upload android base code part3

android/art/runtime/method_bss_mapping.h

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+/*
+ * Copyright (C) 2017 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 ART_RUNTIME_METHOD_BSS_MAPPING_H_
+#define ART_RUNTIME_METHOD_BSS_MAPPING_H_
+
+#include "base/bit_utils.h"
+#include "base/length_prefixed_array.h"
+
+namespace art {
+
+// MethodBssMappingEntry describes a mapping of up to 17 method indexes to their offsets
+// in the .bss. The highest index and its associated .bss offset are stored in plain form
+// as `method_index` and `bss_offset`, respectively, while the additional indexes can be
+// stored in compressed form if their associated .bss entries are consecutive and in the
+// method index order. Each of the 16 bits of the `index_mask` corresponds to one of the
+// previous 16 method indexes and indicates whether there is a .bss entry for that index.
+//
+struct MethodBssMappingEntry {
+  bool CoversIndex(uint32_t method_idx) const {
+    uint32_t diff = method_index - method_idx;
+    return (diff == 0) || (diff <= 16 && ((index_mask >> (16u - diff)) & 1u) != 0);
+  }
+
+  uint32_t GetBssOffset(uint32_t method_idx, size_t entry_size) const {
+    DCHECK(CoversIndex(method_idx));
+    uint32_t diff = method_index - method_idx;
+    if (diff == 0) {
+      return bss_offset;
+    } else {
+      return bss_offset - POPCOUNT(index_mask >> (16u - diff)) * entry_size;
+    }
+  }
+
+  uint16_t method_index;
+  uint16_t index_mask;
+  uint32_t bss_offset;
+};
+
+using MethodBssMapping = LengthPrefixedArray<MethodBssMappingEntry>;
+
+}  // namespace art
+
+#endif  // ART_RUNTIME_METHOD_BSS_MAPPING_H_