adb: switch asocket::enqueue to std::string.

Switch asocket over to taking a std::string instead of apacket* for
data. This allows us to remove asocket specific fields from apacket*.

Test: python test_device.py with x86_64 emulator, walleye
Test: adb_test on host
Change-Id: I9d157ff331a75ba49a54fdd4194e3f6cdff722f4
diff --git a/adb/range.h b/adb/range.h
new file mode 100644
index 0000000..7a0b822
--- /dev/null
+++ b/adb/range.h
@@ -0,0 +1,65 @@
+#pragma once
+
+/*
+ * Copyright (C) 2018 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.
+ */
+
+#include <string>
+
+#include <android-base/logging.h>
+
+struct Range {
+    explicit Range(std::string data) : data_(std::move(data)) {}
+
+    Range(const Range& copy) = delete;
+    Range& operator=(const Range& copy) = delete;
+
+    Range(Range&& move) = default;
+    Range& operator=(Range&& move) = default;
+
+    bool empty() const {
+        return size() == 0;
+    }
+
+    size_t size() const {
+        return data_.size() - begin_offset_ - end_offset_;
+    };
+
+    void drop_front(size_t n) {
+        CHECK_GE(size(), n);
+        begin_offset_ += n;
+    }
+
+    void drop_end(size_t n) {
+        CHECK_GE(size(), n);
+        end_offset_ += n;
+    }
+
+    char* data() {
+        return &data_[0] + begin_offset_;
+    }
+
+    std::string::iterator begin() {
+        return data_.begin() + begin_offset_;
+    }
+
+    std::string::iterator end() {
+        return data_.end() - end_offset_;
+    }
+
+    std::string data_;
+    size_t begin_offset_ = 0;
+    size_t end_offset_ = 0;
+};