Add html.escape_string

core/html/escape.odin

@@ -0,0 +1,59 @@
+package html
+
+// escape_string escapes special characters like '&' to become '&'.
+// It escapes only 5 different characters: & ' < > and ".
+@(require_results)
+escape_string :: proc(s: string, allocator := context.allocator, loc := #caller_location) -> (output: string, was_allocation: bool) {
+	/*
+		& -> &amp;
+		' -> &#39; // &#39; is shorter than &apos; (NOTE: &apos; was not available until HTML 5)
+		< -> &lt;
+		> -> &gt;
+		" -> &#34; // &#34; is shorter than &quot;
+	*/
+
+	b := transmute([]byte)s
+
+	extra_bytes_needed := 0
+
+	for c in b {
+		switch c {
+		case '&':  extra_bytes_needed += 4
+		case '\'': extra_bytes_needed += 4
+		case '<':  extra_bytes_needed += 3
+		case '>':  extra_bytes_needed += 3
+		case '"':  extra_bytes_needed += 4
+		}
+	}
+
+	if extra_bytes_needed == 0 {
+		return s, false
+	}
+
+	t, err := make([]byte, len(s) + extra_bytes_needed, allocator, loc)
+	if err != nil {
+		return
+	}
+	was_allocation = true
+
+	w := 0
+	for c in b {
+		s := ""
+		switch c {
+		case '&':  s = "&amp;"
+		case '\'': s = "&#39;"
+		case '<':  s = "&lt;"
+		case '>':  s = "&gt;"
+		case '"':  s = "&#34;"
+		}
+		if s != "" {
+			copy(t[w:], s)
+			w += len(s)
+		} else {
+			t[w] = c
+			w += 1
+		}
+	}
+	output = string(t[0:w])
+	return
+}