Add "stateful" feature type with initial feature "last n"

Stateful feature extraction functions are functions that require state to be maintained between successive calls.  This is necessary, for example when an accumulation of values is required, or changes need to be measured over time.

The initial xtract_last_n() function accumulates the last N (single) values from *data and writes them to *result

1 files changed, 93 insertions, 0 deletions

diff --git a/src/stateful.c b/src/stateful.c
new file mode 100644
index 0000000..501db45
--- /dev/null
+++ b/src/stateful.c
@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2012 Jamie Bullock
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ */
+
+/* stateful.c: declares functions that extract features that require stateful data to be retained between frames */
+
+#include "../xtract/xtract_stateful.h"
+#include "../xtract/libxtract.h"
+
+#include "c-ringbuf/ringbuf.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <float.h>
+
+struct xtract_last_n_state_
+{
+    ringbuf_t ringbuf;
+};
+
+
+xtract_last_n_state *xtract_last_n_state_new(size_t N)
+{
+    xtract_last_n_state *last_n_state = malloc(sizeof(xtract_last_n_state));
+    
+    if (last_n_state == NULL)
+    {
+        perror("could not allocate memory for xtract_last_n_state");
+        return NULL;
+    }
+    
+    last_n_state->ringbuf = ringbuf_new(N * sizeof(double));
+    
+    if (last_n_state->ringbuf)
+    {
+        perror("could not allocate memory for xtract_last_n_state->ringbuf");
+    }
+        
+    return last_n_state;
+}
+
+void xtract_last_n_state_delete(xtract_last_n_state *last_n_state)
+{
+    ringbuf_free(&last_n_state->ringbuf);
+    free(last_n_state);
+}
+
+int xtract_last_n(const xtract_last_n_state *state, const double *data, const int N, const void *argv, double *result)
+{
+    double *current = (double *)argv;
+    size_t N_bytes = N * sizeof(double);
+    
+    if (N_bytes != ringbuf_capacity(state->ringbuf))
+    {
+        fprintf(stderr, "libxtract: error: xtract_last_n(): inconsitent size");
+        return XTRACT_BAD_STATE;
+    }
+    
+    ringbuf_memcpy_into(state->ringbuf, current, sizeof(double));
+    size_t used = ringbuf_bytes_used(state->ringbuf);
+    ringbuf_memcpy_from(result, state->ringbuf, used, false);
+    
+    if (used < N_bytes)
+    {
+        /* zero pad */
+        for (size_t n = used / sizeof(double); n < N; ++n)
+        {
+            result[n] = 0.0;
+        }
+    }
+    
+    return XTRACT_SUCCESS;
+}
+