1 files changed, 89 insertions, 0 deletions
diff --git a/internal/log/caller.go b/internal/log/caller.go
new file mode 100644
index 000000000..f7062f06a
--- /dev/null
+++ b/internal/log/caller.go
@@ -0,0 +1,89 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package log
+
+import (
+	"runtime"
+	"strings"
+	"sync"
+)
+
+var (
+	// fnCache is a cache of PCs to their calculated function names.
+	fnCache = map[uintptr]string{}
+
+	// strCache is a cache of strings to the originally allocated version
+	// of that string contents. so we don't have hundreds of the same instances
+	// of string floating around in memory.
+	strCache = map[string]string{}
+
+	// cacheMu protects fnCache and strCache.
+	cacheMu sync.Mutex
+)
+
+// Caller fetches the calling function name, skipping 'depth'. Results are cached per PC.
+func Caller(depth int) string {
+	var rpc [1]uintptr
+
+	// Fetch pcs of callers
+	n := runtime.Callers(depth, rpc[:])
+
+	if n > 0 {
+		// Look for value in cache
+		cacheMu.Lock()
+		fn, ok := fnCache[rpc[0]]
+		cacheMu.Unlock()
+
+		if ok {
+			return fn
+		}
+
+		// Fetch frame info for caller pc
+		frame, _ := runtime.CallersFrames(rpc[:]).Next()
+
+		if frame.PC != 0 {
+			name := frame.Function
+
+			// Drop all but the package name and function name, no mod path
+			if idx := strings.LastIndex(name, "/"); idx >= 0 {
+				name = name[idx+1:]
+			}
+
+			// Drop any generic type parameter markers
+			if idx := strings.Index(name, "[...]"); idx >= 0 {
+				name = name[:idx] + name[idx+5:]
+			}
+
+			// Cache this func name
+			cacheMu.Lock()
+			fn, ok := strCache[name]
+			if !ok {
+				// Cache ptr to this allocated str
+				strCache[name] = name
+				fn = name
+			}
+			fnCache[rpc[0]] = fn
+			cacheMu.Unlock()
+
+			return fn
+		}
+	}
+
+	return "???"
+}