[RFC PATCH v3 2/5] Refactor scan_fdinfo and decode-fd functions

[Sahil Siddiq]

Create fdinfo struct. scan_fdinfo can use this
struct to track which fd-specific fields are
available in one pass of /proc/<pid>/fdinfo<fd>.

* src/util.c
  (fdinfo): New struct.
  (scan_fdinfo): Use this struct.
  (get_finfo_for_dev): Likewise.
  (pidfd_get_pid): Likewise.
  (printsignalfd): Likewise.

Signed-off-by: Sahil Siddiq <icegambit91 at gmail.com>
---
Changes v2 -> v3: New commit
- src/util.c
  (fdinfo): New struct.
  (scan_fdinfo): Refactor to use this struct.
  (get_finfo_for_dev): Likewise.
  (pidfd_get_pid): Likewise.
  (printsignalfd): Likewise.

 src/util.c | 69 +++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 53 insertions(+), 16 deletions(-)

diff --git a/src/util.c b/src/util.c
index 4140cb718..f558d342c 100644
--- a/src/util.c
+++ b/src/util.c
@@ -647,9 +647,16 @@ printsocket(struct tcb *tcp, int fd, const char *path)
 
 typedef bool (*scan_fdinfo_fn)(const char *value, void *data);
 
-static bool
-scan_fdinfo(pid_t pid_of_fd, int fd, const char *search_pfx,
-	    size_t search_pfx_len, scan_fdinfo_fn fn, void *data)
+struct fdinfo {
+	const char *search_pfx;
+	size_t search_pfx_len;
+	scan_fdinfo_fn fn;
+	void *data;
+};
+
+static size_t
+scan_fdinfo(pid_t pid_of_fd, int fd, struct fdinfo *fdinfo_search_array,
+            size_t fdinfo_array_size)
 {
 	int proc_pid = 0;
 	translate_pid(NULL, pid_of_fd, PT_TID, &proc_pid);
@@ -665,21 +672,26 @@ scan_fdinfo(pid_t pid_of_fd, int fd, const char *search_pfx,
 
 	char *line = NULL;
 	size_t sz = 0;
-	bool result = false;
+	size_t prefix_matches = 0;
 
 	while (getline(&line, &sz, f) > 0) {
-		const char *value =
-			str_strip_prefix_len(line, search_pfx, search_pfx_len);
-		if (value != line && fn(value, data)) {
-			result = true;
-			break;
+		for (size_t i = 0; i < fdinfo_array_size ; i++) {
+			scan_fdinfo_fn fn = fdinfo_search_array[i].fn;
+			void *data =  fdinfo_search_array[i].data;
+			const char *value =
+				str_strip_prefix_len(line, fdinfo_search_array[i].search_pfx,
+				                     fdinfo_search_array[i].search_pfx_len);
+			if (value != line && fn(value, data)) {
+				prefix_matches += 1;
+				break;
+			}
 		}
 	}
 
 	free(line);
 	fclose(f);
 
-	return result;
+	return prefix_matches;
 }
 
 static bool
@@ -734,8 +746,17 @@ get_finfo_for_dev(pid_t pid, int fd, const char *path, struct finfo *finfo)
 		static const char prefix[] = "tty-index:\t";
 
 		finfo->dev.tty_index = -1;
-		scan_fdinfo(pid, fd, prefix, sizeof(prefix) - 1,
-			    set_tty_index, finfo);
+
+		struct fdinfo fdinfo_lines[] = {
+			{
+				.search_pfx = prefix,
+				.search_pfx_len = sizeof(prefix) - 1,
+				.fn = set_tty_index,
+				.data = finfo
+			}
+		};
+
+		scan_fdinfo(pid, fd, fdinfo_lines, ARRAY_SIZE(fdinfo_lines));
 	}
 
 	return finfo;
@@ -785,8 +806,16 @@ pidfd_get_pid(pid_t pid_of_fd, int fd)
 	static const char pid_pfx[] = "Pid:\t";
 	pid_t pid = -1;
 
-	scan_fdinfo(pid_of_fd, fd, pid_pfx, sizeof(pid_pfx) - 1,
-		    parse_fdinfo_pid, &pid);
+	struct fdinfo fdinfo_lines[] = {
+		{
+			.search_pfx = pid_pfx,
+			.search_pfx_len = sizeof(pid_pfx) - 1,
+			.fn = parse_fdinfo_pid,
+			.data = &pid
+		}
+	};
+
+	scan_fdinfo(pid_of_fd, fd, fdinfo_lines, ARRAY_SIZE(fdinfo_lines));
 	return pid;
 }
 
@@ -854,8 +883,16 @@ printsignalfd(pid_t pid_of_fd, int fd, const char *path)
 	if (strcmp(path, signalfd_path))
 		return false;
 
-	return scan_fdinfo(pid_of_fd, fd, sigmask_pfx, sizeof(sigmask_pfx) - 1,
-			   print_fdinfo_sigmask, NULL);
+	struct fdinfo fdinfo_lines[] = {
+		{
+			.search_pfx = sigmask_pfx,
+			.search_pfx_len = sizeof(sigmask_pfx) - 1,
+			.fn = print_fdinfo_sigmask,
+			.data = NULL
+		}
+	};
+
+	return scan_fdinfo(pid_of_fd, fd, fdinfo_lines, ARRAY_SIZE(fdinfo_lines));
 }
 
 static void
-- 
2.45.0