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LibCore: Rewrite BufferedStream::read_until_any_of() with memmem

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This function used to sometimes return the entire input instead of the
value up to the delimiter, fix that and rewrite it to be a bit more
readable.
This commit is contained in:
Ali Mohammad Pur 2022-02-02 19:06:51 +03:30 committed by Andreas Kling
parent f4d841077d
commit 9ee5107871
Notes: sideshowbarker 2024-07-17 19:43:50 +09:00 
Author: https://github.com/alimpfard
Commit: https://github.com/SerenityOS/serenity/commit/9ee5107871d
Pull-request: https://github.com/SerenityOS/serenity/pull/12235
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/sin-ack ✅
1 changed files with 24 additions and 25 deletions
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49
Userland/Libraries/LibCore/Stream.h
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@ -9,6 +9,7 @@
#include <AK/EnumBits.h>
#include <AK/Function.h>
#include <AK/IPv4Address.h>
#include <AK/MemMem.h>
#include <AK/Noncopyable.h>
#include <AK/Result.h>
#include <AK/Span.h>
@ -594,37 +595,35 @@ public:
// to the caller about why it can't read.
return Error::from_errno(EMSGSIZE);
}
m_buffer.span().slice(0, m_buffered_size).copy_to(buffer);
return exchange(m_buffered_size, 0);
}
size_t longest_match = 0;
size_t maximum_offset = min(m_buffered_size, buffer.size());
for (size_t offset = 0; offset < maximum_offset; offset++) {
// The intention here is to try to match all of the possible
// delimiter candidates and try to find the longest one we can
// remove from the buffer after copying up to the delimiter to the
// user buffer.
StringView remaining_buffer { m_buffer.span().offset(offset), maximum_offset - offset };
for (auto candidate : candidates) {
if (candidate.length() > remaining_buffer.length())
continue;
if (remaining_buffer.starts_with(candidate))
longest_match = max(longest_match, candidate.length());
// The intention here is to try to match all of the possible
// delimiter candidates and try to find the longest one we can
// remove from the buffer after copying up to the delimiter to the
// user buffer.
Optional<size_t> longest_match;
size_t match_size = 0;
for (auto& candidate : candidates) {
auto result = AK::memmem_optional(m_buffer.data(), m_buffered_size, candidate.bytes().data(), candidate.bytes().size());
if (result.has_value()) {
auto previous_match = longest_match.value_or(*result);
if ((previous_match < *result) || (previous_match == *result && match_size < candidate.length())) {
longest_match = result;
match_size = candidate.length();
}
}
}
if (longest_match.has_value()) {
auto size_written_to_user_buffer = *longest_match;
auto buffer_to_take = m_buffer.span().slice(0, size_written_to_user_buffer);
auto buffer_to_shift = m_buffer.span().slice(size_written_to_user_buffer + match_size);
if (longest_match > 0) {
auto buffer_to_take = m_buffer.span().slice(0, offset);
auto buffer_to_shift = m_buffer.span().slice(offset + longest_match);
buffer_to_take.copy_to(buffer);
m_buffer.overwrite(0, buffer_to_shift.data(), buffer_to_shift.size());
buffer_to_take.copy_to(buffer);
m_buffer.overwrite(0, buffer_to_shift.data(), buffer_to_shift.size());
m_buffered_size -= size_written_to_user_buffer + match_size;
m_buffered_size -= offset + longest_match;
return offset;
}
return size_written_to_user_buffer;
}
// If we still haven't found anything, then it's most likely the case