feat: Implemented the RAR vint data type

src/file.rs

@@ -236,6 +236,21 @@ impl<'a> FileReader {
         self.read(&mut buf);
         u128::from_be_bytes(buf)
     }
+
+    pub fn read_vint(&mut self) -> u128 {
+        // as defined in the RAR 5.0 spec
+        let mut result = 0;
+        let mut shift = 0u16;
+        loop {
+            let byte = self.read_u8();
+            result |= ((byte & 0x7F) as u128) << shift;
+            if byte & 0x80 == 0 {
+                break;
+            }
+            shift += 7;
+        }
+        result
+    }
 }
 
 impl Clone for FileReader {
@@ -368,4 +383,20 @@ impl<'a> FileWriter {
     pub fn write_u128be(&mut self, n: &u128) {
         self.write(&n.to_be_bytes());
     }
+
+    pub fn write_vint(&mut self, n: &u128) {
+        // as defined in the RAR 5.0 spec
+        let mut n = *n;
+        loop {
+            let mut byte = (n & 0x7F) as u8;
+            n >>= 7;
+            if n != 0 {
+                byte |= 0x80;
+            }
+            self.write(&[byte]);
+            if n == 0 {
+                break;
+            }
+        }
+    }
 }