From 304bcfc415ffa204ec9e82d5ec535708ed1bcca8 Mon Sep 17 00:00:00 2001
From: Nicolas Mattia <nicolas@nmattia.com>
Date: Fri, 12 Nov 2021 12:12:07 +0100
Subject: [PATCH] Add wasm32 implementation for libc

This adds a wasm32 implementation for `free`, `malloc` and `realloc`.
Originally written by @rodrigorc in
https://github.com/rust-lang/libc/pull/1092 and adapted.
---
 src/ffi.rs      |  9 ++++++++-
 src/ffi/libc.rs | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)
 create mode 100644 src/ffi/libc.rs

diff --git a/src/ffi.rs b/src/ffi.rs
index 074fc0f..09df5e5 100644
--- a/src/ffi.rs
+++ b/src/ffi.rs
@@ -8,10 +8,17 @@ use std::slice;
 use std::fmt;
 use std::os::raw::*;
 use std::ffi::CStr;
-use std::path::*;
 use std::io;
 
 use crate::rustimpl;
+#[cfg(target_arch = "wasm32")]
+mod libc;
+
+#[cfg(target_arch = "wasm32")]
+use std::path::{PathBuf};
+
+#[cfg(not(target_arch = "wasm32"))]
+use std::path::{Path};
 
 macro_rules! lode_error {
     ($e:expr) => {
diff --git a/src/ffi/libc.rs b/src/ffi/libc.rs
new file mode 100644
index 0000000..f500afb
--- /dev/null
+++ b/src/ffi/libc.rs
@@ -0,0 +1,36 @@
+pub type size_t = usize;
+
+const MALLOC_HEADER : isize = 8;
+const MALLOC_ALIGN : usize = 8;
+
+use super::c_void;
+use std::alloc::{self, Layout};
+use std::ptr;
+
+pub unsafe fn malloc(size: size_t) -> *mut c_void {
+    let lay = Layout::from_size_align_unchecked(MALLOC_HEADER as usize + size, MALLOC_ALIGN);
+    let p = alloc::alloc(lay);
+    if p.is_null() {
+        return ptr::null_mut();
+    }
+    *(p as *mut size_t) = size;
+    p.offset(MALLOC_HEADER) as *mut c_void
+}
+pub unsafe fn free(p: *mut c_void) {
+    let p = p.offset(-MALLOC_HEADER) as *mut u8;
+    let size = *(p as *mut size_t);
+    let lay = Layout::from_size_align_unchecked(MALLOC_HEADER as usize + size, MALLOC_ALIGN);
+    alloc::dealloc(p, lay);
+}
+pub unsafe fn realloc(p: *mut c_void, _size: size_t) -> *mut c_void {
+    let p = p.offset(-MALLOC_HEADER) as *mut u8;
+    let size = *(p as *mut size_t);
+    let lay = Layout::from_size_align_unchecked(MALLOC_HEADER as usize + size, MALLOC_ALIGN);
+    let p = alloc::realloc(p, lay, size);
+    if p.is_null() {
+        return ptr::null_mut();
+    }
+    *(p as *mut size_t) = size;
+    p.offset(MALLOC_HEADER) as *mut c_void
+}
+