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-rw-r--r--viterbi27_mmx.c115
1 files changed, 115 insertions, 0 deletions
diff --git a/viterbi27_mmx.c b/viterbi27_mmx.c
new file mode 100644
index 0000000..a6d5125
--- /dev/null
+++ b/viterbi27_mmx.c
@@ -0,0 +1,115 @@
+/* K=7 r=1/2 Viterbi decoder for MMX
+ * Copyright Feb 2004, Phil Karn, KA9Q
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <memory.h>
+#include <mmintrin.h>
+#include "fec.h"
+
+typedef union { char c[64]; __m64 v[8];} decision_t;
+typedef union { unsigned char c[64]; __m64 v[8];} metric_t;
+
+unsigned char Mettab27_1[256][32] __attribute__ ((aligned(16)));
+unsigned char Mettab27_2[256][32] __attribute__ ((aligned(16)));
+static int Init = 0;
+
+/* State info for instance of Viterbi decoder
+ * Don't change this without also changing references in mmxbfly27.s!
+ */
+struct v27 {
+ metric_t metrics1; /* path metric buffer 1 */
+ metric_t metrics2; /* path metric buffer 2 */
+ decision_t *dp; /* Pointer to current decision */
+ metric_t *old_metrics,*new_metrics; /* Pointers to path metrics, swapped on every bit */
+ decision_t *decisions; /* Beginning of decisions for block */
+};
+
+/* Initialize Viterbi decoder for start of new frame */
+int init_viterbi27_mmx(void *p,int starting_state){
+ struct v27 *vp = (struct v27 *)p;
+ int i;
+
+ if(p == NULL)
+ return -1;
+ for(i=0;i<64;i++)
+ vp->metrics1.c[i] = 63;
+
+ vp->old_metrics = &vp->metrics1;
+ vp->new_metrics = &vp->metrics2;
+ vp->dp = vp->decisions;
+ vp->old_metrics->c[starting_state & 63] = 0; /* Bias known start state */
+ return 0;
+}
+
+void set_viterbi27_polynomial_mmx(int polys[2]){
+ int state;
+
+ for(state=0;state < 32;state++){
+ int symbol;
+ for(symbol = 0;symbol < 256;symbol++){
+ int sym;
+
+ sym = parity((2*state) & abs(polys[0])) ^ (polys[0] < 0);
+ Mettab27_1[symbol][state] = (sym ? (255-symbol):symbol) / 16;
+
+ sym = parity((2*state) & abs(polys[1])) ^ (polys[1] < 0);
+ Mettab27_2[symbol][state] = (sym ? (255-symbol):symbol) / 16;
+ }
+ }
+ Init++;
+}
+
+
+/* Create a new instance of a Viterbi decoder */
+void *create_viterbi27_mmx(int len){
+ struct v27 *vp;
+ int polys[2] = { V27POLYA, V27POLYB };
+
+ if(Init == 0){
+ set_viterbi27_polynomial_mmx(polys);
+ }
+ if((vp = (struct v27 *)malloc(sizeof(struct v27))) == NULL)
+ return NULL;
+
+ if((vp->decisions = (decision_t *)malloc((len+6)*sizeof(decision_t))) == NULL){
+ free(vp);
+ return NULL;
+ }
+ init_viterbi27_mmx(vp,0);
+ return vp;
+}
+
+/* Viterbi chainback */
+int chainback_viterbi27_mmx(
+ void *p,
+ unsigned char *data, /* Decoded output data */
+ unsigned int nbits, /* Number of data bits */
+ unsigned int endstate){ /* Terminal encoder state */
+
+ struct v27 *vp = (struct v27 *)p;
+ decision_t *d;
+
+ if(p == NULL)
+ return -1;
+ d = (decision_t *)vp->decisions;
+ endstate &= 63;
+ d += 6; /* Look past tail */
+ while(nbits-- != 0){
+ int k;
+
+ k = d[nbits].c[endstate>>2] & 1;
+ data[nbits>>3] = endstate = (endstate >> 1) | (k << 7);
+ }
+ return 0;
+}
+
+/* Delete instance of a Viterbi decoder */
+void delete_viterbi27_mmx(void *p){
+ struct v27 *vp = p;
+
+ if(vp != NULL){
+ free(vp->decisions);
+ free(vp);
+ }
+}