lbalance: add examples.

diff --git a/ccan/lbalance/_info b/ccan/lbalance/_info
index c0d0ab0e5a4fa7fb362b0ebb8a0a15da53ee9627..e3e9c78e7a32434f858f27a2c4533f8b2afc1bdd 100644 (file)
--- a/ccan/lbalance/_info
+++ b/ccan/lbalance/_info
@@ -9,6 +9,72 @@
  *
  * License: GPL
  * Author: Rusty Russell <rusty@rustcorp.com.au>
+ *
+ * Example:
+ *     // Run 1000 of the given commandline at best-known parallel rate.
+ *     // See tools/lbalance.c for a sligtly more serious example.
+ *     #include <ccan/lbalance/lbalance.h>
+ *      #include <sys/types.h>
+ *      #include <sys/time.h>
+ *      #include <sys/resource.h>
+ *      #include <sys/wait.h>
+ *      #include <err.h>
+ *
+ *     #define MAX 1000
+ *
+ *     static pid_t spawn(char *args[])
+ *     {
+ *             pid_t pid = fork();
+ *
+ *             if (pid == -1)
+ *                     err(1, "forking");
+ *             if (pid == 0) {
+ *                     execvp(args[0], args);
+ *                     err(1, "exec failed");
+ *             }
+ *             return pid;
+ *     }
+ *
+ *     int main(int argc, char *argv[])
+ *     {
+ *             unsigned int num = 0, num_running = 0;
+ *             pid_t pids[MAX];
+ *             struct lbalance_task *tasks[MAX];
+ *             struct lbalance *lb;
+ *
+ *             if (argc == 1)
+ *                     errx(1, "Usage: %s cmdline...", argv[0]);
+ *
+ *             lb = lbalance_new();
+ *
+ *             while (num - num_running < MAX) {
+ *                     struct rusage ru;
+ *                     pid_t pid;
+ *                     unsigned int i;
+ *
+ *                     // Make sure we're running as many as lbalance says to. 
+ *                     while (num_running < lbalance_target(lb) && num < MAX) {
+ *                             pids[num] = spawn(argv+1);
+ *                             tasks[num] = lbalance_task_new(lb);
+ *                             num++;
+ *                             num_running++;
+ *                     }
+ *
+ *                     // Now wait for something to die.
+ *                     pid = wait3(NULL, 0, &ru);
+ *                     // Find it, tell lbalance it's finished.
+ *                     for (i = 0; i < num; i++) {
+ *                             if (pids[i] == pid) {
+ *                                     lbalance_task_free(tasks[i], &ru);
+ *                                     pids[i] = 0;
+ *                                     break;
+ *                             }
+ *                     }
+ *                     num_running--;
+ *             }
+ *             lbalance_free(lb);
+ *             return 0;
+ *     }
  */
 int main(int argc, char *argv[])
 {

diff --git a/ccan/lbalance/lbalance.h b/ccan/lbalance/lbalance.h
index d318a6fe84b78344dd993f2b83a82e19df248d1d..b5de8aa67b33730fdb84a465b160334cace06b3b 100644 (file)
--- a/ccan/lbalance/lbalance.h
+++ b/ccan/lbalance/lbalance.h
@@ -9,12 +9,41 @@ struct rusage;
 
 /**
  * lbalance_new - initialize a load balancing structure.
+ *
+ * Example:
+ *     struct lbalance *lb = lbalance_new();
+ *
+ *     // ...
+ *
+ *     lbalance_free(lb);
+ *     return 0;
  */
 struct lbalance *lbalance_new(void);
 
+/**
+ * lbalance_free - free a load balancing structure.
+ * @lbalance: the load balancer from lbalance_new.
+ *
+ * Also frees any tasks still attached.
+ */
+void lbalance_free(struct lbalance *lbalance);
+
 /**
  * lbalance_task_new - mark the starting of a new task.
  * @lbalance: the load balancer from lbalance_new.
+ *
+ * Example:
+ *     static pid_t run_child(struct lbalance *lb, struct lbalance_task **task)
+ *     {
+ *             pid_t pid = fork();
+ *             if (pid != 0) {
+ *                     // We are the parent, return.
+ *                     *task = lbalance_task_new(lb);
+ *                     return pid;
+ *             }
+ *             // otherwise do some work...
+ *             exit(0);
+ *     }
  */
 struct lbalance_task *lbalance_task_new(struct lbalance *lbalance);
 
@@ -29,6 +58,21 @@ struct lbalance_task *lbalance_task_new(struct lbalance *lbalance);
  *
  * Otherwise, lbalance_task_free() is a noop, which is useful for failure
  * paths.
+ *
+ * Example:
+ *     #include <sys/types.h>
+ *     #include <sys/time.h>
+ *     #include <sys/resource.h>
+ *     #include <sys/wait.h>
+ *
+ *     static void wait_for_child(struct lbalance_task *task)
+ *     {
+ *             struct rusage ru;
+ *             // Wait for child to finish, get usage.
+ *             wait4(-1, NULL, 0, &ru);
+ *             // Tell lbalancer about usage, free struct lbalance_task.
+ *             lbalance_task_free(task, &ru);
+ *     }
  */
 void lbalance_task_free(struct lbalance_task *task,
                        const struct rusage *usage);
@@ -39,14 +83,23 @@ void lbalance_task_free(struct lbalance_task *task,
  *
  * Normally you keep creating tasks until this limit is reached.  It's
  * updated by stats from lbalance_task_free.
+ *
+ * Example:
+ *     int main(void)
+ *     {
+ *             unsigned int num_running = 0;
+ *             struct lbalance *lb = lbalance_new();
+ *
+ *             for (;;) {
+ *                     // Run more until we reach target.
+ *                     while (num_running < lbalance_target(lb)) {
+ *                             // Run another one.
+ *                     }
+ *
+ *                     // Wait for something to finish.
+ *             }
+ *     }
  */
 unsigned lbalance_target(struct lbalance *lbalance);
 
-/**
- * lbalance_free - free a load balancing structure.
- * @lbalance: the load balancer from lbalance_new.
- *
- * Also frees any tasks still attached.
- */
-void lbalance_free(struct lbalance *lbalance);
 #endif /* CCAN_LBALANCE_H */