params = util.values( env, value => sp - value );
return [ op.CALL, functionIndex, delta, params.length ].concat( params );
}
function buildSimplePredicate( expression, negative, context ) {
const match = expression.match|0;
return buildSequence(
[ op.PUSH_CURR_POS ],
[ op.EXPECT_NS_BEGIN ],
generate( expression, {
sp: context.sp + 1,
env: util.clone( context.env ),
action: null,
reportFailures: context.reportFailures,
} ),
[ op.EXPECT_NS_END, negative ? 1 : 0 ],
buildCondition(
negative ? -match : match,
[ negative ? op.IF_ERROR : op.IF_NOT_ERROR ],
buildSequence(
[ op.POP ],
[ negative ? op.POP : op.POP_CURR_POS ],
[ op.PUSH_UNDEFINED ],
),
buildSequence(
[ op.POP ],
[ negative ? op.POP_CURR_POS : op.POP ],
[ op.PUSH_FAILED ],
),
),
);
}
function buildSemanticPredicate( node, negative, context ) {
const functionIndex = addFunctionConst( true, Object.keys( context.env ), node.code );
return buildSequence(
[ op.UPDATE_SAVED_POS ],
buildCall( functionIndex, 0, context.env, context.sp ),
buildCondition(
node.match|0,
[ op.IF ],
buildSequence( [ op.POP ], negative ? [ op.PUSH_FAILED ] : [ op.PUSH_UNDEFINED ] ),
buildSequence( [ op.POP ], negative ? [ op.PUSH_UNDEFINED ] : [ op.PUSH_FAILED ] ),
),
);
}
function buildAppendLoop( expressionCode ) {
return buildLoop(
[ op.WHILE_NOT_ERROR ],
buildSequence( [ op.APPEND ], expressionCode ),
);
}
generate = session.buildVisitor( {
grammar( node ) {
node.rules.forEach( generate );
node.literals = literals;
node.classes = classes;
node.expectations = expectations;
node.functions = functions;
},
rule( node ) {
node.bytecode = generate( node.expression, {
sp: -1, // stack pointer
env: { }, // mapping of label names to stack positions
action: null, // action nodes pass themselves to children here
reportFailures: node.reportFailures, // if `false`, suppress generation of EXPECT opcodes
} );
},
named( node, context ) {
// Do not generate unused constant, if no need it
const nameIndex = context.reportFailures ? addExpectedConst(
{ type: "rule", value: node.name },
) : null;
const expressionCode = generate( node.expression, {
sp: context.sp,
env: context.env,
action: context.action,
reportFailures: false,
} );
// No need to disable report failures if it already disabled
return context.reportFailures ? buildSequence(
[ op.EXPECT, nameIndex ],
[ op.SILENT_FAILS_ON ],
expressionCode,
[ op.SILENT_FAILS_OFF ],
) : expressionCode;
},
choice( node, context ) {
function buildAlternativesCode( alternatives, context ) {
return buildSequence(
generate( alternatives[ 0 ], {
sp: context.sp,
env: util.clone( context.env ),
action: null,
reportFailures: context.reportFailures,
} ),
alternatives.length < 2
? []
: buildCondition(
// If alternative always match no need generate code for next alternatives
-( alternatives[ 0 ].match|0 ),
[ op.IF_ERROR ],
buildSequence(
[ op.POP ],
buildAlternativesCode( alternatives.slice( 1 ), context ),
),
[],
),
);
}
return buildAlternativesCode( node.alternatives, context );
},
action( node, context ) {
const env = util.clone( context.env );
const emitCall = node.expression.type !== "sequence" || node.expression.elements.length === 0;
const expressionCode = generate( node.expression, {
sp: context.sp + ( emitCall ? 1 : 0 ),
env: env,
action: node,
reportFailures: context.reportFailures,
} );
const match = node.expression.match|0;
const functionIndex = emitCall && match >= 0
? addFunctionConst( false, Object.keys( env ), node.code )
: null;
return emitCall === false
? expressionCode
: buildSequence(
[ op.PUSH_CURR_POS ],
expressionCode,
buildCondition(
match,
[ op.IF_NOT_ERROR ],
buildSequence(
[ op.LOAD_SAVED_POS, 1 ],
buildCall( functionIndex, 1, env, context.sp + 2 ),
),
[],
),
[ op.NIP ],
);
},
sequence( node, context ) {
const TOTAL_ELEMENTS = node.elements.length;
function buildElementsCode( elements, context ) {
if ( elements.length > 0 ) {
const processedCount = TOTAL_ELEMENTS - elements.slice( 1 ).length;
return buildSequence(
generate( elements[ 0 ], {
sp: context.sp,
env: context.env,
pluck: context.pluck,
action: null,
reportFailures: context.reportFailures,
} ),
buildCondition(
elements[ 0 ].match|0,
[ op.IF_NOT_ERROR ],
buildElementsCode( elements.slice( 1 ), {
sp: context.sp + 1,
env: context.env,
pluck: context.pluck,
action: context.action,
reportFailures: context.reportFailures,
} ),
buildSequence(
processedCount > 1 ? [ op.POP_N, processedCount ] : [ op.POP ],
[ op.POP_CURR_POS ],
[ op.PUSH_FAILED ],
),
),
);
}
if ( context.pluck.length > 0 )
return buildSequence(
[ op.PLUCK, TOTAL_ELEMENTS + 1, context.pluck.length ],
context.pluck.map( eSP => context.sp - eSP ),
);
if ( context.action )
return buildSequence(
[ op.LOAD_SAVED_POS, TOTAL_ELEMENTS ],
buildCall(
addFunctionConst( // functionIndex
false,
Object.keys( context.env ),
context.action.code,
),
TOTAL_ELEMENTS + 1,
context.env,
context.sp,
),
);
return buildSequence( [ op.WRAP, TOTAL_ELEMENTS ], [ op.NIP ] );
}
return buildSequence(
[ op.PUSH_CURR_POS ],
buildElementsCode( node.elements, {
sp: context.sp + 1,
env: context.env,
pluck: [],
action: context.action,
reportFailures: context.reportFailures,
} ),
);
},
labeled( node, context ) {
let env = context.env;
const label = node.label;
const sp = context.sp + 1;
if ( label !== null ) {
env = util.clone( context.env );
context.env[ label ] = sp;
}
if ( context.pluck && node.pick )
context.pluck.push( sp );
return generate( node.expression, {
sp: context.sp,
env: env,
action: null,
reportFailures: context.reportFailures,
} );
},
text( node, context ) {
return buildSequence(
[ op.PUSH_CURR_POS ],
generate( node.expression, {
sp: context.sp + 1,
env: util.clone( context.env ),
action: null,
reportFailures: context.reportFailures,
} ),
buildCondition(
node.expression.match|0,
[ op.IF_NOT_ERROR ],
buildSequence( [ op.POP ], [ op.TEXT ] ),
[ op.NIP ],
),
);
},
simple_and( node, context ) {
return buildSimplePredicate( node.expression, false, context );
},
simple_not( node, context ) {
return buildSimplePredicate( node.expression, true, context );
},
optional( node, context ) {
return buildSequence(
generate( node.expression, {
sp: context.sp,
env: util.clone( context.env ),
action: null,
reportFailures: context.reportFailures,
} ),
buildCondition(
// If expression always match no need replace FAILED to NULL
-( node.expression.match|0 ),
[ op.IF_ERROR ],
buildSequence( [ op.POP ], [ op.PUSH_NULL ] ),
[],
),
);
},
zero_or_more( node, context ) {
const expressionCode = generate( node.expression, {
sp: context.sp + 1,
env: util.clone( context.env ),
action: null,
reportFailures: context.reportFailures,
} );
return buildSequence(
[ op.PUSH_EMPTY_ARRAY ],
expressionCode,
buildAppendLoop( expressionCode ),
[ op.POP ],
);
},
one_or_more( node, context ) {
const expressionCode = generate( node.expression, {
sp: context.sp + 1,
env: util.clone( context.env ),
action: null,
reportFailures: context.reportFailures,
} );
return buildSequence(
[ op.PUSH_EMPTY_ARRAY ],
expressionCode,
buildCondition(
node.expression.match|0,
[ op.IF_NOT_ERROR ],
buildSequence( buildAppendLoop( expressionCode ), [ op.POP ] ),
buildSequence( [ op.POP ], [ op.POP ], [ op.PUSH_FAILED ] ),
),
);
},
group( node, context ) {
return generate( node.expression, {
sp: context.sp,
env: util.clone( context.env ),
action: null,
reportFailures: context.reportFailures,
} );
},
semantic_and( node, context ) {
return buildSemanticPredicate( node, false, context );
},
semantic_not( node, context ) {
return buildSemanticPredicate( node, true, context );
},
rule_ref( node ) {
return [ op.RULE, ast.indexOfRule( node.name ) ];
},
literal( node, context ) {
if ( node.value.length > 0 ) {
const match = node.match|0;
const needConst = match === 0 || ( match > 0 && ! node.ignoreCase );
const stringIndex = needConst ? addLiteralConst(
node.ignoreCase ? node.value.toLowerCase() : node.value,
) : null;
// Do not generate unused constant, if no need it
const expectedIndex = context.reportFailures ? addExpectedConst( {
type: "literal",
value: node.value,
ignoreCase: node.ignoreCase,
} ) : null;
// For case-sensitive strings the value must match the beginning of the
// remaining input exactly. As a result, we can use |ACCEPT_STRING| and
// save one |substr| call that would be needed if we used |ACCEPT_N|.
return buildSequence(
context.reportFailures ? [ op.EXPECT, expectedIndex ] : [],
buildCondition(
match,
node.ignoreCase
? [ op.MATCH_STRING_IC, stringIndex ]
: [ op.MATCH_STRING, stringIndex ],
node.ignoreCase
? [ op.ACCEPT_N, node.value.length ]
: [ op.ACCEPT_STRING, stringIndex ],
[ op.PUSH_FAILED ],
),
);
}
return [ op.PUSH_EMPTY_STRING ];
},
class( node, context ) {
const match = node.match|0;
const classIndex = match === 0 ? addClassConst( node ) : null;
// Do not generate unused constant, if no need it
const expectedIndex = context.reportFailures ? addExpectedConst( {
type: "class",
value: node.parts,
inverted: node.inverted,
ignoreCase: node.ignoreCase,
} ) : null;
return buildSequence(
context.reportFailures ? [ op.EXPECT, expectedIndex ] : [],
buildCondition(
match,
[ op.MATCH_CLASS, classIndex ],
[ op.ACCEPT_N, 1 ],
[ op.PUSH_FAILED ],
),
);
},
any( node, context ) {
// Do not generate unused constant, if no need it
const expectedIndex = context.reportFailures
? addExpectedConst( { type: "any" } )
: null;
return buildSequence(
context.reportFailures ? [ op.EXPECT, expectedIndex ] : [],
buildCondition(
node.match|0,
[ op.MATCH_ANY ],
[ op.ACCEPT_N, 1 ],
[ op.PUSH_FAILED ],
),
);
},
} );
generate( ast );
}
module.exports = generateBytecode;