detect-file-type
v0.2.8
Published
Detect file type by signature
Downloads
24,177
Readme
detect-file-type
Detect file type by signatures. file-type inspired
Supported types (will be updated)
jpg, png, gif, webp, flif, cr2, tif, bmp, jxr, psd, zip, epub, xpi, tar, rar, gz, bz2, 7z, dmg, mov, mp4, m4v, m4a, 3g2, 3gp, avi, wav, qcp, mid, mkv, webm, wasm, asf, wmv, wma, mpg, mp3, opus, ogg, ogv, oga, ogm, ogx, spx, flac, ape, wv, amr, pdf, exe, swf, rtf, woff, woff2, eot, ttf, otf, ico, cur, flv, ps, xz, sqlite, nes, dex, crx, elf, cab, deb, ar, rpm, Z, lz, msi, mxf, mts, blend, bpg, jp2, jpx, jpm, mj2, aif, xml, svg, mobi, heic, ktx, dcm, mpc, ics, glb, pcap, html
Installation
npm i --save 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 filebufferLength
- (optional) Buffer size (in bytes) starting from the start of file. By default 500. If size of file less than 500 bytes then param the same as size of the filecallback
fromBuffer(buffer, callback)
Detect file type from buffer
buffer
- uint8array/Buffercallback
fromFd(fd, bufferLength?, callback)
Detect file type from buffer
fd
- file descriptorbufferLength
- (optional) Buffer size (in bytes) starting from the start of fd. By default 500. If size of file less than 500 bytes then param the same as size of the filecallback
addSignature(siganture)
Add new signature for file type detecting
signature
- a signature. See section about it below
addCustomFunction(fn)
Add custom function which receive buffer and trying to detect file type.
fn
- function which receive buffer
This method needed for more complicated cases like html or xml for example. Truly uncomfortable to detect html via signatures because html format has a lot of "magic numbers" in the different places. So you can install is-html package for example and use its functionality.
const detect = require('detect-file-type');
const isHtml = require('is-html');
detect.addCustomFunction((buffer) => {
const str = buffer.toString();
if (isHtml(str)) {
return {
ext: 'html',
mime: 'text/html'
}
}
return false;
});
detect.fromFile('./some.html', (err, result) => {
if (err) {
return console.log(err);
}
console.log(result); // { ext: 'html', mime: 'text/html' }
});
Note: custom function should be pure (without any async operations)
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 extensioniana
- optional iana registered mime type - will be added when actual used mime differs from iana, or when the old mime type we used was wrongmime
- mime type of filerules
- 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
,default
search
- a searching rule, that keeps the offset of the searched bytes in a special id.search_ref
- a reference to a previously performed search,start
andend
will be offset by it.
More details about: equal, notEqual, contains & notContains.
equal
- here is required fieldbytes
. We get a dump of buffer fromstart
(equals 0 by default) toend
(equals buffer.length by default). After that we compare the dump with value in parambytes
. If values are equal then this rule is correct.notEqual
- here is required fieldbytes
. We get a dump of buffer fromstart
(equals 0 by default) toend
(equals buffer.length by default). After that we compare the dump with value in parambytes
. If values aren't equal then this rule is correct.contains
- here is required fieldbytes
. We get a dump of buffer fromstart
(equals 0 by default) toend
(equals buffer.length by default). After that we try to find the sequence frombytes
in this dump. If the dump containsbytes
then rules is correct.notContains
- here is required fieldbytes
. We get a dump of buffer fromstart
(equals 0 by default) toend
(equals buffer.length by default). After that we try to find the sequence frombytes
in this dump. If the dump containsbytes
then rules is incorrect.
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 fromrules
should be correct. If at least 1 rule is correct then list are correct too.and
- means that each rule fromrules
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.
The default
type is special and is used as a fallback when a set of or
rules did not match, inside a larger tree with multiple mime detections.
More details about the search
object
id
- id to assign to the result (reference later withsearch_ref
)start
/end
- range to search inbytes
- bytes to search for
License
WTFPL © Dmitry Pavlovsky