1 files changed, 138 insertions, 0 deletions
diff --git a/misc/ring.c b/misc/ring.c
new file mode 100644
index 0000000000..eb139c2cab
--- /dev/null
+++ b/misc/ring.c
@@ -0,0 +1,138 @@
+/*
+ * This file is part of mpv.
+ * Copyright (c) 2012 wm4
+ * Copyright (c) 2013 Stefano Pigozzi <stefano.pigozzi@gmail.com>
+ *
+ * mpv 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.
+ *
+ * mpv is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <inttypes.h>
+#include <libavutil/common.h>
+#include <assert.h>
+#include "talloc.h"
+#include "compat/atomics.h"
+#include "ring.h"
+
+struct mp_ring {
+    uint8_t  *buffer;
+
+    /* Positions of the first readable/writeable chunks. Do not read this
+     * fields but use the atomic private accessors `mp_ring_get_wpos`
+     * and `mp_ring_get_rpos`. */
+    uint32_t rpos, wpos;
+};
+
+static uint32_t mp_ring_get_wpos(struct mp_ring *buffer)
+{
+    mp_memory_barrier();
+    return buffer->wpos;
+}
+
+static uint32_t mp_ring_get_rpos(struct mp_ring *buffer)
+{
+    mp_memory_barrier();
+    return buffer->rpos;
+}
+
+struct mp_ring *mp_ring_new(void *talloc_ctx, int size)
+{
+    struct mp_ring *ringbuffer =
+        talloc_zero(talloc_ctx, struct mp_ring);
+
+    *ringbuffer = (struct mp_ring) {
+        .buffer = talloc_size(talloc_ctx, size),
+    };
+
+    return ringbuffer;
+}
+
+int mp_ring_drain(struct mp_ring *buffer, int len)
+{
+    int buffered  = mp_ring_buffered(buffer);
+    int drain_len = FFMIN(len, buffered);
+    mp_atomic_add_and_fetch(&buffer->rpos, drain_len);
+    mp_memory_barrier();
+    return drain_len;
+}
+
+int mp_ring_read(struct mp_ring *buffer, unsigned char *dest, int len)
+{
+    if (!dest) return mp_ring_drain(buffer, len);
+
+    int size     = mp_ring_size(buffer);
+    int buffered = mp_ring_buffered(buffer);
+    int read_len = FFMIN(len, buffered);
+    int read_ptr = mp_ring_get_rpos(buffer) % size;
+
+    int len1 = FFMIN(size - read_ptr, read_len);
+    int len2 = read_len - len1;
+
+    memcpy(dest, buffer->buffer + read_ptr, len1);
+    memcpy(dest + len1, buffer->buffer, len2);
+
+    mp_atomic_add_and_fetch(&buffer->rpos, read_len);
+    mp_memory_barrier();
+
+    return read_len;
+}
+
+int mp_ring_write(struct mp_ring *buffer, unsigned char *src, int len)
+{
+    int size      = mp_ring_size(buffer);
+    int free      = mp_ring_available(buffer);
+    int write_len = FFMIN(len, free);
+    int write_ptr = mp_ring_get_wpos(buffer) % size;
+
+    int len1 = FFMIN(size - write_ptr, write_len);
+    int len2 = write_len - len1;
+
+    memcpy(buffer->buffer + write_ptr, src, len1);
+    memcpy(buffer->buffer, src + len1, len2);
+
+    mp_atomic_add_and_fetch(&buffer->wpos, write_len);
+    mp_memory_barrier();
+
+    return write_len;
+}
+
+void mp_ring_reset(struct mp_ring *buffer)
+{
+    buffer->wpos = buffer->rpos = 0;
+    mp_memory_barrier();
+}
+
+int mp_ring_available(struct mp_ring *buffer)
+{
+    return mp_ring_size(buffer) - mp_ring_buffered(buffer);
+}
+
+int mp_ring_size(struct mp_ring *buffer)
+{
+    return talloc_get_size(buffer->buffer);
+}
+
+int mp_ring_buffered(struct mp_ring *buffer)
+{
+    return (mp_ring_get_wpos(buffer) - mp_ring_get_rpos(buffer));
+}
+
+char *mp_ring_repr(struct mp_ring *buffer, void *talloc_ctx)
+{
+    return talloc_asprintf(
+        talloc_ctx,
+        "Ringbuffer { .size = %dB, .buffered = %dB, .available = %dB }",
+        mp_ring_size(buffer),
+        mp_ring_buffered(buffer),
+        mp_ring_available(buffer));
+}