Use const reference (#3389)

Summary:
Pull Request resolved: https://github.com/pytorch/audio/pull/3389

Adopt more of const reference in sox source code.

Differential Revision: D46264068

fbshipit-source-id: 809d34a6e16f621c856d4278ef7ce45a5868a717

torchaudio/csrc/sox/types.cpp

@@ -57,7 +57,7 @@ std::string to_string(Encoding v) {
   }
 }
 
-Encoding get_encoding_from_option(const c10::optional<std::string> encoding) {
+Encoding get_encoding_from_option(const c10::optional<std::string>& encoding) {
   if (!encoding.has_value())
     return Encoding::NOT_PROVIDED;
   std::string v = encoding.value();
@@ -74,7 +74,7 @@ Encoding get_encoding_from_option(const c10::optional<std::string> encoding) {
   TORCH_CHECK(false, "Internal Error: unexpected encoding value: ", v);
 }
 
-BitDepth get_bit_depth_from_option(const c10::optional<int64_t> bit_depth) {
+BitDepth get_bit_depth_from_option(const c10::optional<int64_t>& bit_depth) {
   if (!bit_depth.has_value())
     return BitDepth::NOT_PROVIDED;
   int64_t v = bit_depth.value();

torchaudio/csrc/sox/types.h

@@ -38,7 +38,7 @@ enum class Encoding {
 };
 
 std::string to_string(Encoding v);
-Encoding get_encoding_from_option(const c10::optional<std::string> encoding);
+Encoding get_encoding_from_option(const c10::optional<std::string>& encoding);
 
 enum class BitDepth : unsigned {
   NOT_PROVIDED = 0,
@@ -49,7 +49,7 @@ enum class BitDepth : unsigned {
   B64 = 64,
 };
 
-BitDepth get_bit_depth_from_option(const c10::optional<int64_t> bit_depth);
+BitDepth get_bit_depth_from_option(const c10::optional<int64_t>& bit_depth);
 
 std::string get_encoding(sox_encoding_t encoding);
 

torchaudio/csrc/sox/utils.cpp

@@ -93,7 +93,7 @@ void validate_input_file(const SoxFormat& sf, const std::string& path) {
       "Error loading audio file: unknown encoding.");
 }
 
-void validate_input_tensor(const torch::Tensor tensor) {
+void validate_input_tensor(const torch::Tensor& tensor) {
   TORCH_CHECK(tensor.device().is_cpu(), "Input tensor has to be on CPU.");
 
   TORCH_CHECK(tensor.ndimension() == 2, "Input tensor has to be 2D.");
@@ -184,7 +184,7 @@ torch::Tensor convert_to_tensor(
   return t.contiguous();
 }
 
-const std::string get_filetype(const std::string path) {
+const std::string get_filetype(const std::string& path) {
   std::string ext = path.substr(path.find_last_of(".") + 1);
   std::transform(ext.begin(), ext.end(), ext.begin(), ::tolower);
   return ext;
@@ -278,9 +278,9 @@ std::tuple<sox_encoding_t, unsigned> get_save_encoding_for_wav(
 
 std::tuple<sox_encoding_t, unsigned> get_save_encoding(
     const std::string& format,
-    const caffe2::TypeMeta dtype,
-    const c10::optional<std::string> encoding,
-    const c10::optional<int64_t> bits_per_sample) {
+    const caffe2::TypeMeta& dtype,
+    const c10::optional<std::string>& encoding,
+    const c10::optional<int64_t>& bits_per_sample) {
   const Format fmt = get_format_from_string(format);
   const Encoding enc = get_encoding_from_option(encoding);
   const BitDepth bps = get_bit_depth_from_option(bits_per_sample);
@@ -385,7 +385,7 @@ std::tuple<sox_encoding_t, unsigned> get_save_encoding(
   }
 }
 
-unsigned get_precision(const std::string filetype, caffe2::TypeMeta dtype) {
+unsigned get_precision(const std::string& filetype, caffe2::TypeMeta dtype) {
   if (filetype == "mp3")
     return SOX_UNSPEC;
   if (filetype == "flac")
@@ -425,7 +425,7 @@ unsigned get_precision(const std::string filetype, caffe2::TypeMeta dtype) {
 sox_signalinfo_t get_signalinfo(
     const torch::Tensor* waveform,
     const int64_t sample_rate,
-    const std::string filetype,
+    const std::string& filetype,
     const bool channels_first) {
   return sox_signalinfo_t{
       /*rate=*/static_cast<sox_rate_t>(sample_rate),
@@ -476,10 +476,10 @@ sox_encodinginfo_t get_tensor_encodinginfo(caffe2::TypeMeta dtype) {
 
 sox_encodinginfo_t get_encodinginfo_for_save(
     const std::string& format,
-    const caffe2::TypeMeta dtype,
-    const c10::optional<double> compression,
-    const c10::optional<std::string> encoding,
-    const c10::optional<int64_t> bits_per_sample) {
+    const caffe2::TypeMeta& dtype,
+    const c10::optional<double>& compression,
+    const c10::optional<std::string>& encoding,
+    const c10::optional<int64_t>& bits_per_sample) {
   auto enc = get_save_encoding(format, dtype, encoding, bits_per_sample);
   return sox_encodinginfo_t{
       /*encoding=*/std::get<0>(enc),

torchaudio/csrc/sox/utils.h

@@ -53,7 +53,7 @@ struct SoxFormat {
 
 ///
 /// Verify that input Tensor is 2D, CPU and either uin8, int16, int32 or float32
-void validate_input_tensor(const torch::Tensor);
+void validate_input_tensor(const torch::Tensor&);
 
 ///
 /// Get target dtype for the given encoding and precision.
@@ -85,13 +85,13 @@ torch::Tensor convert_to_tensor(
     const bool channels_first);
 
 /// Extract extension from file path
-const std::string get_filetype(const std::string path);
+const std::string get_filetype(const std::string& path);
 
 /// Get sox_signalinfo_t for passing a torch::Tensor object.
 sox_signalinfo_t get_signalinfo(
     const torch::Tensor* waveform,
     const int64_t sample_rate,
-    const std::string filetype,
+    const std::string& filetype,
     const bool channels_first);
 
 /// Get sox_encodinginfo_t for Tensor I/O
@@ -100,10 +100,10 @@ sox_encodinginfo_t get_tensor_encodinginfo(const caffe2::TypeMeta dtype);
 /// Get sox_encodinginfo_t for saving to file/file object
 sox_encodinginfo_t get_encodinginfo_for_save(
     const std::string& format,
-    const caffe2::TypeMeta dtype,
-    const c10::optional<double> compression,
-    const c10::optional<std::string> encoding,
-    const c10::optional<int64_t> bits_per_sample);
+    const caffe2::TypeMeta& dtype,
+    const c10::optional<double>& compression,
+    const c10::optional<std::string>& encoding,
+    const c10::optional<int64_t>& bits_per_sample);
 
 } // namespace torchaudio::sox
 #endif