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LibPDF: Implement Run Length Decoding

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This is a simple decoding process that is needed by some streams.
This commit is contained in:
Rodrigo Tobar 2022-11-21 02:13:47 +08:00 • committed by Andreas Kling
parent e776048309
commit 5277ad1d6d
1 changed files with 25 additions and 3 deletions
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28
Userland/Libraries/LibPDF/Filter.cpp
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@ -227,10 +227,32 @@ ErrorOr<ByteBuffer> Filter::decode_flate(ReadonlyBytes bytes, int predictor, int
return decode_png_prediction(buff, bytes_per_row); return decode_png_prediction(buff, bytes_per_row);
}; };
ErrorOr<ByteBuffer> Filter::decode_run_length(ReadonlyBytes) ErrorOr<ByteBuffer> Filter::decode_run_length(ReadonlyBytes bytes)
{ {
// FIXME: Support RunLength decoding constexpr size_t END_OF_DECODING = 128;
TODO(); ByteBuffer buffer {};
while (true) {
VERIFY(bytes.size() > 0);
auto length = bytes[0];
bytes = bytes.slice(1);
if (length == END_OF_DECODING) {
VERIFY(bytes.is_empty());
break;
}
if (length < 128) {
TRY(buffer.try_append(bytes.slice(0, length + 1)));
bytes = bytes.slice(length + 1);
} else {
VERIFY(bytes.size() > 1);
auto byte_to_append = bytes[0];
bytes = bytes.slice(1);
size_t n_chars = 257 - length;
for (size_t i = 0; i < n_chars; ++i) {
TRY(buffer.try_append(byte_to_append));
}
}
}
return buffer;
}; };
ErrorOr<ByteBuffer> Filter::decode_ccitt(ReadonlyBytes) ErrorOr<ByteBuffer> Filter::decode_ccitt(ReadonlyBytes)