hexo/node_modules/webpack/lib/util/binarySearchBounds.js

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2023-09-25 15:58:56 +08:00
/*
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.indexOf("c") < 0) {
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 =
"(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("");
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)
};