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| -rw-r--r-- | mod/hexit.php | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/mod/hexit.php b/mod/hexit.php new file mode 100644 index 000000000..2c65fd9d4 --- /dev/null +++ b/mod/hexit.php @@ -0,0 +1,181 @@ +<?php + + + + + + + + + + + + + +function hexit_content(&$a) { + + +$o .= <<< EOT + +<script type="text/javascript"> +/** + * 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 str_or_null(x) { + return x === null ? 'null' : x; + } + + // "1.234e+5" -> "12340" + function expandExponential(x) { + var pos = x.indexOf("e"); + if (pos === -1) pos = x.indexOf("E"); + if (pos === -1) return x; + + var base = x.substring(0, pos); + var pow = parseInt(x.substring(pos + 1), 10); + if (pow < 0) return x; // not supported. + + var dotPos = base.indexOf('.'); + if (dotPos === -1) dotPos = base.length; + + var ret = base.replace('.', ''); + while (ret.length < dotPos + pow) ret += '0'; + return ret; + } + + function boldDifference(correct, actual) { + for (var i = 0, j = 0; i < correct.length && j < actual.length; i++, j++) { + if (correct[i] !== actual[j]) { + break; + } + } + if (j < actual.length) { + return actual.substring(0, j) + '<b>' + actual.substring(j) + '</b>'; + } else { + return actual; + } + } + + function convert() { + var input = document.getElementById("in").value; + if (input) { + var aHex = str_or_null(decToHex(input)); + var aDec = str_or_null(hexToDec(input)); + var bHex = '0x' + (parseInt(input, 10)).toString(16); + var bDec = "" + expandExponential("" +parseInt(input, 16)); + + var html = '<p></p><p>To Decimal(' + input + ') = ' + aDec + '</p>'; + html += '<p>To Hex(' + input + ') = ' + aHex + '</p>'; + document.getElementById('result').innerHTML = html; + } + } + convert(); + + +</script> + + <h2>Hexit</h2> + + <p>Type in a hex or decimal string:</p> + <input type="text" size=40 id="in" onkeyup="convert()" value="" /> + <p id="result"></p> + + + +EOT; + +return $o; +} |