--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/mujs/jsintern.c	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,137 @@
+#include "jsi.h"
+
+/* Dynamically grown string buffer */
+
+void js_putc(js_State *J, js_Buffer **sbp, int c)
+{
+	js_Buffer *sb = *sbp;
+	if (!sb) {
+		sb = js_malloc(J, sizeof *sb);
+		sb->n = 0;
+		sb->m = sizeof sb->s;
+		*sbp = sb;
+	} else if (sb->n == sb->m) {
+		sb = js_realloc(J, sb, (sb->m *= 2) + soffsetof(js_Buffer, s));
+		*sbp = sb;
+	}
+	sb->s[sb->n++] = c;
+}
+
+void js_puts(js_State *J, js_Buffer **sb, const char *s)
+{
+	while (*s)
+		js_putc(J, sb, *s++);
+}
+
+void js_putm(js_State *J, js_Buffer **sb, const char *s, const char *e)
+{
+	while (s < e)
+		js_putc(J, sb, *s++);
+}
+
+/* Use an AA-tree to quickly look up interned strings. */
+
+struct js_StringNode
+{
+	js_StringNode *left, *right;
+	int level;
+	char string[1];
+};
+
+static js_StringNode jsS_sentinel = { &jsS_sentinel, &jsS_sentinel, 0, ""};
+
+static js_StringNode *jsS_newstringnode(js_State *J, const char *string, const char **result)
+{
+	size_t n = strlen(string);
+	if (n > JS_STRLIMIT)
+		js_rangeerror(J, "invalid string length");
+	js_StringNode *node = js_malloc(J, soffsetof(js_StringNode, string) + n + 1);
+	node->left = node->right = &jsS_sentinel;
+	node->level = 1;
+	memcpy(node->string, string, n + 1);
+	return *result = node->string, node;
+}
+
+static js_StringNode *jsS_skew(js_StringNode *node)
+{
+	if (node->left->level == node->level) {
+		js_StringNode *temp = node;
+		node = node->left;
+		temp->left = node->right;
+		node->right = temp;
+	}
+	return node;
+}
+
+static js_StringNode *jsS_split(js_StringNode *node)
+{
+	if (node->right->right->level == node->level) {
+		js_StringNode *temp = node;
+		node = node->right;
+		temp->right = node->left;
+		node->left = temp;
+		++node->level;
+	}
+	return node;
+}
+
+static js_StringNode *jsS_insert(js_State *J, js_StringNode *node, const char *string, const char **result)
+{
+	if (node != &jsS_sentinel) {
+		int c = strcmp(string, node->string);
+		if (c < 0)
+			node->left = jsS_insert(J, node->left, string, result);
+		else if (c > 0)
+			node->right = jsS_insert(J, node->right, string, result);
+		else
+			return *result = node->string, node;
+		node = jsS_skew(node);
+		node = jsS_split(node);
+		return node;
+	}
+	return jsS_newstringnode(J, string, result);
+}
+
+static void dumpstringnode(js_StringNode *node, int level)
+{
+	int i;
+	if (node->left != &jsS_sentinel)
+		dumpstringnode(node->left, level + 1);
+	printf("%d: ", node->level);
+	for (i = 0; i < level; ++i)
+		putchar('\t');
+	printf("'%s'\n", node->string);
+	if (node->right != &jsS_sentinel)
+		dumpstringnode(node->right, level + 1);
+}
+
+void jsS_dumpstrings(js_State *J)
+{
+	js_StringNode *root = J->strings;
+	printf("interned strings {\n");
+	if (root && root != &jsS_sentinel)
+		dumpstringnode(root, 1);
+	printf("}\n");
+}
+
+static void jsS_freestringnode(js_State *J, js_StringNode *node)
+{
+	if (node->left != &jsS_sentinel) jsS_freestringnode(J, node->left);
+	if (node->right != &jsS_sentinel) jsS_freestringnode(J, node->right);
+	js_free(J, node);
+}
+
+void jsS_freestrings(js_State *J)
+{
+	if (J->strings && J->strings != &jsS_sentinel)
+		jsS_freestringnode(J, J->strings);
+}
+
+const char *js_intern(js_State *J, const char *s)
+{
+	const char *result;
+	if (!J->strings)
+		J->strings = &jsS_sentinel;
+	J->strings = jsS_insert(J, J->strings, s, &result);
+	return result;
+}