Adding cpp mocks

.cproject

@@ -0,0 +1,106 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<?fileVersion 4.0.0?><cproject storage_type_id="org.eclipse.cdt.core.XmlProjectDescriptionStorage">
+	<storageModule moduleId="org.eclipse.cdt.core.settings">
+		<cconfiguration id="cdt.managedbuild.config.gnu.cross.exe.debug.1510091085">
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+				<externalSettings/>
+				<extensions>
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+					<extension id="org.eclipse.cdt.core.GmakeErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
+					<extension id="org.eclipse.cdt.core.GLDErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
+					<extension id="org.eclipse.cdt.core.CWDLocator" point="org.eclipse.cdt.core.ErrorParser"/>
+					<extension id="org.eclipse.cdt.core.GCCErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
+				</extensions>
+			</storageModule>
+			<storageModule moduleId="cdtBuildSystem" version="4.0.0">
+				<configuration artifactName="${ProjName}" buildArtefactType="org.eclipse.cdt.build.core.buildArtefactType.exe" buildProperties="org.eclipse.cdt.build.core.buildArtefactType=org.eclipse.cdt.build.core.buildArtefactType.exe,org.eclipse.cdt.build.core.buildType=org.eclipse.cdt.build.core.buildType.debug" cleanCommand="rm -rf" description="" id="cdt.managedbuild.config.gnu.cross.exe.debug.1510091085" name="Debug" parent="cdt.managedbuild.config.gnu.cross.exe.debug">
+					<folderInfo id="cdt.managedbuild.config.gnu.cross.exe.debug.1510091085." name="/" resourcePath="">
+						<toolChain id="cdt.managedbuild.toolchain.gnu.cross.exe.debug.574401685" name="Cross GCC" superClass="cdt.managedbuild.toolchain.gnu.cross.exe.debug">
+							<targetPlatform archList="all" binaryParser="org.eclipse.cdt.core.ELF" id="cdt.managedbuild.targetPlatform.gnu.cross.2118034560" isAbstract="false" osList="all" superClass="cdt.managedbuild.targetPlatform.gnu.cross"/>
+							<builder buildPath="${workspace_loc:/Programming-POSIX-Threads}/Debug" id="cdt.managedbuild.builder.gnu.cross.775897058" managedBuildOn="true" name="Gnu Make Builder.Debug" superClass="cdt.managedbuild.builder.gnu.cross"/>
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+								<inputType id="cdt.managedbuild.tool.gnu.c.compiler.input.1609802857" superClass="cdt.managedbuild.tool.gnu.c.compiler.input"/>
+							</tool>
+							<tool id="cdt.managedbuild.tool.gnu.cross.cpp.compiler.255857520" name="Cross G++ Compiler" superClass="cdt.managedbuild.tool.gnu.cross.cpp.compiler">
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+							</tool>
+							<tool id="cdt.managedbuild.tool.gnu.cross.c.linker.2011145861" name="Cross GCC Linker" superClass="cdt.managedbuild.tool.gnu.cross.c.linker">
+								<inputType id="cdt.managedbuild.tool.gnu.c.linker.input.774239090" superClass="cdt.managedbuild.tool.gnu.c.linker.input">
+									<additionalInput kind="additionalinputdependency" paths="$(USER_OBJS)"/>
+									<additionalInput kind="additionalinput" paths="$(LIBS)"/>
+								</inputType>
+							</tool>
+							<tool id="cdt.managedbuild.tool.gnu.cross.cpp.linker.934315138" name="Cross G++ Linker" superClass="cdt.managedbuild.tool.gnu.cross.cpp.linker"/>
+							<tool id="cdt.managedbuild.tool.gnu.cross.archiver.1399421222" name="Cross GCC Archiver" superClass="cdt.managedbuild.tool.gnu.cross.archiver"/>
+							<tool id="cdt.managedbuild.tool.gnu.cross.assembler.267146708" name="Cross GCC Assembler" superClass="cdt.managedbuild.tool.gnu.cross.assembler">
+								<inputType id="cdt.managedbuild.tool.gnu.assembler.input.1509256621" superClass="cdt.managedbuild.tool.gnu.assembler.input"/>
+							</tool>
+						</toolChain>
+					</folderInfo>
+				</configuration>
+			</storageModule>
+			<storageModule moduleId="org.eclipse.cdt.core.externalSettings"/>
+		</cconfiguration>
+		<cconfiguration id="cdt.managedbuild.config.gnu.cross.exe.release.2099010148">
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+				<externalSettings/>
+				<extensions>
+					<extension id="org.eclipse.cdt.core.ELF" point="org.eclipse.cdt.core.BinaryParser"/>
+					<extension id="org.eclipse.cdt.core.GASErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
+					<extension id="org.eclipse.cdt.core.GmakeErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
+					<extension id="org.eclipse.cdt.core.GLDErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
+					<extension id="org.eclipse.cdt.core.CWDLocator" point="org.eclipse.cdt.core.ErrorParser"/>
+					<extension id="org.eclipse.cdt.core.GCCErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
+				</extensions>
+			</storageModule>
+			<storageModule moduleId="cdtBuildSystem" version="4.0.0">
+				<configuration artifactName="${ProjName}" buildArtefactType="org.eclipse.cdt.build.core.buildArtefactType.exe" buildProperties="org.eclipse.cdt.build.core.buildArtefactType=org.eclipse.cdt.build.core.buildArtefactType.exe,org.eclipse.cdt.build.core.buildType=org.eclipse.cdt.build.core.buildType.release" cleanCommand="rm -rf" description="" id="cdt.managedbuild.config.gnu.cross.exe.release.2099010148" name="Release" parent="cdt.managedbuild.config.gnu.cross.exe.release">
+					<folderInfo id="cdt.managedbuild.config.gnu.cross.exe.release.2099010148." name="/" resourcePath="">
+						<toolChain id="cdt.managedbuild.toolchain.gnu.cross.exe.release.2065591112" name="Cross GCC" superClass="cdt.managedbuild.toolchain.gnu.cross.exe.release">
+							<targetPlatform archList="all" binaryParser="org.eclipse.cdt.core.ELF" id="cdt.managedbuild.targetPlatform.gnu.cross.323077387" isAbstract="false" osList="all" superClass="cdt.managedbuild.targetPlatform.gnu.cross"/>
+							<builder buildPath="${workspace_loc:/Programming-POSIX-Threads}/Release" id="cdt.managedbuild.builder.gnu.cross.1940584431" managedBuildOn="true" name="Gnu Make Builder.Release" superClass="cdt.managedbuild.builder.gnu.cross"/>
+							<tool id="cdt.managedbuild.tool.gnu.cross.c.compiler.1471607620" name="Cross GCC Compiler" superClass="cdt.managedbuild.tool.gnu.cross.c.compiler">
+								<option defaultValue="gnu.c.optimization.level.most" id="gnu.c.compiler.option.optimization.level.889418414" superClass="gnu.c.compiler.option.optimization.level" useByScannerDiscovery="false" valueType="enumerated"/>
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+								<inputType id="cdt.managedbuild.tool.gnu.c.compiler.input.1329892514" superClass="cdt.managedbuild.tool.gnu.c.compiler.input"/>
+							</tool>
+							<tool id="cdt.managedbuild.tool.gnu.cross.cpp.compiler.1318921803" name="Cross G++ Compiler" superClass="cdt.managedbuild.tool.gnu.cross.cpp.compiler">
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+							</tool>
+							<tool id="cdt.managedbuild.tool.gnu.cross.c.linker.1454722057" name="Cross GCC Linker" superClass="cdt.managedbuild.tool.gnu.cross.c.linker">
+								<inputType id="cdt.managedbuild.tool.gnu.c.linker.input.494181964" superClass="cdt.managedbuild.tool.gnu.c.linker.input">
+									<additionalInput kind="additionalinputdependency" paths="$(USER_OBJS)"/>
+									<additionalInput kind="additionalinput" paths="$(LIBS)"/>
+								</inputType>
+							</tool>
+							<tool id="cdt.managedbuild.tool.gnu.cross.cpp.linker.455636733" name="Cross G++ Linker" superClass="cdt.managedbuild.tool.gnu.cross.cpp.linker"/>
+							<tool id="cdt.managedbuild.tool.gnu.cross.archiver.1460190311" name="Cross GCC Archiver" superClass="cdt.managedbuild.tool.gnu.cross.archiver"/>
+							<tool id="cdt.managedbuild.tool.gnu.cross.assembler.1037962002" name="Cross GCC Assembler" superClass="cdt.managedbuild.tool.gnu.cross.assembler">
+								<inputType id="cdt.managedbuild.tool.gnu.assembler.input.1811659589" superClass="cdt.managedbuild.tool.gnu.assembler.input"/>
+							</tool>
+						</toolChain>
+					</folderInfo>
+				</configuration>
+			</storageModule>
+			<storageModule moduleId="org.eclipse.cdt.core.externalSettings"/>
+		</cconfiguration>
+	</storageModule>
+	<storageModule moduleId="cdtBuildSystem" version="4.0.0">
+		<project id="Programming-POSIX-Threads.cdt.managedbuild.target.gnu.cross.exe.1111381522" name="Executable" projectType="cdt.managedbuild.target.gnu.cross.exe"/>
+	</storageModule>
+	<storageModule moduleId="scannerConfiguration">
+		<autodiscovery enabled="true" problemReportingEnabled="true" selectedProfileId=""/>
+		<scannerConfigBuildInfo instanceId="cdt.managedbuild.config.gnu.cross.exe.release.2099010148;cdt.managedbuild.config.gnu.cross.exe.release.2099010148.;cdt.managedbuild.tool.gnu.cross.c.compiler.1471607620;cdt.managedbuild.tool.gnu.c.compiler.input.1329892514">
+			<autodiscovery enabled="true" problemReportingEnabled="true" selectedProfileId=""/>
+		</scannerConfigBuildInfo>
+		<scannerConfigBuildInfo instanceId="cdt.managedbuild.config.gnu.cross.exe.debug.1510091085;cdt.managedbuild.config.gnu.cross.exe.debug.1510091085.;cdt.managedbuild.tool.gnu.cross.c.compiler.743521326;cdt.managedbuild.tool.gnu.c.compiler.input.1609802857">
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+	<storageModule moduleId="org.eclipse.cdt.core.LanguageSettingsProviders"/>
+</cproject>

.project

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>Programming-POSIX-Threads</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.cdt.managedbuilder.core.genmakebuilder</name>
+			<triggers>clean,full,incremental,</triggers>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.cdt.managedbuilder.core.ScannerConfigBuilder</name>
+			<triggers>full,incremental,</triggers>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.cdt.core.cnature</nature>
+		<nature>org.eclipse.cdt.managedbuilder.core.managedBuildNature</nature>
+		<nature>org.eclipse.cdt.managedbuilder.core.ScannerConfigNature</nature>
+	</natures>
+</projectDescription>

.settings/language.settings.xml

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<project>
+	<configuration id="cdt.managedbuild.config.gnu.cross.exe.debug.1510091085" name="Debug">
+		<extension point="org.eclipse.cdt.core.LanguageSettingsProvider">
+			<provider copy-of="extension" id="org.eclipse.cdt.ui.UserLanguageSettingsProvider"/>
+			<provider-reference id="org.eclipse.cdt.core.ReferencedProjectsLanguageSettingsProvider" ref="shared-provider"/>
+			<provider-reference id="org.eclipse.cdt.managedbuilder.core.MBSLanguageSettingsProvider" ref="shared-provider"/>
+			<provider class="org.eclipse.cdt.internal.build.crossgcc.CrossGCCBuiltinSpecsDetector" console="false" env-hash="564395207262711818" id="org.eclipse.cdt.build.crossgcc.CrossGCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT Cross GCC Built-in Compiler Settings" parameter="${COMMAND} ${FLAGS} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
+				<language-scope id="org.eclipse.cdt.core.gcc"/>
+				<language-scope id="org.eclipse.cdt.core.g++"/>
+			</provider>
+		</extension>
+	</configuration>
+	<configuration id="cdt.managedbuild.config.gnu.cross.exe.release.2099010148" name="Release">
+		<extension point="org.eclipse.cdt.core.LanguageSettingsProvider">
+			<provider copy-of="extension" id="org.eclipse.cdt.ui.UserLanguageSettingsProvider"/>
+			<provider-reference id="org.eclipse.cdt.core.ReferencedProjectsLanguageSettingsProvider" ref="shared-provider"/>
+			<provider-reference id="org.eclipse.cdt.managedbuilder.core.MBSLanguageSettingsProvider" ref="shared-provider"/>
+			<provider class="org.eclipse.cdt.internal.build.crossgcc.CrossGCCBuiltinSpecsDetector" console="false" env-hash="564395207262711818" id="org.eclipse.cdt.build.crossgcc.CrossGCCBuiltinSpecsDetector" keep-relative-paths="false" name="CDT Cross GCC Built-in Compiler Settings" parameter="${COMMAND} ${FLAGS} -E -P -v -dD &quot;${INPUTS}&quot;" prefer-non-shared="true">
+				<language-scope id="org.eclipse.cdt.core.gcc"/>
+				<language-scope id="org.eclipse.cdt.core.g++"/>
+			</provider>
+		</extension>
+	</configuration>
+</project>

Makefile

@@ -1,11 +1,15 @@
 # Digital UNIX 4.0 compilation flags:
-CFLAGS=-std1 -pthread -g -w1 $(DEBUGFLAGS)
+#CFLAGS=-std1 -pthread -g -w1 $(DEBUGFLAGS)
-RTFLAGS=-lrt
+#RTFLAGS=-lrt
 
 # Solaris 2.5 compilation flags:
 #CFLAGS=-D_POSIX_C_SOURCE=199506 -D_REENTRANT -Xa -lpthread -g $(DEBUGFLAGS)
 #RTFLAGS=-lposix4
 
+# Linux compilation flags:
+CFLAGS=-pthread -O3 $(DEBUGFLAGS)
+RTFLAGS=-lrt
+
 SOURCES=alarm.c	alarm_cond.c	alarm_fork.c	alarm_mutex.c	\
 	alarm_thread.c	atfork.c	backoff.c	\
 	barrier_main.c	cancel.c	cancel_async.c	cancel_cleanup\

alarm_mutex.cpp

@@ -0,0 +1,127 @@
+/*
+ * alarm_mutex.c
+ *
+ * This is an enhancement to the alarm_thread.c program, which
+ * created an "alarm thread" for each alarm command. This new
+ * version uses a single alarm thread, which reads the next
+ * entry in a list. The main thread places new requests onto the
+ * list, in order of absolute expiration time. The list is
+ * protected by a mutex, and the alarm thread sleeps for at
+ * least 1 second, each iteration, to ensure that the main
+ * thread can lock the mutex to add new work to the list.
+ */
+#include <pthread.h>
+#include <time.h>
+#include "errors.h"
+
+#include <list>
+
+#define MIN(X, Y) (((X) < (Y)) ? (X) : (Y))
+
+/*
+ * The "alarm" structure now contains the time_t (time since the
+ * Epoch, in seconds) for each alarm, so that they can be
+ * sorted. Storing the requested number of seconds would not be
+ * enough, since the "alarm thread" cannot tell how long it has
+ * been on the list.
+ */
+struct alarm_tag {
+  int seconds;
+  time_t time; /* seconds from EPOCH */
+  char message[64];
+};
+
+using alarm_t = alarm_tag;
+
+pthread_mutex_t alarm_mutex = PTHREAD_MUTEX_INITIALIZER;
+std::list<alarm_t> alarm_list;
+
+/*
+ * The alarm thread's start routine.
+ */
+void *alarm_thread(void *arg) {
+  int sleep_time;
+  time_t now;
+  int status;
+
+  /*
+   * Loop forever, processing commands. The alarm thread will
+   * be disintegrated when the process exits.
+   */
+  while (1) {
+    status = pthread_mutex_lock(&alarm_mutex);
+    if (status != 0) err_abort(status, "Lock mutex");
+
+    now = time(NULL);
+    sleep_time = 0;
+
+    for (auto it = alarm_list.begin(); it != alarm_list.end();) {
+      if (it->time <= now) {
+        printf("(%d) %s\n", it->seconds, it->message);
+        it = alarm_list.erase(it);
+      } else {
+        sleep_time = MIN(it->time - now, sleep_time);
+        ++it;
+      }
+    }
+
+    /*
+     * Unlock the mutex before waiting, so that the main
+     * thread can lock it to insert a new alarm request. If
+     * the sleep_time is 0, then call sched_yield, giving
+     * the main thread a chance to run if it has been
+     * readied by user input, without delaying the message
+     * if there's no input.
+     */
+    status = pthread_mutex_unlock(&alarm_mutex);
+    if (status != 0) err_abort(status, "Unlock mutex");
+    if (sleep_time > 0)
+      sleep(sleep_time);
+    else
+      sched_yield();
+  }
+}
+
+int main(int argc, char *argv[]) {
+  int status;
+  char line[128];
+  pthread_t thread;
+
+  status = pthread_create(&thread, NULL, alarm_thread, NULL);
+  if (status != 0) err_abort(status, "Create alarm thread");
+  while (1) {
+    printf("alarm> ");
+    if (fgets(line, sizeof(line), stdin) == NULL) exit(0);
+    if (strlen(line) <= 1) continue;
+    alarm_t alarm;
+
+    /*
+     * Parse input line into seconds (%d) and a message
+     * (%64[^\n]), consisting of up to 64 characters
+     * separated from the seconds by whitespace.
+     */
+    if (sscanf(line, "%d %64[^\n]", &alarm.seconds, alarm.message) < 2) {
+      fprintf(stderr, "Bad command\n");
+    } else {
+      alarm.time = time(NULL) + alarm.seconds;
+
+      status = pthread_mutex_lock(&alarm_mutex);
+      if (status != 0) err_abort(status, "Lock mutex");
+
+      /*
+       * Insert the new alarm into the list of alarms.
+       */
+      alarm_list.push_back(alarm);
+
+#ifdef DEBUG
+      printf("[list: ");
+      for (const auto &iAlarm : alarm_list)
+        printf("%d(%d)[\"%s\"] ", iAlarm.time, iAlarm.time - time(NULL),
+               iAlarm.message);
+      printf("]\n");
+#endif
+      status = pthread_mutex_unlock(&alarm_mutex);
+      if (status != 0) err_abort(status, "Unlock mutex");
+    }
+  }
+}

lifecycle.c

@@ -12,6 +12,7 @@
  */
 void *thread_routine (void *arg)
 {
+    printf("Inside thread %i\n", pthread_self());
     return arg;
 }
 
@@ -21,10 +22,13 @@ main (int argc, char *argv[])
     void *thread_result;
     int status;
 
+    printf("Inside thread %i\n", pthread_self());
     status = pthread_create (
         &thread_id, NULL, thread_routine, NULL);
     if (status != 0)
         err_abort (status, "Create thread");
+    sleep(1.0);
+    printf("Main thread created thread %i\n", thread_id);
 
     status = pthread_join (thread_id, &thread_result);
     if (status != 0)

pipe.cpp

@@ -0,0 +1,268 @@
+/*
+ * pipe.c
+ *
+ * Simple demonstration of a pipeline. main() is a loop that
+ * feeds the pipeline with integer values. Each stage of the
+ * pipeline increases the integer by one before passing it along
+ * to the next. Entering the command "=" reads the pipeline
+ * result. (Notice that too many '=' commands will hang.)
+ */
+#include <pthread.h>
+#include "errors.h"
+
+#include <iostream>
+#include <list>
+#include <thread>
+
+/*
+ * Internal structure describing a "stage" in the
+ * pipeline. One for each thread, plus a "result
+ * stage" where the final thread can stash the value.
+ */
+struct stage_tag {
+  pthread_mutex_t mutex;       /* Protect data */
+  pthread_cond_t dataIsAvail;  /* Data available */
+  pthread_cond_t threadIsIdle; /* Ready for data */
+  bool isDataAvail;            /* Data present */
+  long data;                   /* Data to process */
+  pthread_t thread;            /* Thread for stage */
+  stage_tag *next;
+};
+
+using stage_t = stage_tag;
+
+using StageList = std::list<stage_t>;
+
+/*
+ * External structure representing the entire
+ * pipeline.
+ */
+struct pipe_tag {
+  pthread_mutex_t mutex; /* Mutex to protect pipe */
+  StageList stageList;   /* stages list */
+  int nActive;           /* Active data elements */
+};
+
+using pipe_t = pipe_tag;
+
+/*
+ * Internal function to send a "message" to the
+ * specified pipe stage. Threads use this to pass
+ * along the modified data item.
+ */
+int pipe_send(stage_t &stage, long data) {
+  int status;
+
+  status = pthread_mutex_lock(&stage.mutex);
+  if (status != 0) return status;
+
+  /*
+   * If there's data in the pipe stage, wait for it
+   * to be consumed.
+   */
+  while (stage.isDataAvail) {
+    status = pthread_cond_wait(&stage.threadIsIdle, &stage.mutex);
+    if (status != 0) {
+      pthread_mutex_unlock(&stage.mutex);
+      return status;
+    }
+  }
+
+  /*
+   * Send the new data
+   */
+  stage.data = data;
+  stage.isDataAvail = true;
+
+  status = pthread_cond_signal(&stage.dataIsAvail);
+  if (status != 0) {
+    pthread_mutex_unlock(&stage.mutex);
+    return status;
+  }
+
+  status = pthread_mutex_unlock(&stage.mutex);
+  return status;
+}
+
+/*
+ * The thread start routine for pipe stage threads.
+ * Each will wait for a data item passed from the
+ * caller or the previous stage, modify the data
+ * and pass it along to the next (or final) stage.
+ */
+void *pipe_stage(void *arg) {
+  stage_t &stage = *(stage_t *)arg;
+  stage_t &nextStage = *stage.next;
+  int status;
+
+  status = pthread_mutex_lock(&stage.mutex);
+  if (status != 0) err_abort(status, "Lock pipe stage");
+
+  while (1) {
+    while (!stage.isDataAvail) {
+      status = pthread_cond_wait(&stage.dataIsAvail, &stage.mutex);
+      if (status != 0) err_abort(status, "Wait for previous stage");
+    }
+
+    pipe_send(nextStage, stage.data + 1);
+
+    stage.isDataAvail = false;
+
+    status = pthread_cond_signal(&stage.threadIsIdle);
+    if (status != 0) err_abort(status, "Wake next stage");
+  }
+
+  /*
+   * Notice that the routine never unlocks the stage->mutex.
+   * The call to pthread_cond_wait implicitly unlocks the
+   * mutex while the thread is waiting, allowing other threads
+   * to make progress. Because the loop never terminates, this
+   * function has no need to unlock the mutex explicitly.
+   */
+}
+
+/*
+ * External interface to create a pipeline. All the
+ * data is initialized and the threads created. They'll
+ * wait for data.
+ */
+int pipe_create(pipe_t &pipe, size_t nStages) {
+  int status = pthread_mutex_init(&pipe.mutex, NULL);
+  if (status != 0) err_abort(status, "Init pipe mutex");
+
+  pipe.stageList.resize(nStages);
+  pipe.nActive = 0;
+
+  for (auto &iStage : pipe.stageList) {
+    status = pthread_mutex_init(&iStage.mutex, NULL);
+    if (status != 0) err_abort(status, "Init stage mutex");
+    status = pthread_cond_init(&iStage.dataIsAvail, NULL);
+    if (status != 0) err_abort(status, "Init dataIsAvail condition");
+    status = pthread_cond_init(&iStage.threadIsIdle, NULL);
+    if (status != 0) err_abort(status, "Init threadIsIdle condition");
+    iStage.isDataAvail = false;
+  }
+
+  /*
+   * Create the threads for the pipe stages only after all
+   * the data is initialized (including all links). Note
+   * that the last stage doesn't get a thread, it's just
+   * a receptacle for the final pipeline value.
+   *
+   * At this point, proper cleanup on an error would take up
+   * more space than worthwhile in a "simple example", so
+   * instead of cancelling and detaching all the threads
+   * already created, plus the synchronization object and
+   * memory cleanup done for earlier errors, it will simply
+   * abort.
+   */
+  for (auto it = pipe.stageList.begin(), ite = --pipe.stageList.end();
+       it != ite;) {
+    auto iit = it++;
+    iit->next = &(*it);
+
+    status = pthread_create(&iit->thread, NULL, pipe_stage, (void *)&*iit);
+    if (status != 0) err_abort(status, "Create pipe stage");
+  }
+  return 0;
+}
+
+/*
+ * Collect the result of the pipeline. Wait for a
+ * result if the pipeline hasn't produced one.
+ */
+int pipe_result(pipe_t &pipe) {
+  int status;
+
+  status = pthread_mutex_lock(&pipe.mutex);
+  if (status != 0) err_abort(status, "Lock pipe mutex");
+
+  bool isEmpty = false;
+  if (pipe.nActive <= 0)
+    isEmpty = true;
+  else
+    pipe.nActive--;
+
+  status = pthread_mutex_unlock(&pipe.mutex);
+  if (status != 0) err_abort(status, "Unlock pipe mutex");
+
+  if (isEmpty) {
+    printf("Pipe is empty\n");
+    return 0;
+  }
+
+  auto &tail = pipe.stageList.back();
+
+  status = pthread_mutex_lock(&tail.mutex);
+  if (status != 0) err_abort(status, "Lock pipe tail mutex");
+
+  while (!tail.isDataAvail) {
+    pthread_cond_wait(&tail.dataIsAvail, &tail.mutex);
+  }
+
+  long result = tail.data;
+  tail.isDataAvail = false;
+
+  status = pthread_cond_signal(&tail.threadIsIdle);
+  if (status != 0) err_abort(status, "Signal pipe tail threadIsIdle");
+
+  status = pthread_mutex_unlock(&tail.mutex);
+  if (status != 0) err_abort(status, "Unlock pipe tail mutex");
+
+  printf("Result is %ld\n", result);
+
+  return 1;
+}
+
+/*
+ * External interface to start a pipeline by passing
+ * data to the first stage. The routine returns while
+ * the pipeline processes in parallel. Call the
+ * pipe_result return to collect the final stage values
+ * (note that the pipe will stall when each stage fills,
+ * until the result is collected).
+ */
+void pipe_start(pipe_t &pipe, long value) {
+  int status = pthread_mutex_lock(&pipe.mutex);
+  if (status != 0) err_abort(status, "Lock pipe mutex");
+
+  if (pipe.nActive > pipe.stageList.size() - 1) {
+    status = pthread_mutex_unlock(&pipe.mutex);
+    pipe_result(pipe);
+    status = pthread_mutex_lock(&pipe.mutex);
+  }
+
+  pipe.nActive++;
+
+  status = pthread_mutex_unlock(&pipe.mutex);
+  if (status != 0) err_abort(status, "Unlock pipe mutex");
+
+  pipe_send(pipe.stageList.front(), value);
+}
+
+/*
+ * The main program to "drive" the pipeline...
+ */
+int main(int argc, char *argv[]) {
+  pipe_t my_pipe;
+  pipe_create(my_pipe, 2);
+
+  printf("Enter integer values, or \"=\" for next result\n");
+
+  char line[128];
+  while (1) {
+    printf("Data> ");
+    if (fgets(line, sizeof(line), stdin) == NULL) exit(0);
+    printf(line);
+    if (strlen(line) <= 1) continue;
+    if (strlen(line) <= 2 && line[0] == '=') {
+      pipe_result(my_pipe);
+    } else {
+      long value;
+      if (sscanf(line, "%ld", &value) < 1)
+        fprintf(stderr, "Enter an integer value\n");
+      else
+        pipe_start(my_pipe, value);
+    }
+  }
+}

trylock.c

@@ -24,8 +24,7 @@ time_t end_time;
  * Thread start routine that repeatedly locks a mutex and
  * increments a counter.
  */
-void *counter_thread (void *arg)
+void *counter_thread(void *arg) {
-{
   int status;
   int spin;
 
@@ -35,16 +34,13 @@ void *counter_thread (void *arg)
    * sleeps for another second with the mutex locked, to give
    * monitor_thread a reasonable chance of running.
    */
-    while (time (NULL) < end_time)
+  while (time(NULL) < end_time) {
-    {
     status = pthread_mutex_lock(&mutex);
-        if (status != 0)
+    if (status != 0) err_abort(status, "Lock mutex");
-            err_abort (status, "Lock mutex");
+    for (spin = 0; spin < SPIN; spin++) counter++;
-        for (spin = 0; spin < SPIN; spin++)
+    sleep(4);
-            counter++;
     status = pthread_mutex_unlock(&mutex);
-        if (status != 0)
+    if (status != 0) err_abort(status, "Unlock mutex");
-            err_abort (status, "Unlock mutex");
     sleep(1);
   }
   printf("Counter is %#lx\n", counter);
@@ -56,28 +52,22 @@ void *counter_thread (void *arg)
  * seconds, try to lock the mutex and read the counter. If the
  * trylock fails, skip this cycle.
  */
-void *monitor_thread (void *arg)
+void *monitor_thread(void *arg) {
-{
   int status;
   int misses = 0;
 
-
   /*
    * Loop until end_time, checking the counter every 3
    * seconds.
    */
-    while (time (NULL) < end_time)
+  while (time(NULL) < end_time) {
-    {
     sleep(3);
     status = pthread_mutex_trylock(&mutex);
-        if (status != EBUSY)
+    if (status != EBUSY) {
-        {
+      if (status != 0) err_abort(status, "Trylock mutex");
-            if (status != 0)
-                err_abort (status, "Trylock mutex");
       printf("Counter is %ld\n", counter / SPIN);
       status = pthread_mutex_unlock(&mutex);
-            if (status != 0)
+      if (status != 0) err_abort(status, "Unlock mutex");
-                err_abort (status, "Unlock mutex");
     } else
       misses++; /* Count "misses" on the lock */
   }
@@ -85,8 +75,7 @@ void *monitor_thread (void *arg)
   return NULL;
 }
 
-int main (int argc, char *argv[])
+int main(int argc, char *argv[]) {
-{
   int status;
   pthread_t counter_thread_id;
   pthread_t monitor_thread_id;
@@ -102,19 +91,13 @@ int main (int argc, char *argv[])
 #endif
 
   end_time = time(NULL) + 60; /* Run for 1 minute */
-    status = pthread_create (
+  status = pthread_create(&counter_thread_id, NULL, counter_thread, NULL);
-        &counter_thread_id, NULL, counter_thread, NULL);
+  if (status != 0) err_abort(status, "Create counter thread");
-    if (status != 0)
+  status = pthread_create(&monitor_thread_id, NULL, monitor_thread, NULL);
-        err_abort (status, "Create counter thread");
+  if (status != 0) err_abort(status, "Create monitor thread");
-    status = pthread_create (
-        &monitor_thread_id, NULL, monitor_thread, NULL);
-    if (status != 0)
-        err_abort (status, "Create monitor thread");
   status = pthread_join(counter_thread_id, NULL);
-    if (status != 0)
+  if (status != 0) err_abort(status, "Join counter thread");
-        err_abort (status, "Join counter thread");
   status = pthread_join(monitor_thread_id, NULL);
-    if (status != 0)
+  if (status != 0) err_abort(status, "Join monitor thread");
-        err_abort (status, "Join monitor thread");
   return 0;
 }