SVG support, better and more comments, minor code cleanup

src/formats.rs

@@ -89,9 +89,9 @@ impl Format for Script {
 	}
 
 	fn no_known_extension<W: Write>(&self, f: &mut W, path: &PathBuf) -> io::Result<()> {
-		write!(f, "printf No known extension for ")?;
+		write!(f, "echo No known extension for ")?;
 		write_pathbuf(f, path)?;
-		writeln!(f,"\nprintf '\n'")
+		writeln!(f, )
 	}
 
 	fn unreadable<W: Write>(&self, f: &mut W, path: &PathBuf) -> io::Result<()> {
@@ -115,6 +115,6 @@ impl Format for Script {
 	}
 
 	fn footer<W: Write>(&self, _: &Entries, f: &mut W) -> io::Result<()> {
-		writeln!(f, "\nprintf 'Done.\\n'")
+		writeln!(f, "\necho 'Done.'")
 	}
 }

src/inspectors.rs

@@ -17,14 +17,19 @@ use crate::mimedb::MimeDb;
 // unfortunately, the format that requires 262 bytes for identification is tar, an extremely popular format (in the *nix
 // world, at least). however, tar files almost always appear wrapped in other formats (.tar.gz, .tar.zst, etc) anyway,
 // so maybe it's fine...? maybe this should be configurable by the user? i don't know.
-// empirical testing (or rather, starting from 256 and incrementing until it worked) reveals that mime_type requires
+// empirical testing (or rather, starting from 256 and incrementing until it worked) reveals that xdg-mime requires
 // at least 265 bytes to identify a tar file.
+
+// additionally, since many formats can by identified with ≤64 bytes, it's worth reading 64 bytes, checking for the mime
+// type, and then reading the full 512 bytes if necessary. in most cases, this will end up being faster on the whole,
+// even though two reads are needed for certain formats, unless the directory being scanned is predominantly made up of
+// such formats.
+
+const INITIAL_BUF_SIZE: usize = 64;
 const BUF_SIZE: usize = 512;
 
 pub fn mime_type<T: MimeDb>(db: &T, path: &Path) -> io::Result<Option<Mime>> {
-	// attempt to read up to the BUF_SIZE bytes of the file
+	let mut buffer = [0; INITIAL_BUF_SIZE];
-
-	let mut buffer = [0; 64];
 	let mut file = File::open(path)?;
 
 	// this lint can be ignored: it's okay if the file isn't long enough to fill the buffer, as we only care about the
@@ -33,14 +38,21 @@ pub fn mime_type<T: MimeDb>(db: &T, path: &Path) -> io::Result<Option<Mime>> {
 		file.read(&mut buffer)?;
 
 	let r = db.get_type(&buffer);
+
 	if r.is_some() {
 		return Ok(r);
 	}
 
+	// attempt to read up to the BUF_SIZE bytes of the file.
+	// we've already read the first 64 bytes into a buffer, but i can't see an obvious way to reuse those 64 bytes that's
+	// faster than simply moving the seek position back to the start of the file and re-reading the whole 512 bytes.
+	// for example, starting with a buffer of 64 bytes, then creating a new 512 byte buffer from the contents of the first
+	// buffer with (512 - 64) blank bytes, then finally reading the rest, is much slower than simply reading the file
+	// twice. i don't at all doubt that there IS a way to do this efficiently, and i can think of a way in principle, but
+	// i'm not sure how to express it in a way that is both idiomatic/safe and fast.
 	let mut buffer = [0; BUF_SIZE];
 	file.seek(SeekFrom::Start(0))?;
 	file.read(&mut buffer)?;
-	// warn!("dang");
 	Ok(db.get_type(&buffer))
 }
 
@@ -49,13 +61,34 @@ pub fn mime_type<T: MimeDb>(db: &T, path: &Path) -> io::Result<Option<Mime>> {
 cached! {
 	MIMEXT;
 	fn mime_extension_lookup(mime: Mime) -> Option<Vec<String>> = {
-		if mime == mime_guess::mime::IMAGE_JPEG {
+
-			// jpeg files are given the primary extension "jpe", due to the extension list being stored in alphabetical order.
+		// match on the mime's `essence_str` rather than the mime itself - mime_guess::get_mime_extensions ignores the type
-			// to handle this particular case, return a custom vector consisting of just "jpg" and "jpeg".
+		// suffix, treating "image/svg+xml" as "image/svg", and thus fails to find any extensions. passing the essence_str
-			return Some(vec![String::from("jpg"), String::from("jpeg")]);
+		// (which includes the suffix) fixes this.
-		}
+		match mime_guess::get_mime_extensions_str(mime.essence_str()) {
-		match mime_guess::get_mime_extensions(&mime) { // get a list of possible extensions for this mime type
+			Some(exts) => {
-			Some(exts) => Some(exts.iter().map(|e| String::from(*e)).collect()),
+				let possible_exts: Vec<String> = exts.iter().map(|e| String::from(*e)).collect();
+
+				Some(if mime == mime_guess::mime::IMAGE_JPEG {
+					// possible_exts starts with "jpe", because it's alphabetically before "jpeg" and "jpg". however, jpg/jpeg are
+					// far more common than jpe, so it makes sense to suggest one of those rather than jpe. to do this, we can
+					// add "jpg" to the start of the possible_exts list, ensuring that it will be the extension suggested by fif.
+					[vec![String::from("jpg")], possible_exts].concat()
+
+				} else if mime == mime_guess::mime::TEXT_XML {
+					// a somewhat similar case arises with XML files - the first suggested extension is "addin", when it should
+					// (in my opinion) be "xml".
+					// there's also another problem: SVG files can easily be misidentified as XML files, because they usually
+					// *are* valid XML - the more whitespace and comments an SVG file begins with, the more bytes must be read
+					// before it's possible to determine that it's an SVG rather than an XML file. to "fix" this, we can add "svg"
+					// as a valid extension for XML files, ensuring that SVG files misidentified as XML will still be considered
+					// to have valid extensions.
+					[vec![String::from("xml"), String::from("svg")], possible_exts].concat()
+
+				} else {
+					possible_exts
+				})
+			},
 			None => None
 		}
 	}

src/main.rs

@@ -118,13 +118,13 @@ fn scan_file(entry: &DirEntry) -> Result<Findings, (ScanError, PathBuf)> {
 		Some(e) if entry_ext.is_some() => e.contains(&entry_ext.unwrap().to_lowercase().into()),
 		// there is a known set of extensions for this mimetype, but the file has no extension
 		Some(_) => false,
-		// there is no known set of extensions for this mimetype -- assume it's correct
+		// there is no known set of extensions for this mimetype :(
-		None => true,
+		None => false,
 	};
 
 	Ok(Findings {
 		file: entry.path().to_path_buf(),
-		valid, // make this a function
+		valid,
 		mime: result,
 	})
 }
@@ -165,13 +165,13 @@ fn main() {
 	#[cfg(feature = "infer-backend")]
 	MIMEDB
 		.set(mimedb::InferDb::init())
-		.or(Err("Failed to initialise MIMEDB"))
+		.or(Err("Failed to initialise Infer backend!"))
 		.unwrap();
 
 	#[cfg(feature = "xdg-mime-backend")]
 	MIMEDB
 		.set(mimedb::XdgDb::init())
-		.or(Err("Failed to initialise MIMEDB"))
+		.or(Err("Failed to initialise XDG Mime backend!"))
 		.unwrap();
 
 	debug!("Iterating directory: {:?}", args.dirs);
@@ -207,7 +207,7 @@ fn main() {
 					info!(
 						"{:?} should have file extension {}",
 						r.file,
-						r.recommended_extension().unwrap()
+						r.recommended_extension().unwrap_or("???".into())
 					)
 				} else {
 					trace!("{:?} is totally fine", r.file)

src/mimedb.rs

@@ -17,25 +17,49 @@ pub struct InferDb {
 impl MimeDb for InferDb {
 	fn init() -> Self {
 		let mut info = infer::Infer::new();
-		// add a random file type just to make sure adding works and such
+
+		// jpeg2000 support because why the stinch not
 		info.add("image/jpeg2000", ".jp2", |buf| {
 			buf.len() > 23
-				&& buf[0] == 0x00
+			&& buf[..23] == b"\x00\x00\x00\x0C\x6A\x50\x20\x20\x0D\x0A\x87\x0A\x6A\x70\x32\x20"[..]
-				&& buf[1] == 0x00
+		});
-				&& buf[2] == 0x00
+
-				&& buf[3] == 0x0C
+		info.add("image/svg+xml", "svg", |buf| {
-				&& buf[4] == 0x6A
+			// before doing the moderately expensive SVG check, we should make sure that the input is actually SGML-ish
-				&& buf[5] == 0x50
+			// by "SGML-ish", i mean starts with anywhere from zero to ∞-1 whitespace characters, and then a less than sign,
-				&& buf[6] == 0x20
+			// and then there's some other stuff we don't care about right now
-				&& buf[7] == 0x20
+
-				&& buf[8] == 0x0D
+			// so, here comes our fancy pants """""SGML-ish validator"""""
-				&& buf[9] == 0x0A
+			for i in 0..buf.len() {
-				&& buf[10] == 0x87
+				match buf[i] {
-				&& buf[11] == 0x0A
+					// whitespace (according to https://www.w3.org/TR/xml/#NT-S)
-				&& buf[20] == 0x6A
+					b'\t' | b'\r' | b'\n' | b'\x20' => continue,
-				&& buf[21] == 0x70
+					b'<' => break,
-				&& buf[22] == 0x32
+					_ => return false
-				&& buf[23] == 0x20
+				}
+			}
+
+			// finally, to check whether or not the file is an SVG:
+			// - split the buffer up into chunks separated by the less than sign
+			// - check to see if this chunk starts with any of these identifiers:
+			let identifiers: Vec<&[u8]> = vec![
+				"svg".as_bytes(),
+				"SVG".as_bytes(),
+				"!DOCTYPE svg".as_bytes(),
+				"!DOCTYPE SVG".as_bytes()
+			];
+			// - if it does, the nested `any` will short circuit and immediately return true, causing the parent `any` to do
+			//   the same
+			// - and finally, if none of the chunks match, we'll return false
+
+			// TODO: this is kind of messy, i'd like to clean it up somehow :(
+			buf
+				.split(|c| *c == b'<')
+				.any(|buf| {
+					identifiers
+						.iter()
+						.any(|id| buf.starts_with(id))
+				})
 		});
 
 		// unmut