LibPDF: Add support for builtin and custom Encodings

Userland/Libraries/LibPDF/Encoding.cpp

@@ -0,0 +1,164 @@
+/*
+ * Copyright (c) 2022, Matthew Olsson <mattco@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Utf8View.h>
+#include <LibPDF/CommonNames.h>
+#include <LibPDF/Encoding.h>
+
+namespace PDF {
+
+PDFErrorOr<NonnullRefPtr<Encoding>> Encoding::from_object(Document* document, NonnullRefPtr<Object> const& obj)
+{
+    if (obj->is<NameObject>()) {
+        auto name = obj->cast<NameObject>()->name();
+        if (name == "StandardEncoding")
+            return standard_encoding();
+        if (name == "MacRomanEncoding")
+            return mac_encoding();
+        if (name == "WinAnsiEncoding")
+            return windows_encoding();
+
+        VERIFY_NOT_REACHED();
+    }
+
+    // Make a custom encoding
+    auto dict = obj->cast<DictObject>();
+
+    // FIXME: If this entry is absent, the Differences entry shall describe differences
+    //        from an implicit base encoding. For a font program that is embedded in the
+    //        PDF file, the implicit base encoding shall be a font program's built-in
+    //        encoding [...]. Otherwise, for a nonsymbolic font, it shall be
+    //        StandardEncoding, and for a symbolic font, it shall be the font's built-in
+    //        encoding.
+    auto base_encoding_obj = MUST(dict->get_object(document, CommonNames::BaseEncoding));
+    auto base_encoding = TRY(Encoding::from_object(document, base_encoding_obj));
+    auto encoding = adopt_ref(*new Encoding());
+
+    // Build a String -> Character mapping for handling the differences map
+    HashMap<String, CharDescriptor> base_encoding_name_mapping;
+
+    for (auto& [code_point, descriptor] : base_encoding->descriptors()) {
+        encoding->m_descriptors.set(code_point, descriptor);
+        base_encoding_name_mapping.set(descriptor.name, descriptor);
+    }
+
+    auto differences_array = TRY(dict->get_array(document, CommonNames::Differences));
+    HashMap<u16, String> differences_map;
+
+    u16 current_code_point = 0;
+    bool first = true;
+
+    for (auto& item : *differences_array) {
+        if (item.has_u32()) {
+            current_code_point = item.to_int();
+            first = false;
+        } else {
+            VERIFY(item.has<NonnullRefPtr<Object>>());
+            VERIFY(!first);
+            auto& object = item.get<NonnullRefPtr<Object>>();
+            auto name = object->cast<NameObject>()->name();
+
+            auto character = base_encoding_name_mapping.get(name);
+            VERIFY(character.has_value());
+            encoding->m_descriptors.set(current_code_point, character.value());
+
+            current_code_point++;
+        }
+    }
+
+    return encoding;
+}
+
+NonnullRefPtr<Encoding> Encoding::standard_encoding()
+{
+    static NonnullRefPtr<Encoding> encoding = adopt_ref(*new Encoding());
+    if (encoding->m_descriptors.is_empty()) {
+#define ENUMERATE(string, name, standard_code, mac_code, win_code, pdf_code) \
+    auto name##_code_point = *Utf8View(StringView(string)).begin();          \
+    encoding->m_descriptors.set(standard_code, { string, name##_code_point });
+        ENUMERATE_LATIN_CHARACTER_SET(ENUMERATE)
+#undef ENUMERATE
+    }
+
+    return encoding;
+}
+
+NonnullRefPtr<Encoding> Encoding::mac_encoding()
+{
+    static NonnullRefPtr<Encoding> encoding = adopt_ref(*new Encoding());
+    if (encoding->m_descriptors.is_empty()) {
+#define ENUMERATE(string, name, standard_code, mac_code, win_code, pdf_code) \
+    auto name##_code_point = *Utf8View(StringView(string)).begin();          \
+    encoding->m_descriptors.set(mac_code, { string, name##_code_point });
+        ENUMERATE_LATIN_CHARACTER_SET(ENUMERATE)
+#undef ENUMERATE
+    }
+
+    return encoding;
+}
+
+NonnullRefPtr<Encoding> Encoding::windows_encoding()
+{
+    static NonnullRefPtr<Encoding> encoding = adopt_ref(*new Encoding());
+    if (encoding->m_descriptors.is_empty()) {
+#define ENUMERATE(string, name, standard_code, mac_code, win_code, pdf_code) \
+    auto name##_code_point = *Utf8View(StringView(string)).begin();          \
+    encoding->m_descriptors.set(win_code, { string, name##_code_point });
+        ENUMERATE_LATIN_CHARACTER_SET(ENUMERATE)
+#undef ENUMERATE
+    }
+
+    return encoding;
+}
+
+NonnullRefPtr<Encoding> Encoding::pdf_doc_encoding()
+{
+    static NonnullRefPtr<Encoding> encoding = adopt_ref(*new Encoding());
+    if (encoding->m_descriptors.is_empty()) {
+#define ENUMERATE(string, name, standard_code, mac_code, win_code, pdf_code) \
+    auto name##_code_point = *Utf8View(StringView(string)).begin();          \
+    encoding->m_descriptors.set(pdf_code, { string, name##_code_point });
+        ENUMERATE_LATIN_CHARACTER_SET(ENUMERATE)
+#undef ENUMERATE
+    }
+
+    return encoding;
+}
+
+NonnullRefPtr<Encoding> Encoding::symbol_encoding()
+{
+    static NonnullRefPtr<Encoding> encoding = adopt_ref(*new Encoding());
+    if (encoding->m_descriptors.is_empty()) {
+#define ENUMERATE(string, name, code)                               \
+    auto name##_code_point = *Utf8View(StringView(string)).begin(); \
+    encoding->m_descriptors.set(code, { string, name##_code_point });
+        ENUMERATE_SYMBOL_CHARACTER_SET(ENUMERATE)
+#undef ENUMERATE
+    }
+
+    return encoding;
+}
+
+NonnullRefPtr<Encoding> Encoding::zapf_encoding()
+{
+    static NonnullRefPtr<Encoding> encoding = adopt_ref(*new Encoding());
+    if (encoding->m_descriptors.is_empty()) {
+#define ENUMERATE(string, name, code)                               \
+    auto name##_code_point = *Utf8View(StringView(string)).begin(); \
+    encoding->m_descriptors.set(code, { string, name##_code_point });
+        ENUMERATE_ZAPF_DINGBATS_CHARACTER_SET(ENUMERATE)
+#undef ENUMERATE
+    }
+
+    return encoding;
+}
+
+CharDescriptor const& Encoding::get_char_code_descriptor(u16 char_code) const
+{
+    return const_cast<Encoding*>(this)->m_descriptors.ensure(char_code);
+}
+
+}