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-rw-r--r--core/mp_memory_barrier.h23
-rw-r--r--core/mp_ring.c155
-rw-r--r--core/mp_ring.h125
3 files changed, 303 insertions, 0 deletions
diff --git a/core/mp_memory_barrier.h b/core/mp_memory_barrier.h
new file mode 100644
index 0000000000..e27825de8f
--- /dev/null
+++ b/core/mp_memory_barrier.h
@@ -0,0 +1,23 @@
+/*
+ * This file is part of mpv.
+ * 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/>.
+ */
+
+// At this point both gcc and clang had __sync_synchronize support for some
+// time. We only support a full memory barrier.
+
+#define mp_memory_barrier() __sync_synchronize()
+#define mp_atomic_add_and_fetch(a, b) __sync_add_and_fetch(a, b)
diff --git a/core/mp_ring.c b/core/mp_ring.c
new file mode 100644
index 0000000000..207dc62e86
--- /dev/null
+++ b/core/mp_ring.c
@@ -0,0 +1,155 @@
+/*
+ * 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 "core/mp_memory_barrier.h"
+#include "core/mp_ring.h"
+
+struct mp_ring {
+ uint8_t *buffer;
+
+ /* Positions of thes 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_read_cb(struct mp_ring *buffer, void *ctx, int len,
+ void (*func)(void*, void*, int))
+{
+ // The point of this function is defining custom read behaviour, assume
+ // it's a programmers error if func is null.
+ assert(func);
+
+ 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;
+
+ func(ctx, buffer->buffer + read_ptr, len);
+
+ return mp_ring_drain(buffer, 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));
+}
diff --git a/core/mp_ring.h b/core/mp_ring.h
new file mode 100644
index 0000000000..52e885287d
--- /dev/null
+++ b/core/mp_ring.h
@@ -0,0 +1,125 @@
+/*
+ * 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/>.
+ */
+
+#ifndef MPV_MP_RING_H
+#define MPV_MP_RING_H
+
+/**
+ * A simple non-blocking SPSC (single producer, single consumer) ringbuffer
+ * implementation. Thread safety is accomplished through atomic operations.
+ */
+
+struct mp_ring;
+
+/**
+ * Instantiate a new ringbuffer
+ *
+ * talloc_ctx: talloc context of the newly created object
+ * size: total size in bytes
+ * return: the newly created ringbuffer
+ */
+struct mp_ring *mp_ring_new(void *talloc_ctx, int size);
+
+/**
+ * Read data from the ringbuffer
+ *
+ * buffer: target ringbuffer instance
+ * dest: destination buffer for the read data. If NULL read data is discarded.
+ * len: maximum number of bytes to read
+ * return: number of bytes read
+ */
+int mp_ring_read(struct mp_ring *buffer, unsigned char *dest, int len);
+
+/**
+ * Read data from the ringbuffer
+ *
+ * This function behaves similarly to `av_fifo_generic_read` and was actually
+ * added for compatibility with code that was written for it.
+ * This function will drain the returned amount of bytes from the ringbuffer
+ * so you don't have to handle that in inside `func`.
+ *
+ * buffer: target ringbuffer instance
+ * ctx: context for the callback function
+ * len: maximum number of bytes to read
+ * func: callback function to customize reading behaviour
+ * return: number of bytes read
+ */
+int mp_ring_read_cb(struct mp_ring *buffer, void *ctx, int len,
+ void (*func)(void*, void*, int));
+
+/**
+ * Write data to the ringbuffer
+ *
+ * buffer: target ringbuffer instance
+ * src: source buffer for the write data
+ * len: maximum number of bytes to write
+ * return: number of bytes written
+ */
+int mp_ring_write(struct mp_ring *buffer, unsigned char *src, int len);
+
+/**
+ * Drain data from the ringbuffer
+ *
+ * buffer: target ringbuffer instance
+ * len: maximum number of bytes to drain
+ * return: number of bytes drained
+ */
+int mp_ring_drain(struct mp_ring *buffer, int len);
+
+/**
+ * Reset the ringbuffer discarding any content
+ *
+ * buffer: target ringbuffer instance
+ */
+void mp_ring_reset(struct mp_ring *buffer);
+
+/**
+ * Get the available size for writing
+ *
+ * buffer: target ringbuffer instance
+ * return: number of bytes that can be written
+ */
+int mp_ring_available(struct mp_ring *buffer);
+
+/**
+ * Get the total size
+ *
+ * buffer: target ringbuffer instance
+ * return: total ringbuffer size
+ */
+int mp_ring_size(struct mp_ring *buffer);
+
+/**
+ * Get the available size for reading
+ *
+ * buffer: target ringbuffer instance
+ * return: number of bytes ready for reading
+ */
+int mp_ring_buffered(struct mp_ring *buffer);
+
+/**
+ * Get a string representation of the ringbuffer
+ *
+ * buffer: target ringbuffer instance
+ * talloc_ctx: talloc context of the newly created string
+ * return: string representing the ringbuffer
+ */
+char *mp_ring_repr(struct mp_ring *buffer, void *talloc_ctx);
+
+#endif
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-02 15:25:01 +0000