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LibCompress: Simplify logic in deflate implementation.

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asynts 2020-09-05 17:38:46 +02:00 committed by Andreas Kling
parent 6de63782c7
commit 4c317a94c7
Notes: sideshowbarker 2024-07-19 02:53:39 +09:00 
Author: https://github.com/asynts
Commit: https://github.com/SerenityOS/serenity/commit/4c317a94c7c
Pull-request: https://github.com/SerenityOS/serenity/pull/3405
2 changed files with 36 additions and 9 deletions
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30
AK/Tests/TestCircularDuplexStream.cpp
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@ -64,9 +64,8 @@ TEST_CASE(overwritting_is_well_defined)
stream >> Bytes { bytes, sizeof(bytes) };
for (size_t idx = 0; idx < half_capacity; ++idx) {
for (size_t idx = 0; idx < half_capacity; ++idx)
EXPECT_EQ(bytes[idx], idx % 256);
}
for (size_t idx = 0; idx < half_capacity; ++idx)
stream << static_cast<u8>(idx % 256);
@ -84,4 +83,31 @@ TEST_CASE(overwritting_is_well_defined)
EXPECT(stream.eof());
}
TEST_CASE(of_by_one)
{
constexpr size_t half_capacity = 32;
constexpr size_t capacity = half_capacity * 2;
CircularDuplexStream<capacity> stream;
for (size_t idx = 0; idx < half_capacity; ++idx)
stream << static_cast<u8>(0);
for (size_t idx = 0; idx < half_capacity; ++idx)
stream << static_cast<u8>(1);
stream.discard_or_error(capacity);
for (size_t idx = 0; idx < capacity; ++idx) {
u8 byte;
stream.read({ &byte, sizeof(byte) }, capacity);
stream << byte;
if (idx < half_capacity)
EXPECT_EQ(byte, 0);
else
EXPECT_EQ(byte, 1);
}
}
TEST_MAIN(CircularDuplexStream)

15
Libraries/LibCompress/Deflate.cpp
View file

@ -138,17 +138,18 @@ bool DeflateDecompressor::CompressedBlock::try_read_more()
m_eof = true;
return false;
} else {
// FIXME: This assertion depends on user input.
ASSERT(m_distance_codes.has_value());
if (!m_distance_codes.has_value()) {
m_decompressor.set_fatal_error();
return false;
}
const auto run_length = m_decompressor.decode_run_length(symbol);
const auto distance = m_decompressor.decode_distance(m_distance_codes.value().read_symbol(m_decompressor.m_input_stream));
size_t nread = 0;
while (nread < run_length) {
const auto nreserved = min(run_length - nread, m_decompressor.m_output_stream.remaining_contigous_space());
auto bytes = m_decompressor.m_output_stream.reserve_contigous_space(nreserved);
nread += m_decompressor.m_output_stream.read(bytes, distance + nread + nreserved);
for (size_t idx = 0; idx < run_length; ++idx) {
u8 byte = 0;
m_decompressor.m_output_stream.read({ &byte, sizeof(byte) }, distance);
m_decompressor.m_output_stream << byte;
}
return true;