Create tweetdisk.js

Author: 8bitkick

tweetdisk.js

@@ -0,0 +1,58 @@
+const request = require('request');
+const fs = require("fs");
+PNG = require("pngjs").PNG;
+
+function stegDecode(dataIn){
+  const magicWord = 0x12345678;
+  const version   = 0x00000001;
+
+  var image8    = new Uint8Array(dataIn);
+  var data8     = new Uint8Array(900*900);
+  var data32    = new Uint32Array(data8.buffer);
+
+  let i = 0;
+
+  for (let d = 0; d<image8.length; d++){
+    var b    = 0;
+    for (let j = 0; j<4; j++){
+      if (i % 4 == 3) {i++;} // skip alpha bytes
+      b |= (image8[i] & 3) << (j*2);
+      i++;
+    }
+    data8[d] = b;
+  }
+
+  // Check header
+  if (data32[0] != magicWord) {
+    console.log('not a recognised steg file '+data32[0x00].toString(16));return null;
+  }
+
+  var fileLength    = data32[2];
+  var headerLength  = data32[3];
+  var checksum      = data32[4];
+  var fileData      = new Uint8Array(data8.slice(headerLength, fileLength+headerLength));
+
+  // Perform checksum
+  //var crc = crc32.buf(fileData);
+  //if (checksum != crc) {console.log("*** checksum failed ***");return null;} else {console.log("*** checksum passed ***");}
+  return fileData;
+}
+
+async function getTweetDisk(imageURL){
+    return new Promise(function(resolve, reject){
+        request({ uri:imageURL, encoding: null }, function (error, response, body) {
+            if (error) return reject(error);
+            try {
+              var png = PNG.sync.read(body);
+              var diskData = stegDecode(png.data);
+                resolve(diskData);
+            } catch(e) {
+                reject(e);
+            }
+        });
+    });
+}
+
+module.exports = {
+  get: getTweetDisk
+};