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-rw-r--r--ext/lib/ucs2length.js16
1 files changed, 16 insertions, 0 deletions
diff --git a/ext/lib/ucs2length.js b/ext/lib/ucs2length.js
new file mode 100644
index 00000000..120a64d4
--- /dev/null
+++ b/ext/lib/ucs2length.js
@@ -0,0 +1,16 @@
+export default function ucs2length(str) {
+ const len = str.length;
+ let length = 0;
+ let pos = 0;
+ let value;
+ while (pos < len) {
+ length++;
+ value = str.charCodeAt(pos++);
+ if (value >= 0xd800 && value <= 0xdbff && pos < len) {
+ // high surrogate, and there is a next character
+ value = str.charCodeAt(pos);
+ if ((value & 0xfc00) === 0xdc00) pos++; // low surrogate
+ }
+ }
+ return length;
+}