From c4ce04d700a98d23baf00048d8823665da9e994c Mon Sep 17 00:00:00 2001
From: niku <nvdpoel01@gmail.com>
Date: Sun, 13 Aug 2023 13:14:53 +0200
Subject: [PATCH] Implement table cursor
---
src/cursor.rs | 40 ++++++++++++++++++++++++++++++++++++++++
src/lib.rs | 1 +
src/statement.rs | 20 +++++++++++---------
3 files changed, 52 insertions(+), 9 deletions(-)
create mode 100644 src/cursor.rs
diff --git a/src/cursor.rs b/src/cursor.rs
new file mode 100644
index 0000000..8098a6b
--- /dev/null
+++ b/src/cursor.rs
@@ -0,0 +1,40 @@
+use crate::table::Table;
+
+pub type Position = (usize, usize);
+
+pub struct Cursor<'a> {
+ pub table: &'a mut Table,
+ pub row_num: usize,
+ pub end_of_table: bool,
+}
+
+impl<'a> Cursor<'a> {
+ pub fn at_table_start(table: &'a mut Table) -> Self {
+ let end_of_table = table.row_count == 0;
+ Self {
+ table,
+ row_num: 0,
+ end_of_table,
+ }
+ }
+
+ pub fn at_table_end(table: &'a mut Table) -> Self {
+ let row_count = table.row_count;
+ Self {
+ table,
+ row_num: row_count,
+ end_of_table: true,
+ }
+ }
+
+ pub fn position(&self) -> Position {
+ self.table.row_slot(self.row_num)
+ }
+
+ pub fn advance(&mut self) {
+ self.row_num += 1;
+ if self.row_num >= self.table.row_count {
+ self.end_of_table = true;
+ }
+ }
+}
diff --git a/src/lib.rs b/src/lib.rs
index ae2874a..67ad978 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,4 @@
+pub mod cursor;
pub mod layout;
pub mod pager;
pub mod row;
diff --git a/src/statement.rs b/src/statement.rs
index 2e10c78..bb70136 100644
--- a/src/statement.rs
+++ b/src/statement.rs
@@ -1,4 +1,5 @@
use crate::{
+ cursor::Cursor,
layout::{ROW_SIZE, TABLE_MAX_ROWS},
row::{Row, RowBytes},
table::Table,
@@ -6,8 +7,6 @@ use crate::{
use anyhow::Result;
use thiserror::Error;
-type FilteredRows = Vec<Row>;
-
#[derive(Debug)]
pub enum StatementType {
Insert(Box<Row>),
@@ -73,22 +72,25 @@ pub fn execute_insert(row: Row, table: &mut Table) -> Result<()> {
return Err(ExecutionError::TableFull.into());
}
+ let cursor = Cursor::at_table_end(table);
let bytes: RowBytes = row.into();
- let (page_num, offset) = table.row_slot(table.row_count);
+
+ let (page_num, offset) = cursor.position();
let page = table.pager.page(page_num)?;
- // let page = table.pager.pages[page_num].as_mut().unwrap();
page[offset..offset + ROW_SIZE].copy_from_slice(&bytes);
table.row_count += 1;
Ok(())
}
-pub fn execute_select(table: &mut Table) -> Result<FilteredRows> {
- let mut rows: FilteredRows = vec![];
- for i in 0..table.row_count {
- let (page_num, offset) = table.row_slot(i);
- let page = table.pager.page(page_num)?;
+pub fn execute_select(table: &mut Table) -> Result<Vec<Row>> {
+ let mut rows: Vec<Row> = vec![];
+ let mut cursor = Cursor::at_table_start(table);
+ while !cursor.end_of_table {
+ let (page_num, offset) = cursor.position();
+ let page = cursor.table.pager.page(page_num)?;
let row: RowBytes = page[offset..offset + ROW_SIZE].try_into()?;
rows.push(row.into());
+ cursor.advance();
}
Ok(rows)