95 lines
2.2 KiB
Rust
95 lines
2.2 KiB
Rust
extern crate libc;
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use std::marker::PhantomData;
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use std::ops::Deref;
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use std::slice;
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use libc::c_void;
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struct MallocPtr(*mut c_void);
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impl Drop for MallocPtr {
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fn drop(&mut self) {
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unsafe {
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libc::free(self.0);
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}
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}
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}
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/// A type that represents a `malloc`'d chunk of memory.
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pub struct MallocBuffer<T> {
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ptr: MallocPtr,
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len: usize,
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items: PhantomData<[T]>,
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}
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impl<T: Copy> MallocBuffer<T> {
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/// Constructs a new `MallocBuffer` for a `malloc`'d buffer
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/// with the given length at the given pointer.
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/// Returns `None` if the given pointer is null and the length is not 0.
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///
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/// When this `MallocBuffer` drops, the buffer will be `free`'d.
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///
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/// Unsafe because there must be `len` contiguous, valid instances of `T`
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/// at `ptr`.
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pub unsafe fn new(ptr: *mut T, len: usize) -> Option<MallocBuffer<T>> {
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if len > 0 && ptr.is_null() {
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None
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} else {
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Some(MallocBuffer {
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ptr: MallocPtr(ptr as *mut c_void),
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len: len,
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items: PhantomData,
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})
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}
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}
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}
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impl<T> Deref for MallocBuffer<T> {
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type Target = [T];
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fn deref(&self) -> &[T] {
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let ptr = if self.len == 0 && self.ptr.0.is_null() {
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// Even a 0-size slice cannot be null, so just use another pointer
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0x1 as *const T
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} else {
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self.ptr.0 as *const T
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};
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unsafe {
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slice::from_raw_parts(ptr, self.len)
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use std::ptr;
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use libc;
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use super::MallocBuffer;
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#[test]
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fn test_null_buf() {
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let buf = unsafe {
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MallocBuffer::<u32>::new(ptr::null_mut(), 0).unwrap()
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};
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assert!(&*buf == []);
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assert!(Some(&*buf) == Some(&[]));
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let buf = unsafe {
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MallocBuffer::<u32>::new(ptr::null_mut(), 7)
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};
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assert!(buf.is_none());
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}
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#[test]
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fn test_buf() {
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let buf = unsafe {
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let ptr = libc::malloc(12) as *mut u32;
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*ptr = 1;
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*ptr.offset(1) = 2;
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*ptr.offset(2) = 3;
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MallocBuffer::new(ptr, 3).unwrap()
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};
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assert!(&*buf == [1, 2, 3]);
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}
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}
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