edponce commented on a change in pull request #11023:
URL: https://github.com/apache/arrow/pull/11023#discussion_r741377335
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File path: cpp/src/arrow/compute/kernels/scalar_string.cc
##########
@@ -2513,6 +2878,135 @@ void AddSplit(FunctionRegistry* registry) {
#endif
}
+/// An ScalarFunction that promotes integer arguments to Int64.
+struct ScalarCTypeToInt64Function : public ScalarFunction {
+ using ScalarFunction::ScalarFunction;
+
+ Result<const Kernel*> DispatchBest(std::vector<ValueDescr>* values) const
override {
+ RETURN_NOT_OK(CheckArity(*values));
+
+ using arrow::compute::detail::DispatchExactImpl;
+ if (auto kernel = DispatchExactImpl(this, *values)) return kernel;
+
+ EnsureDictionaryDecoded(values);
+
+ for (auto& descr : *values) {
+ if (is_integer(descr.type->id())) {
+ descr.type = int64();
+ }
+ }
+
+ if (auto kernel = DispatchExactImpl(this, *values)) return kernel;
+ return arrow::compute::detail::NoMatchingKernel(this, *values);
+ }
+};
+
+template <typename Type1, typename Type2>
+struct StringRepeatTransform : public StringBinaryTransformBase<Type1, Type2> {
+ using ArrayType1 = typename TypeTraits<Type1>::ArrayType;
+ using ArrayType2 = typename TypeTraits<Type2>::ArrayType;
+
+ Result<int64_t> MaxCodeunits(const int64_t input1_ncodeunits,
+ const int64_t num_repeats) override {
+ ARROW_RETURN_NOT_OK(ValidateRepeatCount(num_repeats));
+ return input1_ncodeunits * num_repeats;
+ }
+
+ Result<int64_t> MaxCodeunits(const int64_t input1_ncodeunits,
+ const ArrayType2& input2) override {
+ int64_t total_num_repeats = 0;
+ for (int64_t i = 0; i < input2.length(); ++i) {
+ auto num_repeats = input2.GetView(i);
+ ARROW_RETURN_NOT_OK(ValidateRepeatCount(num_repeats));
+ total_num_repeats += num_repeats;
+ }
+ return input1_ncodeunits * total_num_repeats;
+ }
+
+ Result<int64_t> MaxCodeunits(const ArrayType1& input1,
+ const int64_t num_repeats) override {
+ ARROW_RETURN_NOT_OK(ValidateRepeatCount(num_repeats));
+ return input1.total_values_length() * num_repeats;
+ }
+
+ Result<int64_t> MaxCodeunits(const ArrayType1& input1,
+ const ArrayType2& input2) override {
+ int64_t total_codeunits = 0;
+ for (int64_t i = 0; i < input2.length(); ++i) {
+ auto num_repeats = input2.GetView(i);
+ ARROW_RETURN_NOT_OK(ValidateRepeatCount(num_repeats));
+ total_codeunits += input1.GetView(i).length() * num_repeats;
+ }
+ return total_codeunits;
+ }
+
+ static Result<int64_t> TransformSimpleLoop(const uint8_t* input,
+ const int64_t
input_string_ncodeunits,
+ const int64_t num_repeats,
uint8_t* output) {
+ uint8_t* output_start = output;
+ for (int64_t i = 0; i < num_repeats; ++i) {
+ std::memcpy(output, input, input_string_ncodeunits);
+ output += input_string_ncodeunits;
+ }
+ return output - output_start;
+ }
+
+ static Result<int64_t> TransformDoublingString(const uint8_t* input,
+ const int64_t
input_string_ncodeunits,
+ const int64_t num_repeats,
+ uint8_t* output) {
+ uint8_t* output_start = output;
+ // Repeated doubling of string
+ std::memcpy(output, input, input_string_ncodeunits);
+ output += input_string_ncodeunits;
+ int64_t i = 1;
+ for (int64_t ilen = input_string_ncodeunits; i <= (num_repeats / 2);
+ i *= 2, ilen *= 2) {
+ std::memcpy(output, output_start, ilen);
+ output += ilen;
+ }
+
+ // Epilogue remainder
+ int64_t rem = (num_repeats ^ i) * input_string_ncodeunits;
Review comment:
Not really, `xor` is just representing `mod 2` but in this case
subtraction is also valid.
Changed it to subtraction and renamed variable to `irep` for improved
readability.
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