fsmonitor-ipc: create client routines for git-fsmonitor--daemon

Create fsmonitor_ipc__*() client routines to spawn the built-in file
system monitor daemon and send it an IPC request using the `Simple
IPC` API.

Stub in empty fsmonitor_ipc__*() functions for unsupported platforms.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 171 insertions, 0 deletions

diff --git a/fsmonitor-ipc.c b/fsmonitor-ipc.c
new file mode 100644
index 0000000000..789e7397ba
--- /dev/null
+++ b/fsmonitor-ipc.c
@@ -0,0 +1,171 @@
+#include "cache.h"
+#include "fsmonitor.h"
+#include "simple-ipc.h"
+#include "fsmonitor-ipc.h"
+#include "run-command.h"
+#include "strbuf.h"
+#include "trace2.h"
+
+#ifndef HAVE_FSMONITOR_DAEMON_BACKEND
+
+/*
+ * A trivial implementation of the fsmonitor_ipc__ API for unsupported
+ * platforms.
+ */
+
+int fsmonitor_ipc__is_supported(void)
+{
+	return 0;
+}
+
+const char *fsmonitor_ipc__get_path(void)
+{
+	return NULL;
+}
+
+enum ipc_active_state fsmonitor_ipc__get_state(void)
+{
+	return IPC_STATE__OTHER_ERROR;
+}
+
+int fsmonitor_ipc__send_query(const char *since_token,
+			      struct strbuf *answer)
+{
+	return -1;
+}
+
+int fsmonitor_ipc__send_command(const char *command,
+				struct strbuf *answer)
+{
+	return -1;
+}
+
+#else
+
+int fsmonitor_ipc__is_supported(void)
+{
+	return 1;
+}
+
+GIT_PATH_FUNC(fsmonitor_ipc__get_path, "fsmonitor--daemon.ipc")
+
+enum ipc_active_state fsmonitor_ipc__get_state(void)
+{
+	return ipc_get_active_state(fsmonitor_ipc__get_path());
+}
+
+static int spawn_daemon(void)
+{
+	const char *args[] = { "fsmonitor--daemon", "start", NULL };
+
+	return run_command_v_opt_tr2(args, RUN_COMMAND_NO_STDIN | RUN_GIT_CMD,
+				    "fsmonitor");
+}
+
+int fsmonitor_ipc__send_query(const char *since_token,
+			      struct strbuf *answer)
+{
+	int ret = -1;
+	int tried_to_spawn = 0;
+	enum ipc_active_state state = IPC_STATE__OTHER_ERROR;
+	struct ipc_client_connection *connection = NULL;
+	struct ipc_client_connect_options options
+		= IPC_CLIENT_CONNECT_OPTIONS_INIT;
+	const char *tok = since_token ? since_token : "";
+	size_t tok_len = since_token ? strlen(since_token) : 0;
+
+	options.wait_if_busy = 1;
+	options.wait_if_not_found = 0;
+
+	trace2_region_enter("fsm_client", "query", NULL);
+	trace2_data_string("fsm_client", NULL, "query/command", tok);
+
+try_again:
+	state = ipc_client_try_connect(fsmonitor_ipc__get_path(), &options,
+				       &connection);
+
+	switch (state) {
+	case IPC_STATE__LISTENING:
+		ret = ipc_client_send_command_to_connection(
+			connection, tok, tok_len, answer);
+		ipc_client_close_connection(connection);
+
+		trace2_data_intmax("fsm_client", NULL,
+				   "query/response-length", answer->len);
+		goto done;
+
+	case IPC_STATE__NOT_LISTENING:
+	case IPC_STATE__PATH_NOT_FOUND:
+		if (tried_to_spawn)
+			goto done;
+
+		tried_to_spawn++;
+		if (spawn_daemon())
+			goto done;
+
+		/*
+		 * Try again, but this time give the daemon a chance to
+		 * actually create the pipe/socket.
+		 *
+		 * Granted, the daemon just started so it can't possibly have
+		 * any FS cached yet, so we'll always get a trivial answer.
+		 * BUT the answer should include a new token that can serve
+		 * as the basis for subsequent requests.
+		 */
+		options.wait_if_not_found = 1;
+		goto try_again;
+
+	case IPC_STATE__INVALID_PATH:
+		ret = error(_("fsmonitor_ipc__send_query: invalid path '%s'"),
+			    fsmonitor_ipc__get_path());
+		goto done;
+
+	case IPC_STATE__OTHER_ERROR:
+	default:
+		ret = error(_("fsmonitor_ipc__send_query: unspecified error on '%s'"),
+			    fsmonitor_ipc__get_path());
+		goto done;
+	}
+
+done:
+	trace2_region_leave("fsm_client", "query", NULL);
+
+	return ret;
+}
+
+int fsmonitor_ipc__send_command(const char *command,
+				struct strbuf *answer)
+{
+	struct ipc_client_connection *connection = NULL;
+	struct ipc_client_connect_options options
+		= IPC_CLIENT_CONNECT_OPTIONS_INIT;
+	int ret;
+	enum ipc_active_state state;
+	const char *c = command ? command : "";
+	size_t c_len = command ? strlen(command) : 0;
+
+	strbuf_reset(answer);
+
+	options.wait_if_busy = 1;
+	options.wait_if_not_found = 0;
+
+	state = ipc_client_try_connect(fsmonitor_ipc__get_path(), &options,
+				       &connection);
+	if (state != IPC_STATE__LISTENING) {
+		die(_("fsmonitor--daemon is not running"));
+		return -1;
+	}
+
+	ret = ipc_client_send_command_to_connection(connection, c, c_len,
+						    answer);
+	ipc_client_close_connection(connection);
+
+	if (ret == -1) {
+		die(_("could not send '%s' command to fsmonitor--daemon"), c);
+		return -1;
+	}
+
+	return 0;
+}
+
+#endif