Initial commit

frontend/node_modules/entities/src/decode-codepoint.ts

@@ -0,0 +1,69 @@
+// Adapted from https://github.com/mathiasbynens/he/blob/36afe179392226cf1b6ccdb16ebbb7a5a844d93a/src/he.js#L106-L134
+
+/**
+ * C1 Unicode control character reference replacements (code points 128–159).
+ * Index i gives the replacement for code point 128+i; 0 means "no replacement".
+ */
+const c1: number[] = [
+    8364, 0, 8218, 402, 8222, 8230, 8224, 8225, 710, 8240, 352, 8249, 338, 0,
+    381, 0, 0, 8216, 8217, 8220, 8221, 8226, 8211, 8212, 732, 8482, 353, 8250,
+    339, 0, 382, 376,
+];
+
+/**
+ * True for NUL, UTF-16 surrogates, and values past U+10FFFF.
+ * @param codePoint Unicode code point to check.
+ */
+function isInvalidCodePoint(codePoint: number): boolean {
+    return (
+        codePoint === 0 ||
+        (codePoint >= 0xd8_00 && codePoint <= 0xdf_ff) ||
+        codePoint > 0x10_ff_ff
+    );
+}
+
+/**
+ * Replace the given code point with U+FFFD if it is NUL (0), a surrogate, or
+ * outside the valid Unicode range. Code points in the C1 controls range
+ * (128–159) are remapped to their Windows-1252 equivalents, following the
+ * HTML spec. All other code points are returned unchanged.
+ * @param codePoint Unicode code point to convert.
+ */
+export function replaceCodePoint(codePoint: number): number {
+    if (isInvalidCodePoint(codePoint)) {
+        return 0xff_fd;
+    }
+
+    if (codePoint >= 128 && codePoint <= 159) {
+        return c1[codePoint - 128] || codePoint;
+    }
+
+    return codePoint;
+}
+
+/**
+ * XML numeric character references are the referenced Unicode code point.
+ * Invalid values still become U+FFFD; the HTML Windows-1252 C1 remap is not
+ * applied.
+ * @see https://www.w3.org/TR/xml/#NT-CharRef
+ * @param codePoint Unicode code point to convert.
+ */
+export function replaceCodePointXML(codePoint: number): number {
+    return isInvalidCodePoint(codePoint) ? 0xff_fd : codePoint;
+}
+
+/**
+ * Convert the code point of a decoded numeric entity to a string, replacing
+ * invalid values.
+ *
+ * Fast path for plain BMP code points: [1..0x7F] and [0xA0..0xD7FF] pass
+ * `replaceCodePoint` unchanged (no NUL, C1 remap, surrogate, or out-of-range
+ * handling) and fit a single charCode. 0xd760 = 0xD800 (the first surrogate)
+ * - 0xA0.
+ * @param codePoint Unicode code point to convert.
+ */
+export function codePointToString(codePoint: number): string {
+    return (codePoint - 1) >>> 0 < 0x7f || (codePoint - 0xa0) >>> 0 < 0xd7_60
+        ? String.fromCharCode(codePoint)
+        : String.fromCodePoint(replaceCodePoint(codePoint));
+}