Add simplistic Dwarf representation

This is only representing a small fragment of Dwarf, **on purpose**: in
practice, the huge majority of Dwarf observed in the wild belongs to
this fragment.

src/SimpleDwarf.hpp

@@ -0,0 +1,51 @@
+/** SimpleDwarf - a simplified representation of Dwarf rules and table
+ *
+ * This class is made to handle a simple subset of the Dwarf table - the subset
+ * that is the most ubiquitous. It should cover most of the real-life cases.
+ */
+
+#pragma once
+
+#include <cstdint>
+#include <vector> // We only need linear swipes, no need for anything fancier
+
+struct SimpleDwarf {
+    /** A machine register (eg. %rip) among the supported ones (x86_64 only
+     * for now) */
+    static const std::size_t HANDLED_REGISTERS_COUNT = 3;
+    enum MachineRegister {
+        REG_RIP, REG_RSP, REG_RBP
+    };
+
+    struct DwRegister {
+        /** Holds a single Dwarf register value */
+
+        DwRegister(): type(REG_UNDEFINED), offset(0), reg(REG_RIP /* 0 */) {}
+
+        /// Type of register (what does the expression mean?)
+        enum Type {
+            REG_UNDEFINED, /**< Undefined register (the value will be
+                             defined at some later IP in the same DIE) */
+            REG_REGISTER, ///< Value of a machine register plus offset
+            REG_CFA_OFFSET, ///< Value stored at some offset from CFA
+            REG_NOT_IMPLEMENTED ///< This type of register is not supported
+        };
+
+        Type type; ///< Type of this register
+        uintptr_t offset; ///< Offset from the expression, if applicable
+        MachineRegister reg; ///< Machine register implied, if applicable
+    };
+
+    struct DwRow {
+        uintptr_t ip;
+        DwRegister cfa;
+        DwRegister regs[HANDLED_REGISTERS_COUNT];
+    };
+
+    struct Fde {
+        uintptr_t beg_ip, end_ip;
+        std::vector<DwRow> rows;
+    };
+
+    std::vector<Fde> fde_list;
+};