More efficient name encoding

Totally spec compliant

Author: laurmaedje

src/object.rs

@@ -124,9 +124,10 @@ impl Primitive for Name<'_> {
     fn write(self, buf: &mut Vec<u8>) {
         buf.push(b'/');
         for &byte in self.0 {
-            // Quite a few characters must be escaped in names, so we take the
-            // safe route and allow only ASCII letters and numbers.
-            if byte.is_ascii_alphanumeric() {
+            // - Number sign shall use hexadecimal escape
+            // - Regular characters within the range exlacamation mark .. tilde
+            //   can be written directly
+            if byte != b'#' && matches!(byte, b'!'..=b'~') && is_regular_character(byte) {
                 buf.push(byte);
             } else {
                 buf.push(b'#');
@@ -136,6 +137,15 @@ impl Primitive for Name<'_> {
     }
 }
 
+/// Regular characters are a PDF concept.
+fn is_regular_character(byte: u8) -> bool {
+    ![
+        b'\0', b'\t', b'\n', b'\x0C', b'\r', b' ', b'(', b')', b'<', b'>', b'[', b']',
+        b'{', b'}', b'/', b'%',
+    ]
+    .contains(&byte)
+}
+
 /// The null object.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
 pub struct Null;

tests/tests.rs

@@ -152,7 +152,9 @@ fn test_primitive_objects() {
     // Test names.
     test_primitive!(Name(b"Filter"), b"/Filter");
     test_primitive!(Name(b"A B"), br"/A#20B");
-    test_primitive!(Name(b"~+c"), br"/#7E#2Bc");
+    test_primitive!(Name(b"~+c"), br"/~+c");
+    test_primitive!(Name(b"/A-B"), br"/#2FA-B");
+    test_primitive!(Name(b"<A>"), br"/#3CA#3E");
     test_primitive!(Name(b"#"), br"/#23");
     test_primitive!(Name(b"\n"), br"/#0A");
 }