[Xen-devel] [PATCH 15 of 21 RESEND] blktap3/drivers: Introduce stats reporting

[Thanos Makatos <thanos.makatos@xxxxxxxxxx>]

This patch copies from blktap2.5 stats reporting functionality.

Signed-off-by: Thanos Makatos <thanos.makatos@xxxxxxxxxx>

diff --git a/tools/blktap3/drivers/tapdisk-stats.c 
b/tools/blktap3/drivers/tapdisk-stats.c
new file mode 100644
--- /dev/null
+++ b/tools/blktap3/drivers/tapdisk-stats.c
@@ -0,0 +1,155 @@
+/*
+ * Copyright (c) 2010, Citrix Systems, Inc.
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of XenSource Inc. nor the names of its contributors
+ *       may be used to endorse or promote products derived from this software
+ *       without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
+ * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <stdarg.h>
+
+#include "tapdisk.h"
+#include "tapdisk-stats.h"
+
+/* TODO already defined elsewhere */
+#define BUG_ON(_cond) if (_cond) { td_panic(); }
+
+static void __stats_vsprintf(td_stats_t * st, const char *fmt, va_list ap)
+{
+    size_t size = st->buf + st->size - st->pos;
+    st->pos += vsnprintf(st->pos, size, fmt, ap);
+}
+
+static void __printf(2, 3)
+__stats_sprintf(td_stats_t * st, const char *fmt, ...)
+{
+    va_list ap;
+
+    va_start(ap, fmt);
+    __stats_vsprintf(st, fmt, ap);
+    va_end(ap);
+}
+
+static void __stats_enter(td_stats_t * st)
+{
+    st->depth++;
+    BUG_ON(st->depth > TD_STATS_MAX_DEPTH);
+    st->n_elem[st->depth] = 0;
+}
+
+static void __stats_leave(td_stats_t * st)
+{
+    st->depth--;
+}
+
+static void __stats_next(td_stats_t * st)
+{
+    int n_elem;
+
+    n_elem = st->n_elem[st->depth];
+    if (n_elem > 0)
+        __stats_sprintf(st, ", ");
+    st->n_elem[st->depth]++;
+}
+
+static void __tapdisk_stats_enter(td_stats_t * st, char t)
+{
+    __stats_sprintf(st, "%c ", t);
+    __stats_enter(st);
+}
+
+void tapdisk_stats_enter(td_stats_t * st, char t)
+{
+    __stats_next(st);
+    __tapdisk_stats_enter(st, t);
+}
+
+void tapdisk_stats_leave(td_stats_t * st, char t)
+{
+    __stats_leave(st);
+    __stats_sprintf(st, " %c", t);
+}
+
+static void
+tapdisk_stats_vval(td_stats_t * st, const char *conv, va_list ap)
+{
+    char t = conv[0], fmt[32];
+
+    __stats_next(st);
+
+    switch (t) {
+    case 's':
+        __stats_vsprintf(st, "\"%s\"", ap);
+        break;
+
+    default:
+        sprintf(fmt, "%%%s", conv);
+        __stats_vsprintf(st, fmt, ap);
+        break;
+    }
+}
+
+void tapdisk_stats_val(td_stats_t * st, const char *conv, ...)
+{
+    va_list ap;
+
+    va_start(ap, conv);
+    tapdisk_stats_vval(st, conv, ap);
+    va_end(ap);
+}
+
+void
+tapdisk_stats_field(td_stats_t * st, const char *key, const char *conv,
+                    ...)
+{
+    va_list ap;
+    int n_elem;
+    char t;
+
+    n_elem = st->n_elem[st->depth]++;
+    if (n_elem > 0)
+        __stats_sprintf(st, ", ");
+
+    __stats_sprintf(st, "\"%s\": ", key);
+
+    if (!conv) {
+        __stats_sprintf(st, "null");
+        return;
+    }
+
+    t = conv[0];
+    switch (t) {
+    case '[':
+    case '{':
+        __tapdisk_stats_enter(st, t);
+        break;
+    default:
+        va_start(ap, conv);
+        __stats_enter(st);
+        tapdisk_stats_vval(st, conv, ap);
+        __stats_leave(st);
+        va_end(ap);
+    }
+}

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