Add infrastructure to run a function asynchronously.
This adds start_async() and finish_async(), which runs a function
asynchronously. Communication with the caller happens only via pipes.
For this reason, this implementation forks off a child process that runs
the function.
[sp: Style nit fixed by removing unnecessary block on if condition
inside of start_async()]
Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
diff --git a/run-command.c b/run-command.c
index d00c03b..d99a6c4 100644
--- a/run-command.c
+++ b/run-command.c
@@ -127,16 +127,11 @@
return 0;
}
-int finish_command(struct child_process *cmd)
+static int wait_or_whine(pid_t pid)
{
- if (cmd->close_in)
- close(cmd->in);
- if (cmd->close_out)
- close(cmd->out);
-
for (;;) {
int status, code;
- pid_t waiting = waitpid(cmd->pid, &status, 0);
+ pid_t waiting = waitpid(pid, &status, 0);
if (waiting < 0) {
if (errno == EINTR)
@@ -144,7 +139,7 @@
error("waitpid failed (%s)", strerror(errno));
return -ERR_RUN_COMMAND_WAITPID;
}
- if (waiting != cmd->pid)
+ if (waiting != pid)
return -ERR_RUN_COMMAND_WAITPID_WRONG_PID;
if (WIFSIGNALED(status))
return -ERR_RUN_COMMAND_WAITPID_SIGNAL;
@@ -158,6 +153,15 @@
}
}
+int finish_command(struct child_process *cmd)
+{
+ if (cmd->close_in)
+ close(cmd->in);
+ if (cmd->close_out)
+ close(cmd->out);
+ return wait_or_whine(cmd->pid);
+}
+
int run_command(struct child_process *cmd)
{
int code = start_command(cmd);
@@ -200,3 +204,34 @@
cmd.env = env;
return run_command(&cmd);
}
+
+int start_async(struct async *async)
+{
+ int pipe_out[2];
+
+ if (pipe(pipe_out) < 0)
+ return error("cannot create pipe: %s", strerror(errno));
+
+ async->pid = fork();
+ if (async->pid < 0) {
+ error("fork (async) failed: %s", strerror(errno));
+ close_pair(pipe_out);
+ return -1;
+ }
+ if (!async->pid) {
+ close(pipe_out[0]);
+ exit(!!async->proc(pipe_out[1], async->data));
+ }
+ async->out = pipe_out[0];
+ close(pipe_out[1]);
+ return 0;
+}
+
+int finish_async(struct async *async)
+{
+ int ret = 0;
+
+ if (wait_or_whine(async->pid))
+ ret = error("waitpid (async) failed");
+ return ret;
+}
diff --git a/run-command.h b/run-command.h
index 35b9fb6..94e1e9d 100644
--- a/run-command.h
+++ b/run-command.h
@@ -43,4 +43,26 @@
*/
int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env);
+/*
+ * The purpose of the following functions is to feed a pipe by running
+ * a function asynchronously and providing output that the caller reads.
+ *
+ * It is expected that no synchronization and mutual exclusion between
+ * the caller and the feed function is necessary so that the function
+ * can run in a thread without interfering with the caller.
+ */
+struct async {
+ /*
+ * proc writes to fd and closes it;
+ * returns 0 on success, non-zero on failure
+ */
+ int (*proc)(int fd, void *data);
+ void *data;
+ int out; /* caller reads from here and closes it */
+ pid_t pid;
+};
+
+int start_async(struct async *async);
+int finish_async(struct async *async);
+
#endif
