--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/source/pdf/pdf-unicode.c	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,157 @@
+// Copyright (C) 2004-2021 Artifex Software, Inc.
+//
+// This file is part of MuPDF.
+//
+// MuPDF is free software: you can redistribute it and/or modify it under the
+// terms of the GNU Affero General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// MuPDF is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+// FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+// details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with MuPDF. If not, see <https://www.gnu.org/licenses/agpl-3.0.en.html>
+//
+// Alternative licensing terms are available from the licensor.
+// For commercial licensing, see <https://www.artifex.com/> or contact
+// Artifex Software, Inc., 39 Mesa Street, Suite 108A, San Francisco,
+// CA 94129, USA, for further information.
+
+#include "mupdf/fitz.h"
+#include "mupdf/pdf.h"
+
+#include <string.h>
+
+/* Load or synthesize ToUnicode map for fonts */
+
+static void
+pdf_remap_cmap_range(fz_context *ctx, pdf_cmap *ucs_from_gid,
+	unsigned int cpt, unsigned int gid, unsigned int n, pdf_cmap *ucs_from_cpt)
+{
+	unsigned int k;
+	int ucsbuf[PDF_MRANGE_CAP];
+	int ucslen;
+
+	for (k = 0; k <= n; ++k)
+	{
+		ucslen = pdf_lookup_cmap_full(ucs_from_cpt, cpt + k, ucsbuf);
+		if (ucslen == 1)
+			pdf_map_range_to_range(ctx, ucs_from_gid, gid + k, gid + k, ucsbuf[0]);
+		else if (ucslen > 1)
+			pdf_map_one_to_many(ctx, ucs_from_gid, gid + k, ucsbuf, ucslen);
+	}
+}
+
+static pdf_cmap *
+pdf_remap_cmap(fz_context *ctx, pdf_cmap *gid_from_cpt, pdf_cmap *ucs_from_cpt)
+{
+	pdf_cmap *ucs_from_gid;
+	unsigned int a, b, x;
+	int i;
+
+	ucs_from_gid = pdf_new_cmap(ctx);
+
+	fz_try(ctx)
+	{
+		if (gid_from_cpt->usecmap)
+			ucs_from_gid->usecmap = pdf_remap_cmap(ctx, gid_from_cpt->usecmap, ucs_from_cpt);
+
+		pdf_add_codespace(ctx, ucs_from_gid, 0, 0x7fffffff, 4);
+
+		for (i = 0; i < gid_from_cpt->rlen; ++i)
+		{
+			a = gid_from_cpt->ranges[i].low;
+			b = gid_from_cpt->ranges[i].high;
+			x = gid_from_cpt->ranges[i].out;
+			pdf_remap_cmap_range(ctx, ucs_from_gid, a, x, b - a, ucs_from_cpt);
+		}
+
+		for (i = 0; i < gid_from_cpt->xlen; ++i)
+		{
+			a = gid_from_cpt->xranges[i].low;
+			b = gid_from_cpt->xranges[i].high;
+			x = gid_from_cpt->xranges[i].out;
+			pdf_remap_cmap_range(ctx, ucs_from_gid, a, x, b - a, ucs_from_cpt);
+		}
+
+		/* Font encoding CMaps don't have one-to-many mappings, so we can ignore the mranges. */
+
+		pdf_sort_cmap(ctx, ucs_from_gid);
+	}
+	fz_catch(ctx)
+	{
+		pdf_drop_cmap(ctx, ucs_from_gid);
+		fz_rethrow(ctx);
+	}
+
+	return ucs_from_gid;
+}
+
+void
+pdf_load_to_unicode(fz_context *ctx, pdf_document *doc, pdf_font_desc *font,
+	const char **strings, char *collection, pdf_obj *cmapstm)
+{
+	unsigned int cpt;
+
+	if (pdf_is_stream(ctx, cmapstm))
+	{
+		pdf_cmap *ucs_from_cpt = pdf_load_embedded_cmap(ctx, doc, cmapstm);
+		fz_try(ctx)
+			font->to_unicode = pdf_remap_cmap(ctx, font->encoding, ucs_from_cpt);
+		fz_always(ctx)
+			pdf_drop_cmap(ctx, ucs_from_cpt);
+		fz_catch(ctx)
+			fz_rethrow(ctx);
+		font->size += pdf_cmap_size(ctx, font->to_unicode);
+	}
+
+	else if (pdf_is_name(ctx, cmapstm))
+	{
+		pdf_cmap *ucs_from_cpt = pdf_load_system_cmap(ctx, pdf_to_name(ctx, cmapstm));
+		fz_try(ctx)
+			font->to_unicode = pdf_remap_cmap(ctx, font->encoding, ucs_from_cpt);
+		fz_always(ctx)
+			pdf_drop_cmap(ctx, ucs_from_cpt);
+		fz_catch(ctx)
+			fz_rethrow(ctx);
+		font->size += pdf_cmap_size(ctx, font->to_unicode);
+	}
+
+	else if (collection)
+	{
+		if (!strcmp(collection, "Adobe-CNS1"))
+			font->to_unicode = pdf_load_system_cmap(ctx, "Adobe-CNS1-UCS2");
+		else if (!strcmp(collection, "Adobe-GB1"))
+			font->to_unicode = pdf_load_system_cmap(ctx, "Adobe-GB1-UCS2");
+		else if (!strcmp(collection, "Adobe-Japan1"))
+			font->to_unicode = pdf_load_system_cmap(ctx, "Adobe-Japan1-UCS2");
+		else if (!strcmp(collection, "Adobe-Korea1"))
+			font->to_unicode = pdf_load_system_cmap(ctx, "Adobe-Korea1-UCS2");
+	}
+
+	if (strings)
+	{
+		/* TODO one-to-many mappings */
+
+		font->cid_to_ucs = Memento_label(fz_malloc_array(ctx, 256, unsigned short), "cid_to_ucs");
+		font->cid_to_ucs_len = 256;
+		font->size += 256 * sizeof *font->cid_to_ucs;
+
+		for (cpt = 0; cpt < 256; cpt++)
+		{
+			if (strings[cpt])
+				font->cid_to_ucs[cpt] = fz_unicode_from_glyph_name(strings[cpt]);
+			else
+				font->cid_to_ucs[cpt] = FZ_REPLACEMENT_CHARACTER;
+		}
+	}
+
+	if (!font->to_unicode && !font->cid_to_ucs)
+	{
+		/* TODO: synthesize a ToUnicode if it's a freetype font with
+		 * cmap and/or post tables or if it has glyph names. */
+	}
+}