detect-file-type

detect-file-type

Detect file type by signatures. file-type inspired

Installation

  npm i detect-file-type

Usage

  var detect = require('detect-file-type');

  detect.fromFile('./image.jpg', function(err, result) {

    if (err) {
      return console.log(err);
    }

    console.log(result); // { ext: 'jpg', mime: 'image/jpeg' }
  });

API

fromFile(filePath, bufferLength, callback)

Detect file type from hard disk

• filePath - path to file
• bufferLength - (optional) Buffer size (in bytes) starting from the start of file. By default 500. If size of file less than 500Kb then param the same as size of the file
• callback

fromBuffer(buffer, callback)

Detect file type from buffer

• buffer - uint8array
• callback

addSignature(siganture)

Add new signature for file type detecting

• signature - a signature. See section about it below

Signature and creating your own signatures

Detecting of file type work via signatures. The simplest signature in JSON format looks like:

{
  "type": "jpg",
  "ext": "jpg",
  "mime": "image/jpeg",
  "rules": [
    { "type": "equal", "start": 0, "end": 2, "bytes": "ffd8"  }
  ]
}

params:

• type - signature type, mostly it's the same as param 'ext'
• ext - file extension
• mime - mime type of file
• rules - list of rules for detecting

More details about param rules:

This param have to be array of objects

• type - a rule type. There are available a few types: equal, notEqual, contains, notContains, or, and

More details about: equal, notEqual, contains и notContains.

• equal - here is required field bytes. We get a dump of buffer from start (equals 0 by default) to end (equals buffer.length by default). After that we compare the dump with value in param bytes. If values are equal then this rule is correct.
• notEqual - обязательно содержит поле bytes. We get a dump of buffer from start (equals 0 by default) to end (equals buffer.length by default). After that we compare the dump with value in param bytes. If values aren't equal then this rule is correct.
• contains - here is required field bytes. We get a dump of buffer from start (equals 0 by default) to end (equals buffer.length by default). After that we try to find the sequence from bytes in this dump. If the dump contains bytes then rules is correct.
• notContains - here is required field bytes. We get a dump of buffer from start (equals 0 by default) to end (equals buffer.length by default). After that we try to find the sequence from bytes in this dump. If the dump contains bytes then rules is correct.

More details about the rule types or and and

Actually, these types are necessary when you work with complicated signatures. For example, when file contains few sequences of bytes in different parts of file. Here is required field 'rules', where you should define set of another rules. See example:

{
  "type": "tif",
  "ext": "tif",
  "mime": "image/tiff",
  "rules": [
    { "type": "and", "rules":
      [
        { "type": "notEqual", "start": 8, "end": 10, "bytes": "4352" },
        { "type": "or", "rules":
            [
             { "type": "equal", "start": 0, "end": 4, "bytes": "49492a00" },
             { "type": "equal", "start": 0, "end": 4,  "bytes": "4d4d002a" }
           ]
          }
      ]
    }
   ]
 }

Explanation: If dump starts from 8th byte and ends to 10th byte isn't equal "4352", and dump starts from 0 and ends to 4th byte is equal "49492a00" or is equal "4d4d002a" then data looks like file with 'tif' format.

• or - means that any rules from rules should be correct. If at least 1 rule is correct then list are correct too.
• and - means that each rule from rules should be correct. If all rules are correct then list is correct. When at least 1 rule fail then all list is incorrect.

The rules or and and can be nested without restrictions.

Documentation in Russian

License

WTFPL © Dmitry Pavlovsky