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#pragma once
#include <string>
#include "result.hpp"
#include "span.hpp"
#include "table.hpp"
namespace database {
class TableReader {
public:
enum ReadError {
OUT_OF_RANGE,
IO_ERROR,
PARSE_ERROR,
};
auto ReadEntryAtIndex(Index_t index) -> cpp::result<DatabaseEntry, ReadError>;
template <typename T>
auto ReadColumnOffsetAtIndex(Column<T> col, Index_t index)
-> cpp::result<IndexOffset_t, ReadError>;
template <typename T>
auto ParseColumnAtIndex(Column<T> col, Index_t index)
-> cpp::result<T, ReadError> {
return ReadColumnOffsetAtIndex(col, index).map([&](IndexOffset_t offset) {
return ReadColumnAtOffset(col, offset);
});
}
template <typename T>
auto ParseColumnAtOffset(Column<T> col, IndexOffset_t offset)
-> cpp::result<T, ReadError> {
return ReadDataAtOffset(col.Filename(), offset)
.flat_map([&](cpp::span<std::byte> data) {
auto res = = col.ParseValue(data);
if (res) {
return *res;
} else {
return cpp::fail(PARSE_ERROR);
}
});
}
private:
auto ReadDataAtOffset(std::string filename, IndexOffset_t offset)
-> cpp::span<std::byte>;
};
} // namespace database
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