Move RelPtr/RelSlice out of arches into common

The bba approach seems widely used enough that it's reasonable for this
to become part of common code.

Signed-off-by: D. Shah <dave@ds0.me>

1 files changed, 39 insertions, 0 deletions

diff --git a/common/relptr.h b/common/relptr.h
new file mode 100644
index 00000000..f8f1d429
--- /dev/null
+++ b/common/relptr.h
@@ -0,0 +1,39 @@
+// This is intended to be included inside arch.h only.
+
+template <typename T> struct RelPtr
+{
+    int32_t offset;
+
+    const T *get() const { return reinterpret_cast<const T *>(reinterpret_cast<const char *>(this) + offset); }
+
+    const T &operator[](size_t index) const { return get()[index]; }
+
+    const T &operator*() const { return *(get()); }
+
+    const T *operator->() const { return get(); }
+
+    RelPtr(const RelPtr &) = delete;
+    RelPtr &operator=(const RelPtr &) = delete;
+};
+
+NPNR_PACKED_STRUCT(template <typename T> struct RelSlice {
+    int32_t offset;
+    uint32_t length;
+
+    const T *get() const { return reinterpret_cast<const T *>(reinterpret_cast<const char *>(this) + offset); }
+
+    const T &operator[](size_t index) const
+    {
+        NPNR_ASSERT(index < length);
+        return get()[index];
+    }
+
+    const T *begin() const { return get(); }
+    const T *end() const { return get() + length; }
+
+    const size_t size() const { return length; }
+
+    const T &operator*() const { return *(get()); }
+
+    const T *operator->() const { return get(); }
+});