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#include "line.hh"
#include "check.hh"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <cstring>
#include <expected>
#include <memory>
#include <string_view>
#include <utility>
namespace line {
namespace {
const char kLineTerminators[] = "\r\n";
class ReaderImpl : public Reader {
public:
ReaderImpl(std::unique_ptr<io::Reader> reader, size_t max_len)
: reader_(std::move(reader)),
max_len_(max_len),
buffer_(std::make_unique_for_overwrite<char[]>(
check::add(max_len, static_cast<size_t>(2)))),
rptr_(buffer_.get()),
wptr_(buffer_.get()),
search_(rptr_),
end_(buffer_.get() + check::add(max_len, static_cast<size_t>(2))) {}
[[nodiscard]] std::expected<std::string_view, io::ReadError> read() override {
while (true) {
search_ = std::find_first_of(search_, wptr_, kLineTerminators,
kLineTerminators + 2);
if (search_ < wptr_) {
if (std::cmp_greater(search_ - rptr_, max_len_)) {
return line(max_len_, 0);
}
size_t tlen;
if (*search_ == '\n') {
tlen = 1;
} else {
if (search_ + 1 == wptr_) {
make_space_if_needed();
auto got = fill();
if (!got.has_value()) {
if (got.error() == io::ReadError::Eof) {
return line(search_ - rptr_, 1);
}
return std::unexpected(got.error());
}
}
if (search_[1] == '\n') {
tlen = 2;
} else {
tlen = 1;
}
}
return line(search_ - rptr_, tlen);
}
if (std::cmp_greater_equal(wptr_ - rptr_, max_len_)) {
return line(max_len_, 0);
}
make_space_if_needed();
auto got = fill();
if (!got.has_value()) {
if (got.error() == io::ReadError::Eof && rptr_ != wptr_) {
return line(wptr_ - rptr_, 0);
}
return std::unexpected(got.error());
}
}
}
[[nodiscard]] uint64_t number() const override { return number_; }
private:
std::string_view line(size_t len, size_t terminator_len) {
assert(len <= max_len_);
auto ret = std::string_view(rptr_, len);
rptr_ += len + terminator_len;
search_ = rptr_;
++number_;
return ret;
}
void make_space_if_needed() {
size_t free = rptr_ - buffer_.get();
if (free == 0)
return;
size_t avail = end_ - wptr_;
if (avail > 1024)
return;
memmove(buffer_.get(), rptr_, wptr_ - rptr_);
search_ -= free;
wptr_ -= free;
rptr_ = buffer_.get();
}
std::expected<size_t, io::ReadError> fill() {
auto ret = reader_->read(wptr_, end_ - wptr_);
if (ret.has_value())
wptr_ += ret.value();
return ret;
}
std::unique_ptr<io::Reader> reader_;
size_t const max_len_;
uint64_t number_{0};
std::unique_ptr<char[]> buffer_;
char* rptr_;
char* wptr_;
char* search_;
char* const end_;
};
} // namespace
std::unique_ptr<Reader> open(std::unique_ptr<io::Reader> reader,
size_t max_len) {
return std::make_unique<ReaderImpl>(std::move(reader), max_len);
}
} // namespace line
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