Attempt at delete
This commit is contained in:
Yuriy Dupyn
parent
3e7e8665fd
commit
53aa5a0127
2 changed files with 93 additions and 41 deletions
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@ -24,10 +24,10 @@ async fn create_store() -> Result<Store<Data>> {
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println!("THE BYTES: {:?}", store.read_all_bytes().await?);
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let mut cursor = store.cursor(AccessMode::Write).await.map_err(|e| e.to_io_or_panic())?;
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let entry0: Entry<u32> = Entry::new_deleted(vec![1, 2, 3, 4, 5]);
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let entry0: Entry<u32> = Entry::new(vec![1, 2, 3, 4, 5]);
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append_entry(&mut cursor, &entry0).await?;
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let entry1: Entry<u32> = Entry::new_deleted(vec![200, 200, 5, 6, 7]);
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let entry1: Entry<u32> = Entry::new(vec![200, 200, 5, 6, 7]);
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append_entry(&mut cursor, &entry1).await?;
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println!("{:?}", store.read_all_bytes().await?);
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@ -83,6 +83,13 @@ async fn main() -> Result<()> {
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let entry0: Entry<u32> = Entry::new(vec![99, 98, 97, 96, 95]);
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append_entry(&mut cursor, &entry0).await?;
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let entry1: Entry<u32> = Entry::new(vec![50,50,50,50,50]);
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let file_position = append_entry(&mut cursor, &entry1).await?;
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println!("CURRENT FILE_POSITION = {}", file_position);
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// Now file_position point to entry1.
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// cursor.mark_deleted_at(file_position).await.map_err(|e| e.to_io_or_panic())?;
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// cursor.seek_to(file_position).await.map_err(|e| e.to_io_or_panic())?;
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cursor.read_entries().await.map_err(|e| e.to_io_or_panic())?;
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@ -35,6 +35,10 @@ pub struct Store<T> {
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// primary_index: Vec<Index<T, FilePosition>>>,
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// indexes: Vec<Option<Index<T, HashSet<FilePosition>>>>,
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// primary_index: Index<PositionOfValue, PositionOfRow>,
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// TODO: It's not good to have StoreHeader copied to all the cursors, since they may modify it.
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// How to sync?
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// All
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header: StoreHeader,
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data_type: PhantomData<T>,
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@ -46,6 +50,9 @@ pub struct Store<T> {
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// list
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}
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// Read Cursors don't modify the rows nor Store Header.
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// Write Cursors can modify both rows and Store Header.
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// Probably should split these into two types. But they will have a lot of functionality in common.
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pub struct Cursor<T> {
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header: StoreHeader,
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file: File,
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@ -54,6 +61,14 @@ pub struct Cursor<T> {
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eof_file_position: FilePosition,
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}
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pub struct WriteCursor<'a, T> {
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header: &'a mut StoreHeader,
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file: File,
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data_type: PhantomData<T>,
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eof_file_position: FilePosition,
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}
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pub enum AccessMode {
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Read,
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Write
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@ -87,10 +102,6 @@ impl StoreHeader {
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pub struct EntryHeader {
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is_deleted: bool,
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}
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impl EntryHeader {
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const IS_DELETED_SIZE: usize = size_of::<bool>();
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const HEADER_SIZE: usize = Self::IS_DELETED_SIZE;
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}
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#[derive(Debug)]
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pub struct EntryHeaderWithDataSize {
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@ -363,13 +374,15 @@ impl <T>Cursor<T> {
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.await?,
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};
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let cursor = Self {
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let mut cursor = Self {
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header: store.header.clone(),
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file,
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data_type: store.data_type,
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eof_file_position: 0,
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eof_file_position: 0, // This will be overwriten by the seek_to_start_of_data
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};
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cursor.seek_to_start_of_data().await?;
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Ok(cursor)
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}
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@ -392,7 +405,8 @@ impl <T>Cursor<T> {
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Ok(result)
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}
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async fn seek_to(&mut self, file_position: FilePosition) -> Result<()> {
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// TODO: make private
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pub async fn seek_to(&mut self, file_position: FilePosition) -> Result<()> {
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self.file.seek(SeekFrom::Start(file_position)).await?;
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Ok(())
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}
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@ -411,27 +425,41 @@ impl <T>Cursor<T> {
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self.seek_to(StoreHeader::SIZE as u64).await
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}
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async fn current_file_position(&mut self) -> Result<FilePosition> {
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// TODO: Make private
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pub async fn current_file_position(&mut self) -> Result<FilePosition> {
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let next_file_position: FilePosition = self.file.stream_position().await?;
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Ok(next_file_position)
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}
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// For debugging.
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// Moves file cursor to the end.
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pub async fn read_all_bytes(&mut self) -> std::result::Result<Vec<u8>, std::io::Error>{
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let mut bytes: Vec<u8> = vec![];
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self.seek_to_start().await.map_err(|e| e.to_io_or_panic())?;
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self.file.read_to_end(&mut bytes).await?;
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Ok(bytes)
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async fn is_at_eof(&mut self) -> Result<bool> {
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Ok(self.current_file_position().await? == self.eof_file_position)
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}
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pub async fn less_than_eq(&mut self, file_position0: FilePosition, file_position1: FilePosition) -> Result<bool> {
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todo!()
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}
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// ===Creation===
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// ===Iteration===
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// Assumes that the current file position is at a valid entry or EOF.
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pub async fn next(&mut self) -> Result<Option<EntryDetailed<T>>>
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where T: Decode
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{
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if self.is_at_eof().await? {
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return Ok(None)
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}
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// ===Append Entry===
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let header = self.read_entry_header().await?;
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let mut data_bytes: Vec<u8> = vec![0; header.size_of_data()];
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self.read_bytes(&mut data_bytes).await?;
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let entry: EntryDetailed<T> =
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EntryDetailed::decode(header, self.header.number_of_columns, &mut data_bytes)?;
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Ok(Some(entry))
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}
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// ===Store Header Manipulation===
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async fn increment_total_count(&mut self) -> Result<()> {
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self.seek_to_start().await?;
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self.seek_to(StoreHeader::TOTAL_COUNT_OFFSET as u64).await?;
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@ -448,7 +476,18 @@ impl <T>Cursor<T> {
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Ok(())
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}
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// ===Entry Header Manipulation===
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// assumes we are at the start of the valid entry.
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async fn set_entry_is_deleted_to(&mut self, is_deleted: bool) -> Result<()> {
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self.seek_to(EntryHeaderWithDataSize::IS_DELETED_OFFSET as u64).await?;
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self.write_bytes(&encode::<bool>(&is_deleted)?).await?;
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Ok(())
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}
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// ===Append Entry===
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// Moves cursor to the end.
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// Returns file position to the start of the new entry.
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pub async fn append_entry(&mut self, entry: &Entry<T>) -> Result<FilePosition>
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where T: Encode
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{
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@ -467,21 +506,34 @@ impl <T>Cursor<T> {
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// ===Deletion===
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pub async fn mark_deleted_at(&mut self, file_position: FilePosition) -> Result<()> {
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self.increment_deleted_count().await?;
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self.seek_to(file_position).await?;
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let entry_header = self.read_entry_header().await?;
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if entry_header.is_deleted {
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Ok(())
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} else {
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self.increment_deleted_count().await?;
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self.seek_to(file_position).await?;
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self.set_entry_is_deleted_to(true).await?;
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// TODO: Now you need to mutate the entry itself
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todo!()
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self.attempt_garbage_collection_if_necessary().await?;
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Ok(())
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}
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}
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async fn attempt_garbage_collection_if_necessary(&mut self) -> Result<()> {
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// TODO: What should be the policy? Counting size of garbage? Counting how many entries are
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// garbage?
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if self.header.deleted_count > 100 {
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todo!()
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} else {
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Ok(())
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}
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}
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// ===Lookup===
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// WARNING: The cursor has to be at the start of an entry. Otherwise garbage data will be
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// decoded as an entry.
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pub async fn read_entry_header_at(&mut self, file_position: FilePosition) -> Result<EntryHeaderWithDataSize> {
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self.seek_to(file_position).await?;
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async fn read_entry_header(&mut self) -> Result<EntryHeaderWithDataSize> {
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let number_of_columns: usize = self.header.number_of_columns;
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let mut header_bytes: Vec<u8> = vec![0; EntryHeaderWithDataSize::size(number_of_columns)];
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self.read_bytes(&mut header_bytes).await?;
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@ -493,6 +545,11 @@ impl <T>Cursor<T> {
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Ok(header)
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}
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pub async fn read_entry_header_at(&mut self, file_position: FilePosition) -> Result<EntryHeaderWithDataSize> {
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self.seek_to(file_position).await?;
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self.read_entry_header().await
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}
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pub async fn search_for(&mut self, index: T) -> Result<()>
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where T: Send
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{
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@ -501,25 +558,13 @@ impl <T>Cursor<T> {
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todo!()
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}
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// Returns None when file_positoin == eof_file_position
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pub async fn read_entry_at(&mut self, file_position: FilePosition) -> Result<Option<EntryDetailed<T>>>
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where T: Decode
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{
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if file_position == self.eof_file_position {
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return Ok(None)
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}
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let header = self.read_entry_header_at(file_position).await?;
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let mut data_bytes: Vec<u8> = vec![0; header.size_of_data()];
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// TODO: Get rid of the println's
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// println!("PREPARED_DATA_BYTES: {:?}", data_bytes);
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self.read_bytes(&mut data_bytes).await?;
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// println!("DATA_BYTES: {:?}", data_bytes);
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let entry: EntryDetailed<T> =
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EntryDetailed::decode(header, self.header.number_of_columns, &mut data_bytes)?;
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Ok(Some(entry))
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self.seek_to(file_position).await?;
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self.next().await
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}
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// TODO: This needs to be some sort of an iterator
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