From 528ffa985ae85daff33821721f27ca2cfaa253c4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Jedelsk=C3=BD?= <hjajet@gmail.com>
Date: Thu, 5 Oct 2017 14:19:25 +0200
Subject: [PATCH] Deduplicate memcpy, memmove, memset and memcmp functions
---
src/externs.rs | 203 +++++++++----------------------------------------
src/lib.rs | 1 +
2 files changed, 36 insertions(+), 168 deletions(-)
diff --git a/src/externs.rs b/src/externs.rs
index 42fb3e63..03bc34cd 100644
--- a/src/externs.rs
+++ b/src/externs.rs
@@ -1,45 +1,25 @@
+use core::mem;
+
+const WORD_SIZE: usize = mem::size_of::<usize>();
+
/// Memcpy
///
/// Copy N bytes of memory from one location to another.
///
/// This faster implementation works by copying bytes not one-by-one, but in
/// groups of 8 bytes (or 4 bytes in the case of 32-bit architectures).
-#[cfg(target_pointer_width = "64")]
#[no_mangle]
pub unsafe extern fn memcpy(dest: *mut u8, src: *const u8,
n: usize) -> *mut u8 {
- let n_64: usize = n/8; // Number of 64-bit groups
- let mut i: usize = 0;
-
- // Copy 8 bytes at a time
- while i < n_64 {
- *((dest as usize + i) as *mut u64) =
- *((src as usize + i) as *const u64);
- i += 8;
- }
-
- // Copy 1 byte at a time
- while i < n {
- *((dest as usize + i) as *mut u8) = *((src as usize + i) as *const u8);
- i += 1;
- }
-
- dest
-}
-// 32-bit version of the function above
-#[cfg(target_pointer_width = "32")]
-#[no_mangle]
-pub unsafe extern fn memcpy(dest: *mut u8, src: *const u8,
- n: usize) -> *mut u8 {
- let n_32: usize = n/4; // Number of 32-bit groups
+ let n_usize: usize = n/WORD_SIZE; // Number of word sized groups
let mut i: usize = 0;
- // Copy 4 bytes at a time
- while i < n_32 {
- *((dest as usize + i) as *mut u32) =
- *((src as usize + i) as *const u32);
- i += 4;
+ // Copy `WORD_SIZE` bytes at a time
+ while i < n_usize {
+ *((dest as usize + i) as *mut usize) =
+ *((src as usize + i) as *const usize);
+ i += WORD_SIZE;
}
// Copy 1 byte at a time
@@ -57,84 +37,37 @@ pub unsafe extern fn memcpy(dest: *mut u8, src: *const u8,
///
/// This faster implementation works by copying bytes not one-by-one, but in
/// groups of 8 bytes (or 4 bytes in the case of 32-bit architectures).
-#[cfg(target_pointer_width = "64")]
-#[no_mangle]
-pub unsafe extern fn memmove(dest: *mut u8, src: *const u8,
- n: usize) -> *mut u8 {
- if src < dest as *const u8 {
- let n_64: usize = n/8; // Number of 64-bit groups
- let mut i: usize = n_64*8;
-
- // Copy 8 bytes at a time
- while i != 0 {
- i -= 8;
- *((dest as usize + i) as *mut u64) =
- *((src as usize + i) as *const u64);
- }
-
- let mut i: usize = n;
-
- // Copy 1 byte at a time
- while i != n_64*8 {
- i -= 1;
- *((dest as usize + i) as *mut u8) =
- *((src as usize + i) as *const u8);
- }
- } else {
- let n_64: usize = n/8; // Number of 64-bit groups
- let mut i: usize = 0;
-
- // Copy 8 bytes at a time
- while i < n_64 {
- *((dest as usize + i) as *mut u64) =
- *((src as usize + i) as *const u64);
- i += 8;
- }
-
- // Copy 1 byte at a time
- while i < n {
- *((dest as usize + i) as *mut u8) =
- *((src as usize + i) as *const u8);
- i += 1;
- }
- }
-
- dest
-}
-
-// 32-bit version of the function above
-#[cfg(target_pointer_width = "32")]
#[no_mangle]
pub unsafe extern fn memmove(dest: *mut u8, src: *const u8,
n: usize) -> *mut u8 {
if src < dest as *const u8 {
- let n_32: usize = n/4; // Number of 32-bit groups
- let mut i: usize = n_32*4;
+ let n_usize: usize = n/WORD_SIZE; // Number of word sized groups
+ let mut i: usize = n_usize*WORD_SIZE;
- // Copy 4 bytes at a time
+ // Copy `WORD_SIZE` bytes at a time
while i != 0 {
- i -= 4;
- *((dest as usize + i) as *mut u32) =
- *((src as usize + i) as *const u32);
+ i -= WORD_SIZE;
+ *((dest as usize + i) as *mut usize) =
+ *((src as usize + i) as *const usize);
}
let mut i: usize = n;
// Copy 1 byte at a time
- while i != n_32*4 {
+ while i != n_usize*WORD_SIZE {
i -= 1;
*((dest as usize + i) as *mut u8) =
*((src as usize + i) as *const u8);
}
} else {
- let n_32: usize = n/4; // Number of 32-bit groups
+ let n_usize: usize = n/WORD_SIZE; // Number of 64-bit groups
let mut i: usize = 0;
- // Copy 4 bytes at a time
- while i < n_32 {
- *((dest as usize + i) as *mut u32) =
- *((src as usize + i) as *const u32);
- i += 4;
+ // Copy `WORD_SIZE` bytes at a time
+ while i < n_usize {
+ *((dest as usize + i) as *mut usize) =
+ *((src as usize + i) as *const usize);
+ i += WORD_SIZE;
}
// Copy 1 byte at a time
@@ -154,45 +87,16 @@ pub unsafe extern fn memmove(dest: *mut u8, src: *const u8,
///
/// This faster implementation works by setting bytes not one-by-one, but in
/// groups of 8 bytes (or 4 bytes in the case of 32-bit architectures).
-#[cfg(target_pointer_width = "64")]
-#[no_mangle]
-pub unsafe extern fn memset(dest: *mut u8, c: i32, n: usize) -> *mut u8 {
- let c = c as u64;
- let c = (c << 56) | (c << 48) | (c << 40) | (c << 32)
- | (c << 24) | (c << 16) | (c << 8) | c;
- let n_64: usize = n/8;
- let mut i: usize = 0;
-
- // Set 8 bytes at a time
- while i < n_64 {
- *((dest as usize + i) as *mut u64) = c;
- i += 8;
- }
-
- let c = c as u8;
-
- // Set 1 byte at a time
- while i < n {
- *((dest as usize + i) as *mut u8) = c;
- i += 1;
- }
-
- dest
-}
-
-// 32-bit version of the function above
-#[cfg(target_pointer_width = "32")]
#[no_mangle]
pub unsafe extern fn memset(dest: *mut u8, c: i32, n: usize) -> *mut u8 {
- let c = c as u32;
- let c = (c << 24) | (c << 16) | (c << 8) | c;
- let n_32: usize = n/4;
+ let c: usize = mem::transmute([c as u8; WORD_SIZE]);
+ let n_usize: usize = n/WORD_SIZE;
let mut i: usize = 0;
- // Set 4 bytes at a time
- while i < n_32 {
- *((dest as usize + i) as *mut u32) = c;
- i += 4;
+ // Set `WORD_SIZE` bytes at a time
+ while i < n_usize {
+ *((dest as usize + i) as *mut usize) = c;
+ i += WORD_SIZE;
}
let c = c as u8;
@@ -212,53 +116,16 @@ pub unsafe extern fn memset(dest: *mut u8, c: i32, n: usize) -> *mut u8 {
///
/// This faster implementation works by comparing bytes not one-by-one, but in
/// groups of 8 bytes (or 4 bytes in the case of 32-bit architectures).
-#[cfg(target_pointer_width = "64")]
-#[no_mangle]
-pub unsafe extern fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
- let n_64: usize = n/8;
- let mut i: usize = 0;
-
- while i < n_64 {
- let a = *((s1 as usize + i) as *const u64);
- let b = *((s2 as usize + i) as *const u64);
- if a != b {
- let n: usize = i + 8;
- // Find the one byte that is not equal
- while i < n {
- let a = *((s1 as usize + i) as *const u8);
- let b = *((s2 as usize + i) as *const u8);
- if a != b {
- return a as i32 - b as i32;
- }
- i += 1;
- }
- }
- i += 8;
- }
-
- while i < n {
- let a = *((s1 as usize + i) as *const u8);
- let b = *((s2 as usize + i) as *const u8);
- if a != b {
- return a as i32 - b as i32;
- }
- i += 1;
- }
-
- 0
-}
-
-#[cfg(target_pointer_width = "32")]
#[no_mangle]
pub unsafe extern fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
- let n_32: usize = n/4;
+ let n_usize: usize = n/WORD_SIZE;
let mut i: usize = 0;
- while i < n_32 {
- let a = *((s1 as usize + i) as *const u32);
- let b = *((s2 as usize + i) as *const u32);
+ while i < n_usize {
+ let a = *((s1 as usize + i) as *const usize);
+ let b = *((s2 as usize + i) as *const usize);
if a != b {
- let n: usize = i + 4;
+ let n: usize = i + WORD_SIZE;
// Find the one byte that is not equal
while i < n {
let a = *((s1 as usize + i) as *const u8);
@@ -269,7 +136,7 @@ pub unsafe extern fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
i += 1;
}
}
- i += 4;
+ i += WORD_SIZE;
}
while i < n {
diff --git a/src/lib.rs b/src/lib.rs
index 92c2dbbc..56ec8f16 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -22,6 +22,7 @@
#![feature(never_type)]
#![feature(thread_local)]
#![feature(unique)]
+#![feature(const_size_of)]
#![no_std]
extern crate alloc_kernel as allocator;
--
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