1 files changed, 182 insertions, 0 deletions
diff --git a/bipbuffer.c b/bipbuffer.c
new file mode 100644
index 0000000..ee48c84
--- /dev/null
+++ b/bipbuffer.c
@@ -0,0 +1,182 @@
+/**
+ * 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.bipbuffer file.
+ *
+ * @file
+ * @author  Willem Thiart himself@willemthiart.com
+ */
+
+#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(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(const bipbuf_t* me)
+{
+    return me->size;
+}
+
+int bipbuf_used(const bipbuf_t* me)
+{
+    return (me->a_end - me->a_start) + me->b_end;
+}
+
+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 = malloc(bipbuf_sizeof(size));
+    if (!me)
+        return NULL;
+    bipbuf_init(me, size);
+    return me;
+}
+
+void bipbuf_free(bipbuf_t* me)
+{
+    free(me);
+}
+
+int bipbuf_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;
+}
+
+/* TODO: DOCUMENT THESE TWO FUNCTIONS */
+unsigned char *bipbuf_request(bipbuf_t* me, const int size)
+{
+    if (bipbuf_unused(me) < size)
+        return 0;
+    if (1 == me->b_inuse)
+    {
+        return (unsigned char *)me->data + me->b_end;
+    }
+    else
+    {
+        return (unsigned char *)me->data + me->a_end;
+    }
+
+    return NULL;
+}
+
+int bipbuf_push(bipbuf_t* me, const int size)
+{
+    if (bipbuf_unused(me) < size)
+        return 0;
+
+    if (1 == me->b_inuse)
+    {
+        me->b_end += size;
+    }
+    else
+    {
+        me->a_end += size;
+    }
+
+    __check_for_switch_to_b(me);
+    return size;
+}
+
+int bipbuf_offer(bipbuf_t* me, const unsigned char *data, const int size)
+{
+    /* not enough space */
+    if (bipbuf_unused(me) < size)
+        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);
+    return size;
+}
+
+unsigned char *bipbuf_peek(const bipbuf_t* me, const unsigned int size)
+{
+    /* make sure we can actually peek at this data */
+    if (me->size < me->a_start + size)
+        return NULL;
+
+    if (bipbuf_is_empty(me))
+        return NULL;
+
+    return (unsigned char *)me->data + me->a_start;
+}
+
+unsigned char *bipbuf_peek_all(const bipbuf_t* me, unsigned int *size)
+{
+    if (bipbuf_is_empty(me))
+        return NULL;
+
+    *size = me->a_end - me->a_start;
+    return (unsigned char*)me->data + me->a_start;
+}
+
+unsigned char *bipbuf_poll(bipbuf_t* me, const unsigned int size)
+{
+    if (bipbuf_is_empty(me))
+        return NULL;
+
+    /* make sure we can actually poll this data */
+    if (me->size < me->a_start + size)
+        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);
+    return end;
+}