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LibGfx: Extract GIF header decoding into separate function

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This commit is contained in:
Peter Nelson 2020-04-25 13:45:41 +01:00 • committed by Andreas Kling
parent d5af7b220c
commit df0d6e241c
1 changed files with 21 additions and 14 deletions
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35
Libraries/LibGfx/GIFLoader.cpp
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@ -102,6 +102,23 @@ struct ImageDescriptor {
Vector<u8> lzw_encoded_bytes; Vector<u8> lzw_encoded_bytes;
}; };
Optional<GIFFormat> decode_gif_header(BufferStream& stream)
{
static const char valid_header_87[] = "GIF87a";
static const char valid_header_89[] = "GIF89a";
char header[6];
for (int i = 0; i < 6; ++i)
stream >> header[i];
if (!memcmp(header, valid_header_87, sizeof(header)))
return GIFFormat::GIF87a;
else if (!memcmp(header, valid_header_89, sizeof(header)))
return GIFFormat::GIF89a;
return {};
}
class LZWDecoder { class LZWDecoder {
public: public:
struct CodeTableEntry { struct CodeTableEntry {
@ -231,22 +248,12 @@ bool load_gif_impl(GIFLoadingContext& context)
auto buffer = ByteBuffer::wrap(context.data, context.data_size); auto buffer = ByteBuffer::wrap(context.data, context.data_size);
BufferStream stream(buffer); BufferStream stream(buffer);
static const char valid_header_87[] = "GIF87a"; Optional<GIFFormat> format = decode_gif_header(stream);
static const char valid_header_89[] = "GIF89a"; if (!format.has_value()) {
char header[6];
for (int i = 0; i < 6; ++i)
stream >> header[i];
GIFFormat format;
if (!memcmp(header, valid_header_87, sizeof(header)))
format = GIFFormat::GIF87a;
else if (!memcmp(header, valid_header_89, sizeof(header)))
format = GIFFormat::GIF89a;
else
return false; return false;
}
printf("Format is %s\n", format == GIFFormat::GIF89a ? "GIF89a" : "GIF87a"); printf("Format is %s\n", format.value() == GIFFormat::GIF89a ? "GIF89a" : "GIF87a");
LogicalScreen logical_screen; LogicalScreen logical_screen;
stream >> logical_screen.width; stream >> logical_screen.width;