py/ringbuf: Add helpers for put16/get16.

py/py.mk

@@ -85,6 +85,7 @@ PY_CORE_O_BASENAME = $(addprefix py/,\
 	runtime_utils.o \
 	scheduler.o \
 	nativeglue.o \
+	ringbuf.o \
 	stackctrl.o \
 	argcheck.o \
 	warning.o \

py/ringbuf.c

@@ -0,0 +1,66 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Jim Mussared
+ *
+ * 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.
+ */
+#include "ringbuf.h"
+
+int ringbuf_get16(ringbuf_t *r) {
+    if (r->iget == r->iput) {
+        return -1;
+    }
+    uint32_t iget_a = r->iget + 1;
+    if (iget_a == r->size) {
+        iget_a = 0;
+    }
+    if (iget_a == r->iput) {
+        return -1;
+    }
+    uint16_t v = (r->buf[r->iget] << 8) | (r->buf[iget_a]);
+    r->iget = iget_a + 1;
+    if (r->iget == r->size) {
+        r->iget = 0;
+    }
+    return v;
+}
+
+int ringbuf_put16(ringbuf_t *r, uint16_t v) {
+    uint32_t iput_a = r->iput + 1;
+    if (iput_a == r->size) {
+        iput_a = 0;
+    }
+    if (iput_a == r->iget) {
+        return -1;
+    }
+    uint32_t iput_b = iput_a + 1;
+    if (iput_b == r->size) {
+        iput_b = 0;
+    }
+    if (iput_b == r->iget) {
+        return -1;
+    }
+    r->buf[r->iput] = (v >> 8) & 0xff;
+    r->buf[iput_a] = v & 0xff;
+    r->iput = iput_b;
+    return 0;
+}

py/ringbuf.h

@@ -26,6 +26,9 @@
 #ifndef MICROPY_INCLUDED_PY_RINGBUF_H
 #define MICROPY_INCLUDED_PY_RINGBUF_H
 
+#include <stddef.h>
+#include <stdint.h>
+
 typedef struct _ringbuf_t {
     uint8_t *buf;
     uint16_t size;
@@ -37,7 +40,7 @@ typedef struct _ringbuf_t {
 // byte buf_array[N];
 // ringbuf_t buf = {buf_array, sizeof(buf_array)};
 
-// Dynamic initialization. This creates root pointer!
+// Dynamic initialization. This needs to become findable as a root pointer!
 #define ringbuf_alloc(r, sz) \
 { \
     (r)->buf = m_new(uint8_t, sz); \
@@ -69,4 +72,16 @@ static inline int ringbuf_put(ringbuf_t *r, uint8_t v) {
     return 0;
 }
 
+static inline size_t ringbuf_free(ringbuf_t *r) {
+    return (r->size + r->iget - r->iput - 1) % r->size;
+}
+
+static inline size_t ringbuf_avail(ringbuf_t *r) {
+    return (r->size + r->iput - r->iget) % r->size;
+}
+
+// Note: big-endian. No-op if not enough room available for both bytes.
+int ringbuf_get16(ringbuf_t *r);
+int ringbuf_put16(ringbuf_t *r, uint16_t v);
+
 #endif // MICROPY_INCLUDED_PY_RINGBUF_H