Add generic filter/plugin infrastructure

The functions cgit_open_filter() and cgit_close_filter() can be used to
execute filters on the output stream from cgit.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/shared.c b/shared.c

index cce0af4..288cfa2 100644
--- a/shared.c
+++ b/shared.c
@@ -355,3 +355,38 @@ int cgit_parse_snapshots_mask(const char *str)
 	}
 	return rv;
 }
+
+int cgit_open_filter(struct cgit_filter *filter)
+{
+
+	filter->old_stdout = chk_positive(dup(STDOUT_FILENO),
+		"Unable to duplicate STDOUT");
+	chk_zero(pipe(filter->pipe_fh), "Unable to create pipe to subprocess");
+	filter->pid = chk_non_negative(fork(), "Unable to create subprocess");
+	if (filter->pid == 0) {
+		close(filter->pipe_fh[1]);
+		chk_non_negative(dup2(filter->pipe_fh[0], STDIN_FILENO),
+			"Unable to use pipe as STDIN");
+		execvp(filter->cmd, filter->argv);
+		die("Unable to exec subprocess %s: %s (%d)", filter->cmd,
+			strerror(errno), errno);
+	}
+	close(filter->pipe_fh[0]);
+	chk_non_negative(dup2(filter->pipe_fh[1], STDOUT_FILENO),
+		"Unable to use pipe as STDOUT");
+	close(filter->pipe_fh[1]);
+	return 0;
+}
+
+int cgit_close_filter(struct cgit_filter *filter)
+{
+	chk_non_negative(dup2(filter->old_stdout, STDOUT_FILENO),
+		"Unable to restore STDOUT");
+	close(filter->old_stdout);
+	if (filter->pid < 0)
+		return 0;
+	waitpid(filter->pid, &filter->exitstatus, 0);
+	if (WIFEXITED(filter->exitstatus) && !WEXITSTATUS(filter->exitstatus))
+		return 0;
+	die("Subprocess %s exited abnormally", filter->cmd);
+}