Add ZixRing.

git-svn-id: http://svn.drobilla.net/zix/trunk@13 df6676b4-ccc9-40e5-b5d6-7c4628a128e3

1 files changed, 224 insertions, 0 deletions

diff --git a/src/ring.c b/src/ring.c
new file mode 100644
index 0000000..1553ba5
--- /dev/null
+++ b/src/ring.c
@@ -0,0 +1,224 @@
+/*
+  Copyright 2011 David Robillard <http://drobilla.net>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef HAVE_MLOCK
+#    include <sys/mman.h>
+#endif
+
+#include "zix/ring.h"
+
+#if defined(__APPLE__)
+#    include <libkern/OSAtomic.h>
+#    define ZIX_FULL_BARRIER() OSMemoryBarrier()
+#elif (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)
+#    define ZIX_FULL_BARRIER() __sync_synchronize()
+#else
+#    warning Memory barriers unsupported, possible bugs on SMP systems
+#    define ZIX_FULL_BARRIER()
+#endif
+
+/* No support for any systems with separate read and write barriers */
+#define ZIX_READ_BARRIER() ZIX_FULL_BARRIER()
+#define ZIX_WRITE_BARRIER() ZIX_FULL_BARRIER()
+
+struct ZixRingImpl {
+	uint32_t write_head;  ///< Read index into buf
+	uint32_t read_head;   ///< Write index into buf
+	uint32_t size;        ///< Size (capacity) in bytes
+	uint32_t size_mask;   ///< Mask for fast modulo
+	char*    buf;         ///< Contents
+};
+
+static inline uint32_t
+next_power_of_two(uint32_t size)
+{
+	// http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
+	size--;
+	size |= size >> 1;
+	size |= size >> 2;
+	size |= size >> 4;
+	size |= size >> 8;
+	size |= size >> 16;
+	size++;
+	return size;
+}
+
+ZixRing*
+zix_ring_new(uint32_t size)
+{
+	ZixRing* ring = (ZixRing*)malloc(sizeof(ZixRing));
+	ring->write_head = 0;
+	ring->read_head  = 0;
+	ring->size       = next_power_of_two(size);
+	ring->size_mask  = ring->size - 1;
+	ring->buf        = malloc(ring->size);
+	assert(zix_ring_read_space(ring) == 0);
+	assert(zix_ring_write_space(ring) == ring->size - 1);
+	return ring;
+}
+
+void
+zix_ring_free(ZixRing* ring)
+{
+	free(ring->buf);
+	free(ring);
+}
+
+void
+zix_ring_mlock(ZixRing* ring)
+{
+#ifdef HAVE_MLOCK
+	mlock(ring, sizeof(ZixRing));
+	mlock(ring->buf, ring->size);
+#else
+#    warning Memory locking (via mlock) unsupported
+#endif
+}
+
+void
+zix_ring_reset(ZixRing* ring)
+{
+	ring->write_head = 0;
+	ring->read_head  = 0;
+}
+
+static inline uint32_t
+read_space_internal(const ZixRing* ring, uint32_t r, uint32_t w)
+{
+	if (w > r) {
+		return w - r;
+	} else {
+		return (w - r + ring->size) & ring->size_mask;
+	}
+}
+
+uint32_t
+zix_ring_read_space(const ZixRing* ring)
+{
+	return read_space_internal(ring, ring->read_head, ring->write_head);
+}
+
+static inline uint32_t
+write_space_internal(const ZixRing* ring, uint32_t r, uint32_t w)
+{
+	if (w > r) {
+		return ((r - w + ring->size) & ring->size_mask) - 1;
+	} else if (w < r) {
+		return (r - w) - 1;
+	} else {
+		return ring->size - 1;
+	}
+}
+
+uint32_t
+zix_ring_write_space(const ZixRing* ring)
+{
+	return write_space_internal(ring, ring->read_head, ring->write_head);
+}
+
+uint32_t
+zix_ring_capacity(const ZixRing* ring)
+{
+	return ring->size - 1;
+}
+
+static inline uint32_t
+peek_internal(const ZixRing* ring, uint32_t r, uint32_t w,
+              uint32_t size, void* dst)
+{
+	if (read_space_internal(ring, r, w) < size) {
+		return 0;
+	}
+
+	if (r + size < ring->size) {
+		memcpy(dst, &ring->buf[r], size);
+	} else {
+		const uint32_t first_size = ring->size - r;
+		memcpy(dst, &ring->buf[r], first_size);
+		memcpy(dst, &ring->buf[0], size - first_size);
+	}
+
+	return size;
+}
+
+uint32_t
+zix_ring_peek(ZixRing* ring, void* dst, uint32_t size)
+{
+	const uint32_t r = ring->read_head;
+	const uint32_t w = ring->write_head;
+
+	return peek_internal(ring, r, w, size, dst);
+}
+
+uint32_t
+zix_ring_read(ZixRing* ring, void* dst, uint32_t size)
+{
+	const uint32_t r = ring->read_head;
+	const uint32_t w = ring->write_head;
+
+	if (peek_internal(ring, r, w, size, dst)) {
+		ZIX_READ_BARRIER();
+		ring->read_head = (r + size) & ring->size_mask;
+		return size;
+	} else {
+		return 0;
+	}
+}
+
+uint32_t
+zix_ring_skip(ZixRing* ring, uint32_t size)
+{
+	const uint32_t r = ring->read_head;
+	const uint32_t w = ring->write_head;
+	if (read_space_internal(ring, r, w) < size) {
+		return 0;
+	}
+
+	ZIX_READ_BARRIER();
+	ring->read_head = (r + size) & ring->size_mask;
+	return size;
+}
+
+uint32_t
+zix_ring_write(ZixRing* ring, const void* src, uint32_t size)
+{
+	const uint32_t r = ring->read_head;
+	const uint32_t w = ring->write_head;
+	if (write_space_internal(ring, r, w) < size) {
+		return 0;
+	}
+
+	if (w + size <= ring->size) {
+		memcpy(&ring->buf[w], src, size);
+		ZIX_WRITE_BARRIER();
+		ring->write_head = (w + size) & ring->size_mask;
+	} else {
+		const uint32_t this_size = ring->size - w;
+		assert(this_size < size);
+		assert(w + this_size <= ring->size);
+		memcpy(&ring->buf[w], src, this_size);
+		memcpy(&ring->buf[0], (char*)src + this_size, size - this_size);
+		ZIX_WRITE_BARRIER();
+		ring->write_head = size - this_size;
+	}
+
+	return size;
+}