Remove num_traits dependency (#30)

Cargo.toml

@@ -9,7 +9,6 @@ publish = false
 
 [dependencies]
 byteorder = "1.4.3"
-num-traits = "0.2.16"
 thiserror = "1.0.47"
 
 [dev-dependencies]

src/loop_filter.rs

@@ -2,7 +2,7 @@
 
 #[inline]
 fn c(val: i32) -> i32 {
-    num_traits::clamp(val, -128, 127)
+    val.max(-128).min(127)
 }
 
 //unsigned to signed

src/lossless.rs

@@ -3,11 +3,7 @@
 //! [Lossless spec](https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification)
 //!
 
-use std::{
-    convert::TryInto,
-    io::Read,
-    ops::{AddAssign, Shl},
-};
+use std::{convert::TryInto, io::Read, mem};
 
 use crate::decoder::DecodingError;
 
@@ -644,18 +640,18 @@ impl BitReader {
         self.buf = buf;
     }
 
-    pub(crate) fn read_bits<T>(&mut self, num: u8) -> Result<T, DecodingError>
-    where
-        T: num_traits::Unsigned + Shl<u8, Output = T> + AddAssign<T> + From<bool>,
-    {
-        let mut value: T = T::zero();
+    pub(crate) fn read_bits<T: TryFrom<u16>>(&mut self, num: u8) -> Result<T, DecodingError> {
+        debug_assert!(num as usize <= 8 * mem::size_of::<T>());
+        debug_assert!(num <= 16);
+
+        let mut value = 0;
 
         for i in 0..num {
             if self.buf.len() <= self.index {
                 return Err(DecodingError::BitStreamError);
             }
             let bit_true = self.buf[self.index] & (1 << self.bit_count) != 0;
-            value += T::from(bit_true) << i;
+            value += u16::from(bit_true) << i;
             self.bit_count = if self.bit_count == 7 {
                 self.index += 1;
                 0
@@ -664,7 +660,10 @@ impl BitReader {
             };
         }
 
-        Ok(value)
+        match value.try_into() {
+            Ok(value) => Ok(value),
+            Err(_) => unreachable!("Value too large to fit in type"),
+        }
     }
 }
 

src/vp8.rs

@@ -13,7 +13,6 @@
 //!
 
 use byteorder::{LittleEndian, ReadBytesExt};
-use num_traits::clamp;
 use std::cmp;
 use std::convert::TryInto;
 use std::default::Default;
@@ -1147,11 +1146,11 @@ impl<R: Read> Vp8Decoder<R> {
 
     fn read_quantization_indices(&mut self) {
         fn dc_quant(index: i32) -> i16 {
-            DC_QUANT[clamp(index, 0, 127) as usize]
+            DC_QUANT[index.max(0).min(127) as usize]
         }
 
         fn ac_quant(index: i32) -> i16 {
-            AC_QUANT[clamp(index, 0, 127) as usize]
+            AC_QUANT[index.max(0).min(127) as usize]
         }
 
         let yac_abs = self.b.read_literal(7);
@@ -2064,13 +2063,13 @@ impl<R: Read> Vp8Decoder<R> {
             }
         }
 
-        filter_level = clamp(filter_level, 0, 63);
+        filter_level = filter_level.max(0).min(63);
 
         if macroblock.luma_mode == LumaMode::B {
             filter_level += self.mode_delta[0];
         }
 
-        let filter_level = clamp(filter_level, 0, 63) as u8;
+        let filter_level = filter_level.max(0).min(63) as u8;
 
         //interior limit
         let mut interior_limit = filter_level;