cpp/src/gandiva/formatting_utils.h

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

#pragma once

#include "arrow/type.h"
#include "arrow/util/formatting.h"
#include "arrow/vendored/double-conversion/double-conversion.h"

namespace gandiva {

/// \brief The entry point for conversion to strings.
template <typename ARROW_TYPE, typename Enable = void>
class GdvStringFormatter;

using arrow_vendored::double_conversion::DoubleToStringConverter;

template <typename ARROW_TYPE>
class FloatToStringGdvMixin
    : public arrow::internal::FloatToStringFormatterMixin<ARROW_TYPE> {
 public:
  using arrow::internal::FloatToStringFormatterMixin<
      ARROW_TYPE>::FloatToStringFormatterMixin;

  // The mixin is a modified version of the existent FloatToStringFormatterMixin, but
  // it defines some specific parameters in the FloatToStringFormatterMixin to cast
  // the float numbers to string using the same patterns like Java.
  //
  // The Java real numbers are represented in two ways following these rules:
  //- If the number is greater or equals than 10^7 and less than 10^(-3)
  //  it will be represented using scientific notation, e.g:
  //      - 0.000012 -> 1.2E-5
  //      - 10000002.3 -> 1.00000023E7
  //- If the numbers are between that interval above, they are showed as is.
  explicit FloatToStringGdvMixin(const std::shared_ptr<arrow::DataType>& = NULLPTR)
      : arrow::internal::FloatToStringFormatterMixin<ARROW_TYPE>(
            DoubleToStringConverter::EMIT_TRAILING_ZERO_AFTER_POINT |
                DoubleToStringConverter::EMIT_TRAILING_DECIMAL_POINT |
                DoubleToStringConverter::EMIT_TRAILING_DECIMAL_POINT_IN_EXPONENTIAL |
                DoubleToStringConverter::EMIT_TRAILING_ZERO_AFTER_POINT_IN_EXPONENTIAL,
            "Infinity", "NaN", 'E', -3, 7, 3, 1) {}
};

template <>
class GdvStringFormatter<arrow::FloatType>
    : public FloatToStringGdvMixin<arrow::FloatType> {
 public:
  using FloatToStringGdvMixin::FloatToStringGdvMixin;
};

template <>
class GdvStringFormatter<arrow::DoubleType>
    : public FloatToStringGdvMixin<arrow::DoubleType> {
 public:
  using FloatToStringGdvMixin::FloatToStringGdvMixin;
};
}  // namespace gandiva