From a1caa7ccacf5f9853b5e3c70b4f5d112272d4900 Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <japaricious@gmail.com>
Date: Sat, 17 Dec 2016 23:01:47 -0500
Subject: [PATCH] add implementations of memcpy et al

behind the "mem" Cargo feature, which used to be named "weak"

fixes #126
---
 Cargo.toml |  9 ++-------
 src/arm.rs |  4 ++++
 src/lib.rs |  7 +++----
 src/mem.rs | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 68 insertions(+), 11 deletions(-)
 create mode 100644 src/mem.rs

diff --git a/Cargo.toml b/Cargo.toml
index 9536423..8340578 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,12 +8,6 @@ version = "0.1.0"
 rustc-cfg = "0.2.0"
 gcc = "0.3.36"
 
-[dependencies]
-
-[dependencies.rlibc]
-git = "https://github.com/alexcrichton/rlibc"
-optional = true
-
 [dev-dependencies]
 quickcheck = "0.3.1"
 rand = "0.3.14"
@@ -26,7 +20,8 @@ c = []
 # Mark this crate as the #![compiler_builtins] crate
 compiler-builtins = []
 default = ["compiler-builtins"]
+# Include implementations of memory operations like memcpy
+mem = []
 rustbuild = ["compiler-builtins"]
-weak = ["rlibc/weak"]
 
 [workspace]
diff --git a/src/arm.rs b/src/arm.rs
index b74458f..345ff24 100644
--- a/src/arm.rs
+++ b/src/arm.rs
@@ -1,5 +1,8 @@
 use core::intrinsics;
 
+#[cfg(feature = "mem")]
+use mem::{memcpy, memmove, memset};
+
 // NOTE This function and the ones below are implemented using assembly because they using a custom
 // calling convention which can't be implemented using a normal Rust function
 #[naked]
@@ -100,6 +103,7 @@ pub extern "C" fn __aeabi_uidiv(a: u32, b: u32) -> u32 {
     ::int::udiv::__udivsi3(a, b)
 }
 
+#[cfg(not(feature = "mem"))]
 extern "C" {
     fn memcpy(dest: *mut u8, src: *const u8, n: usize) -> *mut u8;
     fn memmove(dest: *mut u8, src: *const u8, n: usize) -> *mut u8;
diff --git a/src/lib.rs b/src/lib.rs
index dc8f411..b104def 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -11,7 +11,6 @@
 #![feature(asm)]
 #![feature(compiler_builtins)]
 #![feature(core_intrinsics)]
-#![feature(linkage)]
 #![feature(naked_functions)]
 #![feature(staged_api)]
 #![no_builtins]
@@ -102,9 +101,6 @@ extern crate compiler_rt;
 #[cfg(test)]
 extern crate rand;
 
-#[cfg(feature = "weak")]
-extern crate rlibc;
-
 #[cfg(test)]
 #[macro_use]
 mod qc;
@@ -112,6 +108,9 @@ mod qc;
 pub mod int;
 pub mod float;
 
+#[cfg(feature = "mem")]
+pub mod mem;
+
 #[cfg(target_arch = "arm")]
 pub mod arm;
 
diff --git a/src/mem.rs b/src/mem.rs
new file mode 100644
index 0000000..31d6712
--- /dev/null
+++ b/src/mem.rs
@@ -0,0 +1,59 @@
+#[no_mangle]
+pub unsafe extern "C" fn memcpy(dest: *mut u8,
+                                src: *const u8,
+                                n: usize)
+                                -> *mut u8 {
+    let mut i = 0;
+    while i < n {
+        *dest.offset(i as isize) = *src.offset(i as isize);
+        i += 1;
+    }
+    dest
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn memmove(dest: *mut u8,
+                                 src: *const u8,
+                                 n: usize)
+                                 -> *mut u8 {
+    if src < dest as *const u8 {
+        // copy from end
+        let mut i = n;
+        while i != 0 {
+            i -= 1;
+            *dest.offset(i as isize) = *src.offset(i as isize);
+        }
+    } else {
+        // copy from beginning
+        let mut i = 0;
+        while i < n {
+            *dest.offset(i as isize) = *src.offset(i as isize);
+            i += 1;
+        }
+    }
+    dest
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn memset(s: *mut u8, c: i32, n: usize) -> *mut u8 {
+    let mut i = 0;
+    while i < n {
+        *s.offset(i as isize) = c as u8;
+        i += 1;
+    }
+    s
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
+    let mut i = 0;
+    while i < n {
+        let a = *s1.offset(i as isize);
+        let b = *s2.offset(i as isize);
+        if a != b {
+            return a as i32 - b as i32;
+        }
+        i += 1;
+    }
+    0
+}