source: imaps-frontend/node_modules/webpack/lib/util/binarySearchBounds.js@ 79a0317

/*
        MIT License http://www.opensource.org/licenses/mit-license.php
        Author Mikola Lysenko @mikolalysenko
*/

"use strict";

/* cspell:disable-next-line */
// Refactor: Peter Somogyvari @petermetz

/** @typedef {">=" | "<=" | "<" | ">" | "-" } BinarySearchPredicate */
/** @typedef {"GE" | "GT" | "LT" | "LE" | "EQ" } SearchPredicateSuffix */

/**
 * Helper function for compiling binary search functions.
 *
 * The generated code uses a while loop to repeatedly divide the search interval
 * in half until the desired element is found, or the search interval is empty.
 *
 * The following is an example of a generated function for calling `compileSearch("P", "c(x,y)<=0", true, ["y", "c"], false)`:
 *
 * ```js
 * function P(a,l,h,y,c){var i=l-1;while(l<=h){var m=(l+h)>>>1,x=a[m];if(c(x,y)<=0){i=m;l=m+1}else{h=m-1}}return i};
 * ```
 * @param {string} funcName The name of the function to be compiled.
 * @param {string} predicate The predicate / comparison operator to be used in the binary search.
 * @param {boolean} reversed Whether the search should be reversed.
 * @param {string[]} extraArgs Extra arguments to be passed to the function.
 * @param {boolean=} earlyOut Whether the search should return as soon as a match is found.
 * @returns {string} The compiled binary search function.
 */
const compileSearch = (funcName, predicate, reversed, extraArgs, earlyOut) => {
        const code = [
                "function ",
                funcName,
                "(a,l,h,",
                extraArgs.join(","),
                "){",
                earlyOut ? "" : "var i=",
                reversed ? "l-1" : "h+1",
                ";while(l<=h){var m=(l+h)>>>1,x=a[m]"
        ];

        if (earlyOut) {
                if (!predicate.includes("c")) {
                        code.push(";if(x===y){return m}else if(x<=y){");
                } else {
                        code.push(";var p=c(x,y);if(p===0){return m}else if(p<=0){");
                }
        } else {
                code.push(";if(", predicate, "){i=m;");
        }
        if (reversed) {
                code.push("l=m+1}else{h=m-1}");
        } else {
                code.push("h=m-1}else{l=m+1}");
        }
        code.push("}");
        if (earlyOut) {
                code.push("return -1};");
        } else {
                code.push("return i};");
        }
        return code.join("");
};

/**
 * This helper functions generate code for two binary search functions:
 * A(): Performs a binary search on an array using the comparison operator specified.
 * P(): Performs a binary search on an array using a _custom comparison function_
 * `c(x,y)` **and** comparison operator specified by `predicate`.
 * @param {BinarySearchPredicate} predicate The predicate / comparison operator to be used in the binary search.
 * @param {boolean} reversed Whether the search should be reversed.
 * @param {SearchPredicateSuffix} suffix The suffix to be used in the function name.
 * @param {boolean=} earlyOut Whether the search should return as soon as a match is found.
 * @returns {Function} The compiled binary search function.
 */
const compileBoundsSearch = (predicate, reversed, suffix, earlyOut) => {
        const arg1 = compileSearch("A", `x${predicate}y`, reversed, ["y"], earlyOut);

        const arg2 = compileSearch(
                "P",
                `c(x,y)${predicate}0`,
                reversed,
                ["y", "c"],
                earlyOut
        );

        const fnHeader = "function dispatchBinarySearch";

        const fnBody =
                // eslint-disable-next-line no-multi-str
                "(a,y,c,l,h){\
if(typeof(c)==='function'){\
return P(a,(l===void 0)?0:l|0,(h===void 0)?a.length-1:h|0,y,c)\
}else{\
return A(a,(c===void 0)?0:c|0,(l===void 0)?a.length-1:l|0,y)\
}}\
return dispatchBinarySearch";

        const fnArgList = [arg1, arg2, fnHeader, suffix, fnBody, suffix];
        const fnSource = fnArgList.join("");
        // eslint-disable-next-line no-new-func
        const result = new Function(fnSource);
        return result();
};

/**
 * These functions are used to perform binary searches on arrays.
 * @example
 * ```js
 * const { gt, le} = require("./binarySearchBounds");
 * const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
 *
 * // Find the index of the first element greater than 5
 * const index1 = gt(arr, 5); // index1 === 3
 *
 * // Find the index of the first element less than or equal to 5
 * const index2 = le(arr, 5); // index2 === 4
 * ```
 */
module.exports = {
        ge: compileBoundsSearch(">=", false, "GE"),
        gt: compileBoundsSearch(">", false, "GT"),
        lt: compileBoundsSearch("<", true, "LT"),
        le: compileBoundsSearch("<=", true, "LE"),
        eq: compileBoundsSearch("-", true, "EQ", true)
};