Adding upstream version 2.4.38.upstream/2.4.38upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 306 insertions, 0 deletions

diff --git a/server/util_time.c b/server/util_time.c
new file mode 100644
index 0000000..3632d0d
--- /dev/null
+++ b/server/util_time.c
@@ -0,0 +1,306 @@
+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "util_time.h"
+
+
+/* Number of characters needed to format the microsecond part of a timestamp.
+ * Microseconds have 6 digits plus one separator character makes 7.
+ *   */
+#define AP_CTIME_USEC_LENGTH      7
+
+/* Length of ISO 8601 date/time */
+#define AP_CTIME_COMPACT_LEN      20
+
+
+/* Cache for exploded values of recent timestamps
+ */
+
+struct exploded_time_cache_element {
+    apr_int64_t t;
+    apr_time_exp_t xt;
+    apr_int64_t t_validate; /* please see comments in cached_explode() */
+};
+
+/* the "+ 1" is for the current second: */
+#define TIME_CACHE_SIZE (AP_TIME_RECENT_THRESHOLD + 1)
+
+/* Note that AP_TIME_RECENT_THRESHOLD is defined to
+ * be a power of two minus one in util_time.h, so that
+ * we can replace a modulo operation with a bitwise AND
+ * when hashing items into a cache of size
+ * AP_TIME_RECENT_THRESHOLD+1
+ */
+#define TIME_CACHE_MASK (AP_TIME_RECENT_THRESHOLD)
+
+static struct exploded_time_cache_element exploded_cache_localtime[TIME_CACHE_SIZE];
+static struct exploded_time_cache_element exploded_cache_gmt[TIME_CACHE_SIZE];
+
+
+static apr_status_t cached_explode(apr_time_exp_t *xt, apr_time_t t,
+                                   struct exploded_time_cache_element *cache,
+                                   int use_gmt)
+{
+    apr_int64_t seconds = apr_time_sec(t);
+    struct exploded_time_cache_element *cache_element =
+        &(cache[seconds & TIME_CACHE_MASK]);
+    struct exploded_time_cache_element cache_element_snapshot;
+
+    /* The cache is implemented as a ring buffer.  Each second,
+     * it uses a different element in the buffer.  The timestamp
+     * in the element indicates whether the element contains the
+     * exploded time for the current second (vs the time
+     * 'now - AP_TIME_RECENT_THRESHOLD' seconds ago).  If the
+     * cached value is for the current time, we use it.  Otherwise,
+     * we compute the apr_time_exp_t and store it in this
+     * cache element. Note that the timestamp in the cache
+     * element is updated only after the exploded time.  Thus
+     * if two threads hit this cache element simultaneously
+     * at the start of a new second, they'll both explode the
+     * time and store it.  I.e., the writers will collide, but
+     * they'll be writing the same value.
+     */
+    if (cache_element->t >= seconds) {
+        /* There is an intentional race condition in this design:
+         * in a multithreaded app, one thread might be reading
+         * from this cache_element to resolve a timestamp from
+         * TIME_CACHE_SIZE seconds ago at the same time that
+         * another thread is copying the exploded form of the
+         * current time into the same cache_element.  (I.e., the
+         * first thread might hit this element of the ring buffer
+         * just as the element is being recycled.)  This can
+         * also happen at the start of a new second, if a
+         * reader accesses the cache_element after a writer
+         * has updated cache_element.t but before the writer
+         * has finished updating the whole cache_element.
+         *
+         * Rather than trying to prevent this race condition
+         * with locks, we allow it to happen and then detect
+         * and correct it.  The detection works like this:
+         *   Step 1: Take a "snapshot" of the cache element by
+         *           copying it into a temporary buffer.
+         *   Step 2: Check whether the snapshot contains consistent
+         *           data: the timestamps at the start and end of
+         *           the cache_element should both match the 'seconds'
+         *           value that we computed from the input time.
+         *           If these three don't match, then the snapshot
+         *           shows the cache_element in the middle of an
+         *           update, and its contents are invalid.
+         *   Step 3: If the snapshot is valid, use it.  Otherwise,
+         *           just give up on the cache and explode the
+         *           input time.
+         */
+        memcpy(&cache_element_snapshot, cache_element,
+               sizeof(struct exploded_time_cache_element));
+        if ((seconds != cache_element_snapshot.t) ||
+            (seconds != cache_element_snapshot.t_validate)) {
+            /* Invalid snapshot */
+            if (use_gmt) {
+                return apr_time_exp_gmt(xt, t);
+            }
+            else {
+                return apr_time_exp_lt(xt, t);
+            }
+        }
+        else {
+            /* Valid snapshot */
+            memcpy(xt, &(cache_element_snapshot.xt),
+                   sizeof(apr_time_exp_t));
+        }
+    }
+    else {
+        apr_status_t r;
+        if (use_gmt) {
+            r = apr_time_exp_gmt(xt, t);
+        }
+        else {
+            r = apr_time_exp_lt(xt, t);
+        }
+        if (r != APR_SUCCESS) {
+            return r;
+        }
+        cache_element->t = seconds;
+        memcpy(&(cache_element->xt), xt, sizeof(apr_time_exp_t));
+        cache_element->t_validate = seconds;
+    }
+    xt->tm_usec = (int)apr_time_usec(t);
+    return APR_SUCCESS;
+}
+
+
+AP_DECLARE(apr_status_t) ap_explode_recent_localtime(apr_time_exp_t * tm,
+                                                     apr_time_t t)
+{
+    return cached_explode(tm, t, exploded_cache_localtime, 0);
+}
+
+AP_DECLARE(apr_status_t) ap_explode_recent_gmt(apr_time_exp_t * tm,
+                                               apr_time_t t)
+{
+    return cached_explode(tm, t, exploded_cache_gmt, 1);
+}
+
+AP_DECLARE(apr_status_t) ap_recent_ctime(char *date_str, apr_time_t t)
+{
+    int len = APR_CTIME_LEN;
+    return ap_recent_ctime_ex(date_str, t, AP_CTIME_OPTION_NONE, &len);
+}
+
+AP_DECLARE(apr_status_t) ap_recent_ctime_ex(char *date_str, apr_time_t t,
+                                            int option, int *len)
+{
+    /* ### This code is a clone of apr_ctime(), except that it
+     * uses ap_explode_recent_localtime() instead of apr_time_exp_lt().
+     */
+    apr_time_exp_t xt;
+    const char *s;
+    int real_year;
+    int needed;
+
+
+    /* Calculate the needed buffer length */
+    if (option & AP_CTIME_OPTION_COMPACT)
+        needed = AP_CTIME_COMPACT_LEN;
+    else
+        needed = APR_CTIME_LEN;
+
+    if (option & AP_CTIME_OPTION_USEC) {
+        needed += AP_CTIME_USEC_LENGTH;
+    }
+
+    /* Check the provided buffer length */
+    if (len && *len >= needed) {
+        *len = needed;
+    }
+    else {
+        if (len != NULL) {
+            *len = 0;
+        }
+        return APR_ENOMEM;
+    }
+
+    /* example without options: "Wed Jun 30 21:49:08 1993" */
+    /*                           123456789012345678901234  */
+    /* example for compact format: "1993-06-30 21:49:08" */
+    /*                              1234567890123456789  */
+
+    ap_explode_recent_localtime(&xt, t);
+    real_year = 1900 + xt.tm_year;
+    if (option & AP_CTIME_OPTION_COMPACT) {
+        int real_month = xt.tm_mon + 1;
+        *date_str++ = real_year / 1000 + '0';
+        *date_str++ = real_year % 1000 / 100 + '0';
+        *date_str++ = real_year % 100 / 10 + '0';
+        *date_str++ = real_year % 10 + '0';
+        *date_str++ = '-';
+        *date_str++ = real_month / 10 + '0';
+        *date_str++ = real_month % 10 + '0';
+        *date_str++ = '-';
+    }
+    else {
+        s = &apr_day_snames[xt.tm_wday][0];
+        *date_str++ = *s++;
+        *date_str++ = *s++;
+        *date_str++ = *s++;
+        *date_str++ = ' ';
+        s = &apr_month_snames[xt.tm_mon][0];
+        *date_str++ = *s++;
+        *date_str++ = *s++;
+        *date_str++ = *s++;
+        *date_str++ = ' ';
+    }
+    *date_str++ = xt.tm_mday / 10 + '0';
+    *date_str++ = xt.tm_mday % 10 + '0';
+    *date_str++ = ' ';
+    *date_str++ = xt.tm_hour / 10 + '0';
+    *date_str++ = xt.tm_hour % 10 + '0';
+    *date_str++ = ':';
+    *date_str++ = xt.tm_min / 10 + '0';
+    *date_str++ = xt.tm_min % 10 + '0';
+    *date_str++ = ':';
+    *date_str++ = xt.tm_sec / 10 + '0';
+    *date_str++ = xt.tm_sec % 10 + '0';
+    if (option & AP_CTIME_OPTION_USEC) {
+        int div;
+        int usec = (int)xt.tm_usec;
+        *date_str++ = '.';
+        for (div=100000; div>0; div=div/10) {
+            *date_str++ = usec / div + '0';
+            usec = usec % div;
+        }
+    }
+    if (!(option & AP_CTIME_OPTION_COMPACT)) {
+        *date_str++ = ' ';
+        *date_str++ = real_year / 1000 + '0';
+        *date_str++ = real_year % 1000 / 100 + '0';
+        *date_str++ = real_year % 100 / 10 + '0';
+        *date_str++ = real_year % 10 + '0';
+    }
+    *date_str++ = 0;
+
+    return APR_SUCCESS;
+}
+
+AP_DECLARE(apr_status_t) ap_recent_rfc822_date(char *date_str, apr_time_t t)
+{
+    /* ### This code is a clone of apr_rfc822_date(), except that it
+     * uses ap_explode_recent_gmt() instead of apr_time_exp_gmt().
+     */
+    apr_time_exp_t xt;
+    const char *s;
+    int real_year;
+
+    ap_explode_recent_gmt(&xt, t);
+
+    /* example: "Sat, 08 Jan 2000 18:31:41 GMT" */
+    /*           12345678901234567890123456789  */
+
+    s = &apr_day_snames[xt.tm_wday][0];
+    *date_str++ = *s++;
+    *date_str++ = *s++;
+    *date_str++ = *s++;
+    *date_str++ = ',';
+    *date_str++ = ' ';
+    *date_str++ = xt.tm_mday / 10 + '0';
+    *date_str++ = xt.tm_mday % 10 + '0';
+    *date_str++ = ' ';
+    s = &apr_month_snames[xt.tm_mon][0];
+    *date_str++ = *s++;
+    *date_str++ = *s++;
+    *date_str++ = *s++;
+    *date_str++ = ' ';
+    real_year = 1900 + xt.tm_year;
+    /* This routine isn't y10k ready. */
+    *date_str++ = real_year / 1000 + '0';
+    *date_str++ = real_year % 1000 / 100 + '0';
+    *date_str++ = real_year % 100 / 10 + '0';
+    *date_str++ = real_year % 10 + '0';
+    *date_str++ = ' ';
+    *date_str++ = xt.tm_hour / 10 + '0';
+    *date_str++ = xt.tm_hour % 10 + '0';
+    *date_str++ = ':';
+    *date_str++ = xt.tm_min / 10 + '0';
+    *date_str++ = xt.tm_min % 10 + '0';
+    *date_str++ = ':';
+    *date_str++ = xt.tm_sec / 10 + '0';
+    *date_str++ = xt.tm_sec % 10 + '0';
+    *date_str++ = ' ';
+    *date_str++ = 'G';
+    *date_str++ = 'M';
+    *date_str++ = 'T';
+    *date_str++ = 0;
+    return APR_SUCCESS;
+}