Merge pull request #142 from mryndzionek/bipbuffer

Use a bip buffer instead of a ring buffer

CMakeLists.txt

@@ -41,7 +41,7 @@ if(PICO_BOARD STREQUAL "pico")
       event.c
       usb_descriptors.c
       usb_audio_device.c
-      ring_buffer_lib.c
+      bipbuffer.c
       squelch.c
   )
 

bipbuffer.c

@@ -0,0 +1,188 @@
+/**
+ * Copyright (c) 2011, Willem-Hendrik Thiart
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ *
+ * @file
+ * @author  Willem Thiart [email protected]
+ */
+
+#include "stdio.h"
+#include <stdlib.h>
+
+/* for memcpy */
+#include <string.h>
+
+#include "bipbuffer.h"
+
+static size_t bipbuf_sizeof(const unsigned int size)
+{
+    return sizeof(bipbuf_t) + size;
+}
+
+int bipbuf_unused(bipbuf_t *me)
+{
+    critical_section_enter_blocking(&me->crit);
+    int ret;
+    if (1 == me->b_inuse)
+        /* distance between region B and region A */
+        ret = me->a_start - me->b_end;
+    else
+        ret = me->size - me->a_end;
+    critical_section_exit(&me->crit);
+    return ret;
+}
+
+static inline int _unused(const bipbuf_t *me)
+{
+    if (1 == me->b_inuse)
+        /* distance between region B and region A */
+        return me->a_start - me->b_end;
+    else
+        return me->size - me->a_end;
+}
+
+int bipbuf_size(bipbuf_t *me)
+{
+    critical_section_enter_blocking(&me->crit);
+    int ret = me->size;
+    critical_section_exit(&me->crit);
+    return ret;
+}
+
+int bipbuf_used(bipbuf_t *me)
+{
+    critical_section_enter_blocking(&me->crit);
+    int ret = (me->a_end - me->a_start) + me->b_end;
+    critical_section_exit(&me->crit);
+    return ret;
+}
+
+static void bipbuf_init(bipbuf_t *me, const unsigned int size)
+{
+    me->a_start = me->a_end = me->b_end = 0;
+    me->size = size;
+    me->b_inuse = 0;
+}
+
+bipbuf_t *bipbuf_new(const unsigned int size)
+{
+    bipbuf_t *me = calloc(1, bipbuf_sizeof(size));
+    if (!me)
+        return NULL;
+    bipbuf_init(me, size);
+    critical_section_init(&me->crit);
+    return me;
+}
+
+void bipbuf_free(bipbuf_t *me)
+{
+    critical_section_deinit(&me->crit);
+    free(me);
+}
+
+int bipbuf_is_empty(bipbuf_t *me)
+{
+    critical_section_enter_blocking(&me->crit);
+    int ret = me->a_start == me->a_end;
+    critical_section_exit(&me->crit);
+    return ret;
+}
+
+static inline int _is_empty(const bipbuf_t *me)
+{
+    return me->a_start == me->a_end;
+}
+
+/* find out if we should turn on region B
+ * ie. is the distance from A to buffer's end less than B to A? */
+static void __check_for_switch_to_b(bipbuf_t *me)
+{
+    if (me->size - me->a_end < me->a_start - me->b_end)
+        me->b_inuse = 1;
+}
+
+int bipbuf_offer(bipbuf_t *me, const unsigned char *data, const int size)
+{
+    critical_section_enter_blocking(&me->crit);
+    /* not enough space */
+    if (_unused(me) < size)
+    {
+        critical_section_exit(&me->crit);
+        return 0;
+    }
+
+    if (1 == me->b_inuse)
+    {
+        memcpy(me->data + me->b_end, data, size);
+        me->b_end += size;
+    }
+    else
+    {
+        memcpy(me->data + me->a_end, data, size);
+        me->a_end += size;
+    }
+
+    __check_for_switch_to_b(me);
+    critical_section_exit(&me->crit);
+    return size;
+}
+
+unsigned char *bipbuf_peek(bipbuf_t *me, const unsigned int size)
+{
+    critical_section_enter_blocking(&me->crit);
+    /* make sure we can actually peek at this data */
+    if (me->size < me->a_start + size)
+    {
+        critical_section_exit(&me->crit);
+        return NULL;
+    }
+
+    if (_is_empty(me))
+    {
+        critical_section_exit(&me->crit);
+        return NULL;
+    }
+
+    critical_section_exit(&me->crit);
+    return (unsigned char *)me->data + me->a_start;
+}
+
+unsigned char *bipbuf_poll(bipbuf_t *me, const unsigned int size)
+{
+    critical_section_enter_blocking(&me->crit);
+    if (_is_empty(me))
+    {
+        critical_section_exit(&me->crit);
+        return NULL;
+    }
+
+    /* make sure we can actually poll this data */
+    if (me->size < me->a_start + size)
+    {
+        critical_section_exit(&me->crit);
+        return NULL;
+    }
+
+    void *end = me->data + me->a_start;
+    me->a_start += size;
+
+    /* we seem to be empty.. */
+    if (me->a_start == me->a_end)
+    {
+        /* replace a with region b */
+        if (1 == me->b_inuse)
+        {
+            me->a_start = 0;
+            me->a_end = me->b_end;
+            me->b_end = me->b_inuse = 0;
+        }
+        else
+            /* safely move cursor back to the start because we are empty */
+            me->a_start = me->a_end = 0;
+    }
+
+    __check_for_switch_to_b(me);
+    critical_section_exit(&me->crit);
+    return end;
+}

bipbuffer.h

@@ -0,0 +1,76 @@
+#pragma once
+
+#include "pico/critical_section.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+typedef struct
+{
+    unsigned long int size;
+
+    /* region A */
+    unsigned int a_start, a_end;
+
+    /* region B */
+    unsigned int b_end;
+
+    /* is B inuse? */
+    int b_inuse;
+    critical_section_t crit;
+    unsigned char data[];
+} bipbuf_t;
+
+/**
+ * Create a new bip buffer.
+ *
+ * malloc()s space
+ *
+ * @param[in] size The size of the buffer */
+bipbuf_t *bipbuf_new(const unsigned int size);
+
+/**
+ * Free the bip buffer */
+void bipbuf_free(bipbuf_t *me);
+
+/**
+ * @param[in] data The data to be offered to the buffer
+ * @param[in] size The size of the data to be offered
+ * @return number of bytes offered */
+int bipbuf_offer(bipbuf_t *me, const unsigned char *data, const int size);
+
+/**
+ * Look at data. Don't move cursor
+ *
+ * @param[in] len The length of the data to be peeked
+ * @return data on success, NULL if we can't peek at this much data */
+unsigned char *bipbuf_peek(bipbuf_t* me, const unsigned int len);
+
+/**
+ * Get pointer to data to read. Move the cursor on.
+ *
+ * @param[in] len The length of the data to be polled
+ * @return pointer to data, NULL if we can't poll this much data */
+unsigned char *bipbuf_poll(bipbuf_t* me, const unsigned int size);
+
+/**
+ * @return the size of the bipbuffer */
+int bipbuf_size(bipbuf_t* me);
+
+/**
+ * @return 1 if buffer is empty; 0 otherwise */
+int bipbuf_is_empty(bipbuf_t* me);
+
+/**
+ * @return how much space we have assigned */
+int bipbuf_used(bipbuf_t* cb);
+
+/**
+ * @return bytes of unused space */
+int bipbuf_unused(bipbuf_t* me);
+
+#ifdef __cplusplus
+}
+#endif