pitrou commented on a change in pull request #7901:
URL: https://github.com/apache/arrow/pull/7901#discussion_r465734624
##########
File path: cpp/src/arrow/util/formatting.h
##########
@@ -40,12 +40,51 @@ namespace arrow {
namespace internal {
/// \brief The entry point for conversion to strings.
+///
+/// Specializations of FormatValueTraits for `ARROW_TYPE` must define:
+/// - A member type `value_type` which will be formatted.
+/// - A static member function `MaxSize(const ARROW_TYPE& t)` indicating the
+/// maximum number of characters which formatting a `value_type` may yield.
+/// - The static member function `Convert`, callable with signature
Review comment:
Why not call it `Format`?
##########
File path: cpp/src/arrow/util/formatting.cc
##########
@@ -36,38 +31,29 @@ const char digit_pairs[] =
"6061626364656667686970717273747576777879"
"8081828384858687888990919293949596979899";
-} // namespace detail
-
-struct FloatToStringFormatter::Impl {
- Impl()
- : converter_(DoubleToStringConverter::EMIT_POSITIVE_EXPONENT_SIGN,
"inf", "nan",
- 'e', -6, 10, 6, 0) {}
-
- DoubleToStringConverter converter_;
-};
-
-FloatToStringFormatter::FloatToStringFormatter() : impl_(new Impl()) {}
+using util::double_conversion::DoubleToStringConverter;
-FloatToStringFormatter::~FloatToStringFormatter() {}
+static DoubleToStringConverter g_double_converter(
+ DoubleToStringConverter::EMIT_POSITIVE_EXPONENT_SIGN, "inf", "nan", 'e',
-6, 10, 6,
+ 0);
-int FloatToStringFormatter::FormatFloat(float v, char* out_buffer, int
out_size) {
- DCHECK_GE(out_size, kMinBufferSize);
+int FormatFloat(float v, size_t buffer_size, char* buffer) {
// StringBuilder checks bounds in debug mode for us
- util::double_conversion::StringBuilder builder(out_buffer, out_size);
- bool result = impl_->converter_.ToShortestSingle(v, &builder);
+ util::double_conversion::StringBuilder builder(buffer,
static_cast<int>(buffer_size));
+ bool result = g_double_converter.ToShortestSingle(v, &builder);
DCHECK(result);
ARROW_UNUSED(result);
return builder.position();
}
-int FloatToStringFormatter::FormatFloat(double v, char* out_buffer, int
out_size) {
- DCHECK_GE(out_size, kMinBufferSize);
- util::double_conversion::StringBuilder builder(out_buffer, out_size);
- bool result = impl_->converter_.ToShortest(v, &builder);
+int FormatFloat(double v, size_t buffer_size, char* buffer) {
+ util::double_conversion::StringBuilder builder(buffer,
static_cast<int>(buffer_size));
+ bool result = g_double_converter.ToShortest(v, &builder);
DCHECK(result);
ARROW_UNUSED(result);
return builder.position();
}
+} // namespace detail
Review comment:
Why not use the anonymous namespace for private functions?
##########
File path: cpp/src/arrow/util/formatting.cc
##########
@@ -36,38 +31,29 @@ const char digit_pairs[] =
"6061626364656667686970717273747576777879"
"8081828384858687888990919293949596979899";
-} // namespace detail
-
-struct FloatToStringFormatter::Impl {
- Impl()
- : converter_(DoubleToStringConverter::EMIT_POSITIVE_EXPONENT_SIGN,
"inf", "nan",
- 'e', -6, 10, 6, 0) {}
-
- DoubleToStringConverter converter_;
-};
-
-FloatToStringFormatter::FloatToStringFormatter() : impl_(new Impl()) {}
+using util::double_conversion::DoubleToStringConverter;
-FloatToStringFormatter::~FloatToStringFormatter() {}
+static DoubleToStringConverter g_double_converter(
+ DoubleToStringConverter::EMIT_POSITIVE_EXPONENT_SIGN, "inf", "nan", 'e',
-6, 10, 6,
+ 0);
-int FloatToStringFormatter::FormatFloat(float v, char* out_buffer, int
out_size) {
- DCHECK_GE(out_size, kMinBufferSize);
+int FormatFloat(float v, size_t buffer_size, char* buffer) {
Review comment:
It's weird to take a `size_t` buffer size and return a `int` for the
number of bytes written.
##########
File path: cpp/src/arrow/compute/kernels/scalar_cast_internal.cc
##########
@@ -270,6 +272,30 @@ void AddCommonCasts(Type::type out_type_id, OutputType
out_ty, CastFunction* fun
MemAllocation::NO_PREALLOCATE));
}
+// TODO(bkietz): provide a generic from-string parsing cast
Review comment:
TODOs should be kept in JIRA, not sprinkled around source code, IMHO.
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