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/ThreadEntry.h b/libbacktrace/ThreadEntry.h
new file mode 100644
index 0000000..94becf2
--- /dev/null
+++ b/libbacktrace/ThreadEntry.h
@@ -0,0 +1,71 @@
+/*
+ * 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_THREAD_ENTRY_H
+#define _LIBBACKTRACE_THREAD_ENTRY_H
+
+#include <pthread.h>
+#include <sys/types.h>
+#include <ucontext.h>
+
+class ThreadEntry {
+public:
+  static ThreadEntry* Get(pid_t pid, pid_t tid, bool create = true);
+
+  static void Remove(ThreadEntry* entry);
+
+  void Wake();
+
+  void Wait(int);
+
+  void CopyUcontextFromSigcontext(void*);
+
+  inline void Lock() {
+    pthread_mutex_lock(&mutex_);
+
+    // Always reset the wait value since this could be the first or nth
+    // time this entry is locked.
+    wait_value_ = 0;
+  }
+
+  inline void Unlock() {
+    pthread_mutex_unlock(&mutex_);
+  }
+
+  inline ucontext_t* GetUcontext() { return &ucontext_; }
+
+private:
+  ThreadEntry(pid_t pid, pid_t tid);
+  ~ThreadEntry();
+
+  bool Match(pid_t chk_pid, pid_t chk_tid) { return (chk_pid == pid_ && chk_tid == tid_); }
+
+  pid_t pid_;
+  pid_t tid_;
+  int ref_count_;
+  pthread_mutex_t mutex_;
+  pthread_mutex_t wait_mutex_;
+  pthread_cond_t wait_cond_;
+  int wait_value_;
+  ThreadEntry* next_;
+  ThreadEntry* prev_;
+  ucontext_t ucontext_;
+
+  static ThreadEntry* list_;
+  static pthread_mutex_t list_mutex_;
+};
+
+#endif // _LIBBACKTRACE_THREAD_ENTRY_H