started simple server

Author: Emmanuel Massaquoi

p1/ReadWrite.c

@@ -1,96 +1,137 @@
 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
+#include <unistd.h>
 #include <pthread.h>
+#include <time.h>
 
-#define NUM_THREADS 10
+#define NUM_READERS 5
+#define NUM_READS 5
+#define NUM_WRITERS 5
+#define NUM_WRITES 5
 
-//
-// Created by Emmanuel Massaquoi on 6/19/17.
-//
+unsigned int gSharedValue = 0;
+int gWaitingReaders = 0;
+int gReaders = 0;
 
-int shared_var = 0;
-int resource_use;
-int num_reader = 0;
 
-int reading = 0;
-int writing = 1;
+pthread_mutex_t gSharedMemoryLock = PTHREAD_MUTEX_INITIALIZER;
+pthread_cond_t gReadPhase = PTHREAD_COND_INITIALIZER;
+pthread_cond_t gWritePhase = PTHREAD_COND_INITIALIZER;
 
-pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
-pthread_cond_t read_phase = PTHREAD_COND_INITIALIZER;
-pthread_cond_t write_phase = PTHREAD_COND_INITIALIZER;
+void *reader(void *param);
+void *writer(void *param);
+int usleep(__useconds_t sec);
 
-void *reader (void *param);
-void *writer (void *param);
+//void waitFor(unsigned int secs);
 
 
 int main(int argc, char *argv[]) {
 
- pthread_t tid[NUM_THREADS];
+ int readerNum[NUM_READERS];
+ int writerNum[NUM_WRITERS];
 
- for (int i = 0; i < 5; i++) {
+ pthread_t readerThreadIDs[NUM_READERS];
+ pthread_t writerThreadIDs[NUM_WRITERS];
 
- printf("Create Reader\n");
- if(pthread_create(&tid[i], NULL, reader, NULL) != 0) {
+ srandom((unsigned int)time(NULL));
+
+
+ for (int i = 0; i < NUM_READERS; i++) {
+ readerNum[i] = i;
+
+ if(pthread_create(&readerThreadIDs[i], NULL, reader, &readerNum[i]) != 0) {
  fprintf(stderr, "Unable to create reader thread");
  exit(1);
  }
+ }
+
+ for (int i = 0; i < NUM_WRITERS; i++) {
+ writerNum[i] = i;
 
- printf("Create Writer\n");
- if(pthread_create(&tid[i+5], NULL, writer, NULL) != 0) {
+ if(pthread_create(&writerThreadIDs[i], NULL, writer, &writerNum[i]) != 0) {
  fprintf(stderr, "Unable to create writer thread");
  exit(1);
  }
  }
 
- for (int j = 0; j < NUM_THREADS; ++j) {
- pthread_join(tid[j], NULL);
+
+ for (int i = 0; i < NUM_READERS; i++) {
+ pthread_join(readerThreadIDs[i], NULL);
  }
 
- printf("Parent quiting\n");
+ for (int i = 0; i < NUM_WRITERS; i++) {
+ pthread_join(writerThreadIDs[i], NULL);
+ }
 
  return 0;
 }
 
 void *reader(void *param) {
 
- for (int i = 1; i <=20; i++) {
+ int id = *((int*)param);
+ int numReaders = 0;
+
+ for (int i = 0; i < NUM_READS; i++) {
+
+ usleep(1000 * (random() % NUM_READERS + NUM_WRITERS));
 
- pthread_mutex_lock(&m);
+ pthread_mutex_lock(&gSharedMemoryLock);
 
- while (resource_use == writing) {
- pthread_cond_wait(&read_phase, &m);
+ gWaitingReaders++;
+ while (gReaders == -1) {
+ pthread_cond_wait(&gReadPhase, &gSharedMemoryLock);
  }
+ gWaitingReaders--;
+ numReaders = ++gReaders;
 
- printf("Reader Value: %d\n", shared_var);
- printf("Number of Readers Present: %d\n", num_reader);
+ pthread_mutex_unlock(&gSharedMemoryLock);
 
- resource_use = reading;
- pthread_cond_broadcast(&write_phase);
+ fprintf(stdout, "[r%d] reading %u [readers: %2d]\n", id, gSharedValue, numReaders);
 
- pthread_mutex_unlock(&m);
+ pthread_mutex_lock(&gSharedMemoryLock);
+ gReaders--;
+ if (gReaders == 0) {
+ pthread_cond_signal(&gWritePhase);
+ }
+ pthread_mutex_unlock(&gSharedMemoryLock);
  }
 
- return 0;
+ pthread_exit(0);
 }
 
 void *writer(void *param) {
 
- for (int i = 1; i <= 20; ++i) {
- pthread_mutex_lock(&m);
-
- while (resource_use == reading || num_reader != 0) {
- pthread_cond_wait(&write_phase, &m);
- }
+ int id = *((int*)param);
+ int numReaders = 0;
 
- shared_var = i;
- printf("Written Value: %d\n", shared_var);
- printf("Number of Readers Present: %d\n", num_reader);
+ for (int i = 0; i < NUM_WRITES; ++i) {
 
- resource_use = writing;
- pthread_cond_broadcast(&read_phase);
+ usleep(1000 * (random() % NUM_READERS + NUM_WRITERS));
 
- pthread_mutex_unlock(&m);
+ pthread_mutex_lock(&gSharedMemoryLock);
+ while (gReaders != 0) {
+ pthread_cond_wait(&gWritePhase, &gSharedMemoryLock);
+ }
+ gReaders = -1;
+ numReaders = gReaders;
+ pthread_mutex_unlock(&gSharedMemoryLock);
+
+ fprintf(stdout, "[w%d] writing %u* [readers: %2d]\n", id, ++gSharedValue, numReaders);
+
+ pthread_mutex_lock(&gSharedMemoryLock);
+ gReaders = 0;
+ if(gWaitingReaders > 0) {
+ pthread_cond_broadcast(&gReadPhase);
+ } else {
+ pthread_cond_signal(&gWritePhase);
+ }
+ pthread_mutex_unlock(&gSharedMemoryLock);
  }
 
-}
+ pthread_exit(0);
+}
+
+/*void waitFor (unsigned int secs) {
+ unsigned int retTime = time(0) + secs;
+ while(time(0) < retTime);
+}*/

p1/p1.iml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="WEB_MODULE" version="4">
+ <component name="NewModuleRootManager" inherit-compiler-output="true">
+ <exclude-output />
+ <content url="file://$MODULE_DIR$" />
+ <orderEntry type="inheritedJdk" />
+ <orderEntry type="sourceFolder" forTests="false" />
+ </component>
+</module>