nodejs:
var test = 'VdEU+Q2J5qfwsn9xshAcEImDSnxTR8RkRLlLmyNaeos=';
var result = new Buffer(test, 'base64').toString()
//var buf = Buffer.from(test, 'base64');
//var result = new Buffer(test, 'base64').toString("utf8");
var fs = require('fs');
fs.writeFile("test.txt",result,function(e){//会先清空原先的内容
if(e) throw e;
})
python:
import base64
result = base64.b64decode('VdEU+Q2J5qfwsn9xshAcEImDSnxTR8RkRLlLmyNaeos=')
file_object = open('thefile.txt', 'w')
file_object.write(result)
file_object.close( )
c++: (I use libcef's base library's base64):
const std::string kText = "VdEU+Q2J5qfwsn9xshAcEImDSnxTR8RkRLlLmyNaeos=";
std::string encoded;
base::Base64Decode(kText, &encoded);
FILE *pFile = fopen("1.txt", "wb+");
fwrite(encoded.c_str(), encoded.length(), 1, pFile);
fclose(pFile);
the result is python c++ is the same, but nodejs is different
You simply need to not call toString():
var result = new Buffer(test, 'base64');
Then the Node code does the same as the others.
Related
I trying to convert pdf file to pdfa3 file by using PDFTron.
I added current url_path.
the my code below:
var input_url = './utils/';
var input_filename = 'test.pdf';
var output_filename = 'test_pdfa.pdf';
var convert = true;
var pwd = '';
var exceptions;
var max_ref_objs = 10;
var url_input = input_url + input_filename;
console.log('Converting input document: ' + input_filename);
var pdfa = await PDFNet.PDFACompliance.createFromUrl(true, url_input, '', PDFNet.PDFACompliance.Conformance.e_Level2B, exceptions, max_ref_objs);
get error:
'NetworkError(Unsupported protocol ${this._url.protocol})',
Does anyone know what the problem is,
And why doesn't it recognize the location?
I changed the code to :
here.
Now it's working!!
The following code snippet is working in Node 0.12.18 (replace Buffer.from to new Buffer) but it's not working with the latest Node version (7.10.0)
Can anybody explain me why this is happening?? Anything is missing in below code.
/* Node.js */
var crypto = require('crypto');
var algorithm = 'aes-256-ctr';
var data = "Dhanet-Kalan-Chittorgarh"
var encryption_key = "VHUz1dxrhsowwEYGqUnPcE4wvAyz7Vmb";
var encryption_data = _encrypt()
console.log('data for encryption :: ' + data);
console.log('encrypted data :: ' + encryption_data);
console.log('decrypted data :: ' + _decrypt(encryption_data));
function _decrypt(_encryption_data){
var decipher, dec, chunks, itr_str;
// remove itr string
itr_str = _encryption_data.substring(_encryption_data.length-24);
_encryption_data = _encryption_data.substring(0, _encryption_data.length-24);
decipher = crypto.createDecipheriv(algorithm, encryption_key, Buffer.from(itr_str, "base64"));
chunks = []
chunks.push( decipher.update( Buffer.from(_encryption_data, "base64").toString("binary")) );
chunks.push( decipher.final('binary') );
dec = chunks.join("");
dec = Buffer.from(dec, "binary").toString("utf-8");
return dec;
}
function _encrypt(){
//random alpha-numeric string
var itr_str = Buffer.from(randomString(16)).toString('base64') ; // "3V5eo6XrkTtDFMz2QrF3og==";
var cipher = crypto.createCipheriv(algorithm, encryption_key, Buffer.from(itr_str, "base64"));
var chunks = [];
chunks.push(cipher.update( Buffer.from(data), 'utf8', 'base64'));
chunks.push(cipher.final('base64'));
var crypted = chunks.join('');
crypted = crypted.concat(itr_str);
return crypted;
}
function randomString(len, an)
{
an = an&&an.toLowerCase();
var str="", i=0, min=an=="a"?10:0, max=an=="n"?10:62;
for(;i++<len;){
var r = Math.random()*(max-min)+min <<0;
str += String.fromCharCode(r+=r>9?r<36?55:61:48);
}
return str;
}
Node.js v6 introduced some backward-incompatible changes to crypto which are causing this.
I've documented the exact reason in this answer, but because that question is related to hashing I'm reluctant to close your question as a duplicate.
The fix is similar, though (you need to pass binary as encoding for decipher.update(), otherwise it will default to utf-8):
chunks.push( decipher.update( Buffer.from(_encryption_data, "base64"), 'binary') );
I want to use Node.js to create a simple logging system which prints a line before the past line into a .txt file. However, I don't know how the file system functionality from Node.js works.
Can someone explain it?
Inserting data into the middle of a text file is not a simple task. If possible, you should append it to the end of your file.
The easiest way to append data some text file is to use build-in fs.appendFile(filename, data[, options], callback) function from fs module:
var fs = require('fs')
fs.appendFile('log.txt', 'new data', function (err) {
if (err) {
// append failed
} else {
// done
}
})
But if you want to write data to log file several times, then it'll be best to use fs.createWriteStream(path[, options]) function instead:
var fs = require('fs')
var logger = fs.createWriteStream('log.txt', {
flags: 'a' // 'a' means appending (old data will be preserved)
})
logger.write('some data') // append string to your file
logger.write('more data') // again
logger.write('and more') // again
Node will keep appending new data to your file every time you'll call .write, until your application will be closed, or until you'll manually close the stream calling .end:
logger.end() // close string
Note that logger.write in the above example does not write to a new line. To write data to a new line:
var writeLine = (line) => logger.write(`\n${line}`);
writeLine('Data written to a new line');
Simply use fs module and something like this:
fs.appendFile('server.log', 'string to append', function (err) {
if (err) return console.log(err);
console.log('Appended!');
});
Step 1
If you have a small file
Read all the file data in to memory
Step 2
Convert file data string into Array
Step 3
Search the array to find a location where you want to insert the text
Step 4
Once you have the location insert your text
yourArray.splice(index,0,"new added test");
Step 5
convert your array to string
yourArray.join("");
Step 6
write your file like so
fs.createWriteStream(yourArray);
This is not advised if your file is too big
I created a log file which prints data into text file using "Winston" logger. The source code is here below,
const { createLogger, format, transports } = require('winston');
var fs = require('fs')
var logger = fs.createWriteStream('Data Log.txt', {
flags: 'a'
})
const os = require('os');
var sleep = require('system-sleep');
var endOfLine = require('os').EOL;
var t = ' ';
var s = ' ';
var q = ' ';
var array1=[];
var array2=[];
var array3=[];
var array4=[];
array1[0] = 78;
array1[1] = 56;
array1[2] = 24;
array1[3] = 34;
for (var n=0;n<4;n++)
{
array2[n]=array1[n].toString();
}
for (var k=0;k<4;k++)
{
array3[k]=Buffer.from(' ');
}
for (var a=0;a<4;a++)
{
array4[a]=Buffer.from(array2[a]);
}
for (m=0;m<4;m++)
{
array4[m].copy(array3[m],0);
}
logger.write('Date'+q);
logger.write('Time'+(q+' '))
logger.write('Data 01'+t);
logger.write('Data 02'+t);
logger.write('Data 03'+t);
logger.write('Data 04'+t)
logger.write(endOfLine);
logger.write(endOfLine);
function mydata() //user defined function
{
logger.write(datechar+s);
logger.write(timechar+s);
for ( n = 0; n < 4; n++)
{
logger.write(array3[n]);
}
logger.write(endOfLine);
}
var now = new Date();
var dateFormat = require('dateformat');
var date = dateFormat(now,"isoDate");
var time = dateFormat(now, "h:MM:ss TT ");
var datechar = date.toString();
var timechar = time.toString();
mydata();
sleep(5*1000);
Good evening, community.
I have a question regarding changing exif meta data on jpegs using node.js. I have a set of coordinates which I need to attach to the image file, but for some reason, I cannot find the right library on npm for that. There are plenty of extracting libraries, like exif, exif-js, no-exif and so on, but all of the are retrieving data from images. I'm going the opposite direction, and extracting coordinates/gps data from the kml file and based on that updating the images, which do not have geo-location metadata.
What is the best approach for doing this?
I have written a library to modify exif on client-side. It would help you even on Node.js.
https://github.com/hMatoba/piexifjs
I tried to run the library on Node.js. No error occurred and got a new jpeg modified exif.
var piexif = require("piexif.js");
var fs = required("fs");
var jpeg = fs.readFileSync(filename1);
var data = jpeg.toString("binary");
var exifObj = piexif.load(data);
exifObj["GPS"][piexif.GPSIFD.GPSVersionID] = [7, 7, 7, 7];
exifObj["GPS"][piexif.GPSIFD.GPSDateStamp] = "1999:99:99 99:99:99";
var exifbytes = piexif.dump(exifObj);
var newData = piexif.insert(exifbytes, data);
var newJpeg = new Buffer(newData, "binary");
fs.writeFileSync(filename2, newJpeg);
This worked best for me. eg. to write a coordinate of 23.2342 N, 2.343 W
const piexifjs = require("piexifjs");
var filename1 = "image.jpg";
var filename2 = "out.jpg";
var jpeg = fs.readFileSync(filename1);
var data = jpeg.toString("binary");
var exifObj = piexif.load(data);
exifObj.GPS[piexif.GPSIFD.GPSLatitude] = degToDmsRational(23.2342);
exifObj.GPS[piexif.GPSIFD.GPSLatitudeRef] = "N";
exifObj.GPS[piexif.GPSIFD.GPSLongitude] = degToDmsRational(2.343);
exifObj.GPS[piexif.GPSIFD.GPSLongitudeRef] = "W";
var exifbytes = piexif.dump(exifObj);
var newData = piexif.insert(exifbytes, data);
var newJpeg = Buffer.from(newData, "binary");
fs.writeFileSync(filename2, newJpeg);
function degToDmsRational(degFloat) {
var minFloat = degFloat % 1 * 60
var secFloat = minFloat % 1 * 60
var deg = Math.floor(degFloat)
var min = Math.floor(minFloat)
var sec = Math.round(secFloat * 100)
deg = Math.abs(deg) * 1
min = Math.abs(min) * 1
sec = Math.abs(sec) * 1
return [[deg, 1], [min, 1], [sec, 100]]
}
Using the package hashids, I can obtain hashes (with encode and decode) from numbers.
var Hashids = require("hashids"),
hashids = new Hashids("this is my salt", 8);
var id = hashids.encode(1);
Is there a similar package to obtain hashes from strings?
(with encode and decode)
var Hashids = require("hashids");
var hashids = new Hashids("this is my salt");
var hex = Buffer.from('Hello World', 'utf8').toString('hex');
console.log (hex); // '48656c6c6f20576f726c64'
var encoded = hashids.encodeHex(hex);
console.log (encoded); // 'rZ4pPgYxegCarB3eXbg'
var decodedHex = hashids.decodeHex('rZ4pPgYxegCarB3eXbg');
console.log (decodedHex); // '48656c6c6f20576f726c64'
var string = Buffer.from('48656c6c6f20576f726c64', 'hex').toString('utf8');
console.log (string); // 'Hello World'
Getting hex without Node's Buffer.from ( to use with hashids.decodeHex)
const toHex = (str: string): string => str.split("")
.reduce((hex, c) => hex += c.charCodeAt(0).toString(16).padStart(2, "0"), "")
const toUTF8 = (num: string): string =>
num.match(/.{1,2}/g)
.reduce((acc, char) => acc + String.fromCharCode(parseInt(char, 16)),"");