Add ring buffer object

The new ring buffer object will be used to buffer a byte-stream between
two sockets.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>

Makefile.am

@@ -37,6 +37,7 @@ nodist_libkmscon_core_la_SOURCES = \
 	src/output_shaders.c
 
 libkmscon_core_la_SOURCES = \
+	src/misc.c src/misc.h \
 	src/console.c src/console.h \
 	src/output.c src/output.h \
 	src/output_context.c \

src/misc.c

@@ -0,0 +1,166 @@
+/*
+ * kmscon - Miscellaneous Helpers
+ *
+ * Copyright (c) 2011 David Herrmann <dh.herrmann@googlemail.com>
+ * Copyright (c) 2011 University of Tuebingen
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/*
+ * Miscellaneous Helpers
+ * Rings: Rings are used to buffer a byte-stream of data. It works like a FIFO
+ * queue but in-memory.
+ */
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define RING_SIZE 512
+
+struct ring_entry {
+	struct ring_entry *next;
+	size_t len;
+	char buf[];
+};
+
+struct kmscon_ring {
+	struct ring_entry *first;
+	struct ring_entry *last;
+};
+
+int kmscon_ring_new(struct kmscon_ring **out)
+{
+	struct kmscon_ring *ring;
+
+	if (!out)
+		return -EINVAL;
+
+	ring = malloc(sizeof(*ring));
+	if (!ring)
+		return -ENOMEM;
+
+	memset(ring, 0, sizeof(*ring));
+
+	*out = ring;
+	return 0;
+}
+
+void kmscon_ring_free(struct kmscon_ring *ring)
+{
+	struct ring_entry *tmp;
+
+	if (!ring)
+		return;
+
+	while (ring->first) {
+		tmp = ring->first;
+		ring->first = tmp->next;
+		free(tmp);
+	}
+	free(ring);
+}
+
+bool kmscon_ring_is_empty(struct kmscon_ring *ring)
+{
+	if (!ring)
+		return false;
+
+	return ring->first;
+}
+
+int kmscon_ring_write(struct kmscon_ring *ring, const char *val, size_t len)
+{
+	struct ring_entry *ent;
+	size_t space, cp;
+
+	if (!ring || !val || !len)
+		return -EINVAL;
+
+next:
+	ent = ring->last;
+	if (!ent || ent->len >= RING_SIZE) {
+		ent = malloc(sizeof(*ent) + RING_SIZE);
+		if (!ent)
+			return -ENOMEM;
+
+		ent->len = 0;
+		ent->next = NULL;
+		if (ring->last)
+			ring->last->next = ent;
+		else
+			ring->first = ent;
+		ring->last = ent;
+	}
+
+	space = RING_SIZE - ent->len;
+	if (len >= space)
+		cp = space;
+	else
+		cp = len;
+
+	memcpy(&ent->buf[ent->len], val, cp);
+	ent->len += cp;
+
+	val = &val[cp];
+	len -= cp;
+	if (len > 0)
+		goto next;
+
+	return 0;
+}
+
+const char *kmscon_ring_peek(struct kmscon_ring *ring, size_t *len)
+{
+	if (!ring || !ring->first)
+		return NULL;
+
+	*len = ring->first->len;
+	return ring->first->buf;
+}
+
+void kmscon_ring_drop(struct kmscon_ring *ring, size_t len)
+{
+	struct ring_entry *ent;
+
+	if (!ring || !len)
+		return;
+
+next:
+	ent = ring->first;
+	if (!ent)
+		return;
+
+	if (len >= ent->len) {
+		len -= ent->len;
+		ring->first = ent->next;
+		free(ent);
+		if (!ring->first)
+			ring->last = NULL;
+
+		if (len)
+			goto next;
+	} else {
+		memmove(ent->buf, &ent->buf[len], ent->len - len);
+		ent->len -= len;
+	}
+}

src/misc.h

@@ -0,0 +1,48 @@
+/*
+ * kmscon - Miscellaneous Helpers
+ *
+ * Copyright (c) 2011 David Herrmann <dh.herrmann@googlemail.com>
+ * Copyright (c) 2011 University of Tuebingen
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/*
+ * Miscellaneous Helpers
+ * This provides several helper objects like memory-rings or similar.
+ */
+
+#ifndef KMSCON_MISC_H
+#define kMSCON_MISC_H
+
+#include <stdbool.h>
+#include <stdlib.h>
+
+struct kmscon_ring;
+
+int kmscon_ring_new(struct kmscon_ring **out);
+void kmscon_ring_free(struct kmscon_ring *ring);
+bool kmscon_ring_is_empty(struct kmscon_ring *ring);
+
+int kmscon_ring_write(struct kmscon_ring *ring, const char *val, size_t len);
+const char *kmscon_ring_peek(struct kmscon_ring *ring, size_t *len);
+void kmscon_ring_drop(struct kmscon_ring *ring, size_t len);
+
+#endif /* KMSCON_MISC_H */