Rework cudf::io::text::byte_range_info class member functions (#16518)

Adds `const` declarations to appropriate member functions in class `cudf::io::text::byte_range_info` and moves the ctor implementation to .cpp file.
This helps with using the `byte_range_info` objects in `const` variables and inside of `const` functions.

Found while working on #15983

Authors:
  - David Wendt (https://github.com/davidwendt)

Approvers:
  - Muhammad Haseeb (https://github.com/mhaseeb123)
  - Bradley Dice (https://github.com/bdice)

URL: #16518

cpp/include/cudf/io/text/byte_range_info.hpp

@@ -16,7 +16,6 @@
 
 #pragma once
 
-#include <cudf/utilities/error.hpp>
 #include <cudf/utilities/export.hpp>
 
 #include <cstdint>
@@ -40,53 +39,49 @@ class byte_range_info {
   int64_t _size{};    ///< size in bytes
 
  public:
-  constexpr byte_range_info() = default;
+  byte_range_info() = default;
   /**
    * @brief Constructs a byte_range_info object
    *
    * @param offset offset in bytes
    * @param size size in bytes
    */
-  constexpr byte_range_info(int64_t offset, int64_t size) : _offset(offset), _size(size)
-  {
-    CUDF_EXPECTS(offset >= 0, "offset must be non-negative");
-    CUDF_EXPECTS(size >= 0, "size must be non-negative");
-  }
+  byte_range_info(int64_t offset, int64_t size);
 
   /**
    * @brief Copy constructor
    *
    * @param other byte_range_info object to copy
    */
-  constexpr byte_range_info(byte_range_info const& other) noexcept = default;
+  byte_range_info(byte_range_info const& other) noexcept = default;
   /**
    * @brief  Copy assignment operator
    *
    * @param other byte_range_info object to copy
    * @return this object after copying
    */
-  constexpr byte_range_info& operator=(byte_range_info const& other) noexcept = default;
+  byte_range_info& operator=(byte_range_info const& other) noexcept = default;
 
   /**
    * @brief Get the offset in bytes
    *
    * @return Offset in bytes
    */
-  [[nodiscard]] constexpr int64_t offset() { return _offset; }
+  [[nodiscard]] int64_t offset() const { return _offset; }
 
   /**
    * @brief Get the size in bytes
    *
    * @return Size in bytes
    */
-  [[nodiscard]] constexpr int64_t size() { return _size; }
+  [[nodiscard]] int64_t size() const { return _size; }
 
   /**
    * @brief Returns whether the span is empty.
    *
-   * @return true iff the span is empty, i.e. `size() == 0`
+   * @return true iff the range is empty, i.e. `size() == 0`
    */
-  [[nodiscard]] constexpr bool empty() { return size() == 0; }
+  [[nodiscard]] bool is_empty() const { return size() == 0; }
 };
 
 /**

cpp/src/io/text/byte_range_info.cpp

@@ -16,13 +16,20 @@
 
 #include <cudf/detail/utilities/integer_utils.hpp>
 #include <cudf/io/text/byte_range_info.hpp>
+#include <cudf/utilities/error.hpp>
 
 #include <limits>
 
 namespace cudf {
 namespace io {
 namespace text {
 
+byte_range_info::byte_range_info(int64_t offset, int64_t size) : _offset(offset), _size(size)
+{
+  CUDF_EXPECTS(offset >= 0, "offset must be non-negative");
+  CUDF_EXPECTS(size >= 0, "size must be non-negative");
+}
+
 byte_range_info create_byte_range_info_max() { return {0, std::numeric_limits<int64_t>::max()}; }
 
 std::vector<byte_range_info> create_byte_range_infos_consecutive(int64_t total_bytes,

cpp/src/io/text/multibyte_split.cu

@@ -310,7 +310,7 @@ std::unique_ptr<cudf::column> multibyte_split(cudf::io::text::data_chunk_source
 {
   CUDF_FUNC_RANGE();
 
-  if (byte_range.empty()) { return make_empty_column(type_id::STRING); }
+  if (byte_range.is_empty()) { return make_empty_column(type_id::STRING); }
 
   auto device_delim = cudf::string_scalar(delimiter, true, stream, mr);