Add a new library for collecting stack traces.

Supports collecting the stack trace of the current thread,
another thread in the same process, or a thread in a
different process (using ptrace).

Change-Id: Ica2594e4436edde4ceb7bcc3d78e6c31a7902cbf
diff --git a/libcorkscrew/backtrace-helper.c b/libcorkscrew/backtrace-helper.c
new file mode 100644
index 0000000..bf9d3f3
--- /dev/null
+++ b/libcorkscrew/backtrace-helper.c
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2011 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.
+ */
+
+#define LOG_TAG "Corkscrew"
+//#define LOG_NDEBUG 0
+
+#include "backtrace-helper.h"
+
+#include <cutils/log.h>
+
+backtrace_frame_t* add_backtrace_entry(uintptr_t pc, backtrace_frame_t* backtrace,
+        size_t ignore_depth, size_t max_depth,
+        size_t* ignored_frames, size_t* returned_frames) {
+    if (*ignored_frames < ignore_depth) {
+        *ignored_frames += 1;
+        return NULL;
+    }
+    if (*returned_frames >= max_depth) {
+        return NULL;
+    }
+    backtrace_frame_t* frame = &backtrace[*returned_frames];
+    frame->absolute_pc = pc;
+    frame->stack_top = 0;
+    frame->stack_size = 0;
+    *returned_frames += 1;
+    return frame;
+}