rustc: Implement conversions from interior vector data to unsafe pointers and vice-versa

Author: pcwalton

src/lib/ivec.rs

@@ -12,6 +12,8 @@ native "rust-intrinsic" mod rusti {
 native "rust" mod rustrt {
     fn ivec_reserve[T](&mutable T[] v, uint n);
     fn ivec_on_heap[T](&T[] v) -> bool;
+    fn ivec_to_ptr[T](&T[] v) -> *T;
+    fn ivec_copy_from_buf[T](&mutable T[] v, *T ptr, uint count);
 }
 
 /// Reserves space for `n` elements in the given vector.
@@ -23,3 +25,17 @@ fn on_heap[T](&T[] v) -> bool {
     ret rustrt::ivec_on_heap(v);
 }
 
+fn to_ptr[T](&T[] v) -> *T {
+    ret rustrt::ivec_to_ptr(v);
+}
+
+fn len[T](&T[] v) -> uint {
+    ret rusti::ivec_len(v);
+}
+
+mod unsafe {
+    fn copy_from_buf[T](&mutable T[] v, *T ptr, uint count) {
+        ret rustrt::ivec_copy_from_buf(v, ptr, count);
+    }
+}
+

src/rt/rust_builtin.cpp

@@ -616,6 +616,43 @@ ivec_on_heap(rust_task *task, type_desc *ty, rust_ivec *v)
     return !v->fill && v->payload.ptr;
 }
 
+/**
+ * Returns an unsafe pointer to the data part of an interior vector.
+ */
+extern "C" void *
+ivec_to_ptr(rust_task *task, type_desc *ty, rust_ivec *v)
+{
+    return v->fill ? v->payload.data : v->payload.ptr->data;
+}
+
+/**
+ * Copies elements in an unsafe buffer to the given interior vector. The
+ * vector must have size zero.
+ */
+extern "C" void
+ivec_copy_from_buf(rust_task *task, type_desc *ty, rust_ivec *v, void *ptr,
+                   size_t count)
+{
+    if (v->fill || (v->payload.ptr && v->payload.ptr->fill)) {
+        task->fail(1);
+        return;
+    }
+
+    ivec_reserve(task, ty, v, count);
+
+    size_t new_size = count * ty->size;
+    if (v->fill) {
+        // On stack.
+        memmove(v->payload.data, ptr, new_size);
+        v->fill = new_size;
+        return;
+    }
+
+    // On heap.
+    memmove(v->payload.ptr->data, ptr, new_size);
+    v->payload.ptr->fill = new_size;
+}
+
 
 //
 // Local Variables:

src/rt/rustrt.def.in

@@ -9,8 +9,10 @@ debug_trap
 debug_tydesc
 do_gc
 get_time
+ivec_copy_from_buf
 ivec_on_heap
 ivec_reserve
+ivec_to_ptr
 last_os_error
 rand_free
 rand_new

src/test/run-pass/lib-ivec.rs

@@ -10,7 +10,32 @@ fn test_reserve_and_on_heap() {
     assert (ivec::on_heap(v));
 }
 
+fn test_unsafe_ptrs() {
+    // Test on-stack copy-from-buf.
+    auto a = ~[ 1, 2, 3 ];
+    auto ptr = ivec::to_ptr(a);
+    auto b = ~[];
+    ivec::unsafe::copy_from_buf(b, ptr, 3u);
+    assert (ivec::len(b) == 3u);
+    assert (b.(0) == 1);
+    assert (b.(1) == 2);
+    assert (b.(2) == 3);
+
+    // Test on-heap copy-from-buf.
+    auto c = ~[ 1, 2, 3, 4, 5 ];
+    ptr = ivec::to_ptr(c);
+    auto d = ~[];
+    ivec::unsafe::copy_from_buf(d, ptr, 5u);
+    assert (ivec::len(d) == 5u);
+    assert (d.(0) == 1);
+    assert (d.(1) == 2);
+    assert (d.(2) == 3);
+    assert (d.(3) == 4);
+    assert (d.(4) == 5);
+}
+
 fn main() {
     test_reserve_and_on_heap();
+    test_unsafe_ptrs();
 }