问题描述
如题，想要实现如下功能，入参可以是代表16进制的字符串或者一个buffer，是小端的
// return {@string}function converHexStrToDecStrLittleEnd(strOrBuffer){ hexToDecLE(strOrBuffer)}//test case assert( converHexStrToDecStrLittleEnd(’a4fb02129a907c4a’) === ’5367323847320337316’ )
求 converHexStrToDecStrLittleEnd 这个函数怎么实现
直接用Buffer.from(’a4fb02129a907c4a’,’hex’).readUIntLE(0,8)只能得到5367323847320337000明显是溢出了
======最后结果如下========================================
/** * A function for converting hex <-> dec w/o loss of precision. * * The problem is that parseInt('0x12345...') isn’t precise enough to convert * 64-bit integers correctly. * * Internally, this uses arrays to encode decimal digits starting with the least * significant: * 8 = [8] * 16 = [6, 1] * 1024 = [4, 2, 0, 1] */// Adds two arrays for the given base (10 or 16), returning the result.// This turns out to be the only 'primitive' operation we need.function add(x, y, base) { var z = []; var n = Math.max(x.length, y.length); var carry = 0; var i = 0; while (i < n || carry) { var xi = i < x.length ? x[i] : 0; var yi = i < y.length ? y[i] : 0; var zi = carry + xi + yi; z.push(zi % base); carry = Math.floor(zi / base); i++; } return z;}// Returns a*x, where x is an array of decimal digits and a is an ordinary// JavaScript number. base is the number base of the array x.function multiplyByNumber(num, x, base) { if (num < 0) return null; if (num == 0) return []; var result = []; var power = x; while (true) { if (num & 1) { result = add(result, power, base); } num = num >> 1; if (num === 0) break; power = add(power, power, base); } return result;}function parseToDigitsArray(str, base) { var digits = str.split(’’); var ary = []; for (var i = digits.length - 1; i >= 0; i--) { var n = parseInt(digits[i], base); if (isNaN(n)) return null; ary.push(n); } return ary;}function convertBase(str, fromBase, toBase) { var digits = parseToDigitsArray(str, fromBase); if (digits === null) return null; var outArray = []; var power = [1]; for (var i = 0; i < digits.length; i++) { // invariant: at this point, fromBase^i = power if (digits[i]) { outArray = add(outArray, multiplyByNumber(digits[i], power, toBase), toBase); } power = multiplyByNumber(fromBase, power, toBase); } var out = ’’; for (var i = outArray.length - 1; i >= 0; i--) { out += outArray[i].toString(toBase); } return out;}function decToHex(decStr) { var hex = convertBase(decStr, 10, 16); return hex ? ’0x’ + hex : null;}function hexToDec(hexStr) { if (hexStr.substring(0, 2) === ’0x’) hexStr = hexStr.substring(2); hexStr = hexStr.toLowerCase(); return convertBase(hexStr, 16, 10);}function hexToDecLE(hexStr) { var len = hexStr.length,arr = []; for(var i=len;i>0;i-=2){arr.push(hexStr.slice(i-2,i)) } return hexToDec(arr.join(’’));}hexToDecLE(’a4fb02129a907c4a’);
问题解答
回答1：js扩展 http://www.danvk.org/hex2dec.html
/** * A function for converting hex <-> dec w/o loss of precision. * * The problem is that parseInt('0x12345...') isn’t precise enough to convert * 64-bit integers correctly. * * Internally, this uses arrays to encode decimal digits starting with the least * significant: * 8 = [8] * 16 = [6, 1] * 1024 = [4, 2, 0, 1] */// Adds two arrays for the given base (10 or 16), returning the result.// This turns out to be the only 'primitive' operation we need.function add(x, y, base) { var z = []; var n = Math.max(x.length, y.length); var carry = 0; var i = 0; while (i < n || carry) { var xi = i < x.length ? x[i] : 0; var yi = i < y.length ? y[i] : 0; var zi = carry + xi + yi; z.push(zi % base); carry = Math.floor(zi / base); i++; } return z;}// Returns a*x, where x is an array of decimal digits and a is an ordinary// JavaScript number. base is the number base of the array x.function multiplyByNumber(num, x, base) { if (num < 0) return null; if (num == 0) return []; var result = []; var power = x; while (true) { if (num & 1) { result = add(result, power, base); } num = num >> 1; if (num === 0) break; power = add(power, power, base); } return result;}function parseToDigitsArray(str, base) { var digits = str.split(’’); var ary = []; for (var i = digits.length - 1; i >= 0; i--) { var n = parseInt(digits[i], base); if (isNaN(n)) return null; ary.push(n); } return ary;}function convertBase(str, fromBase, toBase) { var digits = parseToDigitsArray(str, fromBase); if (digits === null) return null; var outArray = []; var power = [1]; for (var i = 0; i < digits.length; i++) { // invariant: at this point, fromBase^i = power if (digits[i]) { outArray = add(outArray, multiplyByNumber(digits[i], power, toBase), toBase); } power = multiplyByNumber(fromBase, power, toBase); } var out = ’’; for (var i = outArray.length - 1; i >= 0; i--) { out += outArray[i].toString(toBase); } return out;}function decToHex(decStr) { var hex = convertBase(decStr, 10, 16); return hex ? ’0x’ + hex : null;}function hexToDec(hexStr) { if (hexStr.substring(0, 2) === ’0x’) hexStr = hexStr.substring(2); hexStr = hexStr.toLowerCase(); return convertBase(hexStr, 16, 10);}
调用:
console.log( hexToDec('a4fb02129a907c4a') );// '11888097920300383306'// parseInt会溢出被截短console.log( parseInt('a4fb02129a907c4a' ,16));// 11888097920300384000
Python的结果
print(int('a4fb02129a907c4a', 16))# 11888097920300383306
