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64 lines
2.1 KiB
Rust
64 lines
2.1 KiB
Rust
// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
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// Workaround for https://github.com/rust-lang/libz-sys/issues/55
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// See https://github.com/rust-lang/flate2-rs/blob/31fb07820345691352aaa64f367c1e482ad9cfdc/src/ffi/c.rs#L60
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use std::alloc::Layout;
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use std::alloc::{self};
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use std::os::raw::c_void;
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use std::ptr;
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const ALIGN: usize = std::mem::align_of::<usize>();
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fn align_up(size: usize, align: usize) -> usize {
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(size + align - 1) & !(align - 1)
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}
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pub extern "C" fn zalloc(
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_ptr: *mut c_void,
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items: u32,
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item_size: u32,
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) -> *mut c_void {
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// We need to multiply `items` and `item_size` to get the actual desired
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// allocation size. Since `zfree` doesn't receive a size argument we
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// also need to allocate space for a `usize` as a header so we can store
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// how large the allocation is to deallocate later.
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let size = match (items as usize)
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.checked_mul(item_size as usize)
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.map(|size| align_up(size, ALIGN))
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.and_then(|i| i.checked_add(std::mem::size_of::<usize>()))
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{
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Some(i) => i,
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None => return ptr::null_mut(),
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};
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// Make sure the `size` isn't too big to fail `Layout`'s restrictions
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let layout = match Layout::from_size_align(size, ALIGN) {
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Ok(layout) => layout,
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Err(_) => return ptr::null_mut(),
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};
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// SAFETY: `layout` has non-zero size, guaranteed to be a sentinel address
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// or a null pointer.
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unsafe {
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// Allocate the data, and if successful store the size we allocated
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// at the beginning and then return an offset pointer.
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let ptr = alloc::alloc(layout) as *mut usize;
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if ptr.is_null() {
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return ptr as *mut c_void;
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}
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*ptr = size;
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ptr.add(1) as *mut c_void
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}
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}
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pub extern "C" fn zfree(_ptr: *mut c_void, address: *mut c_void) {
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// SAFETY: Move our address being free'd back one pointer, read the size we
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// stored in `zalloc`, and then free it using the standard Rust
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// allocator.
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unsafe {
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let ptr = (address as *mut usize).offset(-1);
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let size = *ptr;
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let layout = Layout::from_size_align_unchecked(size, ALIGN);
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alloc::dealloc(ptr as *mut u8, layout)
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}
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}
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