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Diffstat (limited to 'misc/ring.c')
-rw-r--r-- | misc/ring.c | 138 |
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)); +} |