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-rw-r--r--plugins/alsa/ringbuf.c347
1 files changed, 347 insertions, 0 deletions
diff --git a/plugins/alsa/ringbuf.c b/plugins/alsa/ringbuf.c
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+++ b/plugins/alsa/ringbuf.c
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+/*
+ * ringbuf.c - C ring buffer (FIFO) implementation.
+ *
+ * Written in 2011 by Drew Hess <dhess-src@bothan.net>.
+ *
+ * To the extent possible under law, the author(s) have dedicated all
+ * copyright and related and neighboring rights to this software to
+ * the public domain worldwide. This software is distributed without
+ * any warranty.
+ *
+ * You should have received a copy of the CC0 Public Domain Dedication
+ * along with this software. If not, see
+ * <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
+
+#include "ringbuf.h"
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <sys/param.h>
+#include <assert.h>
+
+/*
+ * The code is written for clarity, not cleverness or performance, and
+ * contains many assert()s to enforce invariant assumptions and catch
+ * bugs. Feel free to optimize the code and to remove asserts for use
+ * in your own projects, once you're comfortable that it functions as
+ * intended.
+ */
+
+struct ringbuf_t
+{
+ uint8_t *buf;
+ uint8_t *head, *tail;
+ size_t size;
+};
+
+ringbuf_t
+ringbuf_new(size_t capacity)
+{
+ ringbuf_t rb = malloc(sizeof(struct ringbuf_t));
+ if (rb) {
+
+ /* One byte is used for detecting the full condition. */
+ rb->size = capacity + 1;
+ rb->buf = malloc(rb->size);
+ if (rb->buf)
+ ringbuf_reset(rb);
+ else {
+ free(rb);
+ return 0;
+ }
+ }
+ return rb;
+}
+
+size_t
+ringbuf_buffer_size(const struct ringbuf_t *rb)
+{
+ return rb->size;
+}
+
+void
+ringbuf_reset(ringbuf_t rb)
+{
+ rb->head = rb->tail = rb->buf;
+}
+
+void
+ringbuf_free(ringbuf_t *rb)
+{
+ assert(rb && *rb);
+ free((*rb)->buf);
+ free(*rb);
+ *rb = 0;
+}
+
+size_t
+ringbuf_capacity(const struct ringbuf_t *rb)
+{
+ return ringbuf_buffer_size(rb) - 1;
+}
+
+/*
+ * Return a pointer to one-past-the-end of the ring buffer's
+ * contiguous buffer. You shouldn't normally need to use this function
+ * unless you're writing a new ringbuf_* function.
+ */
+static const uint8_t *
+ringbuf_end(const struct ringbuf_t *rb)
+{
+ return rb->buf + ringbuf_buffer_size(rb);
+}
+
+size_t
+ringbuf_bytes_free(const struct ringbuf_t *rb)
+{
+ if (rb->head >= rb->tail)
+ return ringbuf_capacity(rb) - (rb->head - rb->tail);
+ else
+ return rb->tail - rb->head - 1;
+}
+
+size_t
+ringbuf_bytes_used(const struct ringbuf_t *rb)
+{
+ return ringbuf_capacity(rb) - ringbuf_bytes_free(rb);
+}
+
+int
+ringbuf_is_full(const struct ringbuf_t *rb)
+{
+ return ringbuf_bytes_free(rb) == 0;
+}
+
+int
+ringbuf_is_empty(const struct ringbuf_t *rb)
+{
+ return ringbuf_bytes_free(rb) == ringbuf_capacity(rb);
+}
+
+const void *
+ringbuf_tail(const struct ringbuf_t *rb)
+{
+ return rb->tail;
+}
+
+const void *
+ringbuf_head(const struct ringbuf_t *rb)
+{
+ return rb->head;
+}
+
+/*
+ * Given a ring buffer rb and a pointer to a location within its
+ * contiguous buffer, return the a pointer to the next logical
+ * location in the ring buffer.
+ */
+static uint8_t *
+ringbuf_nextp(ringbuf_t rb, const uint8_t *p)
+{
+ /*
+ * The assert guarantees the expression (++p - rb->buf) is
+ * non-negative; therefore, the modulus operation is safe and
+ * portable.
+ */
+ assert((p >= rb->buf) && (p < ringbuf_end(rb)));
+ return rb->buf + ((++p - rb->buf) % ringbuf_buffer_size(rb));
+}
+
+size_t
+ringbuf_findchr(const struct ringbuf_t *rb, int c, size_t offset)
+{
+ const uint8_t *bufend = ringbuf_end(rb);
+ size_t bytes_used = ringbuf_bytes_used(rb);
+ if (offset >= bytes_used)
+ return bytes_used;
+
+ const uint8_t *start = rb->buf +
+ (((rb->tail - rb->buf) + offset) % ringbuf_buffer_size(rb));
+ assert(bufend > start);
+ size_t n = MIN(bufend - start, bytes_used - offset);
+ const uint8_t *found = memchr(start, c, n);
+ if (found)
+ return offset + (found - start);
+ else
+ return ringbuf_findchr(rb, c, offset + n);
+}
+
+size_t
+ringbuf_memset(ringbuf_t dst, int c, size_t len)
+{
+ const uint8_t *bufend = ringbuf_end(dst);
+ size_t nwritten = 0;
+ size_t count = MIN(len, ringbuf_buffer_size(dst));
+ int overflow = count > ringbuf_bytes_free(dst);
+
+ while (nwritten != count) {
+
+ /* don't copy beyond the end of the buffer */
+ assert(bufend > dst->head);
+ size_t n = MIN(bufend - dst->head, count - nwritten);
+ memset(dst->head, c, n);
+ dst->head += n;
+ nwritten += n;
+
+ /* wrap? */
+ if (dst->head == bufend)
+ dst->head = dst->buf;
+ }
+
+ if (overflow) {
+ dst->tail = ringbuf_nextp(dst, dst->head);
+ assert(ringbuf_is_full(dst));
+ }
+
+ return nwritten;
+}
+
+void *
+ringbuf_memcpy_into(ringbuf_t dst, const void *src, size_t count)
+{
+ const uint8_t *u8src = src;
+ const uint8_t *bufend = ringbuf_end(dst);
+ int overflow = count > ringbuf_bytes_free(dst);
+ size_t nread = 0;
+
+ while (nread != count) {
+ /* don't copy beyond the end of the buffer */
+ assert(bufend > dst->head);
+ size_t n = MIN(bufend - dst->head, count - nread);
+ memcpy(dst->head, u8src + nread, n);
+ dst->head += n;
+ nread += n;
+
+ /* wrap? */
+ if (dst->head == bufend)
+ dst->head = dst->buf;
+ }
+
+ if (overflow) {
+ dst->tail = ringbuf_nextp(dst, dst->head);
+ assert(ringbuf_is_full(dst));
+ }
+
+ return dst->head;
+}
+
+ssize_t
+ringbuf_read(int fd, ringbuf_t rb, size_t count)
+{
+ const uint8_t *bufend = ringbuf_end(rb);
+ size_t nfree = ringbuf_bytes_free(rb);
+
+ /* don't write beyond the end of the buffer */
+ assert(bufend > rb->head);
+ count = MIN(bufend - rb->head, count);
+ ssize_t n = read(fd, rb->head, count);
+ if (n > 0) {
+ assert(rb->head + n <= bufend);
+ rb->head += n;
+
+ /* wrap? */
+ if (rb->head == bufend)
+ rb->head = rb->buf;
+
+ /* fix up the tail pointer if an overflow occurred */
+ if (n > nfree) {
+ rb->tail = ringbuf_nextp(rb, rb->head);
+ assert(ringbuf_is_full(rb));
+ }
+ }
+
+ return n;
+}
+
+void *
+ringbuf_memcpy_from(void *dst, ringbuf_t src, size_t count)
+{
+ size_t bytes_used = ringbuf_bytes_used(src);
+ if (count > bytes_used)
+ return 0;
+
+ uint8_t *u8dst = dst;
+ const uint8_t *bufend = ringbuf_end(src);
+ size_t nwritten = 0;
+ while (nwritten != count) {
+ assert(bufend > src->tail);
+ size_t n = MIN(bufend - src->tail, count - nwritten);
+ memcpy(u8dst + nwritten, src->tail, n);
+ src->tail += n;
+ nwritten += n;
+
+ /* wrap ? */
+ if (src->tail == bufend)
+ src->tail = src->buf;
+ }
+
+ assert(count + ringbuf_bytes_used(src) == bytes_used);
+ return src->tail;
+}
+
+ssize_t
+ringbuf_write(int fd, ringbuf_t rb, size_t count)
+{
+ size_t bytes_used = ringbuf_bytes_used(rb);
+ if (count > bytes_used)
+ return 0;
+
+ const uint8_t *bufend = ringbuf_end(rb);
+ assert(bufend > rb->head);
+ count = MIN(bufend - rb->tail, count);
+ ssize_t n = write(fd, rb->tail, count);
+ if (n > 0) {
+ assert(rb->tail + n <= bufend);
+ rb->tail += n;
+
+ /* wrap? */
+ if (rb->tail == bufend)
+ rb->tail = rb->buf;
+
+ assert(n + ringbuf_bytes_used(rb) == bytes_used);
+ }
+
+ return n;
+}
+
+void *
+ringbuf_copy(ringbuf_t dst, ringbuf_t src, size_t count)
+{
+ size_t src_bytes_used = ringbuf_bytes_used(src);
+ if (count > src_bytes_used)
+ return 0;
+ int overflow = count > ringbuf_bytes_free(dst);
+
+ const uint8_t *src_bufend = ringbuf_end(src);
+ const uint8_t *dst_bufend = ringbuf_end(dst);
+ size_t ncopied = 0;
+ while (ncopied != count) {
+ assert(src_bufend > src->tail);
+ size_t nsrc = MIN(src_bufend - src->tail, count - ncopied);
+ assert(dst_bufend > dst->head);
+ size_t n = MIN(dst_bufend - dst->head, nsrc);
+ memcpy(dst->head, src->tail, n);
+ src->tail += n;
+ dst->head += n;
+ ncopied += n;
+
+ /* wrap ? */
+ if (src->tail == src_bufend)
+ src->tail = src->buf;
+ if (dst->head == dst_bufend)
+ dst->head = dst->buf;
+ }
+
+ assert(count + ringbuf_bytes_used(src) == src_bytes_used);
+
+ if (overflow) {
+ dst->tail = ringbuf_nextp(dst, dst->head);
+ assert(ringbuf_is_full(dst));
+ }
+
+ return dst->head;
+}