forked from zhurui/management
106 lines
2.9 KiB
JavaScript
106 lines
2.9 KiB
JavaScript
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'use strict';
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var fs = require('fs');
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var path = require('path');
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var detector = require('./detector');
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var handlers = {};
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var types = require('./types');
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// load all available handlers
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types.forEach(function (type) {
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handlers[type] = require('./types/' + type);
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});
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// Maximum buffer size, with a default of 128 kilobytes.
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// TO-DO: make this adaptive based on the initial signature of the image
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var MaxBufferSize = 128*1024;
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function lookup (buffer, filepath) {
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// detect the file type.. don't rely on the extension
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var type = detector(buffer, filepath);
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// find an appropriate handler for this file type
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if (type in handlers) {
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var size = handlers[type].calculate(buffer, filepath);
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if (size !== false) {
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size.type = type;
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return size;
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}
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}
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// throw up, if we don't understand the file
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throw new TypeError('unsupported file type: ' + type + ' (file: ' + filepath + ')');
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}
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function asyncFileToBuffer (filepath, callback) {
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// open the file in read only mode
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fs.open(filepath, 'r', function (err, descriptor) {
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if (err) { return callback(err); }
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var size = fs.fstatSync(descriptor).size;
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if (size <= 0){return callback(new Error("File size is not greater than 0 —— " + filepath)); }
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var bufferSize = Math.min(size, MaxBufferSize);
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var buffer = new Buffer(bufferSize);
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// read first buffer block from the file, asynchronously
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fs.read(descriptor, buffer, 0, bufferSize, 0, function (err) {
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if (err) { return callback(err); }
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// close the file, we are done
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fs.close(descriptor, function (err) {
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callback(err, buffer);
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});
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});
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});
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}
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function syncFileToBuffer (filepath) {
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// read from the file, synchronously
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var descriptor = fs.openSync(filepath, 'r');
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var size = fs.fstatSync(descriptor).size;
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var bufferSize = Math.min(size, MaxBufferSize);
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var buffer = new Buffer(bufferSize);
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fs.readSync(descriptor, buffer, 0, bufferSize, 0);
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fs.closeSync(descriptor);
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return buffer;
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}
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/**
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* @params input - buffer or relative/absolute path of the image file
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* @params callback - optional function for async detection
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*/
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module.exports = function (input, callback) {
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// Handle buffer input
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if (Buffer.isBuffer(input)) {
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return lookup(input);
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}
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// input should be a string at this point
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if (typeof input !== 'string') {
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throw new TypeError('invalid invocation');
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}
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// resolve the file path
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var filepath = path.resolve(input);
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if (typeof callback === 'function') {
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asyncFileToBuffer(filepath, function (err, buffer) {
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if (err) { return callback(err); }
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// return the dimensions
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var dimensions;
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try {
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dimensions = lookup(buffer, filepath);
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} catch (e) {
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err = e;
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}
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callback(err, dimensions);
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});
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} else {
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var buffer = syncFileToBuffer(filepath);
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return lookup(buffer, filepath);
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}
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};
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module.exports.types = types;
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