Method PreExec

cpp/src/arrow/compute/kernels/scalar_string_utf8.cc:909–917

  explicit Utf8PadTransform(const PadOptions& options) : options_(options) {}

  Status PreExec(KernelContext* ctx, const ExecSpan& batch, ExecResult* out) override {
    auto str = reinterpret_cast<const uint8_t*>(options_.padding.data());
    auto strlen = options_.padding.size();
    if (util::UTF8Length(str, str + strlen) != 1) {
      return Status::Invalid("Padding must be one codepoint, got '", options_.padding,
                             "'");
    }
    return Status::OK();
  }

  int64_t MaxCodeunits(int64_t ninputs, int64_t input_ncodeunits) override {
    // This is likely very overallocated but hard to do better without