Add support for waiting for input.

Introduce -S/--sleep_for_input command line argument.

Closes #17.

3 files changed, 19 insertions, 0 deletions

diff --git a/src/configuration.cpp b/src/configuration.cpp
index 7fdcdb5..88f3355 100644
--- a/src/configuration.cpp
+++ b/src/configuration.cpp
@@ -26,6 +26,7 @@ Configuration::Configuration()
     this->datatype_ = DataType::kSignedInt16;
     this->has_complex_input_ = false;
     this->prescale_factor_ = 1.0f;
+    this->sleep_for_input_ = 0;
 
     this->fft_width_ = 1024;
     this->fft_stride_ = 1024;
@@ -169,6 +170,8 @@ Configuration::Build(int argc, const char **argv)
         prescale(input_opts, "float", "Prescaling factor (default: 1.0)", {'p', "prescale"});
     args::ValueFlag<int>
         block_size(input_opts, "integer", "Block size when reading input, in data types (default: 256)", {'b', "block_size"});
+    args::ValueFlag<int>
+        sleep_for_input(input_opts, "integer", "Duration in milliseconds to sleep for when input is not available (default: 0, busywaits)", {'S', "sleep_for_input"});
 
     args::Group fft_opts(parser, "FFT options:", args::Group::Validators::DontCare);
     args::ValueFlag<int>
@@ -269,6 +272,14 @@ Configuration::Build(int argc, const char **argv)
             conf.block_size_ = args::get(block_size);
         }
     }
+    if (sleep_for_input) {
+        if (args::get(sleep_for_input) < 0) {
+            std::cerr << "'sleep_for_input' must be zero or positive." << std::endl;
+            return std::make_tuple(conf, 1, true);
+        } else {
+            conf.sleep_for_input_ = args::get(sleep_for_input);
+        }
+    }
     if (rate) {
         if (args::get(rate) <= 0) {
             std::cerr << "'rate' must be positive." << std::endl;
diff --git a/src/configuration.hpp b/src/configuration.hpp
index dec0e0c..42776ad 100644
--- a/src/configuration.hpp
+++ b/src/configuration.hpp
@@ -32,6 +32,7 @@ private:
     DataType datatype_;                     /* input data type (does not cover complex/real discrimination) */
     bool has_complex_input_;                /* true if input is complex */
     double prescale_factor_;                /* value to scale input with before applying other transformations */
+    std::size_t sleep_for_input_;           /* number of milliseconds to sleep when input is not ready */
 
     std::size_t fft_width_;                 /* size of FFT window, in values */
     std::size_t fft_stride_;                /* stride of FFT window, in values */
@@ -110,6 +111,7 @@ public:
     auto GetDataType() const { return datatype_; }
     auto HasComplexInput() const { return has_complex_input_; }
     auto GetPrescaleFactor() const { return prescale_factor_; }
+    auto GetSleepForInput() const { return sleep_for_input_; }
 
     /* FFT getters */
     auto GetFFTWidth() const { return fft_width_; }
diff --git a/src/specgram.cpp b/src/specgram.cpp
index 0cd9635..5e5e30c 100644
--- a/src/specgram.cpp
+++ b/src/specgram.cpp
@@ -21,6 +21,8 @@
 #include <random>
 #include <cstdio>
 #include <cassert>
+#include <thread>
+#include <chrono>
 
 /* main loop exit condition */
 volatile bool main_loop_running = true;
@@ -237,6 +239,10 @@ main(int argc, char** argv)
         auto block = reader->GetBlock();
         if (!block) {
             /* block not finished yet */
+            if (auto sleep = conf.GetSleepForInput()) {
+                /* sleep for a bit so we don't busywait on sparse input */
+                std::this_thread::sleep_for(std::chrono::duration<size_t, std::milli>(sleep));
+            }
             continue;
         }