Add inline(always) to critical path functions

- Inline get_bit(), read_node(), and to_usize() functions
- Provides ~1.3% performance improvement in benchmarks
- Functions are called extensively during IP lookup traversal

Author: oschwald

src/maxminddb/decoder.rs

@@ -42,12 +42,14 @@ impl<'de> Decoder<'de> {
         }
     }
 
+    #[inline(always)]
     fn eat_byte(&mut self) -> u8 {
         let b = self.buf[self.current_ptr];
         self.current_ptr += 1;
         b
     }
 
+    #[inline(always)]
     fn size_from_ctrl_byte(&mut self, ctrl_byte: u8, type_num: u8) -> usize {
         let size = (ctrl_byte & 0x1f) as usize;
         // extended
@@ -69,6 +71,7 @@ impl<'de> Decoder<'de> {
         }
     }
 
+    #[inline(always)]
     fn size_and_type(&mut self) -> (usize, u8) {
         let ctrl_byte = self.eat_byte();
         let mut type_num = ctrl_byte >> 5;
@@ -102,6 +105,7 @@ impl<'de> Decoder<'de> {
         }
     }
 
+    #[inline(always)]
     fn decode_any_value(&mut self) -> DecodeResult<Value<'_, 'de>> {
         let (size, type_num) = self.size_and_type();
 

src/maxminddb/lib.rs

@@ -104,6 +104,7 @@ impl IpInt {
         }
     }
 
+    #[inline(always)]
     fn get_bit(&self, index: usize) -> bool {
         match self {
             IpInt::V4(ip) => (ip >> (31 - index)) & 1 == 1,
@@ -473,6 +474,7 @@ impl<'de, S: AsRef<[u8]>> Reader<S> {
         Ok(node)
     }
 
+    #[inline(always)]
     fn read_node(&self, node_number: usize, index: usize) -> Result<usize, MaxMindDbError> {
         let buf = self.buf.as_ref();
         let base_offset = node_number * (self.metadata.record_size as usize) / 4;
@@ -535,6 +537,7 @@ impl<'de, S: AsRef<[u8]>> Reader<S> {
 
 // I haven't moved all patterns of this form to a generic function as
 // the FromPrimitive trait is unstable
+#[inline(always)]
 fn to_usize(base: u8, bytes: &[u8]) -> usize {
     bytes
         .iter()