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LibPDF: Ignore whitespace in the ASCII hex filter

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The spec tells us that any amount of whitespace may appear between the
hex digits and that it should just be ignored.
This commit is contained in:
Julian Offenhäuser 2023-03-24 21:58:51 +01:00 • committed by Andrew Kaster
parent 29796f8f5e
commit 320f5f91ab
1 changed files with 23 additions and 19 deletions
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42
Userland/Libraries/LibPDF/Filter.cpp
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@ -56,29 +56,33 @@ PDFErrorOr<ByteBuffer> Filter::decode(ReadonlyBytes bytes, DeprecatedFlyString c
PDFErrorOr<ByteBuffer> Filter::decode_ascii_hex(ReadonlyBytes bytes)
{
if (bytes.size() % 2 == 0)
return TRY(decode_hex(bytes));
ByteBuffer output;
// FIXME: Integrate this padding into AK/Hex?
auto output = TRY(ByteBuffer::create_zeroed(bytes.size() / 2 + 1));
for (size_t i = 0; i < bytes.size() / 2; ++i) {
auto const c1 = decode_hex_digit(static_cast<char>(bytes[i * 2]));
if (c1 >= 16)
return AK::Error::from_string_literal("Hex string contains invalid digit");
auto const c2 = decode_hex_digit(static_cast<char>(bytes[i * 2 + 1]));
if (c2 >= 16)
return AK::Error::from_string_literal("Hex string contains invalid digit");
output[i] = (c1 << 4) + c2;
bool have_read_high_nibble = false;
u8 high_nibble = 0;
for (u8 byte : bytes) {
// 3.3.1 ASCIIHexDecode Filter
// All white-space characters [...] are ignored.
// FIXME: Any other characters cause an error.
if (is_ascii_hex_digit(byte)) {
u8 hex_digit = decode_hex_digit(byte);
if (have_read_high_nibble) {
u8 full_byte = (high_nibble << 4) | hex_digit;
TRY(output.try_append(full_byte));
have_read_high_nibble = false;
} else {
high_nibble = hex_digit;
have_read_high_nibble = true;
}
}
}
// Process last byte with a padded zero
output[output.size() - 1] = decode_hex_digit(static_cast<char>(bytes[bytes.size() - 1])) * 16;
// If the filter encounters the EOD marker after reading an odd number
// of hexadecimal digits, it behaves as if a 0 followed the last digit.
if (have_read_high_nibble)
TRY(output.try_append(high_nibble << 4));
return { move(output) };
return output;
};
PDFErrorOr<ByteBuffer> Filter::decode_ascii85(ReadonlyBytes bytes)