Vendor things

third-party/vendor/backtrace/src/symbolize/gimli/stash.rs

@@ -0,0 +1,50 @@
+// only used on Linux right now, so allow dead code elsewhere
+#![cfg_attr(not(target_os = "linux"), allow(dead_code))]
+
+use super::Mmap;
+use alloc::vec;
+use alloc::vec::Vec;
+use core::cell::UnsafeCell;
+
+/// A simple arena allocator for byte buffers.
+pub struct Stash {
+    buffers: UnsafeCell<Vec<Vec<u8>>>,
+    mmaps: UnsafeCell<Vec<Mmap>>,
+}
+
+impl Stash {
+    pub fn new() -> Stash {
+        Stash {
+            buffers: UnsafeCell::new(Vec::new()),
+            mmaps: UnsafeCell::new(Vec::new()),
+        }
+    }
+
+    /// Allocates a buffer of the specified size and returns a mutable reference
+    /// to it.
+    pub fn allocate(&self, size: usize) -> &mut [u8] {
+        // SAFETY: this is the only function that ever constructs a mutable
+        // reference to `self.buffers`.
+        let buffers = unsafe { &mut *self.buffers.get() };
+        let i = buffers.len();
+        buffers.push(vec![0; size]);
+        // SAFETY: we never remove elements from `self.buffers`, so a reference
+        // to the data inside any buffer will live as long as `self` does.
+        &mut buffers[i]
+    }
+
+    /// Stores a `Mmap` for the lifetime of this `Stash`, returning a pointer
+    /// which is scoped to just this lifetime.
+    pub fn cache_mmap(&self, map: Mmap) -> &[u8] {
+        // SAFETY: this is the only location for a mutable pointer to
+        // `mmaps`, and this structure isn't threadsafe to shared across
+        // threads either. We also never remove elements from `self.mmaps`,
+        // so a reference to the data inside the map will live as long as
+        // `self` does.
+        unsafe {
+            let mmaps = &mut *self.mmaps.get();
+            mmaps.push(map);
+            mmaps.last().unwrap()
+        }
+    }
+}