Make variable names more accurate

Make functions more functional
Make comments more commentary

inc/globals.hpp

@@ -1,4 +1,10 @@
 #define N 8
+#define timescale 5
+
+//function defines, renaming wait and signal
+#define wait(x) sem_wait(&x)
+#define signal(x) sem_post(&x)
+
 // Shared memory through global variables
 // Create all of memory
 extern block memory[N];
@@ -7,6 +13,8 @@ extern list lists[3];
 extern list *freelist, *list1, *list2;
 
 // count semaphores
-extern sem_t semfl, seml1, seml2;
+extern sem_t sem_freelist, sem_list1, sem_list2;
 // binary semaphores
-extern sem_t mutfl, mutl1, mutl2;
+extern sem_t mut_freelist, mut_list1, mut_list2;
+// binary semaphores for reading/writing
+extern sem_t mut_take, mut_give;

inc/list.hpp

@@ -14,7 +14,7 @@ struct list {
 
 // list operations:
 //   list_unlink: unlinks the last block in the list, and returns a pointer to it
-block *list_unlink (list *l);
+block* list_unlink (list* l, bool lastblock=0);
 //   list_link:   links the block b onto the end of the list
 void   list_link   (list *l, block *b);
 //   list_init:   links an array of blocks onto the end of a list

src/consumer.cpp

@@ -1,29 +1,35 @@
 #include <semaphore.h>
 #include <unistd.h>
-#include "list.hpp"
-#include "globals.hpp" // freelist list1 list2
+#include "list.hpp"    // list implementation
+#include "globals.hpp" // lists, sems, muts
 #include "consumer.hpp"
 
+#define unlink(x) list_unlink(x)
+#define link(x)   list_link(x)
+
 int consume(block* c);
 
 void *consumer (void *) {
    while (true) {
-      sem_wait(&seml2); // decrease seml2
-      sem_wait(&mutl2);
+
+      wait(sem_list2);
+      wait(mut_list2);
       block* c = list_unlink(list2);
-      sem_post(&mutl2);
+      signal(mut_list2);
+
       //* consume information in block c
       consume(c);
-      sem_wait(&mutfl);
+
+      wait(mut_freelist);
       list_link(freelist, c);
-      sem_post(&mutfl);
-      sem_post(&semfl); // increase freelist
+      signal(mut_freelist);
+      signal(sem_freelist);
+
    }
    return nullptr;
 }
 
 int consume(block *c) {
-   c->data = -c->data;
-   usleep(75);
-   return 0;
+   usleep(75*timescale);
+   return c->data;
 }

src/list.cpp

@@ -1,8 +1,34 @@
 #include "list.hpp"
 #include <cstdio>
 
+// dequeue the first block
+block* list_dequeue (list* l) {
+   // we need a list
+   if (!l) return nullptr;
+   block* b = l->start;
+   // can't unlink from an empty list
+   if (!b) return nullptr;
+   // remove b
+   if (b->next) {
+      // b is not the only element of the list
+      // chop of the head
+      l->start = b->next;
+      // bandage the wound
+      l->start->prev = nullptr;
+      // wrap the severed head
+      b->next = nullptr;
+   } else {
+      // b is the only element of the list
+      l->start = nullptr;
+      l->end = nullptr;
+   }
+   // if we get here, we've removed element b from the list
+   l->length--;
+   return b;
+}
+
 // pop the last block
-block* list_unlink (list* l) {
+block* list_pop (list* l) {
    // we need a list
    if (!l) return nullptr;
    block* b = l->end;
@@ -27,6 +53,10 @@ block* list_unlink (list* l) {
    return b;
 }
 
+block* list_unlink (list* l, bool lastblock) {
+   return (lastblock?list_pop:list_dequeue)(l);
+}
+
 // push a block
 void list_link (list* l, block* b) {
    // can't link to a nonexistent list

src/main.cpp

@@ -16,21 +16,27 @@ list lists[3] = {0};
 list *freelist = &lists[0], *list1 = &lists[1], *list2 = &lists[2];
 
 // count semaphores
-sem_t semfl, seml1, seml2;
+sem_t sem_freelist, sem_list1, sem_list2;
 // binary semaphores
-sem_t mutfl, mutl1, mutl2;
+sem_t mut_freelist, mut_list1, mut_list2;
+// binary semaphores for reading/writing
+sem_t mut_take, mut_give;
 
 int main (int argc, char* argv[]) {
    // initialize the freelist
    list_init(freelist, memory, N);
 
    //TODO: Implement a semaphore solution to the problem
-   sem_init(&semfl, 0, freelist->length);
-   sem_init(&seml1, 0, 0);
-   sem_init(&seml2, 0, 0);
-   sem_init(&mutfl, 0, 1);
-   sem_init(&mutl1, 0, 1);
-   sem_init(&mutl2, 0, 1);
+   // counting semaphores measure the length
+   sem_init(&sem_freelist, 0, freelist->length);
+   sem_init(&sem_list1, 0, 0);
+   sem_init(&sem_list2, 0, 0);
+   // binary semaphores create mutual exclusion
+   sem_init(&mut_freelist, 0, 1);
+   sem_init(&mut_list1, 0, 1);
+   sem_init(&mut_list2, 0, 1);
+   sem_init(&mut_take,  0, 1);
+   sem_init(&mut_give,  0, 1);
 
    //TODO: Use pthreads to split execution
    // Make some pthreads
@@ -46,10 +52,11 @@ int main (int argc, char* argv[]) {
    pthread_create(&thread3, NULL, consumer, NULL);
 
    while (true) {
+      printf("\033c");
       list_print(freelist);
       list_print(list1);
       list_print(list2);
-      sleep(1);
+      usleep(100*timescale);
    }
    // Wait for them to finish
    pthread_join(thread1, NULL);

src/producer.cpp

@@ -1,32 +1,32 @@
 #include <semaphore.h>
 #include <unistd.h>
-#include "list.hpp"
-#include "globals.hpp" // freelist list1 list2
+#include "list.hpp"    // list implementation
+#include "globals.hpp" // lists, sems, muts
 #include "producer.hpp"
 
-#define wait(x) sem_wait(&x)
-#define sgnl(x) sem_post(&x)
-
 void produce(block* b);
 
 void *producer (void *) {
    while (true) {
-      wait(semfl); // wait for freelist not empty
-      wait(mutfl); // lock freelist
+
+      wait(sem_freelist); // wait for freelist not empty
+      wait(mut_freelist); // lock freelist
       block *b = list_unlink(freelist);
-      sgnl(mutfl); // unlock freelist
+      signal(mut_freelist); // unlock freelist
+
       //* Produce information in block b
       produce(b);
-      wait(mutl1); // lock l1
+
+      wait(mut_list1); // lock l1
       list_link(list1, b);
-      sgnl(mutl1); // unlock l1
-      sgnl(seml1);
+      signal(mut_list1); // unlock l1
+      signal(sem_list1);
+
    }
    return nullptr;
 }
 
 void produce(block *b) {
-   b->data++;
-   usleep(65);
+   usleep(65*timescale);
    return;
 }

src/test.cpp

@@ -16,9 +16,9 @@ list *freelist = &lists[0],
      *list2 = &lists[2];
 
 // count semaphores
-sem_t semfl, seml1, seml2;
+sem_t sem_freelist, sem_list1, sem_list2;
 // binary semaphores
-sem_t mutfl, mutl1, mutl2;
+sem_t mut_freelist, mut_list1, mut_list2;
 
 void producer_test();
 void transfer_test();

src/transformer.cpp

@@ -1,7 +1,7 @@
 #include <semaphore.h>
 #include <unistd.h>
-#include "list.hpp"
-#include "globals.hpp" // freelist list1 list2
+#include "list.hpp"    // list implementation
+#include "globals.hpp" // lists, sems, muts
 #include "transformer.hpp"
 
 void transform(block* x, block* y);
@@ -9,36 +9,35 @@ void transform(block* x, block* y);
 void *transformer (void *) {
    block *x, *y;
    while (true) {
-      sem_wait(&seml1); // decrease seml1
-      sem_wait(&mutl1);
-      x = list_unlink(list1);
-      sem_post(&mutl1);
 
-      sem_wait(&semfl); // decrease semfl
-      sem_wait(&mutfl);
+      wait(sem_list1);
+      wait(mut_list1);
+      x = list_unlink(list1);
+      signal(mut_list1);
+
+      wait(sem_freelist);
+      wait(mut_freelist);
       y = list_unlink(freelist);
-      sem_post(&mutfl);
+      signal(mut_freelist);
 
       //* use block x to produce info in y
       transform(x, y);
 
-      sem_wait(&mutfl);
+      wait(mut_freelist);
       list_link(freelist, x);
-      sem_post(&mutfl);
-      sem_post(&semfl);
+      signal(mut_freelist);
+      signal(sem_freelist);
 
-      sem_wait(&mutl2);
+      wait(mut_list2);
       list_link(list2, y);
-      sem_post(&mutl2);
-      sem_post(&seml2);
+      signal(mut_list2);
+      signal(sem_list2);
+
    }
    return nullptr;
 }
 
 void transform(block *x, block *y) {
-   x->data ^= y->data;
-   y->data ^= x->data;
-   x->data ^= y->data;
-   usleep(55);
+   usleep(55*timescale);
    return;
 }