LibTextCodec: Add EUC-KR decoder

Author: https://github.com/skyrising
Commit: 7f3b457e62
Pull-request: https://github.com/SerenityOS/serenity/pull/24485
Reviewed-by: https://github.com/ADKaster

Meta/Lagom/Tools/CodeGenerators/LibTextCodec/GenerateEncodingIndexes.cpp

@@ -210,6 +210,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
             { "big5"sv, prepare_table(data.get("big5"sv)->as_array()) },
             { "jis0208"sv, prepare_table(data.get("jis0208"sv)->as_array()) },
             { "jis0212"sv, prepare_table(data.get("jis0212"sv)->as_array()) },
+            { "euc_kr"sv, prepare_table(data.get("euc-kr"sv)->as_array()) },
         },
     };
 

Userland/Libraries/LibTextCodec/Decoder.cpp

@@ -33,6 +33,7 @@ Big5Decoder s_big5_decoder;
 EUCJPDecoder s_euc_jp_decoder;
 ISO2022JPDecoder s_iso_2022_jp_decoder;
 ShiftJISDecoder s_shift_jis_decoder;
+EUCKRDecoder s_euc_kr_decoder;
 
 // clang-format off
 // https://encoding.spec.whatwg.org/index-ibm866.txt
@@ -308,6 +309,8 @@ Optional<Decoder&> decoder_for(StringView a_encoding)
             return s_big5_decoder;
         if (encoding.value().equals_ignoring_ascii_case("euc-jp"sv))
             return s_euc_jp_decoder;
+        if (encoding.value().equals_ignoring_ascii_case("euc-kr"sv))
+            return s_euc_kr_decoder;
         if (encoding.value().equals_ignoring_ascii_case("gbk"sv))
             return s_gb18030_decoder;
         if (encoding.value().equals_ignoring_ascii_case("gb18030"sv))
@@ -1707,4 +1710,71 @@ ErrorOr<void> ShiftJISDecoder::process(StringView input, Function<ErrorOr<void>(
     }
 }
 
+// https://encoding.spec.whatwg.org/#euc-kr-decoder
+ErrorOr<void> EUCKRDecoder::process(StringView input, Function<ErrorOr<void>(u32)> on_code_point)
+{
+    // EUC-KR’s decoder has an associated EUC-KR lead (initially 0x00).
+    u8 euc_kr_lead = 0x00;
+
+    // EUC-KR’s decoder’s handler, given ioQueue and byte, runs these steps:
+    size_t index = 0;
+    while (true) {
+        // 1. If byte is end-of-queue and EUC-KR lead is not 0x00, set EUC-KR lead to 0x00 and return error.
+        if (index >= input.length() && euc_kr_lead != 0x00) {
+            euc_kr_lead = 0x00;
+            TRY(on_code_point(replacement_code_point));
+            continue;
+        }
+
+        // 2. If byte is end-of-queue and EUC-KR lead is 0x00, return finished.
+        if (index >= input.length() && euc_kr_lead == 0x00)
+            return {};
+
+        u8 const byte = input[index++];
+
+        // 3. If EUC-KR lead is not 0x00, let lead be EUC-KR lead, let pointer be null, set EUC-KR lead to 0x00, and then:
+        if (euc_kr_lead != 0x00) {
+            auto lead = euc_kr_lead;
+            Optional<u32> pointer;
+            euc_kr_lead = 0x00;
+
+            // 1. If byte is in the range 0x41 to 0xFE, inclusive, set pointer to (lead − 0x81) × 190 + (byte − 0x41).
+            if (byte >= 0x41 && byte <= 0xFE)
+                pointer = (lead - 0x81) * 190 + (byte - 0x41);
+
+            // 2. Let code point be null if pointer is null, otherwise the index code point for pointer in index EUC-KR.
+            auto code_point = pointer.has_value() ? index_euc_kr_code_point(pointer.value()) : Optional<u32> {};
+
+            // 3. If code point is non-null, return a code point whose value is code point.
+            if (code_point.has_value()) {
+                TRY(on_code_point(code_point.value()));
+                continue;
+            }
+
+            // 4. If byte is an ASCII byte, restore byte to ioQueue.
+            if (byte <= 0x7F)
+                index--;
+
+            // 5. Return error.
+            TRY(on_code_point(replacement_code_point));
+            continue;
+        }
+
+        // 4. If byte is an ASCII byte, return a code point whose value is byte.
+        if (byte <= 0x7F) {
+            TRY(on_code_point(byte));
+            continue;
+        }
+
+        // 5. If byte is in the range 0x81 to 0xFE, inclusive, set EUC-KR lead to byte and return continue.
+        if (byte >= 0x81 && byte <= 0xFE) {
+            euc_kr_lead = byte;
+            continue;
+        }
+
+        // 6. Return error.
+        TRY(on_code_point(replacement_code_point));
+    }
+}
+
 }

Userland/Libraries/LibTextCodec/Decoder.h

@@ -120,6 +120,11 @@ public:
     virtual ErrorOr<void> process(StringView, Function<ErrorOr<void>(u32)> on_code_point) override;
 };
 
+class EUCKRDecoder final : public Decoder {
+public:
+    virtual ErrorOr<void> process(StringView, Function<ErrorOr<void>(u32)> on_code_point) override;
+};
+
 Optional<Decoder&> decoder_for(StringView encoding);
 Optional<StringView> get_standardized_encoding(StringView encoding);