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

@@ -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);
+}