crit: add FindPs method on PsTree

crit/utils.go

@@ -232,3 +232,17 @@ func getUnixSkFilePath(dir string, file *fdinfo.FileEntry, fID uint32) (string,
 
 	return "unix[?]", nil
 }
+
+// FindPs performs a short-circuiting depth-first search to find
+// a process with a given PID in a process tree.
+func (ps *PsTree) FindPs(pid uint32) *PsTree {
+	if ps.PID == pid {
+		return ps
+	}
+	for _, child := range ps.Children {
+		if process := child.FindPs(pid); process != nil {
+			return process
+		}
+	}
+	return nil
+}

crit/utils_test.go

@@ -0,0 +1,45 @@
+package crit
+
+import (
+	"testing"
+)
+
+func TestFindPs(t *testing.T) {
+	root := &PsTree{
+		PID: 1,
+		Children: []*PsTree{
+			{
+				PID: 2,
+				Children: []*PsTree{
+					{
+						PID: 3,
+					},
+				},
+			},
+			{
+				PID: 4,
+				Children: []*PsTree{
+					{
+						PID: 5,
+					},
+				},
+			},
+		},
+	}
+
+	// Test Case 1: Find an existing process with a valid PID
+	ps := root.FindPs(3)
+	if ps == nil {
+		t.Errorf("FindPs(3) returned nil, expected a valid process")
+	}
+	if ps != nil && ps.PID != 3 {
+		t.Errorf("FindPs(3) returned a process with PID %d, expected 3", ps.PID)
+	}
+
+	// Test Case 2: Find a non-existing process with an invalid PID
+	nonExistentPID := uint32(999)
+	notFoundProcess := root.FindPs(nonExistentPID)
+	if notFoundProcess != nil {
+		t.Errorf("FindPs(%d) returned a process, expected nil", nonExistentPID)
+	}
+}