ce4c83ff
 wxy
初始提交
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'use strict';
var fs = require('fs');
var path = require('path');
var detector = require('./detector');
var handlers = {};
var types = require('./types');
// load all available handlers
types.forEach(function (type) {
handlers[type] = require('./types/' + type);
});
// Maximum buffer size, with a default of 128 kilobytes.
// TO-DO: make this adaptive based on the initial signature of the image
var MaxBufferSize = 128*1024;
function lookup (buffer, filepath) {
// detect the file type.. don't rely on the extension
var type = detector(buffer, filepath);
// find an appropriate handler for this file type
if (type in handlers) {
var size = handlers[type].calculate(buffer, filepath);
if (size !== false) {
size.type = type;
return size;
}
}
// throw up, if we don't understand the file
throw new TypeError('unsupported file type: ' + type + ' (file: ' + filepath + ')');
}
function asyncFileToBuffer (filepath, callback) {
// open the file in read only mode
fs.open(filepath, 'r', function (err, descriptor) {
if (err) { return callback(err); }
var size = fs.fstatSync(descriptor).size;
if (size <= 0){return callback(new Error("File size is not greater than 0 —— " + filepath)); }
var bufferSize = Math.min(size, MaxBufferSize);
var buffer = new Buffer(bufferSize);
// read first buffer block from the file, asynchronously
fs.read(descriptor, buffer, 0, bufferSize, 0, function (err) {
if (err) { return callback(err); }
// close the file, we are done
fs.close(descriptor, function (err) {
callback(err, buffer);
});
});
});
}
function syncFileToBuffer (filepath) {
// read from the file, synchronously
var descriptor = fs.openSync(filepath, 'r');
var size = fs.fstatSync(descriptor).size;
var bufferSize = Math.min(size, MaxBufferSize);
var buffer = new Buffer(bufferSize);
fs.readSync(descriptor, buffer, 0, bufferSize, 0);
fs.closeSync(descriptor);
return buffer;
}
/**
* @params input - buffer or relative/absolute path of the image file
* @params callback - optional function for async detection
*/
module.exports = function (input, callback) {
// Handle buffer input
if (Buffer.isBuffer(input)) {
return lookup(input);
}
// input should be a string at this point
if (typeof input !== 'string') {
throw new TypeError('invalid invocation');
}
// resolve the file path
var filepath = path.resolve(input);
if (typeof callback === 'function') {
asyncFileToBuffer(filepath, function (err, buffer) {
if (err) { return callback(err); }
// return the dimensions
var dimensions;
try {
dimensions = lookup(buffer, filepath);
} catch (e) {
err = e;
}
callback(err, dimensions);
});
} else {
var buffer = syncFileToBuffer(filepath);
return lookup(buffer, filepath);
}
};
module.exports.types = types;
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