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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/platform/basic.h"
#include "mongo/util/itoa.h"
#include <cstdint>
#include <type_traits>
#include "mongo/base/string_data.h"
#include "mongo/platform/bits.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/itoa_table_4.h" // Generated by generate_itoa_table.py
namespace mongo {
namespace {
constexpr std::size_t kTableDigits = 4;
constexpr std::size_t pow10(std::size_t n) {
return n ? 10 * pow10(n - 1) : 1;
}
constexpr std::size_t kTableSize = pow10(kTableDigits);
// Cheesing gTable initializer out to Python and CPP due to compiler-imposed constexpr
// complexity restrictions (clang, msvc). C'est la vie. See `generate_itoa_table.py`.
constexpr struct {
std::uint8_t n;
char s[kTableDigits];
} gTable[] = {
#define EXPAND_PACK_(...) __VA_ARGS__
#define MAKE_ENTRY_(n, digitPack) \
{ n, EXPAND_PACK_ digitPack }
#define COMMA_ ,
ITOA_TABLE_EXPAND_4(MAKE_ENTRY_, COMMA_)
#undef COMMA_
#undef MAKE_ENTRY_
#undef EXPAND_PACK_
};
static_assert(std::extent_v<decltype(gTable)> == kTableSize, "gTable has correct size.");
} // namespace
ItoA::ItoA(std::uint64_t val) {
if (val < kTableSize) {
const auto& e = gTable[val];
std::size_t n = e.n;
_str = StringData(std::end(e.s) - n, n);
return;
}
char* p = std::end(_buf);
while (val >= kTableSize) {
std::size_t idx = val % kTableSize;
val /= kTableSize;
const auto& e = gTable[idx];
p -= kTableDigits;
memcpy(p, std::end(e.s) - kTableDigits, kTableDigits);
}
const auto& e = gTable[val];
auto n = e.n;
p -= n;
memcpy(p, std::end(e.s) - n, n);
_str = StringData(p, std::end(_buf) - p);
}
} // namespace mongo
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