From b0969d077818a74f2fd26b5a7bec2263a4517b07 Mon Sep 17 00:00:00 2001
From: Richard Braun <rbraun@sceen.net>
Date: Fri, 31 Aug 2018 01:15:43 +0200
Subject: mbuf: new module

---
 src/mbuf.c | 165 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 165 insertions(+)
 create mode 100644 src/mbuf.c

(limited to 'src/mbuf.c')

diff --git a/src/mbuf.c b/src/mbuf.c
new file mode 100644
index 0000000..27d6221
--- /dev/null
+++ b/src/mbuf.c
@@ -0,0 +1,165 @@
+/*
+ * Copyright (c) 2018 Richard Braun.
+ *
+ * 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.
+ *
+ * Upstream site with license notes :
+ * http://git.sceen.net/rbraun/librbraun.git/
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "mbuf.h"
+
+/*
+ * Message header.
+ *
+ * The size denotes the size of the data, without the header.
+ */
+struct mbuf_hdr {
+    uint32_t size;
+    char data[];
+};
+
+static int
+mbuf_hdr_init(struct mbuf_hdr *hdr, size_t size)
+{
+    hdr->size = size;
+
+    if (hdr->size != size) {
+        return EMSGSIZE;
+    }
+
+    return 0;
+}
+
+static size_t
+mbuf_hdr_total_size(const struct mbuf_hdr *hdr)
+{
+    return sizeof(*hdr) + hdr->size;
+}
+
+static size_t
+mbuf_hdr_msg_size(const struct mbuf_hdr *hdr)
+{
+    return hdr->size;
+}
+
+void
+mbuf_init(struct mbuf *mbuf, void *buf, size_t capacity)
+{
+    cbuf_init(&mbuf->cbuf, buf, capacity);
+}
+
+void
+mbuf_clear(struct mbuf *mbuf)
+{
+    return cbuf_clear(&mbuf->cbuf);
+}
+
+static void
+mbuf_clear_old_msgs(struct mbuf *mbuf, size_t total_size)
+{
+    struct mbuf_hdr hdr;
+    size_t size;
+    int error;
+
+    do {
+        size = sizeof(hdr);
+        error = cbuf_pop(&mbuf->cbuf, &hdr, &size);
+        assert(!error);
+
+        if (size == 0) {
+            break;
+        }
+
+        size = mbuf_hdr_msg_size(&hdr);
+        error = cbuf_pop(&mbuf->cbuf, NULL, &size);
+        assert(!error && (size == mbuf_hdr_msg_size(&hdr)));
+    } while (cbuf_avail_size(&mbuf->cbuf) < total_size);
+}
+
+int
+mbuf_push(struct mbuf *mbuf, const void *buf, size_t size, bool erase)
+{
+    struct mbuf_hdr hdr;
+    size_t total_size;
+    int error;
+
+    error = mbuf_hdr_init(&hdr, size);
+
+    if (error) {
+        return error;
+    }
+
+    total_size = mbuf_hdr_total_size(&hdr);
+
+    if (total_size > cbuf_avail_size(&mbuf->cbuf)) {
+        if (!erase || (total_size > cbuf_capacity(&mbuf->cbuf))) {
+            return EMSGSIZE;
+        }
+
+        mbuf_clear_old_msgs(mbuf, total_size);
+    }
+
+    error = cbuf_push(&mbuf->cbuf, &hdr, sizeof(hdr), erase);
+    assert(!error);
+    error = cbuf_push(&mbuf->cbuf, buf, size, erase);
+    assert(!error);
+
+    return 0;
+}
+
+int
+mbuf_pop(struct mbuf *mbuf, void *buf, size_t *sizep)
+{
+    struct mbuf_hdr hdr;
+    size_t start, size;
+    int error;
+
+    start = cbuf_start(&mbuf->cbuf);
+
+    size = sizeof(hdr);
+    error = cbuf_read(&mbuf->cbuf, start, &hdr, &size);
+    assert(!error);
+
+    if (size == 0) {
+        return EAGAIN;
+    }
+
+    assert(size == sizeof(hdr));
+    size = mbuf_hdr_msg_size(&hdr);
+
+    if (size > *sizep) {
+        error = EMSGSIZE;
+        goto out;
+    }
+
+    cbuf_set_start(&mbuf->cbuf, start + sizeof(hdr));
+    error = cbuf_pop(&mbuf->cbuf, buf, &size);
+    assert(!error && (size == mbuf_hdr_msg_size(&hdr)));
+
+out:
+    *sizep = size;
+    return error;
+}
-- 
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