aliu 0.1.22

Albert Liu's utilities
Documentation 
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use crate::alloc_api::*;
use crate::basic::*;
use std::ffi::*;

type Ptr = *const ();

pub use os::*;

#[cfg(target_family = "unix")]
mod os {
    use super::*;

    pub fn read_file_static(path: &str) -> &'static str {
        // let filepath = expect(CString::new(path));

        // TODO how do I check this?
        // let flags = libc::O_RDONLY; // | libc::O_LARGEFILE;
        // let fd = unsafe { libc::open(filepath.as_ptr(), flags) };
        // if fd == -1 {}

        // let flags = libc::MAP_SHARED;
        // let protection = libc::PROT_READ;

        return "";
    }

    pub unsafe fn delete_file_static(file: &'static str) {}

    pub unsafe fn map_region(base: Ptr, size: usize) -> Result<Ptr, AllocError> {
        let mut flags = libc::MAP_PRIVATE | libc::MAP_ANON;

        if !base.is_null() {
            flags |= libc::MAP_FIXED;
        }

        let protection = libc::PROT_WRITE | libc::PROT_READ;
        let result = libc::mmap(base as *mut _, size, protection, flags, -1, 0);

        if result == libc::MAP_FAILED {
            return Err(AllocError);
        }

        return Ok(result as Ptr);
    }

    pub unsafe fn unmap_region(base: Ptr, size: usize) -> Result<(), AllocError> {
        let result = libc::munmap(base as *mut _, size);

        if result == 0 {
            return Ok(());
        }

        return Err(AllocError);
    }
}

#[cfg(target_family = "windows")]
mod os {
    use super::*;

    pub unsafe fn map_region(base: Ptr, size: usize) -> Result<Ptr, AllocError> {
        use winapi::um::memoryapi::VirtualAlloc;
        use winapi::um::winnt::{MEM_COMMIT, MEM_RESERVE, PAGE_READWRITE, PVOID};

        let flags = MEM_COMMIT | MEM_RESERVE;
        let protection = PAGE_READWRITE;

        let allocation = VirtualAlloc(base as PVOID, size, flags, protection);

        if allocation.is_null() {
            return Err(AllocError);
        }

        Ok(allocation as Ptr)
    }

    pub unsafe fn unmap_region(base: Ptr, _size: usize) -> Result<(), AllocError> {
        use winapi::shared::minwindef::FALSE;
        use winapi::um::memoryapi::VirtualFree;
        use winapi::um::winnt::{MEM_RELEASE, PVOID};

        let result = VirtualFree(base as PVOID, 0, MEM_RELEASE);

        if result == FALSE {
            return Err(AllocError);
        }

        return Ok(());
    }
}

#[cfg(all(target_family = "wasm", not(target_os = "emscripten")))]
mod os {
    use super::*;
    use core::alloc::Layout;
    use core::ptr::NonNull;

    pub unsafe fn map_region(base: Ptr, size: usize) -> Result<Ptr, AllocError> {
        if !base.is_null() {
            panic!("aliu::map_region caused an error: can't give value for base pointer on webassembly");
        }

        let layout = Layout::from_size_align(size, 8).map_err(|e| AllocError)?;
        let alloc = Global.allocate(layout)?;

        let ptr = &*alloc.as_ptr();
        return Ok(ptr.as_ptr() as *const ());
    }

    pub unsafe fn unmap_region(base: Ptr, size: usize) -> Result<(), AllocError> {
        let layout = Layout::from_size_align(size, 8).map_err(|e| AllocError)?;
        let ptr = NonNull::new(base as *mut _).ok_or(AllocError)?;
        Global.deallocate(ptr, layout);

        return Ok(());
    }
}

#[test]
fn mapping() {
    unsafe {
        let ptr = map_region(core::ptr::null(), 4096).unwrap();
        unmap_region(ptr, 4096).unwrap();
    }
}