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skip tab len

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This commit is contained in:
Dmitry Belyaev 2022-10-07 23:00:09 +03:00
parent 9316bbbf5c
commit 73e8b34af4
1 changed files with 32 additions and 24 deletions
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48
src/main.rs
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@ -242,15 +242,17 @@ fn read_from_db2(id: u32) -> Option<Question> {
let input = fs::File::open("test.bin").expect("open input");
let mut input = std::io::BufReader::with_capacity(4 * 1024, input);
let mut len_data: [u8; LEN_SIZE] = [0; LEN_SIZE];
input.read_exact(&mut len_data).expect("read len");
let tab_len = LSize::from_le_bytes(len_data) as usize;
let mut first_data: [u8; LEN_SIZE] = [0; LEN_SIZE];
input.read_exact(&mut first_data).expect("read first");
let first_pos = LSize::from_le_bytes(first_data);
let tab_len = (first_pos as usize) / LEN_SIZE;
let records_count = tab_len - 1;
// println!(
// "read tab_len done: {}, pos {}",
// "read tab_len done: {}, pos {}, first_pos {}",
// tab_len,
// input.stream_position().unwrap()
// input.stream_position().unwrap(),
// first_pos
// );
let index = match id {
@ -264,29 +266,36 @@ fn read_from_db2(id: u32) -> Option<Question> {
// println!("index {}", index);
assert!(index < records_count);
let tab_tail_len = (tab_len - (index + 2)) * LEN_SIZE;
let data_pos = if 0 == index {
first_pos
} else {
let mut pos_curr_data: [u8; LEN_SIZE] = [0; LEN_SIZE];
let mut pos_next_data: [u8; LEN_SIZE] = [0; LEN_SIZE];
input
.seek_relative((index * LEN_SIZE).try_into().expect("index to i64"))
.seek_relative(((index - 1) * LEN_SIZE).try_into().expect("index to i64"))
.expect("seek to tab pos");
input
.read_exact(&mut pos_curr_data)
.expect("read current pos");
LSize::from_le_bytes(pos_curr_data)
};
let mut pos_next_data: [u8; LEN_SIZE] = [0; LEN_SIZE];
input.read_exact(&mut pos_next_data).expect("read next pos");
let data_pos = LSize::from_le_bytes(pos_curr_data);
let data_pos_next = LSize::from_le_bytes(pos_next_data);
let data_len = data_pos_next - data_pos;
// println!(
// "pos {} | next {} | len {} | tab_tail_len {}",
// data_pos, data_pos_next, data_len, tab_tail_len
// );
let data_pos = data_pos + tab_tail_len as LSize;
let tab_pos = input.stream_position().expect("stream pos") as u32;
input.seek_relative(data_pos as i64).expect("q seek");
// println!(
// "pos {} | next {} | len {} | tab_pos {}",
// data_pos, data_pos_next, data_len, tab_pos
// );
let advance_len = data_pos - tab_pos as LSize;
// println!("advance_len {}", advance_len);
input.seek_relative(advance_len as i64).expect("q seek");
let reader = input.take(data_len as u64);
let data = zstd::decode_all(reader).expect("zstd decode data");
@ -344,12 +353,11 @@ fn db_writer2_task(rx: mpsc::Receiver<Question>) {
buf.set_position(0);
let tab_data = vec![0u8; (table.len() + 1) * LEN_SIZE];
let tab_data = vec![0u8; table.len() * LEN_SIZE];
let mut tab_cursor = Cursor::new(tab_data);
let len_data = (table.len() as LSize).to_le_bytes();
tab_cursor.write_all(&len_data).expect("write len");
let tab_size = (table.len() * LEN_SIZE) as LSize;
for pos in table {
let pos_data = pos.to_le_bytes();
let pos_data = (pos + tab_size).to_le_bytes();
tab_cursor.write_all(&pos_data).expect("write pos");
}