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pegjs/lib/compiler/passes/generate-bytecode.js

619 lines
15 KiB
JavaScript

"use strict";
let asts = require("../asts");
let js = require("../js");
let op = require("../opcodes");
let visitor = require("../visitor");
// Generates bytecode.
//
// Instructions
// ============
//
// Stack Manipulation
// ------------------
//
// [0] PUSH c
//
// stack.push(consts[c]);
//
// [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, consts[s].length) === consts[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, consts[s].length).toLowerCase() === consts[s]) {
// interpret(ip + 4, ip + 4 + a);
// } else {
// interpret(ip + 4 + a, ip + 4 + a + f);
// }
//
// [20] MATCH_REGEXP r, a, f, ...
//
// if (consts[r].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(consts[s]);
// currPos += consts[s].length;
//
// [23] FAIL e
//
// stack.push(FAILED);
// fail(consts[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 = consts[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--;
function generateBytecode(ast) {
let consts = [];
function addConst(value) {
let index = consts.indexOf(value);
return index === -1 ? consts.push(value) - 1 : index;
}
function addFunctionConst(params, code) {
return addConst(
"function(" + params.join(", ") + ") {" + code + "}"
);
}
function cloneEnv(env) {
let clone = {};
Object.keys(env).forEach(name => {
clone[name] = env[name];
});
return clone;
}
function buildSequence() {
return Array.prototype.concat.apply([], arguments);
}
function buildCondition(condCode, thenCode, 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) {
let params = Object.keys(env).map(name => sp - env[name]);
return [op.CALL, functionIndex, delta, params.length].concat(params);
}
function buildSimplePredicate(expression, negative, context) {
return buildSequence(
[op.PUSH_CURR_POS],
[op.SILENT_FAILS_ON],
generate(expression, {
sp: context.sp + 1,
env: cloneEnv(context.env),
action: null
}),
[op.SILENT_FAILS_OFF],
buildCondition(
[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(code, negative, context) {
let functionIndex = addFunctionConst(Object.keys(context.env), code);
return buildSequence(
[op.UPDATE_SAVED_POS],
buildCall(functionIndex, 0, context.env, context.sp),
buildCondition(
[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)
);
}
let generate = visitor.build({
grammar(node) {
node.rules.forEach(generate);
node.consts = consts;
},
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
});
},
named(node, context) {
let nameIndex = addConst(
"peg$otherExpectation(\"" + js.stringEscape(node.name) + "\")"
);
// The code generated below is slightly suboptimal because |FAIL| pushes
// to the stack, so we need to stick a |POP| in front of it. We lack a
// dedicated instruction that would just report the failure and not touch
// the stack.
return buildSequence(
[op.SILENT_FAILS_ON],
generate(node.expression, context),
[op.SILENT_FAILS_OFF],
buildCondition([op.IF_ERROR], [op.FAIL, nameIndex], [])
);
},
choice(node, context) {
function buildAlternativesCode(alternatives, context) {
return buildSequence(
generate(alternatives[0], {
sp: context.sp,
env: cloneEnv(context.env),
action: null
}),
alternatives.length > 1
? buildCondition(
[op.IF_ERROR],
buildSequence(
[op.POP],
buildAlternativesCode(alternatives.slice(1), context)
),
[]
)
: []
);
}
return buildAlternativesCode(node.alternatives, context);
},
action(node, context) {
let env = cloneEnv(context.env);
let emitCall = node.expression.type !== "sequence"
|| node.expression.elements.length === 0;
let expressionCode = generate(node.expression, {
sp: context.sp + (emitCall ? 1 : 0),
env: env,
action: node
});
let functionIndex = addFunctionConst(Object.keys(env), node.code);
return emitCall
? buildSequence(
[op.PUSH_CURR_POS],
expressionCode,
buildCondition(
[op.IF_NOT_ERROR],
buildSequence(
[op.LOAD_SAVED_POS, 1],
buildCall(functionIndex, 1, env, context.sp + 2)
),
[]
),
[op.NIP]
)
: expressionCode;
},
sequence(node, context) {
function buildElementsCode(elements, context) {
if (elements.length > 0) {
let processedCount = node.elements.length - elements.slice(1).length;
return buildSequence(
generate(elements[0], {
sp: context.sp,
env: context.env,
action: null
}),
buildCondition(
[op.IF_NOT_ERROR],
buildElementsCode(elements.slice(1), {
sp: context.sp + 1,
env: context.env,
action: context.action
}),
buildSequence(
processedCount > 1 ? [op.POP_N, processedCount] : [op.POP],
[op.POP_CURR_POS],
[op.PUSH_FAILED]
)
)
);
} else {
if (context.action) {
let functionIndex = addFunctionConst(
Object.keys(context.env),
context.action.code
);
return buildSequence(
[op.LOAD_SAVED_POS, node.elements.length],
buildCall(
functionIndex,
node.elements.length,
context.env,
context.sp
),
[op.NIP]
);
} else {
return buildSequence([op.WRAP, node.elements.length], [op.NIP]);
}
}
}
return buildSequence(
[op.PUSH_CURR_POS],
buildElementsCode(node.elements, {
sp: context.sp + 1,
env: context.env,
action: context.action
})
);
},
labeled(node, context) {
let env = cloneEnv(context.env);
context.env[node.label] = context.sp + 1;
return generate(node.expression, {
sp: context.sp,
env: env,
action: null
});
},
text(node, context) {
return buildSequence(
[op.PUSH_CURR_POS],
generate(node.expression, {
sp: context.sp + 1,
env: cloneEnv(context.env),
action: null
}),
buildCondition(
[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: cloneEnv(context.env),
action: null
}),
buildCondition(
[op.IF_ERROR],
buildSequence([op.POP], [op.PUSH_NULL]),
[]
)
);
},
zero_or_more(node, context) {
let expressionCode = generate(node.expression, {
sp: context.sp + 1,
env: cloneEnv(context.env),
action: null
});
return buildSequence(
[op.PUSH_EMPTY_ARRAY],
expressionCode,
buildAppendLoop(expressionCode),
[op.POP]
);
},
one_or_more(node, context) {
let expressionCode = generate(node.expression, {
sp: context.sp + 1,
env: cloneEnv(context.env),
action: null
});
return buildSequence(
[op.PUSH_EMPTY_ARRAY],
expressionCode,
buildCondition(
[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: cloneEnv(context.env),
action: null
});
},
semantic_and(node, context) {
return buildSemanticPredicate(node.code, false, context);
},
semantic_not(node, context) {
return buildSemanticPredicate(node.code, true, context);
},
rule_ref(node) {
return [op.RULE, asts.indexOfRule(ast, node.name)];
},
literal(node) {
if (node.value.length > 0) {
let stringIndex = addConst("\""
+ js.stringEscape(
node.ignoreCase ? node.value.toLowerCase() : node.value
)
+ "\""
);
let expectedIndex = addConst(
"peg$literalExpectation("
+ "\"" + js.stringEscape(node.value) + "\", "
+ node.ignoreCase
+ ")"
);
// 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 buildCondition(
node.ignoreCase
? [op.MATCH_STRING_IC, stringIndex]
: [op.MATCH_STRING, stringIndex],
node.ignoreCase
? [op.ACCEPT_N, node.value.length]
: [op.ACCEPT_STRING, stringIndex],
[op.FAIL, expectedIndex]
);
} else {
let stringIndex = addConst("\"\"");
return [op.PUSH, stringIndex];
}
},
class(node) {
let regexp = "/^["
+ (node.inverted ? "^" : "")
+ node.parts.map(part =>
Array.isArray(part)
? js.regexpClassEscape(part[0])
+ "-"
+ js.regexpClassEscape(part[1])
: js.regexpClassEscape(part)
).join("")
+ "]/" + (node.ignoreCase ? "i" : "");
let parts = "["
+ node.parts.map(part =>
Array.isArray(part)
? "[\"" + js.stringEscape(part[0]) + "\", \"" + js.stringEscape(part[1]) + "\"]"
: "\"" + js.stringEscape(part) + "\""
).join(", ")
+ "]";
let regexpIndex = addConst(regexp);
let expectedIndex = addConst(
"peg$classExpectation("
+ parts + ", "
+ node.inverted + ", "
+ node.ignoreCase
+ ")"
);
return buildCondition(
[op.MATCH_REGEXP, regexpIndex],
[op.ACCEPT_N, 1],
[op.FAIL, expectedIndex]
);
},
any() {
let expectedIndex = addConst("peg$anyExpectation()");
return buildCondition(
[op.MATCH_ANY],
[op.ACCEPT_N, 1],
[op.FAIL, expectedIndex]
);
}
});
generate(ast);
}
module.exports = generateBytecode;