Rename "simd" feature to not(platform_independent)

Also return fn pointers rather than using has_* functions.

Author: veluca93

Cargo.toml

@@ -27,5 +27,5 @@ name = "large_image"
 harness = false
 
 [features]
-default = ["rayon", "simd"]
-simd = []
+default = ["rayon"]
+platform_independent = []

src/arch/mod.rs

@@ -7,52 +7,27 @@ use std::is_x86_feature_detected;
 
 /// Arch-specific implementation of YCbCr conversion. Returns the number of pixels that were
 /// converted.
-pub fn color_convert_line_ycbcr(y: &[u8], cb: &[u8], cr: &[u8], output: &mut [u8]) -> usize {
+pub fn get_color_convert_line_ycbcr() -> Option<unsafe fn(&[u8], &[u8], &[u8], &mut [u8]) -> usize>
+{
     #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     #[allow(unsafe_code)]
     {
         if is_x86_feature_detected!("ssse3") {
-            unsafe {
-                return ssse3::color_convert_line_ycbcr(y, cb, cr, output);
-            }
+            return Some(ssse3::color_convert_line_ycbcr);
         }
     }
-    return 0;
+    None
 }
 
 /// Arch-specific implementation of 8x8 IDCT.
-pub fn dequantize_and_idct_block_8x8(
-    coefficients: &[i16],
-    quantization_table: &[u16; 64],
-    output_linestride: usize,
-    output: &mut [u8],
-) {
+pub fn get_dequantize_and_idct_block_8x8() -> Option<unsafe fn(&[i16], &[u16; 64], usize, &mut [u8])>
+{
     #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     #[allow(unsafe_code)]
     {
         if is_x86_feature_detected!("ssse3") {
-            unsafe {
-                ssse3::dequantize_and_idct_block_8x8(
-                    coefficients,
-                    quantization_table,
-                    output_linestride,
-                    output,
-                );
-                return;
-            }
+            return Some(ssse3::dequantize_and_idct_block_8x8);
         }
     }
-    unreachable!("No arch-specific IDCT available");
-}
-
-/// Returns true if an arch-specific IDCT is avaliable, false otherwise.
-pub fn has_arch_specific_idct() -> bool {
-    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
-    #[allow(unsafe_code)]
-    {
-        if is_x86_feature_detected!("ssse3") {
-            return true;
-        }
-    }
-    return false;
+    None
 }

src/decoder.rs

@@ -1257,10 +1257,19 @@ fn color_convert_line_ycbcr(data: &[Vec<u8>], output: &mut [u8]) {
     assert!(data.len() == 3, "wrong number of components for ycbcr");
     let [y, cb, cr]: &[_; 3] = data.try_into().unwrap();
 
-    #[cfg(feature = "simd")]
-    let arch_specific_pixels = crate::arch::color_convert_line_ycbcr(y, cb, cr, output);
+    #[cfg(not(feature = "platform_independent"))]
+    let arch_specific_pixels = {
+        if let Some(ycbcr) = crate::arch::get_color_convert_line_ycbcr() {
+            #[allow(unsafe_code)]
+            unsafe {
+                ycbcr(y, cb, cr, output)
+            }
+        } else {
+            0
+        }
+    };
 
-    #[cfg(not(feature = "simd"))]
+    #[cfg(feature = "platform_independent")]
     let arch_specific_pixels = 0;
 
     for (((chunk, y), cb), cr) in output

src/idct.rs

@@ -244,14 +244,12 @@ pub fn dequantize_and_idct_block_8x8(
     output_linestride: usize,
     output: &mut [u8],
 ) {
-    #[cfg(feature = "simd")]
-    if crate::arch::has_arch_specific_idct() {
-        return crate::arch::dequantize_and_idct_block_8x8(
-            coefficients,
-            quantization_table,
-            output_linestride,
-            output,
-        );
+    #[cfg(not(feature = "platform_independent"))]
+    if let Some(idct) = crate::arch::get_dequantize_and_idct_block_8x8() {
+        #[allow(unsafe_code)]
+        unsafe {
+            return idct(coefficients, quantization_table, output_linestride, output);
+        }
     }
 
     let output = output.chunks_mut(output_linestride);
@@ -638,8 +636,8 @@ fn test_dequantize_and_idct_block_8x8_all_zero() {
 #[test]
 fn test_dequantize_and_idct_block_8x8_saturated() {
     // Arch-specific IDCT implementations need not handle i16::MAX values.
-    #[cfg(feature = "simd")]
-    if crate::arch::has_arch_specific_idct() {
+    #[cfg(not(feature = "platform_independent"))]
+    if crate::arch::get_dequantize_and_idct_block_8x8().is_some() {
         return;
     }
     let mut output = [0u8; 8 * 8];

src/lib.rs

@@ -28,6 +28,7 @@
 
 #![deny(missing_docs)]
 #![deny(unsafe_code)]
+#![cfg_attr(feature = "platform_independent", forbid(unsafe_code))]
 
 extern crate alloc;
 extern crate core;
@@ -41,7 +42,7 @@ pub use parser::CodingProcess;
 
 use std::io;
 
-#[cfg(feature = "simd")]
+#[cfg(not(feature = "platform_independent"))]
 mod arch;
 mod decoder;
 mod error;