fix and add test for soundio_device_nearest_sample_rate

src/soundio.cpp

@@ -763,21 +763,29 @@ bool soundio_device_supports_sample_rate(struct SoundIoDevice *device, int sampl
     return false;
 }
 
+static int abs_diff_int(int a, int b) {
+    int x = a - b;
+    return (x >= 0) ? x : -x;
+}
+
 int soundio_device_nearest_sample_rate(struct SoundIoDevice *device, int sample_rate) {
     int best_rate = -1;
     int best_delta = -1;
     for (int i = 0; i < device->sample_rate_count; i += 1) {
         SoundIoSampleRateRange *range = &device->sample_rates[i];
-        if (sample_rate < range->min) {
+        int candidate_rate = clamp(range->min, sample_rate, range->max);
-            int delta = range->min - sample_rate;
+        if (candidate_rate == sample_rate)
-            if (best_delta == -1 || delta < best_delta) {
+            return candidate_rate;
+
+        int delta = abs_diff_int(candidate_rate, sample_rate);
+        bool best_rate_too_small = best_rate < sample_rate;
+        bool candidate_rate_too_small = candidate_rate < sample_rate;
+        if (best_rate == -1 ||
+            (best_rate_too_small && !candidate_rate_too_small) ||
+            ((best_rate_too_small || !candidate_rate_too_small) && delta < best_delta))
+        {
+            best_rate = candidate_rate;
             best_delta = delta;
-                best_rate = range->min;
-            }
-        } else if (best_rate == -1 && sample_rate > range->max) {
-            best_rate = range->max;
-        } else {
-            return sample_rate;
         }
     }
     return best_rate;

test/unit_tests.cpp

@@ -183,6 +183,33 @@ static void test_mirrored_memory(void) {
     soundio_os_deinit_mirrored_memory(&mem);
 }
 
+static void test_nearest_sample_rate(void) {
+    struct SoundIoDevice device;
+    struct SoundIoSampleRateRange sample_rates[2] = {
+        {
+            44100,
+            48000
+        },
+        {
+            96000,
+            96000,
+        },
+    };
+
+    device.sample_rate_count = 2;
+    device.sample_rates = sample_rates;
+
+    assert(soundio_device_nearest_sample_rate(&device, 100) == 44100);
+    assert(soundio_device_nearest_sample_rate(&device, 44099) == 44100);
+    assert(soundio_device_nearest_sample_rate(&device, 44100) == 44100);
+    assert(soundio_device_nearest_sample_rate(&device, 45000) == 45000);
+    assert(soundio_device_nearest_sample_rate(&device, 48000) == 48000);
+    assert(soundio_device_nearest_sample_rate(&device, 48001) == 96000);
+    assert(soundio_device_nearest_sample_rate(&device, 90000) == 96000);
+    assert(soundio_device_nearest_sample_rate(&device, 96001) == 96000);
+    assert(soundio_device_nearest_sample_rate(&device, 9999999) == 96000);
+}
+
 struct Test {
     const char *name;
     void (*fn)(void);
@@ -194,6 +221,7 @@ static struct Test tests[] = {
     {"ring buffer basic", test_ring_buffer_basic},
     {"ring buffer threaded", test_ring_buffer_threaded},
     {"mirrored memory", test_mirrored_memory},
+    {"soundio_device_nearest_sample_rate", test_nearest_sample_rate},
     {NULL, NULL},
 };