From e68790d579316e52d660f0f56a32e9117a0c8dd4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian@centricular.com>
Date: Tue, 16 Nov 2021 18:19:03 +0200
Subject: [PATCH] gstreamer: Directly format into a `NUL`-terminated C string
 for debug log messages

And also replace `%` with `%%` for < 1.20 inline, and for >= 1.20 use
the new `gst_debug_log_literal()` function that doesn't require this and
also reduces string allocations further.
---
 gstreamer/src/log.rs | 75 ++++++++++++++++++++++++++++++++++++++------
 1 file changed, 65 insertions(+), 10 deletions(-)

diff --git a/gstreamer/src/log.rs b/gstreamer/src/log.rs
index cb0099692..297ca0332 100644
--- a/gstreamer/src/log.rs
+++ b/gstreamer/src/log.rs
@@ -155,6 +155,7 @@ impl DebugCategory {
 
     #[inline]
     #[doc(alias = "gst_debug_log")]
+    #[doc(alias = "gst_debug_log_literal")]
     pub fn log<O: IsA<glib::Object>>(
         self,
         obj: Option<&O>,
@@ -180,16 +181,70 @@ impl DebugCategory {
             None => ptr::null_mut(),
         };
 
-        unsafe {
-            ffi::gst_debug_log(
-                cat.as_ptr(),
-                level.into_glib(),
-                file.to_glib_none().0,
-                module.to_glib_none().0,
-                line as i32,
-                obj_ptr,
-                fmt::format(args).replace("%", "%%").to_glib_none().0,
-            );
+        #[cfg(feature = "v1_20")]
+        {
+            let mut w = glib::GStringBuilder::default();
+
+            // Can't really happen but better safe than sorry
+            if fmt::write(&mut w, args).is_err() {
+                return;
+            }
+
+            unsafe {
+                ffi::gst_debug_log_literal(
+                    cat.as_ptr(),
+                    level.into_glib(),
+                    file.to_glib_none().0,
+                    module.to_glib_none().0,
+                    line as i32,
+                    obj_ptr,
+                    w.into_string().to_glib_none().0,
+                );
+            }
+        }
+        #[cfg(not(feature = "v1_20"))]
+        {
+            // Replace literal percentage signs with two so that they are not interpreted as printf
+            // format specifiers
+            struct Write(glib::GStringBuilder);
+            impl fmt::Write for Write {
+                fn write_str(&mut self, mut s: &str) -> Result<(), fmt::Error> {
+                    while let Some((prefix, suffix)) = s.split_once('%') {
+                        self.0.append(prefix);
+                        self.0.append("%%");
+                        s = suffix;
+                    }
+                    self.0.append(s);
+                    Ok(())
+                }
+
+                fn write_char(&mut self, c: char) -> fmt::Result {
+                    if c == '%' {
+                        self.0.append("%%");
+                    } else {
+                        self.0.append_c(c);
+                    }
+                    Ok(())
+                }
+            }
+            let mut w = Write(glib::GStringBuilder::default());
+
+            // Can't really happen but better safe than sorry
+            if fmt::write(&mut w, args).is_err() {
+                return;
+            }
+
+            unsafe {
+                ffi::gst_debug_log(
+                    cat.as_ptr(),
+                    level.into_glib(),
+                    file.to_glib_none().0,
+                    module.to_glib_none().0,
+                    line as i32,
+                    obj_ptr,
+                    w.0.into_string().to_glib_none().0,
+                );
+            }
         }
     }