lua: minimal UTF-16 support needed for LSP

1 files changed, 18 insertions, 0 deletions

diff --git a/runtime/doc/if_lua.txt b/runtime/doc/if_lua.txt
index 7ddcb6cc92..a9b8c5fae8 100644
--- a/runtime/doc/if_lua.txt
+++ b/runtime/doc/if_lua.txt
@@ -459,6 +459,24 @@ vim.stricmp({a}, {b})					*vim.stricmp()*
         are equal, {a} is greater than {b} or {a} is lesser than {b},
         respectively.
 
+vim.str_utfindex({str}[, {index}])			*vim.str_utfindex()*
+        Convert byte index to UTF-32 and UTF-16 indicies. If {index} is not
+        supplied, the length of the string is used. All indicies are zero-based.
+        Returns two values: the UTF-32 and UTF-16 indicies respectively.
+
+        Embedded NUL bytes are treated as terminating the string. Invalid
+        UTF-8 bytes, and embedded surrogates are counted as one code
+        point each. An {index} in the middle of a UTF-8 sequence is rounded
+        upwards to the end of that sequence.
+
+vim.str_byteindex({str}, {index}[, {use_utf16}])	*vim.str_byteindex()*
+        Convert UTF-32 or UTF-16 {index} to byte index. If {use_utf16} is not
+        supplied, it defaults to false (use UTF-32). Returns the byte index.
+
+        Invalid UTF-8 and NUL is treated like by |vim.str_byteindex()|. An {index}
+        in the middle of a UTF-16 sequence is rounded upwards to the end of that
+        sequence.
+
 vim.schedule({callback})				*vim.schedule()*
         Schedules {callback} to be invoked soon by the main event-loop. Useful
         to avoid |textlock| or other temporary restrictions.