Add context pointer to getsample callback

src/apt.h

@@ -42,8 +42,9 @@ extern "C" {
 // Maximum height of an APT image in number of scanlines
 #define APT_MAX_HEIGHT 3000
 
-// apt_getpixelrow callback function to get audio samples
-typedef int (*apt_getsample_t)(float *samples, int count);
+// apt_getpixelrow callback function to get audio samples.
+// context is the same as passed to apt_getpixelrow.
+typedef int (*apt_getsample_t)(void *context, float *samples, int count);
 
 typedef struct {
 	float *prow[APT_MAX_HEIGHT]; // Row buffers
@@ -59,7 +60,7 @@ typedef struct {
 } apt_rgb_t;
 
 int APT_API apt_init(double sample_rate);
-int APT_API apt_getpixelrow(float *pixelv, int nrow, int *zenith, int reset, apt_getsample_t getsample);
+int APT_API apt_getpixelrow(float *pixelv, int nrow, int *zenith, int reset, apt_getsample_t getsample, void *context);
 
 void APT_API apt_histogramEqualise(float **prow, int nrow, int offset, int width);
 void APT_API apt_linearEnhance(float **prow, int nrow, int offset, int width);

src/dsp.c

@@ -131,7 +131,7 @@ static double pll(double I, double Q) {
 }
 
 // Convert samples into pixels
-static int getamp(double *ampbuff, int count, apt_getsample_t getsample) {
+static int getamp(double *ampbuff, int count, apt_getsample_t getsample, void *context) {
 	static float inbuff[BLKIN];
 	static int idxin = 0;
 	static int nin = 0;
@@ -147,7 +147,7 @@ static int getamp(double *ampbuff, int count, apt_getsample_t getsample) {
 			idxin = 0;
 
 			// Read some samples
-			res = getsample(&(inbuff[nin]), BLKIN - nin);
+			res = getsample(context, &(inbuff[nin]), BLKIN - nin);
 			nin += res;
 
 			// Make sure there is enough samples to continue
@@ -168,7 +168,7 @@ static int getamp(double *ampbuff, int count, apt_getsample_t getsample) {
 }
 
 // Sub-pixel offsetting + FIR compensation
-int getpixelv(float *pvbuff, int count, apt_getsample_t getsample) {
+int getpixelv(float *pvbuff, int count, apt_getsample_t getsample, void *context) {
 	// Amplitude buffer
 	static double ampbuff[BLKAMP];
 	static int nam = 0;
@@ -187,7 +187,7 @@ int getpixelv(float *pvbuff, int count, apt_getsample_t getsample) {
 			int res;
 			memmove(ampbuff, &(ampbuff[idxam]), nam * sizeof(double));
 			idxam = 0;
-			res = getamp(&(ampbuff[nam]), BLKAMP - nam, getsample);
+			res = getamp(&(ampbuff[nam]), BLKAMP - nam, getsample, context);
 			nam += res;
 			if (nam < m)
 				return n;
@@ -207,7 +207,7 @@ int getpixelv(float *pvbuff, int count, apt_getsample_t getsample) {
 }
 
 // Get an entire row of pixels, aligned with sync markers
-int apt_getpixelrow(float *pixelv, int nrow, int *zenith, int reset, apt_getsample_t getsample) {
+int apt_getpixelrow(float *pixelv, int nrow, int *zenith, int reset, apt_getsample_t getsample, void *context) {
 	static float pixels[PixelLine + SyncFilterLen];
 	static int npv;
 	static int synced = 0;
@@ -225,7 +225,7 @@ int apt_getpixelrow(float *pixelv, int nrow, int *zenith, int reset, apt_getsamp
 
 	// Get the sync line
 	if (npv < SyncFilterLen + 2) {
-		res = getpixelv(&(pixelv[npv]), SyncFilterLen + 2 - npv, getsample);
+		res = getpixelv(&(pixelv[npv]), SyncFilterLen + 2 - npv, getsample, context);
 		npv += res;
 		if (npv < SyncFilterLen + 2)
 			return 0;
@@ -256,7 +256,7 @@ int apt_getpixelrow(float *pixelv, int nrow, int *zenith, int reset, apt_getsamp
         static int lastmshift;
 
 		if (npv < PixelLine + SyncFilterLen) {
-			res = getpixelv(&(pixelv[npv]), PixelLine + SyncFilterLen - npv, getsample);
+			res = getpixelv(&(pixelv[npv]), PixelLine + SyncFilterLen - npv, getsample, context);
 			npv += res;
 			if (npv < PixelLine + SyncFilterLen)
 				return 0;
@@ -294,7 +294,7 @@ int apt_getpixelrow(float *pixelv, int nrow, int *zenith, int reset, apt_getsamp
 
 	// Get the rest of this row
 	if (npv < PixelLine) {
-		res = getpixelv(&(pixelv[npv]), PixelLine - npv, getsample);
+		res = getpixelv(&(pixelv[npv]), PixelLine - npv, getsample, context);
 		npv += res;
 		if (npv < PixelLine)
 			return 0;

src/main.c

@@ -46,7 +46,7 @@ int channels = 1;
 
 // Function declarations
 static int initsnd(char *filename);
-int getsample(float *sample, int nb);
+int getsample(void *context, float *sample, int nb);
 static int processAudio(char *filename, options_t *opts);
 
 #ifdef _MSC_VER
@@ -165,7 +165,7 @@ static int processAudio(char *filename, options_t *opts){
 			img.prow[img.nrow] = (float *) malloc(sizeof(float) * 2150);
 
 			// Write into memory and break the loop when there are no more samples to read
-			if (apt_getpixelrow(img.prow[img.nrow], img.nrow, &img.zenith, (img.nrow == 0), getsample) == 0)
+			if (apt_getpixelrow(img.prow[img.nrow], img.nrow, &img.zenith, (img.nrow == 0), getsample, NULL) == 0)
 				break;
 
 			if(opts->realtime) pushRow(img.prow[img.nrow], IMG_WIDTH);
@@ -299,7 +299,7 @@ static int initsnd(char *filename) {
 }
 
 // Read samples from the audio file
-int getsample(float *sample, int nb) {
+int getsample(void *context, float *sample, int nb) {
 	if(channels == 1){
 		return (int)sf_read_float(audioFile, sample, nb);
 	}else{