From 2d3250d2d35dda415840d8403b7b8957ca40914a Mon Sep 17 00:00:00 2001
From: Tyge Løvset <tylo@norceresearch.no>
Date: Sun, 4 Jun 2023 22:16:38 +0200
Subject: Added dining_philosophers.c coroutine example. Fixed cco_stop() when
 in state 0. Renamed cco_timer_with(msec) => cco_timer_from(msec) Renamed
 cco_sem_with(val) => cco_sem_from(val)

---
 include/stc/algo/coroutine.h        | 15 +++---
 misc/examples/dining_philosophers.c | 99 +++++++++++++++++++++++++++++++++++++
 2 files changed, 106 insertions(+), 8 deletions(-)
 create mode 100644 misc/examples/dining_philosophers.c

diff --git a/include/stc/algo/coroutine.h b/include/stc/algo/coroutine.h
index d3f73229..05307b08 100644
--- a/include/stc/algo/coroutine.h
+++ b/include/stc/algo/coroutine.h
@@ -98,15 +98,13 @@ enum {
 
 #define cco_stop(co) \
     do { \
-        int* _state = &(co)->cco_state; \
-        if (*_state > 0) *_state = cco_state_final; \
+        int* _s = &(co)->cco_state; \
+        if (*_s > 0) *_s = cco_state_final; \
+        else if (*_s == 0) *_s = cco_state_done; \
     } while (0)
 
 #define cco_reset(co) \
-    do { \
-        int* _state = &(co)->cco_state; \
-        if (*_state == cco_state_done) *_state = 0; \
-    } while (0)
+    (void)((co)->cco_state = 0)
 
 /*
  * Semaphore
@@ -125,7 +123,8 @@ typedef struct {
     } while (0)
 
 #define cco_sem_release(sem) ++(sem)->count
-#define cco_sem_with(value) ((cco_sem){value})
+#define cco_sem_from(value) ((cco_sem){value})
+#define cco_sem_set(sem, value) ((sem)->count = value)
 
 /*
  * Timer
@@ -165,7 +164,7 @@ static inline void cco_timer_start(cco_timer* tm, long msec) {
     tm->start = clock();
 }
 
-static inline cco_timer cco_timer_with(long msec) {
+static inline cco_timer cco_timer_from(long msec) {
     cco_timer tm = {msec*(CLOCKS_PER_SEC/1000), clock()};
     return tm;
 }
diff --git a/misc/examples/dining_philosophers.c b/misc/examples/dining_philosophers.c
new file mode 100644
index 00000000..0bf421c6
--- /dev/null
+++ b/misc/examples/dining_philosophers.c
@@ -0,0 +1,99 @@
+// https://en.wikipedia.org/wiki/Dining_philosophers_problem
+#include <stdio.h>
+#include <stc/crand.h>
+#include <stc/algo/coroutine.h>
+ 
+// Define the number of philosophers and forks
+enum {
+    num_philosophers = 5,
+    num_forks = num_philosophers,
+};
+
+struct Philosopher {
+    int id;
+    cco_timer tm;
+    cco_sem* left_fork;
+    cco_sem* right_fork;
+    int cco_state; // required
+};
+
+struct Dining {
+    // Define semaphores for the forks
+    cco_sem forks[num_forks];
+    struct Philosopher ph[num_philosophers];
+    int ph_idx;
+    int cco_state; // required
+};
+
+ 
+// Philosopher coroutine
+void philosopher(struct Philosopher* p)
+{
+    cco_routine(p) {
+        while (1) {
+            int duration = (int)(1000 + crand() % 2000); // 1-3 seconds
+            printf("Philosopher %d is thinking for %d minutes...\n", p->id, duration/100);
+            cco_timer_await(&p->tm, duration);
+
+            printf("Philosopher %d is hungry...\n", p->id);
+            cco_sem_await(p->left_fork);
+            cco_sem_await(p->right_fork);
+            
+            duration = (int)(500 + crand() % 1000);
+            printf("Philosopher %d is eating for %d minutes...\n", p->id, duration/100);
+            cco_timer_await(&p->tm, duration);
+            
+            cco_sem_release(p->left_fork);
+            cco_sem_release(p->right_fork);
+        }
+        
+        cco_final:
+        printf("Philosopher %d finished\n", p->id);
+    }
+}
+
+
+// Dining coroutine
+void dining(struct Dining* d)
+{
+    cco_routine(d) {
+        for (int i = 0; i < num_forks; ++i)
+            cco_sem_set(&d->forks[i], 1); // all forks available
+        for (int i = 0; i < num_philosophers; ++i) {
+            cco_reset(&d->ph[i]);
+            d->ph[i].id = i + 1;
+            d->ph[i].left_fork = &d->forks[i];
+            d->ph[i].right_fork = &d->forks[(i + 1) % num_forks];
+        }
+
+        while (1) {
+            for (d->ph_idx = 0; d->ph_idx < num_philosophers; ++d->ph_idx) {
+                philosopher(&d->ph[d->ph_idx]);
+                cco_yield();
+            }
+        }
+
+        cco_final:
+        for (int i = 0; i < num_philosophers; ++i) {
+            cco_stop(&d->ph[i]);
+            philosopher(&d->ph[i]);
+        }
+        puts("Dining finished");
+    }
+}
+
+
+int main()
+{
+    struct Dining dine;
+    cco_reset(&dine);
+    cco_timer tm = cco_timer_from(10000);
+    csrand((uint64_t)time(NULL));
+
+    while (!cco_done(&dine)) {
+        if (cco_timer_expired(&tm))
+            cco_stop(&dine);
+        dining(&dine);
+        cco_sleep(1);
+    }
+}
-- 
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