From 6bcc6bfa1ca871d2aae71e2b76d6eca36d24b5e5 Mon Sep 17 00:00:00 2001
From: default <nobody@localhost>
Date: Mon, 6 Feb 2023 11:29:46 +0100
Subject: [PATCH] New functions job_post() and job_wait() (untested).

---
 httpd.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 85 insertions(+), 1 deletion(-)

diff --git a/httpd.c b/httpd.c
index d068af3..2708437 100644
--- a/httpd.c
+++ b/httpd.c
@@ -13,6 +13,7 @@
 
 #include <setjmp.h>
 #include <pthread.h>
+#include <semaphore.h>
 
 
 /* nodeinfo 2.0 template */
@@ -319,6 +320,80 @@ static void *connection_thread(void *arg)
 }
 
 
+/** job control **/
+
+/* mutex to access the lists of jobs */
+static pthread_mutex_t job_mutex;
+
+/* semaphre to trigger job processing */
+static sem_t job_sem;
+
+/* list of input sockets */
+xs_list *job_sockets = NULL;
+
+/* list of queue items */
+xs_list *job_qitems = NULL;
+
+
+void job_post(FILE *socket, const xs_dict *q_item)
+/* posts a job, being an input connection or another queue item */
+{
+    /* lock the mutex */
+    pthread_mutex_lock(&job_mutex);
+
+    /* add to the appropriate fifo */
+    if (socket != NULL) {
+        xs *d = xs_data_new(&socket, sizeof(FILE *));
+        job_sockets = xs_list_append(job_sockets, d);
+    }
+    else
+    if (q_item != NULL)
+        job_qitems = xs_list_append(job_qitems, q_item);
+
+    /* unlock the mutex */
+    pthread_mutex_unlock(&job_mutex);
+
+    /* ask for someone to attend it */
+    sem_post(&job_sem);
+}
+
+
+int job_wait(FILE **socket, xs_dict **q_item)
+/* waits for an available job; returns 0 if nothing left to do */
+{
+    int done = 1;
+
+    *socket = NULL;
+    *q_item = NULL;
+
+    if (sem_wait(&job_sem) == 0) {
+        /* lock the mutex */
+        pthread_mutex_lock(&job_mutex);
+
+        /* try first to get a socket to process */
+        xs *job_socket = NULL;
+        job_sockets = xs_list_shift(job_sockets, &job_socket);
+
+        /* if empty, try a q_item */
+        if (job_socket == NULL)
+            job_qitems = xs_list_shift(job_qitems, q_item);
+
+        /* unlock the mutex */
+        pthread_mutex_unlock(&job_mutex);
+
+        if (job_socket != NULL) {
+            xs_data_get(job_socket, socket);
+            done = 0;
+        }
+        else
+        if (*q_item != NULL)
+            done = 0;
+    }
+
+    return done;
+}
+
+
 #ifndef MAX_THREADS
 #define MAX_THREADS 256
 #endif
@@ -348,8 +423,14 @@ void httpd(void)
 
     srv_log(xs_fmt("httpd start %s:%d %s", address, port, USER_AGENT));
 
-    /* thread creation */
+    /* initialize the job control engine */
+    pthread_mutex_init(&job_mutex, NULL);
+    sem_init(&job_sem, 0, 0);
+    job_sockets = xs_list_new();
+    job_qitems = xs_list_new();
+
 #ifdef _SC_NPROCESSORS_ONLN
+    /* get number of CPUs on the machine */
     n_threads = sysconf(_SC_NPROCESSORS_ONLN);
 #endif
 
@@ -380,5 +461,8 @@ void httpd(void)
     /* wait for the background thread to end */
     pthread_join(threads[0], NULL);
 
+    job_sockets = xs_free(job_sockets);
+    job_qitems  = xs_free(job_qitems);
+
     srv_log(xs_fmt("httpd stop %s:%d", address, port));
 }