[RFC PATCH 1/5] perf/kselftest: convert prefix.pl to Python

[Breno Rodrigues Alves <breno3011alves@gmail.com>]

Faithful re-implementation of tools/testing/selftests/kselftest/
prefix.pl in Python 3 (stdlib only). Same unbuffered stdin-to-stdout
processing, same "# " prefix behavior.

Verified byte-for-byte identical to the Perl version.

Signed-off-by: Breno Rodrigues Alves <breno3011alves@gmail.com>
---
 tools/testing/selftests/kselftest/prefix.py | 24 +++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100755 tools/testing/selftests/kselftest/prefix.py

diff --git a/tools/testing/selftests/kselftest/prefix.py b/tools/testing/selftests/kselftest/prefix.py
new file mode 100755
index 000000000..2bf16b37d
--- /dev/null
+++ b/tools/testing/selftests/kselftest/prefix.py
@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+# Prefix all lines with "# ", unbuffered.
+
+import sys
+
+
+def main():
+    needed = True
+    while True:
+        char = sys.stdin.buffer.read(1)
+        if not char:
+            return 0
+        if needed:
+            sys.stdout.buffer.write(b"# ")
+            needed = False
+        sys.stdout.buffer.write(char)
+        sys.stdout.buffer.flush()
+        if char == b"\n":
+            needed = True
+
+
+if __name__ == "__main__":
+    sys.exit(main())
\ No newline at end of file
-- 
2.43.0