Refactor the code.

The object hierarchy was confusing and convoluted. This removes
a lot of unnecessary code, and consolidates the BacktraceCurrent
and BacktraceThread code into BacktraceCurrent.

Change-Id: I01c8407d493712a48169df49dd3ff46db4a7c3ae
diff --git a/libbacktrace/BacktraceCurrent.h b/libbacktrace/BacktraceCurrent.h
new file mode 100644
index 0000000..81ea81d
--- /dev/null
+++ b/libbacktrace/BacktraceCurrent.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _LIBBACKTRACE_BACKTRACE_CURRENT_H
+#define _LIBBACKTRACE_BACKTRACE_CURRENT_H
+
+#include <stdint.h>
+#include <sys/types.h>
+#include <ucontext.h>
+
+#include <backtrace/Backtrace.h>
+
+// The signal used to cause a thread to dump the stack.
+#if defined(__GLIBC__)
+// In order to run the backtrace_tests on the host, we can't use
+// the internal real time signals used by GLIBC. To avoid this,
+// use SIGRTMIN for the signal to dump the stack.
+#define THREAD_SIGNAL SIGRTMIN
+#else
+#define THREAD_SIGNAL (__SIGRTMIN+1)
+#endif
+
+class BacktraceMap;
+
+class BacktraceCurrent : public Backtrace {
+public:
+  BacktraceCurrent(pid_t pid, pid_t tid, BacktraceMap* map) : Backtrace(pid, tid, map) {}
+  virtual ~BacktraceCurrent() {}
+
+  size_t Read(uintptr_t addr, uint8_t* buffer, size_t bytes) override;
+
+  bool ReadWord(uintptr_t ptr, word_t* out_value) override;
+
+  bool Unwind(size_t num_ignore_frames, ucontext_t* ucontext) override;
+
+private:
+  bool UnwindThread(size_t num_ignore_frames);
+
+  virtual bool UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucontext) = 0;
+};
+
+#endif // _LIBBACKTRACE_BACKTRACE_CURRENT_H