Move code around

src/libutil/rust-ffi.cc

@@ -0,0 +1,12 @@
+#include "logging.hh"
+#include "rust.hh"
+
+namespace nix {
+
+extern "C" std::exception_ptr * make_error(rust::StringSlice s)
+{
+    // FIXME: leak
+    return new std::exception_ptr(std::make_exception_ptr(Error(std::string(s.ptr, s.size))));
+}
+
+}

src/libutil/rust-ffi.hh

@@ -0,0 +1,97 @@
+#include "serialise.hh"
+
+namespace rust {
+
+// Depending on the internal representation of Rust slices is slightly
+// evil...
+template<typename T>
+struct Slice
+{
+    T * ptr;
+    size_t size;
+
+    Slice(T * ptr, size_t size) : ptr(ptr), size(size)
+    {
+        assert(ptr);
+    }
+};
+
+struct StringSlice : Slice<char>
+{
+    StringSlice(const std::string & s): Slice((char *) s.data(), s.size()) {}
+};
+
+struct Source
+{
+    size_t (*fun)(void * source_this, rust::Slice<uint8_t> data);
+    nix::Source * _this;
+
+    Source(nix::Source & _this)
+        : fun(sourceWrapper), _this(&_this)
+    {}
+
+    // FIXME: how to propagate exceptions?
+    static size_t sourceWrapper(void * _this, rust::Slice<uint8_t> data)
+    {
+        auto n = ((nix::Source *) _this)->read(data.ptr, data.size);
+        return n;
+    }
+};
+
+/* C++ representation of Rust's Result<T, CppException>. */
+template<typename T>
+struct Result
+{
+    unsigned int tag;
+
+    union {
+        T data;
+        std::exception_ptr * exc;
+    };
+
+    /* Rethrow the wrapped exception or return the wrapped value. */
+    T unwrap()
+    {
+        if (tag == 0)
+            return data;
+        else if (tag == 1)
+            std::rethrow_exception(*exc);
+        else
+            abort();
+    }
+};
+
+template<typename T>
+struct CBox
+{
+    T * ptr;
+
+    T * operator ->()
+    {
+        return ptr;
+    }
+
+    CBox(T * ptr) : ptr(ptr) { }
+    CBox(const CBox &) = delete;
+    CBox(CBox &&) = delete;
+
+    ~CBox()
+    {
+        free(ptr);
+    }
+};
+
+// Grrr, this is only needed because 'extern "C"' functions don't
+// support non-POD return types (and CBox has a destructor so it's not
+// POD).
+template<typename T>
+struct CBox2
+{
+    T * ptr;
+    CBox<T> use()
+    {
+        return CBox(ptr);
+    }
+};
+
+}