[gjs] utils: Add inline function to remove from unsorted vectors

[Philip Chimento <pchimento src gnome org>]

commit 5ca326a66cc6cfb7b1fdcfbf0f4a1da66f63e8fa
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Sun May 16 17:27:05 2021 +0200

    utils: Add inline function to remove from unsorted vectors
    
    Erasing a value from a vector can be very verbose in C++, mostly if we
    want to use some optimized path.
    
    So add a generic function to handle it for the case of unsorted vectors
    (the ones we care mostly in gjs).

 gi/utils-inl.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
---
diff --git a/gi/utils-inl.h b/gi/utils-inl.h
index bcd85876..a8155bcd 100644
--- a/gi/utils-inl.h
+++ b/gi/utils-inl.h
@@ -7,6 +7,8 @@
 #include <stdint.h>
 
 #include <type_traits>  // IWYU pragma: keep
+#include <utility>
+#include <vector>
 
 template <typename T>
 constexpr void* gjs_int_to_pointer(T v) {
@@ -37,3 +39,23 @@ template <>
 inline bool gjs_pointer_to_int<bool>(void* p) {
     return !!gjs_pointer_to_int<int8_t>(p);
 }
+
+namespace Gjs {
+
+template <typename T>
+inline bool remove_one_from_unsorted_vector(std::vector<T>* v, const T& value) {
+    // This assumes that there's only a copy of the same value in the vector
+    // so this needs to be ensured when populating it.
+    // We use the swap and pop idiom to avoid moving all the values.
+    auto it = std::find(v->begin(), v->end(), value);
+    if (it != v->end()) {
+        std::swap(*it, v->back());
+        v->pop_back();
+        g_assert(std::find(v->begin(), v->end(), value) == v->end());
+        return true;
+    }
+
+    return false;
+}
+
+}  // namespace Gjs