Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 118 insertions, 0 deletions

diff --git a/util/fifo8.c b/util/fifo8.c
new file mode 100644
index 000000000..d4d1c135e
--- /dev/null
+++ b/util/fifo8.c
@@ -0,0 +1,118 @@
+/*
+ * Generic FIFO component, implemented as a circular buffer.
+ *
+ * Copyright (c) 2012 Peter A. G. Crosthwaite
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "migration/vmstate.h"
+#include "qemu/fifo8.h"
+
+void fifo8_create(Fifo8 *fifo, uint32_t capacity)
+{
+    fifo->data = g_new(uint8_t, capacity);
+    fifo->capacity = capacity;
+    fifo->head = 0;
+    fifo->num = 0;
+}
+
+void fifo8_destroy(Fifo8 *fifo)
+{
+    g_free(fifo->data);
+}
+
+void fifo8_push(Fifo8 *fifo, uint8_t data)
+{
+    assert(fifo->num < fifo->capacity);
+    fifo->data[(fifo->head + fifo->num) % fifo->capacity] = data;
+    fifo->num++;
+}
+
+void fifo8_push_all(Fifo8 *fifo, const uint8_t *data, uint32_t num)
+{
+    uint32_t start, avail;
+
+    assert(fifo->num + num <= fifo->capacity);
+
+    start = (fifo->head + fifo->num) % fifo->capacity;
+
+    if (start + num <= fifo->capacity) {
+        memcpy(&fifo->data[start], data, num);
+    } else {
+        avail = fifo->capacity - start;
+        memcpy(&fifo->data[start], data, avail);
+        memcpy(&fifo->data[0], &data[avail], num - avail);
+    }
+
+    fifo->num += num;
+}
+
+uint8_t fifo8_pop(Fifo8 *fifo)
+{
+    uint8_t ret;
+
+    assert(fifo->num > 0);
+    ret = fifo->data[fifo->head++];
+    fifo->head %= fifo->capacity;
+    fifo->num--;
+    return ret;
+}
+
+const uint8_t *fifo8_pop_buf(Fifo8 *fifo, uint32_t max, uint32_t *num)
+{
+    uint8_t *ret;
+
+    assert(max > 0 && max <= fifo->num);
+    *num = MIN(fifo->capacity - fifo->head, max);
+    ret = &fifo->data[fifo->head];
+    fifo->head += *num;
+    fifo->head %= fifo->capacity;
+    fifo->num -= *num;
+    return ret;
+}
+
+void fifo8_reset(Fifo8 *fifo)
+{
+    fifo->num = 0;
+    fifo->head = 0;
+}
+
+bool fifo8_is_empty(Fifo8 *fifo)
+{
+    return (fifo->num == 0);
+}
+
+bool fifo8_is_full(Fifo8 *fifo)
+{
+    return (fifo->num == fifo->capacity);
+}
+
+uint32_t fifo8_num_free(Fifo8 *fifo)
+{
+    return fifo->capacity - fifo->num;
+}
+
+uint32_t fifo8_num_used(Fifo8 *fifo)
+{
+    return fifo->num;
+}
+
+const VMStateDescription vmstate_fifo8 = {
+    .name = "Fifo8",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_VBUFFER_UINT32(data, Fifo8, 1, NULL, capacity),
+        VMSTATE_UINT32(head, Fifo8),
+        VMSTATE_UINT32(num, Fifo8),
+        VMSTATE_END_OF_LIST()
+    }
+};