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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <vespa/vespalib/stllike/string.h>
#include <mutex>
#include <vector>
#include <map>
#include <memory>
namespace vespalib::eval {
class ValueType;
class Function;
/**
* Pre-computed index tables used by DenseLambdaPeekFunction. The
* underlying index tables are shared between operations.
**/
class IndexLookupTable
{
private:
using Key = vespalib::string;
struct Value {
size_t num_refs;
std::vector<uint32_t> data;
struct ctor_tag {};
Value(ctor_tag) : num_refs(1), data() {}
};
using Map = std::map<Key,Value>;
static std::mutex _lock;
static Map _cached;
static void release(Map::iterator entry) {
std::lock_guard<std::mutex> guard(_lock);
if (--(entry->second.num_refs) == 0) {
_cached.erase(entry);
}
}
public:
/**
* A token represents shared ownership of a cached index lookup
* table.
**/
class Token
{
private:
friend class IndexLookupTable;
struct ctor_tag {};
IndexLookupTable::Map::iterator _entry;
public:
Token(Token &&) = delete;
Token(const Token &) = delete;
Token &operator=(Token &&) = delete;
Token &operator=(const Token &) = delete;
using UP = std::unique_ptr<Token>;
Token(IndexLookupTable::Map::iterator entry, ctor_tag) : _entry(entry) {}
const std::vector<uint32_t> &get() const { return _entry->second.data; }
~Token() { IndexLookupTable::release(_entry); }
};
IndexLookupTable() = delete;
static size_t num_cached();
static size_t count_refs();
static Token::UP create(const Function &idx_fun, const ValueType &type);
};
}
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