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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/db/pipeline/granularity_rounder.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/platform/bits.h"
namespace mongo {
using boost::intrusive_ptr;
using std::string;
REGISTER_GRANULARITY_ROUNDER(POWERSOF2, GranularityRounderPowersOfTwo::create);
intrusive_ptr<GranularityRounder> GranularityRounderPowersOfTwo::create(
const boost::intrusive_ptr<ExpressionContext>& expCtx) {
return new GranularityRounderPowersOfTwo(expCtx);
}
namespace {
void uassertNonNegativeNumber(Value value) {
uassert(40265,
str::stream() << "A granularity rounder can only round numeric values, but found type: "
<< typeName(value.getType()),
value.numeric());
double number = value.coerceToDouble();
uassert(40266, "A granularity rounder cannot round NaN", !std::isnan(number));
uassert(40267, "A granularity rounder can only round non-negative numbers", number >= 0.0);
}
} // namespace
Value GranularityRounderPowersOfTwo::roundUp(Value value) {
uassertNonNegativeNumber(value);
if (value.coerceToDouble() == 0.0) {
return value;
}
Value exp;
if (value.getType() == BSONType::NumberDouble) {
exp = Value(static_cast<int>(std::floor(std::log2(value.getDouble())) + 1.0));
} else if (value.getType() == BSONType::NumberDecimal) {
Decimal128 input = value.getDecimal();
exp = Value(Decimal128(
static_cast<int>((std::floor(input.logarithm(Decimal128(2)).toDouble()) + 1.0))));
} else {
long long number = value.getLong();
// We can find the log_2 of 'number' by counting the number of leading zeros to find its
// first bit set. This is safe to do because we are working with positive values.
exp = Value(63 - countLeadingZeros64(number) + 1);
}
return ExpressionPow::create(getExpCtx(), Value(2), exp)
->evaluate(Document(), &getExpCtx()->variables);
}
Value GranularityRounderPowersOfTwo::roundDown(Value value) {
uassertNonNegativeNumber(value);
if (value.coerceToDouble() == 0.0) {
return value;
}
Value exp;
if (value.getType() == BSONType::NumberDouble) {
exp = Value(static_cast<int>(std::ceil(std::log2(value.getDouble())) - 1.0));
} else if (value.getType() == BSONType::NumberDecimal) {
Decimal128 input = value.getDecimal();
exp = Value(Decimal128(
static_cast<int>((std::ceil(input.logarithm(Decimal128(2)).toDouble()) - 1.0))));
} else {
long long number = value.getLong();
int leadingZeros = countLeadingZeros64(number);
int trailingZeros = countTrailingZeros64(number);
if (leadingZeros + trailingZeros == 63) {
// If number is a power of 2, then we need to subtract an extra 1 so we round down to
// the next power of 2.
exp = Value(63 - leadingZeros - 1);
} else {
exp = Value(63 - leadingZeros);
}
}
return ExpressionPow::create(getExpCtx(), Value(2), exp)
->evaluate(Document(), &getExpCtx()->variables);
}
string GranularityRounderPowersOfTwo::getName() {
return _name;
}
} // namespace mongo
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