pouchdb-collate
Version:
Collation functions for PouchDB map/reduce
386 lines (354 loc) • 10.4 kB
JavaScript
;
Object.defineProperty(exports, '__esModule', { value: true });
function pad(str, padWith, upToLength) {
var padding = '';
var targetLength = upToLength - str.length;
/* istanbul ignore next */
while (padding.length < targetLength) {
padding += padWith;
}
return padding;
}
function padLeft(str, padWith, upToLength) {
var padding = pad(str, padWith, upToLength);
return padding + str;
}
var MIN_MAGNITUDE = -324; // verified by -Number.MIN_VALUE
var MAGNITUDE_DIGITS = 3; // ditto
var SEP = ''; // set to '_' for easier debugging
function collate(a, b) {
if (a === b) {
return 0;
}
a = normalizeKey(a);
b = normalizeKey(b);
var ai = collationIndex(a);
var bi = collationIndex(b);
if ((ai - bi) !== 0) {
return ai - bi;
}
switch (typeof a) {
case 'number':
return a - b;
case 'boolean':
return a < b ? -1 : 1;
case 'string':
return stringCollate(a, b);
}
return Array.isArray(a) ? arrayCollate(a, b) : objectCollate(a, b);
}
// couch considers null/NaN/Infinity/-Infinity === undefined,
// for the purposes of mapreduce indexes. also, dates get stringified.
function normalizeKey(key) {
switch (typeof key) {
case 'undefined':
return null;
case 'number':
if (key === Infinity || key === -Infinity || isNaN(key)) {
return null;
}
return key;
case 'object':
var origKey = key;
if (Array.isArray(key)) {
var len = key.length;
key = new Array(len);
for (var i = 0; i < len; i++) {
key[i] = normalizeKey(origKey[i]);
}
/* istanbul ignore next */
} else if (key instanceof Date) {
return key.toJSON();
} else if (key !== null) { // generic object
key = {};
for (var k in origKey) {
if (Object.prototype.hasOwnProperty.call(origKey, k)) {
var val = origKey[k];
if (typeof val !== 'undefined') {
key[k] = normalizeKey(val);
}
}
}
}
}
return key;
}
function indexify(key) {
if (key !== null) {
switch (typeof key) {
case 'boolean':
return key ? 1 : 0;
case 'number':
return numToIndexableString(key);
case 'string':
// We've to be sure that key does not contain \u0000
// Do order-preserving replacements:
// 0 -> 1, 1
// 1 -> 1, 2
// 2 -> 2, 2
/* eslint-disable no-control-regex */
return key
.replace(/\u0002/g, '\u0002\u0002')
.replace(/\u0001/g, '\u0001\u0002')
.replace(/\u0000/g, '\u0001\u0001');
/* eslint-enable no-control-regex */
case 'object':
var isArray = Array.isArray(key);
var arr = isArray ? key : Object.keys(key);
var i = -1;
var len = arr.length;
var result = '';
if (isArray) {
while (++i < len) {
result += toIndexableString(arr[i]);
}
} else {
while (++i < len) {
var objKey = arr[i];
result += toIndexableString(objKey) +
toIndexableString(key[objKey]);
}
}
return result;
}
}
return '';
}
// convert the given key to a string that would be appropriate
// for lexical sorting, e.g. within a database, where the
// sorting is the same given by the collate() function.
function toIndexableString(key) {
var zero = '\u0000';
key = normalizeKey(key);
return collationIndex(key) + SEP + indexify(key) + zero;
}
function parseNumber(str, i) {
var originalIdx = i;
var num;
var zero = str[i] === '1';
if (zero) {
num = 0;
i++;
} else {
var neg = str[i] === '0';
i++;
var numAsString = '';
var magAsString = str.substring(i, i + MAGNITUDE_DIGITS);
var magnitude = parseInt(magAsString, 10) + MIN_MAGNITUDE;
/* istanbul ignore next */
if (neg) {
magnitude = -magnitude;
}
i += MAGNITUDE_DIGITS;
while (true) {
var ch = str[i];
if (ch === '\u0000') {
break;
} else {
numAsString += ch;
}
i++;
}
numAsString = numAsString.split('.');
if (numAsString.length === 1) {
num = parseInt(numAsString, 10);
} else {
/* istanbul ignore next */
num = parseFloat(numAsString[0] + '.' + numAsString[1]);
}
/* istanbul ignore next */
if (neg) {
num = num - 10;
}
/* istanbul ignore next */
if (magnitude !== 0) {
// parseFloat is more reliable than pow due to rounding errors
// e.g. Number.MAX_VALUE would return Infinity if we did
// num * Math.pow(10, magnitude);
num = parseFloat(num + 'e' + magnitude);
}
}
return {num: num, length : i - originalIdx};
}
// move up the stack while parsing
// this function moved outside of parseIndexableString for performance
function pop(stack, metaStack) {
var obj = stack.pop();
if (metaStack.length) {
var lastMetaElement = metaStack[metaStack.length - 1];
if (obj === lastMetaElement.element) {
// popping a meta-element, e.g. an object whose value is another object
metaStack.pop();
lastMetaElement = metaStack[metaStack.length - 1];
}
var element = lastMetaElement.element;
var lastElementIndex = lastMetaElement.index;
if (Array.isArray(element)) {
element.push(obj);
} else if (lastElementIndex === stack.length - 2) { // obj with key+value
var key = stack.pop();
element[key] = obj;
} else {
stack.push(obj); // obj with key only
}
}
}
function parseIndexableString(str) {
var stack = [];
var metaStack = []; // stack for arrays and objects
var i = 0;
/*eslint no-constant-condition: ["error", { "checkLoops": false }]*/
while (true) {
var collationIndex = str[i++];
if (collationIndex === '\u0000') {
if (stack.length === 1) {
return stack.pop();
} else {
pop(stack, metaStack);
continue;
}
}
switch (collationIndex) {
case '1':
stack.push(null);
break;
case '2':
stack.push(str[i] === '1');
i++;
break;
case '3':
var parsedNum = parseNumber(str, i);
stack.push(parsedNum.num);
i += parsedNum.length;
break;
case '4':
var parsedStr = '';
/*eslint no-constant-condition: ["error", { "checkLoops": false }]*/
while (true) {
var ch = str[i];
if (ch === '\u0000') {
break;
}
parsedStr += ch;
i++;
}
// perform the reverse of the order-preserving replacement
// algorithm (see above)
/* eslint-disable no-control-regex */
parsedStr = parsedStr.replace(/\u0001\u0001/g, '\u0000')
.replace(/\u0001\u0002/g, '\u0001')
.replace(/\u0002\u0002/g, '\u0002');
/* eslint-enable no-control-regex */
stack.push(parsedStr);
break;
case '5':
var arrayElement = { element: [], index: stack.length };
stack.push(arrayElement.element);
metaStack.push(arrayElement);
break;
case '6':
var objElement = { element: {}, index: stack.length };
stack.push(objElement.element);
metaStack.push(objElement);
break;
/* istanbul ignore next */
default:
throw new Error(
'bad collationIndex or unexpectedly reached end of input: ' +
collationIndex);
}
}
}
function arrayCollate(a, b) {
var len = Math.min(a.length, b.length);
for (var i = 0; i < len; i++) {
var sort = collate(a[i], b[i]);
if (sort !== 0) {
return sort;
}
}
return (a.length === b.length) ? 0 :
(a.length > b.length) ? 1 : -1;
}
function stringCollate(a, b) {
// See: https://github.com/daleharvey/pouchdb/issues/40
// This is incompatible with the CouchDB implementation, but its the
// best we can do for now
return (a === b) ? 0 : ((a > b) ? 1 : -1);
}
function objectCollate(a, b) {
var ak = Object.keys(a), bk = Object.keys(b);
var len = Math.min(ak.length, bk.length);
for (var i = 0; i < len; i++) {
// First sort the keys
var sort = collate(ak[i], bk[i]);
if (sort !== 0) {
return sort;
}
// if the keys are equal sort the values
sort = collate(a[ak[i]], b[bk[i]]);
if (sort !== 0) {
return sort;
}
}
return (ak.length === bk.length) ? 0 :
(ak.length > bk.length) ? 1 : -1;
}
// The collation is defined by erlangs ordered terms
// the atoms null, true, false come first, then numbers, strings,
// arrays, then objects
// null/undefined/NaN/Infinity/-Infinity are all considered null
function collationIndex(x) {
var id = ['boolean', 'number', 'string', 'object'];
var idx = id.indexOf(typeof x);
//false if -1 otherwise true, but fast!!!!1
if (~idx) {
if (x === null) {
return 1;
}
if (Array.isArray(x)) {
return 5;
}
return idx < 3 ? (idx + 2) : (idx + 3);
}
/* istanbul ignore next */
if (Array.isArray(x)) {
return 5;
}
}
// conversion:
// x yyy zz...zz
// x = 0 for negative, 1 for 0, 2 for positive
// y = exponent (for negative numbers negated) moved so that it's >= 0
// z = mantisse
function numToIndexableString(num) {
if (num === 0) {
return '1';
}
// convert number to exponential format for easier and
// more succinct string sorting
var expFormat = num.toExponential().split(/e\+?/);
var magnitude = parseInt(expFormat[1], 10);
var neg = num < 0;
var result = neg ? '0' : '2';
// first sort by magnitude
// it's easier if all magnitudes are positive
var magForComparison = ((neg ? -magnitude : magnitude) - MIN_MAGNITUDE);
var magString = padLeft((magForComparison).toString(), '0', MAGNITUDE_DIGITS);
result += SEP + magString;
// then sort by the factor
var factor = Math.abs(parseFloat(expFormat[0])); // [1..10)
/* istanbul ignore next */
if (neg) { // for negative reverse ordering
factor = 10 - factor;
}
var factorStr = factor.toFixed(20);
// strip zeros from the end
factorStr = factorStr.replace(/\.?0+$/, '');
result += SEP + factorStr;
return result;
}
exports.collate = collate;
exports.normalizeKey = normalizeKey;
exports.toIndexableString = toIndexableString;
exports.parseIndexableString = parseIndexableString;