[igt-dev] [PATCH i-g-t] lib/igt_audio: make audio_signal_detect take const data

Simon Ser
2019-05-13T13:53:09Z

audio_signal_detect uses gsl_fft_real_radix2_transform which mutates the data
array. This can be surprising when calling audio_signal_detect and then read
again the data (e.g. for another check).

Instead of mutating the array, make audio_signal_detect less error-prone by
taking a const parameter. Do an internal copy before calling the gsl function.

Signed-off-by: Simon Ser <simon.ser@intel.com>
---
lib/igt_audio.c | 13 +++++++++++--
lib/igt_audio.h | 2 +-
2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/lib/igt_audio.c b/lib/igt_audio.c
index fd8cf07c0de3..a1dda50a3c09 100644
--- a/lib/igt_audio.c
+++ b/lib/igt_audio.c
@@ -251,11 +251,14 @@ void audio_signal_fill(struct audio_signal *signal, int16_t *buffer,
* Checks that frequencies specified in signal, and only those, are included
* in the input data.
*
- * sampling_rate is given in Hz. data_len is the number of elements in data.
+ * sampling_rate is given in Hz. samples_len is the number of elements in
+ * samples.
*/
bool audio_signal_detect(struct audio_signal *signal, int sampling_rate,
- int channel, double *data, size_t data_len)
+ int channel, const double *samples, size_t samples_len)
{
+ double *data;
+ size_t data_len = samples_len;
size_t bin_power_len = data_len / 2 + 1;
double bin_power[bin_power_len];
bool detected[FREQS_MAX];
@@ -264,6 +267,10 @@ bool audio_signal_detect(struct audio_signal *signal, int sampling_rate,
size_t i, j;
bool above, success;

+ /* gsl will mutate the array in-place, so make a copy */
+ data = malloc(samples_len * sizeof(double));
+ memcpy(data, samples, samples_len * sizeof(double));
+
/* Allowed error in Hz due to FFT step */
freq_accuracy = sampling_rate / data_len;
igt_debug("Allowed freq. error: %d Hz\n", freq_accuracy);
@@ -372,6 +379,8 @@ bool audio_signal_detect(struct audio_signal *signal, int sampling_rate,
}
}

+ free(data);
+
return success;
}

diff --git a/lib/igt_audio.h b/lib/igt_audio.h
index 466e772a75a4..d5ba1caaca63 100644
--- a/lib/igt_audio.h
+++ b/lib/igt_audio.h
@@ -43,7 +43,7 @@ void audio_signal_reset(struct audio_signal *signal);
void audio_signal_fill(struct audio_signal *signal, int16_t *buffer,
size_t buffer_len);
bool audio_signal_detect(struct audio_signal *signal, int sampling_rate,
- int channel, double *data, size_t data_len);
+ int channel, const double *samples, size_t samples_len);
size_t audio_extract_channel_s32_le(double *dst, size_t dst_cap,
int32_t *src, size_t src_len,
int n_channels, int channel);
--
2.21.0