blktrace support: speedup reading of data

[fio.git] / fifo.c

diff --git a/fifo.c b/fifo.c
new file mode 100644 (file)
index 0000000..1e55b63
--- /dev/null
+++ b/fifo.c
@@ -0,0 +1,88 @@
+/*
+ * A simple kernel FIFO implementation.
+ *
+ * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "fifo.h"
+
+struct fifo *fifo_alloc(unsigned int size)
+{
+       struct fifo *fifo;
+
+       fifo = malloc(sizeof(struct fifo));
+       if (!fifo)
+               return 0;
+
+       fifo->buffer = malloc(size);
+       fifo->size = size;
+       fifo->in = fifo->out = 0xffff0000;
+
+       return fifo;
+}
+
+void fifo_free(struct fifo *fifo)
+{
+       free(fifo->buffer);
+       free(fifo);
+}
+
+unsigned int fifo_put(struct fifo *fifo, void *buffer, unsigned int len)
+{
+       unsigned int l;
+
+       len = min(len, fifo->size - fifo->in + fifo->out);
+
+       /* first put the data starting from fifo->in to buffer end */
+       l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
+       memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
+
+       /* then put the rest (if any) at the beginning of the buffer */
+       memcpy(fifo->buffer, buffer + l, len - l);
+
+       /*
+        * Ensure that we add the bytes to the fifo -before-
+        * we update the fifo->in index.
+        */
+
+       fifo->in += len;
+
+       return len;
+}
+
+unsigned int fifo_get(struct fifo *fifo, void *buffer, unsigned int len)
+{
+       unsigned int l;
+
+       len = min(len, fifo->in - fifo->out);
+
+       /* first get the data from fifo->out until the end of the buffer */
+       l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
+       memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
+
+       /* then get the rest (if any) from the beginning of the buffer */
+       memcpy(buffer + l, fifo->buffer, len - l);
+
+       fifo->out += len;
+
+       return len;
+}