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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef SQL_STATEMENT_ID_H_
#define SQL_STATEMENT_ID_H_
#include <cstddef>
#include "base/component_export.h"
namespace sql {
// Identifies a compiled SQLite statement in a statement cache.
//
// This is a value type with the same performance characteristics as
// std::string_view. Instances are thread-unsafe, but not thread-hostile.
//
// StatementID instances should be constructed by using the SQL_FROM_HERE
// macro, which produces an unique ID based on the source file name and line.
class COMPONENT_EXPORT(SQL) StatementID {
public:
// Creates an ID representing a line in the source tree.
//
// SQL_FROM_HERE should be preferred to calling this constructor directly.
//
// |source_file| should point to a C-style string that lives for the duration
// of the program.
explicit StatementID(const char* source_file, size_t source_line) noexcept
: source_file_(source_file), source_line_(source_line) {}
// Copying intentionally allowed.
StatementID(const StatementID&) noexcept = default;
StatementID& operator=(const StatementID&) noexcept = default;
// Facilitates storing StatementID instances in maps.
bool operator<(const StatementID& rhs) const noexcept;
private:
// Instances cannot be immutable because they support being used as map keys.
//
// It seems tempting to merge source_file_ and source_line_ in a single
// source_location_ member, and to have SQL_FROM_HERE use C++ preprocessor
// magic to generate strings like "sql/connection.cc:42". This causes a
// non-trivial binary size increase, because Chrome uses -fmerge-constants and
// SQL_FROM_HERE tends to be used many times in the same few files.
const char* source_file_;
size_t source_line_;
};
} // namespace sql
// Produces a StatementID based on the current line in the source tree.
#define SQL_FROM_HERE sql::StatementID(__FILE__, __LINE__)
#endif // SQL_STATEMENT_ID_H_
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