itoa.cpp

/**
 *    Copyright (C) 2015 MongoDB Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    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
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    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 GNU Affero General 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/assert_util.h"
#include "mongo/util/itoa.h"

namespace mongo {
namespace {
const char kIndexTable[] =
    "0\0"
    "1\0"
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    "954\0"
    "955\0"
    "956\0"
    "957\0"
    "958\0"
    "959\0"
    "960\0"
    "961\0"
    "962\0"
    "963\0"
    "964\0"
    "965\0"
    "966\0"
    "967\0"
    "968\0"
    "969\0"
    "970\0"
    "971\0"
    "972\0"
    "973\0"
    "974\0"
    "975\0"
    "976\0"
    "977\0"
    "978\0"
    "979\0"
    "980\0"
    "981\0"
    "982\0"
    "983\0"
    "984\0"
    "985\0"
    "986\0"
    "987\0"
    "988\0"
    "989\0"
    "990\0"
    "991\0"
    "992\0"
    "993\0"
    "994\0"
    "995\0"
    "996\0"
    "997\0"
    "998\0"
    "999\0";
}  // namespace

constexpr size_t ItoA::kBufSize;

ItoA::ItoA(std::uint32_t val) {
    if (val < 10u) {
        _str = kIndexTable + (2 * val);
        _len = 1;
    } else if (val < 100u) {
        _str = kIndexTable + (2 * 10) + (3 * (val - 10));
        _len = 2;
    } else if (val < 1000u) {
        _str = kIndexTable + (2 * 10) + (3 * 90) + (4 * (val - 100));
        _len = 3;
    } else {
        auto len = sizeof(_buf) - 1;
        _buf[len] = '\0';
        auto pos = len;

        while (val > 0) {
            dassert(pos > 0);
            --pos;
            _buf[pos] = static_cast<char>((val % 10) + static_cast<std::uint32_t>('0'));
            val /= 10;
        }

        _str = _buf + pos;
        _len = len - pos;
    }
}

}  // namespace mongo