161 lines
2.9 KiB
JavaScript
161 lines
2.9 KiB
JavaScript
/*!
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* range-parser
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* Copyright(c) 2012-2014 TJ Holowaychuk
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* Copyright(c) 2015-2016 Douglas Christopher Wilson
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* MIT Licensed
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*/
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'use strict';
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/**
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* Module exports.
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* @public
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*/
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module.exports = rangeParser;
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/**
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* Parse "Range" header `str` relative to the given file `size`.
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*
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* @param {Number} size
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* @param {String} str
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* @param {Object} [options]
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* @return {Array}
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* @public
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*/
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function rangeParser(size, str, options) {
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if (typeof str !== 'string') {
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throw new TypeError('argument str must be a string');
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}
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var index = str.indexOf('=');
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if (index === -1) {
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return -2;
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}
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// split the range string
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var arr = str.slice(index + 1).split(',');
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var ranges = [];
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// add ranges type
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ranges.type = str.slice(0, index);
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// parse all ranges
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for (var i = 0; i < arr.length; i++) {
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var range = arr[i].split('-');
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var start = parseInt(range[0], 10);
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var end = parseInt(range[1], 10);
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// -nnn
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if (isNaN(start)) {
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start = size - end;
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end = size - 1;
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// nnn-
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} else if (isNaN(end)) {
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end = size - 1;
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}
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// limit last-byte-pos to current length
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if (end > size - 1) {
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end = size - 1;
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}
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// invalid or unsatisifiable
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if (isNaN(start) || isNaN(end) || start > end || start < 0) {
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continue;
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}
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// add range
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ranges.push({
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start: start,
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end: end,
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});
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}
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if (ranges.length < 1) {
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// unsatisifiable
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return -1;
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}
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return options && options.combine ? combineRanges(ranges) : ranges;
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}
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/**
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* Combine overlapping & adjacent ranges.
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* @private
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*/
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function combineRanges(ranges) {
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var ordered = ranges.map(mapWithIndex).sort(sortByRangeStart);
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for (var j = 0, i = 1; i < ordered.length; i++) {
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var range = ordered[i];
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var current = ordered[j];
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if (range.start > current.end + 1) {
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// next range
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ordered[++j] = range;
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} else if (range.end > current.end) {
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// extend range
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current.end = range.end;
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current.index = Math.min(current.index, range.index);
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}
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}
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// trim ordered array
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ordered.length = j + 1;
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// generate combined range
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var combined = ordered.sort(sortByRangeIndex).map(mapWithoutIndex);
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// copy ranges type
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combined.type = ranges.type;
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return combined;
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}
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/**
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* Map function to add index value to ranges.
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* @private
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*/
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function mapWithIndex(range, index) {
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return {
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start: range.start,
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end: range.end,
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index: index,
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};
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}
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/**
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* Map function to remove index value from ranges.
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* @private
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*/
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function mapWithoutIndex(range) {
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return {
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start: range.start,
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end: range.end,
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};
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}
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/**
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* Sort function to sort ranges by index.
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* @private
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*/
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function sortByRangeIndex(a, b) {
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return a.index - b.index;
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}
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/**
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* Sort function to sort ranges by start position.
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* @private
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*/
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function sortByRangeStart(a, b) {
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return a.start - b.start;
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}
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