1 files changed, 121 insertions, 0 deletions
diff --git a/src/timer.cc b/src/timer.cc
new file mode 100644
index 0000000..45fdd80
--- /dev/null
+++ b/src/timer.cc
@@ -0,0 +1,121 @@
+/**
+ * Copyright (c) 2015, Suresh Sundriyal
+ *
+ * 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 the copyright holder 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 REGENTS 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 REGENTS 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 "timer.hh"
+
+#include "base/lnav_log.hh"
+#include "config.h"
+
+static const struct itimerval DISABLE_TV = {{0, 0}, {0, 0}};
+
+timer::error::error(int err) : e_err(err) {}
+
+timer::interrupt_timer::interrupt_timer(struct timeval t,
+                                        sighandler_t_ sighandler = SIG_IGN)
+    : new_handler(sighandler), new_val((struct itimerval){{0, 0}, t}),
+      old_val(DISABLE_TV), armed(false)
+{
+    memset(&this->old_handler, 0, sizeof(this->old_handler));
+}
+
+int
+timer::interrupt_timer::arm_timer()
+{
+    struct sigaction sa;
+
+    // Disable the interval timer before setting the handler and arming the
+    // interval timer or else we will have a race-condition where the timer
+    // might fire and the appropriate handler might not be set.
+    if (setitimer(ITIMER_REAL, &DISABLE_TV, &this->old_val) != 0) {
+        log_error("Unable to disable the timer: %s", strerror(errno));
+        return -1;
+    }
+    memset(&sa, 0, sizeof(sa));
+    sa.sa_handler = this->new_handler;
+    if (sigaction(SIGALRM, &sa, &this->old_handler) == -1) {
+        log_error("Unable to set the signal handler: %s", strerror(errno));
+        if (setitimer(ITIMER_REAL, &this->old_val, NULL) != 0) {
+            log_error("Unable to reset the interrupt timer: %s",
+                      strerror(errno));
+            throw timer::error(errno);
+        }
+        return -1;
+    }
+
+    if (setitimer(ITIMER_REAL, &this->new_val, NULL) != 0) {
+        if (sigaction(SIGALRM, &this->old_handler, NULL) == -1) {
+            log_error("Unable to reset the signal handler: %s",
+                      strerror(errno));
+            throw timer::error(errno);
+        }
+        log_error("Unable to set the timer: %s", strerror(errno));
+        return -1;
+    }
+    this->armed = true;
+    return 0;
+}
+
+bool
+timer::interrupt_timer::is_armed()
+{
+    return this->armed;
+}
+
+void
+timer::interrupt_timer::disarm_timer()
+{
+    if (this->armed) {
+        // Disable the interval timer before resetting the handler and rearming
+        // the previous interval timer or else we will have a race-condition
+        // where the timer might fire and the appropriate handler might not be
+        // set.
+        if (setitimer(ITIMER_REAL, &DISABLE_TV, NULL) != 0) {
+            log_error("Failed to disable the timer: %s", strerror(errno));
+            throw timer::error(errno);
+        }
+        if (sigaction(SIGALRM, &this->old_handler, NULL) == -1) {
+            log_error("Failed to reinstall previous SIGALRM handler: %s",
+                      strerror(errno));
+            throw timer::error(errno);
+        }
+        if (setitimer(ITIMER_REAL, &this->old_val, NULL) != 0) {
+            log_error("Failed to reset the timer to previous value: %s",
+                      strerror(errno));
+            throw timer::error(errno);
+        }
+        this->armed = false;
+        this->old_val = DISABLE_TV;
+        memset(&this->old_handler, 0, sizeof(this->old_handler));
+    }
+}
+
+timer::interrupt_timer::~interrupt_timer()
+{
+    this->disarm_timer();
+}