From 088ab4f0cb6bbd97b743122702d320bcec8732de Mon Sep 17 00:00:00 2001
From: Jonathan Behrens <fintelia@gmail.com>
Date: Tue, 26 Dec 2023 15:22:00 -0500
Subject: [PATCH] Remove num_traits dependency (#30)

---
 Cargo.lock.msrv    | 10 ----------
 Cargo.toml         |  1 -
 src/loop_filter.rs |  2 +-
 src/lossless.rs    | 23 +++++++++++------------
 src/vp8.rs         |  9 ++++-----
 5 files changed, 16 insertions(+), 29 deletions(-)

diff --git a/Cargo.lock.msrv b/Cargo.lock.msrv
index 91cfa9e..0e5ee11 100644
--- a/Cargo.lock.msrv
+++ b/Cargo.lock.msrv
@@ -70,15 +70,6 @@ dependencies = [
  "simd-adler32",
 ]
 
-[[package]]
-name = "num-traits"
-version = "0.2.16"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f30b0abd723be7e2ffca1272140fac1a2f084c77ec3e123c192b66af1ee9e6c2"
-dependencies = [
- "autocfg",
-]
-
 [[package]]
 name = "paste"
 version = "1.0.14"
@@ -164,7 +155,6 @@ name = "webp"
 version = "0.1.0"
 dependencies = [
  "byteorder",
- "num-traits",
  "paste",
  "png",
  "thiserror",
diff --git a/Cargo.toml b/Cargo.toml
index 36280a5..77cd254 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,7 +9,6 @@ publish = false
 
 [dependencies]
 byteorder = "1.4.3"
-num-traits = "0.2.16"
 thiserror = "1.0.47"
 
 [dev-dependencies]
diff --git a/src/loop_filter.rs b/src/loop_filter.rs
index 9412cd5..fe08504 100644
--- a/src/loop_filter.rs
+++ b/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
diff --git a/src/lossless.rs b/src/lossless.rs
index 12007fc..99e1a9a 100644
--- a/src/lossless.rs
+++ b/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"),
+        }
     }
 }
 
diff --git a/src/vp8.rs b/src/vp8.rs
index 0d1c93b..fba5e63 100644
--- a/src/vp8.rs
+++ b/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;