55 lines
976 B
JavaScript
55 lines
976 B
JavaScript
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var Stream = require('stream');
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function prop(propName) {
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return function (data) {
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return data[propName];
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};
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}
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module.exports = unique;
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function unique(propName) {
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var keyfn = JSON.stringify;
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if (typeof propName === 'string') {
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keyfn = prop(propName);
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} else if (typeof propName === 'function') {
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keyfn = propName;
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}
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var seen = {};
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var s = new Stream();
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s.readable = true;
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s.writable = true;
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var pipes = 0;
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s.write = function (data) {
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var key = keyfn(data);
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if (seen[key] === undefined) {
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seen[key] = true;
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s.emit('data', data);
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}
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};
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var ended = 0;
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s.end = function (data) {
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if (arguments.length) s.write(data);
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ended++;
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if (ended === pipes || pipes === 0) {
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s.writable = false;
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s.emit('end');
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}
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};
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s.destroy = function (data) {
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s.writable = false;
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};
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s.on('pipe', function () {
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pipes++;
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});
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s.on('unpipe', function () {
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pipes--;
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});
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return s;
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}
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