From 9389177e5f9bd1d0ce558356f653963f0e438e52 Mon Sep 17 00:00:00 2001
From: Lucas CHOLLET <lucas.chollet@free.fr>
Date: Sat, 29 Apr 2023 20:34:33 -0400
Subject: [PATCH] LibGfx/JPEG: Make `generate_huffman_codes` be a method of
 `HuffmanTable`

And call it when reading the table definition instead of when starting
to decode the stream.
---
 .../LibGfx/ImageFormats/JPEGLoader.cpp        | 29 ++++++++-----------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/Userland/Libraries/LibGfx/ImageFormats/JPEGLoader.cpp b/Userland/Libraries/LibGfx/ImageFormats/JPEGLoader.cpp
index be3a0f45b7..7654c87d82 100644
--- a/Userland/Libraries/LibGfx/ImageFormats/JPEGLoader.cpp
+++ b/Userland/Libraries/LibGfx/ImageFormats/JPEGLoader.cpp
@@ -186,6 +186,16 @@ struct HuffmanTable {
     u8 code_counts[16] = { 0 };
     Vector<u8> symbols;
     Vector<u16> codes;
+
+    void generate_codes()
+    {
+        unsigned code = 0;
+        for (auto number_of_codes : code_counts) {
+            for (int i = 0; i < number_of_codes; i++)
+                codes.append(code++);
+            code <<= 1;
+        }
+    }
 };
 
 class HuffmanStream {
@@ -378,16 +388,6 @@ struct JPEGLoadingContext {
     Optional<ByteBuffer> icc_data;
 };
 
-static void generate_huffman_codes(HuffmanTable& table)
-{
-    unsigned code = 0;
-    for (auto number_of_codes : table.code_counts) {
-        for (int i = 0; i < number_of_codes; i++)
-            table.codes.append(code++);
-        code <<= 1;
-    }
-}
-
 static inline auto* get_component(Macroblock& block, unsigned component)
 {
     switch (component) {
@@ -671,13 +671,6 @@ static void reset_decoder(JPEGLoadingContext& context)
 
 static ErrorOr<void> decode_huffman_stream(JPEGLoadingContext& context, Vector<Macroblock>& macroblocks)
 {
-    // Compute huffman codes for DC and AC tables.
-    for (auto it = context.dc_tables.begin(); it != context.dc_tables.end(); ++it)
-        generate_huffman_codes(it->value);
-
-    for (auto it = context.ac_tables.begin(); it != context.ac_tables.end(); ++it)
-        generate_huffman_codes(it->value);
-
     for (u32 vcursor = 0; vcursor < context.mblock_meta.vcount; vcursor += context.vsample_factor) {
         for (u32 hcursor = 0; hcursor < context.mblock_meta.hcount; hcursor += context.hsample_factor) {
             u32 i = vcursor * context.mblock_meta.hpadded_count + hcursor;
@@ -900,6 +893,8 @@ static ErrorOr<void> read_huffman_table(Stream& stream, JPEGLoadingContext& cont
             table.symbols.append(symbol);
         }
 
+        table.generate_codes();
+
         auto& huffman_table = table.type == 0 ? context.dc_tables : context.ac_tables;
         huffman_table.set(table.destination_id, table);
         VERIFY(huffman_table.size() <= 2);