core/conv/conv_acc.c: use static allocation for vdecoder

Allocation of a new memory is an expensive operation, which
takes place when it's initially unknown, how much memory will
we need, or in order to decrease total memory usage.

The vdecoder struct wasn't require dynamic allocation itself,
so let's use static allocation in order to increase performance.

Change-Id: Id1b140d3cb61db7352dcfc217a8fc36091e945ab

1 files changed, 19 insertions, 23 deletions

diff --git a/src/conv_acc.c b/src/conv_acc.c
index 7f036284..f45d50f0 100644
--- a/src/conv_acc.c
+++ b/src/conv_acc.c
@@ -498,7 +498,7 @@ static int traceback(struct vdecoder *dec, uint8_t *out, int term, int len)
 }
 
 /* Release decoder object */
-static void free_vdec(struct vdecoder *dec)
+static void vdec_deinit(struct vdecoder *dec)
 {
 	if (!dec)
 		return;
@@ -509,22 +509,18 @@ static void free_vdec(struct vdecoder *dec)
 		vdec_free(dec->paths[0]);
 		free(dec->paths);
 	}
-
-	free(dec);
 }
 
-/* Allocate decoder object
+/* Initialize decoder object with code specific params
  * Subtract the constraint length K on the normalization interval to
  * accommodate the initialization path metric at state zero.
  */
-static struct vdecoder *alloc_vdec(const struct osmo_conv_code *code)
+static int vdec_init(struct vdecoder *dec, const struct osmo_conv_code *code)
 {
 	int i, ns;
-	struct vdecoder *dec;
 
 	ns = NUM_STATES(code->K);
 
-	dec = (struct vdecoder *) calloc(1, sizeof(struct vdecoder));
 	dec->n = code->N;
 	dec->k = code->K;
 	dec->recursive = conv_code_recursive(code);
@@ -542,7 +538,7 @@ static struct vdecoder *alloc_vdec(const struct osmo_conv_code *code)
 			dec->metric_func = osmo_conv_metrics_k5_n4;
 			break;
 		default:
-			goto fail;
+			return -EINVAL;
 		}
 	} else if (dec->k == 7) {
 		switch (dec->n) {
@@ -556,10 +552,10 @@ static struct vdecoder *alloc_vdec(const struct osmo_conv_code *code)
 			dec->metric_func = osmo_conv_metrics_k7_n4;
 			break;
 		default:
-			goto fail;
+			return -EINVAL;
 		}
 	} else {
-		goto fail;
+		return -EINVAL;
 	}
 
 	if (code->term == CONV_TERM_FLUSH)
@@ -569,24 +565,24 @@ static struct vdecoder *alloc_vdec(const struct osmo_conv_code *code)
 
 	dec->trellis = generate_trellis(code);
 	if (!dec->trellis)
-		goto fail;
+		goto enomem;
 
 	dec->paths = (int16_t **) malloc(sizeof(int16_t *) * dec->len);
 	if (!dec->paths)
-		goto fail;
+		goto enomem;
 
 	dec->paths[0] = vdec_malloc(ns * dec->len);
 	if (!dec->paths[0])
-		goto fail;
+		goto enomem;
 
 	for (i = 1; i < dec->len; i++)
 		dec->paths[i] = &dec->paths[0][i * ns];
 
-	return dec;
+	return 0;
 
-fail:
-	free_vdec(dec);
-	return NULL;
+enomem:
+	vdec_deinit(dec);
+	return -ENOMEM;
 }
 
 /* Depuncture sequence with nagative value terminated puncturing matrix */
@@ -697,7 +693,7 @@ int osmo_conv_decode_acc(const struct osmo_conv_code *code,
 	const sbit_t *input, ubit_t *output)
 {
 	int rc;
-	struct vdecoder *vdec;
+	struct vdecoder dec;
 
 	if (!init_complete)
 		osmo_conv_init();
@@ -706,14 +702,14 @@ int osmo_conv_decode_acc(const struct osmo_conv_code *code,
 		((code->K != 5) && (code->K != 7)))
 		return -EINVAL;
 
-	vdec = alloc_vdec(code);
-	if (!vdec)
-		return -EFAULT;
+	rc = vdec_init(&dec, code);
+	if (rc)
+		return rc;
 
-	rc = conv_decode(vdec, input, code->puncture,
+	rc = conv_decode(&dec, input, code->puncture,
 		output, code->len, code->term);
 
-	free_vdec(vdec);
+	vdec_deinit(&dec);
 
 	return rc;
 }