node.js - NodeJS write binary buffer into a file

Question

I can't rewrite a file that I am getting from a binary buffer, I have checked with the original file and all bytes are the same.

This is the file create from NodeJS:

# hd test.txt  | head
00000000  47 49 46 38 39 61 32 00  32 00 f7 00 00 96 8c 73  |GIF89a2.2.?....s|
00000010  66 5e 45 c6 bb 9f 7b 72  5a 47 47 47 8a 81 65 ca  |f^E?.{rZGGG..e?|
00000020  c1 a6 c9 c1 ac ee ea dd  c8 c5 bc 8c 87 7a d3 c9  |??????????..z??|
00000030  ab 43 3b 26 eb e5 d1 fa  fa fa e5 e4 e2 a6 9d 83  |?C;&??????????..|
00000040  86 7e 67 c1 b4 8e e4 dc  c6 82 82 82 e1 dd d1 e3  |.~g??.???...????|
00000050  dd ca e4 da bc f5 f1 e6  26 25 25 9c 91 73 f8 f3  |???????&%%..s??|
00000060  e4 c3 b9 9d d3 ca b4 4a  42 2a d1 c6 a2 6c 62 46  |?ù.??JB*??lbF|
00000070  ea e6 db bb b3 9c db d3  bb 5c 54 3d f1 ee e6 dc  |????.??T=????|
00000080  da d3 e7 e4 dc ce c2 9f  f8 f6 f2 76 6c 53 fc fb  |???????.???vlS??|
00000090  f9 e9 e1 ca 17 13 09 67  4d 00 f8 f4 e8 dc d3 b5  |????...gM.?????|

This the original one:

$ hd runner_small.gif   | head
00000000  47 49 46 38 39 61 32 00  32 00 f7 00 00 96 8c 73  |GIF89a2.2......s|
00000010  66 5e 45 c6 bb 9f 7b 72  5a 47 47 47 8a 81 65 ca  |f^E...{rZGGG..e.|
00000020  c1 a6 c9 c1 ac ee ea dd  c8 c5 bc 8c 87 7a d3 c9  |.............z..|
00000030  ab 43 3b 26 eb e5 d1 fa  fa fa e5 e4 e2 a6 9d 83  |.C;&............|
00000040  86 7e 67 c1 b4 8e e4 dc  c6 82 82 82 e1 dd d1 e3  |.~g.............|
00000050  dd ca e4 da bc f5 f1 e6  26 25 25 9c 91 73 f8 f3  |........&%%..s..|
00000060  e4 c3 b9 9d d3 ca b4 4a  42 2a d1 c6 a2 6c 62 46  |.......JB*...lbF|
00000070  ea e6 db bb b3 9c db d3  bb 5c 54 3d f1 ee e6 dc  |.........T=....|
00000080  da d3 e7 e4 dc ce c2 9f  f8 f6 f2 76 6c 53 fc fb  |...........vlS..|
00000090  f9 e9 e1 ca 17 13 09 67  4d 00 f8 f4 e8 dc d3 b5  |.......gM.......|

You can compare these two files and every bytes are the same, I am guessing that the encoding from NodeJS is not the right one.

This is the piece of code

var foo = "71%73%70%56%57%97%50%0%50%0%247%0%0%150%140%115%102%94%69%198%187%159%123%114%90%71%71%71%138%129%101%202%193%166%201%193%172%238%234%221%200%197%188%140$"
var bytes = foo.split("%");

var b = new Buffer(bytes.length);
for (var i = 0;i < bytes.length;i++) {
        b[i] = bytes[i];
}

fs.writeFile("test.txt", b,  "binary",function(err) {
    if(err) {
        console.log(err);
    } else {
        console.log("The file was saved!");
    }
});

You can try to run it on your NodeJS and see that the result is wrong.

What can I do to fix it?

Answer 1

I am not sure if this would help but try to change the b variable to the bytes variable in the line below at least you would be able to view the file in a test editor

fs.writeFile("test.txt", b,  "binary",function(err) { });

If you would like to have the numbers space separated try the code below:

var fs = require('fs');

var foo = "71%73%70%56%57%97%50%0%50%0%247%0%0%150%140%115%102%94%69%198%187%159%123%114%90%71%71%71%138%129%101%202%193%166%201%193%172%238%234%221%200%197%188%140"
var bytes = foo.split("%");

var b = new Buffer(bytes.length);
var c = "";
for (var i = 0;i < bytes.length;i++) {
    b[i] = bytes[i];
    c = c + " " + bytes[i]
}

fs.writeFile("test.txt", c,  "binary",function(err) {
    if(err) {
        console.log(err);
    } else {
        console.log("The file was saved!");
    }
});