366 lines
10 KiB
JavaScript
366 lines
10 KiB
JavaScript
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// @ts-check
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"use strict";
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const { SourceNode } = require("source-map-generator");
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const GrammarLocation = require("../grammar-location.js");
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/**
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* @typedef {(string|SourceNode)[]} SourceArray
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*/
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/** Utility class that helps generating code for C-like languages. */
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class Stack {
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/**
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* Constructs the helper for tracking variable slots of the stack virtual machine
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*
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* @param {string} ruleName The name of rule that will be used in error messages
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* @param {string} varName The prefix for generated names of variables
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* @param {string} type The type of the variables. For JavaScript there are `var` or `let`
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* @param {number[]} bytecode Bytecode for error messages
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*/
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constructor(ruleName, varName, type, bytecode) {
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/** Last used variable in the stack. */
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this.sp = -1;
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/** Maximum stack size. */
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this.maxSp = -1;
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this.varName = varName;
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this.ruleName = ruleName;
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this.type = type;
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this.bytecode = bytecode;
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/**
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* Map from stack index, to label targetting that index
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* @type {Record<number,{label:string,location:import("../peg.js").LocationRange}>}
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*/
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this.labels = {};
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/**
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* Stack of in-flight source mappings
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* @type {[SourceArray, number, PEG.LocationRange][]}
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*/
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this.sourceMapStack = [];
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}
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/**
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* Returns name of the variable at the index `i`.
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*
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* @param {number} i Index for which name must be generated
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* @return {string} Generated name
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*
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* @throws {RangeError} If `i < 0`, which means a stack underflow (there are more `pop`s than `push`es)
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*/
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name(i) {
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if (i < 0) {
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throw new RangeError(
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`Rule '${this.ruleName}': The variable stack underflow: attempt to use a variable '${this.varName}<x>' at an index ${i}.\nBytecode: ${this.bytecode}`
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);
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}
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return this.varName + i;
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}
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/**
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*
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* @param {PEG.LocationRange} location
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* @param {SourceArray} chunks
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* @param {string} [name]
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* @returns
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*/
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static sourceNode(location, chunks, name) {
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const start = GrammarLocation.offsetStart(location);
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return new SourceNode(
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start.line,
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start.column ? start.column - 1 : null,
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String(location.source),
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chunks,
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name
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);
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}
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/**
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* Assigns `exprCode` to the new variable in the stack, returns generated code.
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* As the result, the size of a stack increases on 1.
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*
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* @param {string} exprCode Any expression code that must be assigned to the new variable in the stack
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* @return {string|SourceNode} Assignment code
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*/
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push(exprCode) {
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if (++this.sp > this.maxSp) { this.maxSp = this.sp; }
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const label = this.labels[this.sp];
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const code = [this.name(this.sp), " = ", exprCode, ";"];
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if (label) {
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if (this.sourceMapStack.length) {
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const sourceNode = Stack.sourceNode(
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label.location,
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code.splice(0, 2),
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label.label
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);
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const { parts, location } = this.sourceMapPopInternal();
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const newLoc = (location.start.offset < label.location.end.offset)
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? {
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start: label.location.end,
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end: location.end,
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source: location.source,
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}
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: location;
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const outerNode = Stack.sourceNode(
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newLoc,
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code.concat("\n")
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);
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this.sourceMapStack.push([parts, parts.length + 1, location]);
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return new SourceNode(
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null,
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null,
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label.location.source,
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[sourceNode, outerNode]
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);
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} else {
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return Stack.sourceNode(
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label.location,
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code.concat("\n")
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);
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}
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}
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return code.join("");
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}
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/**
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* @overload
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* @param {undefined} [n]
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* @return {string}
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*/
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/**
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* @overload
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* @param {number} n
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* @return {string[]}
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*/
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/**
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* Returns name or `n` names of the variable(s) from the top of the stack.
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*
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* @param {number} [n] Quantity of variables, which need to be removed from the stack
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* @returns {string[]|string} Generated name(s). If n is defined then it returns an
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* array of length `n`
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*
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* @throws {RangeError} If the stack underflow (there are more `pop`s than `push`es)
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*/
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pop(n) {
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if (n !== undefined) {
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this.sp -= n;
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return Array.from({ length: n }, (v, i) => this.name(this.sp + 1 + i));
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}
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return this.name(this.sp--);
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}
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/**
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* Returns name of the first free variable. The same as `index(0)`.
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*
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* @return {string} Generated name
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*
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* @throws {RangeError} If the stack is empty (there was no `push`'s yet)
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*/
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top() { return this.name(this.sp); }
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/**
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* Returns name of the variable at index `i`.
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*
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* @param {number} i Index of the variable from top of the stack
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* @return {string} Generated name
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*
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* @throws {RangeError} If `i < 0` or more than the stack size
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*/
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index(i) {
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if (i < 0) {
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throw new RangeError(
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`Rule '${this.ruleName}': The variable stack overflow: attempt to get a variable at a negative index ${i}.\nBytecode: ${this.bytecode}`
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);
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}
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return this.name(this.sp - i);
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}
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/**
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* Returns variable name that contains result (bottom of the stack).
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*
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* @return {string} Generated name
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*
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* @throws {RangeError} If the stack is empty (there was no `push`es yet)
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*/
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result() {
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if (this.maxSp < 0) {
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throw new RangeError(
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`Rule '${this.ruleName}': The variable stack is empty, can't get the result.\nBytecode: ${this.bytecode}`
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);
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}
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return this.name(0);
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}
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/**
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* Returns defines of all used variables.
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*
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* @return {string} Generated define variable expression with the type `this.type`.
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* If the stack is empty, returns empty string
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*/
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defines() {
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if (this.maxSp < 0) {
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return "";
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}
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return this.type + " " + Array.from({ length: this.maxSp + 1 }, (v, i) => this.name(i)).join(", ") + ";";
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}
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/**
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* Checks that code in the `generateIf` and `generateElse` move the stack pointer in the same way.
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*
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* @template T
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* @param {number} pos Opcode number for error messages
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* @param {() => T} generateIf First function that works with this stack
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* @param {(() => T)|null} [generateElse] Second function that works with this stack
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* @return {T[]}
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*
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* @throws {Error} If `generateElse` is defined and the stack pointer moved differently in the
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* `generateIf` and `generateElse`
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*/
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checkedIf(pos, generateIf, generateElse) {
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const baseSp = this.sp;
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const ifResult = generateIf();
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if (!generateElse) {
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return [ifResult];
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}
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const thenSp = this.sp;
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this.sp = baseSp;
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const elseResult = generateElse();
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if (thenSp !== this.sp) {
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throw new Error(
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"Rule '" + this.ruleName + "', position " + pos + ": "
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+ "Branches of a condition can't move the stack pointer differently "
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+ "(before: " + baseSp + ", after then: " + thenSp + ", after else: " + this.sp + "). "
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+ "Bytecode: " + this.bytecode
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);
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}
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return [ifResult, elseResult];
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}
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/**
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* Checks that code in the `generateBody` do not move stack pointer.
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*
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* @template T
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* @param {number} pos Opcode number for error messages
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* @param {() => T} generateBody Function that works with this stack
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* @return {T}
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*
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* @throws {Error} If `generateBody` move the stack pointer (if it contains unbalanced `push`es and `pop`s)
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*/
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checkedLoop(pos, generateBody) {
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const baseSp = this.sp;
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const result = generateBody();
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if (baseSp !== this.sp) {
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throw new Error(
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"Rule '" + this.ruleName + "', position " + pos + ": "
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+ "Body of a loop can't move the stack pointer "
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+ "(before: " + baseSp + ", after: " + this.sp + "). "
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+ "Bytecode: " + this.bytecode
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);
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}
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return result;
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}
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/**
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*
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* @param {SourceArray} parts
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* @param {PEG.LocationRange} location
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*/
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sourceMapPush(parts, location) {
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if (this.sourceMapStack.length) {
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const top = this.sourceMapStack[this.sourceMapStack.length - 1];
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// If the current top of stack starts at the same location as
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// the about to be pushed item, we should update its start location to
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// be past the new one. Otherwise any code it generates will
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// get allocated to the inner node.
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if (top[2].start.offset === location.start.offset
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&& top[2].end.offset > location.end.offset) {
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top[2] = {
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start: location.end,
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end: top[2].end,
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source: top[2].source,
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};
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}
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}
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this.sourceMapStack.push([
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parts,
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parts.length,
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location,
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]);
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}
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/**
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* @returns {{parts:SourceArray,location:PEG.LocationRange}}
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*/
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sourceMapPopInternal() {
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const elt = this.sourceMapStack.pop();
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if (!elt) {
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throw new RangeError(
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`Rule '${this.ruleName}': Attempting to pop an empty source map stack.\nBytecode: ${this.bytecode}`
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);
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}
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const [
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parts,
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index,
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location,
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] = elt;
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const chunks = parts.splice(index).map(
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chunk => (chunk instanceof SourceNode
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? chunk
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: chunk + "\n"
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)
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);
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if (chunks.length) {
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const start = GrammarLocation.offsetStart(location);
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parts.push(new SourceNode(
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start.line,
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start.column - 1,
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String(location.source),
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chunks
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));
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}
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return { parts, location };
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}
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/**
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* @param {number} [offset]
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* @returns {[SourceArray, number, PEG.LocationRange]|undefined}
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*/
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sourceMapPop(offset) {
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const { location } = this.sourceMapPopInternal();
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if (this.sourceMapStack.length
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&& location.end.offset
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< this.sourceMapStack[this.sourceMapStack.length - 1][2].end.offset) {
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const { parts, location: outer } = this.sourceMapPopInternal();
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const newLoc = (outer.start.offset < location.end.offset)
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? {
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start: location.end,
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end: outer.end,
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source: outer.source,
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}
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: outer;
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this.sourceMapStack.push([
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parts,
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parts.length + (offset || 0),
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newLoc,
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]);
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}
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return undefined;
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}
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}
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module.exports = Stack;
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