Add Python ASR examples with alsa (#646)

sherpa-onnx/python/csrc/faked-alsa.cc

@@ -0,0 +1,47 @@
+// sherpa-onnx/python/csrc/faked-alsa.cc
+//
+// Copyright (c)  2024  Xiaomi Corporation
+
+#include "sherpa-onnx/csrc/macros.h"
+#include "sherpa-onnx/python/csrc/alsa.h"
+
+namespace sherpa_onnx {
+
+class FakedAlsa {
+ public:
+  explicit FakedAlsa(const char *) {
+    SHERPA_ONNX_LOGE("This function is for Linux only.");
+#if (SHERPA_ONNX_ENABLE_ALSA == 0) && (defined(__unix__) || defined(__unix))
+    SHERPA_ONNX_LOGE(R"doc(
+sherpa-onnx is compiled without alsa support. To enable that, please run
+  (1) sudo apt-get install alsa-utils libasound2-dev
+  (2) rebuild sherpa-onnx
+)doc");
+#endif
+    exit(-1);
+  }
+
+  std::vector<float> Read(int32_t) const { return {}; }
+  int32_t GetExpectedSampleRate() const { return -1; }
+  int32_t GetActualSampleRate() const { return -1; }
+};
+
+void PybindAlsa(py::module *m) {
+  using PyClass = FakedAlsa;
+  py::class_<PyClass>(*m, "Alsa")
+      .def(py::init<const char *>(), py::arg("device_name"))
+      .def(
+          "read",
+          [](PyClass &self, int32_t num_samples) -> std::vector<float> {
+            return self.Read(num_samples);
+          },
+          py::arg("num_samples"), py::call_guard<py::gil_scoped_release>())
+      .def_property_readonly("expected_sample_rate",
+                             &PyClass::GetExpectedSampleRate)
+      .def_property_readonly("actual_sample_rate",
+                             &PyClass::GetActualSampleRate);
+}
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_PYTHON_CSRC_FAKED_ALSA_H_