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Commit 0a72d1cb authored by Jeremy Soller's avatar Jeremy Soller Committed by GitHub
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Merge pull request #11 from pi-pi3/faster-externs 

A faster implementation of the memcpy family
parents 56a533fb 5c1e6190
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with 224 additions and 9 deletions
src/externs.rs
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/// 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 mut i = 0;
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/8; // Number of 32-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 1 byte at a time
while i < n {
*((dest as usize + i) as *mut u8) = *((src as usize + i) as *const u8);
i += 1;
......@@ -16,19 +54,93 @@ pub unsafe extern fn memcpy(dest: *mut u8, src: *const u8,
/// Memmove
///
/// Copy N bytes of memory from src to dest. The memory areas may overlap.
///
/// 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 mut i = n;
let n_64: usize = n/8; // Number of 64-bit groups
let mut i: usize = n_64;
// 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;
// Copy 4 bytes at a time
while i != 0 {
i -= 4;
*((dest as usize + i) as *mut u32) =
*((src as usize + i) as *const u32);
}
let mut i: usize = n;
// Copy 1 byte at a time
while i != n_32*4 {
i -= 1;
*((dest as usize + i) as *mut u8) = *((src as usize + i) as *const u8);
*((dest as usize + i) as *mut u8) =
*((src as usize + i) as *const u8);
}
} else {
let mut i = 0;
let n_32: usize = n/4; // Number of 32-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 1 byte at a time
while i < n {
*((dest as usize + i) as *mut u8) = *((src as usize + i) as *const u8);
*((dest as usize + i) as *mut u8) =
*((src as usize + i) as *const u8);
i += 1;
}
}
......@@ -39,11 +151,55 @@ pub unsafe extern fn memmove(dest: *mut u8, src: *const u8,
/// Memset
///
/// Fill a block of memory with a specified value.
///
/// 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 mut i = 0;
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 as u8;
*((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 mut i: usize = 0;
// Set 4 bytes at a time
while i < n_32 {
*((dest as usize + i) as *mut u32) = c;
i += 4;
}
let c = c as u8;
// Set 1 byte at a time
while i < n {
*((dest as usize + i) as *mut u8) = c;
i += 1;
}
......@@ -53,15 +209,74 @@ pub unsafe extern fn memset(dest: *mut u8, c: i32, n: usize) -> *mut u8 {
/// Memcmp
///
/// Compare two blocks of memory.
///
/// 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 mut i = 0;
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 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);
if a != b {
let n: usize = i + 4;
// 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 += 4;
}
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
return a as i32 - b as i32;
}
i += 1;
}
......
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