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/*
* Copyright (C) 2014 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_COMPILER_GC_MAP_BUILDER_H_
#define ART_COMPILER_GC_MAP_BUILDER_H_
#include <vector>
#include "base/bit_utils.h"
#include "gc_map.h"
namespace art {
class GcMapBuilder {
public:
template <typename Alloc>
GcMapBuilder(std::vector<uint8_t, Alloc>* table, size_t entries, uint32_t max_native_offset,
size_t references_width)
: entries_(entries), references_width_(entries != 0u ? references_width : 0u),
native_offset_width_(entries != 0 && max_native_offset != 0
? sizeof(max_native_offset) - CLZ(max_native_offset) / 8u
: 0u),
in_use_(entries) {
// Resize table and set up header.
table->resize((EntryWidth() * entries) + sizeof(uint32_t));
table_ = table->data();
CHECK_LT(native_offset_width_, 1U << 3);
(*table)[0] = native_offset_width_ & 7;
CHECK_LT(references_width_, 1U << 13);
(*table)[0] |= (references_width_ << 3) & 0xFF;
(*table)[1] = (references_width_ >> 5) & 0xFF;
CHECK_LT(entries, 1U << 16);
(*table)[2] = entries & 0xFF;
(*table)[3] = (entries >> 8) & 0xFF;
}
void AddEntry(uint32_t native_offset, const uint8_t* references) {
size_t table_index = TableIndex(native_offset);
while (in_use_[table_index]) {
table_index = (table_index + 1) % entries_;
}
in_use_[table_index] = true;
SetCodeOffset(table_index, native_offset);
DCHECK_EQ(native_offset, GetCodeOffset(table_index));
SetReferences(table_index, references);
}
private:
size_t TableIndex(uint32_t native_offset) {
return NativePcOffsetToReferenceMap::Hash(native_offset) % entries_;
}
uint32_t GetCodeOffset(size_t table_index) {
uint32_t native_offset = 0;
size_t table_offset = (table_index * EntryWidth()) + sizeof(uint32_t);
for (size_t i = 0; i < native_offset_width_; i++) {
native_offset |= table_[table_offset + i] << (i * 8);
}
return native_offset;
}
void SetCodeOffset(size_t table_index, uint32_t native_offset) {
size_t table_offset = (table_index * EntryWidth()) + sizeof(uint32_t);
for (size_t i = 0; i < native_offset_width_; i++) {
table_[table_offset + i] = (native_offset >> (i * 8)) & 0xFF;
}
}
void SetReferences(size_t table_index, const uint8_t* references) {
size_t table_offset = (table_index * EntryWidth()) + sizeof(uint32_t);
memcpy(&table_[table_offset + native_offset_width_], references, references_width_);
}
size_t EntryWidth() const {
return native_offset_width_ + references_width_;
}
// Number of entries in the table.
const size_t entries_;
// Number of bytes used to encode the reference bitmap.
const size_t references_width_;
// Number of bytes used to encode a native offset.
const size_t native_offset_width_;
// Entries that are in use.
std::vector<bool> in_use_;
// The table we're building.
uint8_t* table_;
};
} // namespace art
#endif // ART_COMPILER_GC_MAP_BUILDER_H_
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