AK: Add a Utf16View::code_unit_offset_of(Utf16CodePointIterator) helper

This helper can be used to used to retrieve the code unit offset of an
active Utf16CodePointIterator efficiently.

2 files changed, 9 insertions, 0 deletions

diff --git a/AK/Utf16View.cpp b/AK/Utf16View.cpp
index 03fe01d0d9..287b006bd3 100644
--- a/AK/Utf16View.cpp
+++ b/AK/Utf16View.cpp
@@ -165,6 +165,14 @@ size_t Utf16View::code_unit_offset_of(size_t code_point_offset) const
     return code_unit_offset;
 }
 
+size_t Utf16View::code_unit_offset_of(Utf16CodePointIterator const& it) const
+{
+    VERIFY(it.m_ptr >= begin_ptr());
+    VERIFY(it.m_ptr <= end_ptr());
+
+    return it.m_ptr - begin_ptr();
+}
+
 Utf16View Utf16View::substring_view(size_t code_unit_offset, size_t code_unit_length) const
 {
     VERIFY(!Checked<size_t>::addition_would_overflow(code_unit_offset, code_unit_length));
diff --git a/AK/Utf16View.h b/AK/Utf16View.h
index f6906714c4..3fb954b952 100644
--- a/AK/Utf16View.h
+++ b/AK/Utf16View.h
@@ -93,6 +93,7 @@ public:
 
     size_t code_point_offset_of(size_t code_unit_offset) const;
     size_t code_unit_offset_of(size_t code_point_offset) const;
+    size_t code_unit_offset_of(Utf16CodePointIterator const&) const;
 
     Utf16View substring_view(size_t code_unit_offset, size_t code_unit_length) const;
     Utf16View substring_view(size_t code_unit_offset) const { return substring_view(code_unit_offset, length_in_code_units() - code_unit_offset); }