added the builder

src/builder.rs

@@ -0,0 +1,44 @@
+use std::mem;
+use crate::page::{self, Page};
+use crate::record::Record;
+
+struct Builder {
+    current_page: Page,
+    n_records_on_current_page: u16,
+    leaf_pages: Vec<Page>,
+}
+
+
+impl Builder {
+    pub fn new() -> Self {
+        Self {
+            current_page: Page::new_leaf(),
+            n_records_on_current_page: 0,
+            leaf_pages: Vec::new(),
+        }
+    }
+
+    pub fn add_record(&mut self, record: Record) {
+        if self.current_page_is_full(&record) {
+            self.finish_current_page();
+            self.leaf_pages.push(mem::replace(&mut self.current_page, Page::new_leaf()));
+            self.n_records_on_current_page = 0;
+        }
+
+        self.current_page.key = record.rowid; //clone?
+        self.current_page.put_vec_u8_bw(record.to_bytes());
+        self.current_page.put_u16(self.current_page.get_bw_position() as u16);
+        self.n_records_on_current_page += 1;
+    }
+
+    fn current_page_is_full(&self, record: &Record) -> bool {
+        self.current_page.get_bw_position() - record.get_length() <= self.current_page.get_fw_position() + 5
+    }
+
+    fn finish_current_page(&mut self) {
+        self.current_page.set_fw_position(page::POSITION_CELL_COUNT);
+        self.current_page.put_u16(self.n_records_on_current_page);
+        self.current_page.put_u16(self.current_page.get_bw_position());
+    }
+}
+

src/bytebuffer.rs

@@ -6,14 +6,14 @@ use byteorder::{BigEndian, ByteOrder};
 /// - big endian only
 pub struct ByteBuffer {
     pub data: Vec<u8>,
-    pub fw_position: usize,
+    pub fw_position: u16,
-    pub bw_position: usize,
+    pub bw_position: u16,
 }
 
 impl ByteBuffer {
-    pub fn new(size: usize) -> Self {
+    pub fn new(size: u16) -> Self {
         Self {
-            data: vec![0; size],
+            data: vec![0; size as usize],
             fw_position: 0,
             bw_position: size,
         }
@@ -22,23 +22,31 @@ impl ByteBuffer {
     /// forward put unsigned byte array
     pub fn put_u8a(&mut self, bytes: &[u8]) {
         for v in bytes {
-            self.data[self.fw_position] = *v;
+            self.data[self.fw_position as usize] = *v;
             self.fw_position += 1;
         }
     }
 
     pub fn put_u8v(&mut self, bytes: &Vec<u8>) {
         for v in bytes {
-            self.data[self.fw_position] = *v;
+            self.data[self.fw_position as usize] = *v;
             self.fw_position += 1;
         }
     }
 
     /// backward put unsigned byte array
     pub fn put_u8a_bw(&mut self, bytes: &[u8]) {
-        self.bw_position -= bytes.len();
+        self.bw_position -= bytes.len() as u16;
         for v in bytes {
-            self.data[self.bw_position] = *v;
+            self.data[self.bw_position as usize] = *v;
+            self.bw_position += 1;
+        }
+    }
+
+    pub fn put_vec_u8_bw(&mut self, bytes: Vec<u8>) {
+        self.bw_position -= bytes.len() as u16;
+        for v in bytes {
+            self.data[self.bw_position as usize] = v;
             self.bw_position += 1;
         }
     }

src/lib.rs

@@ -4,7 +4,7 @@ mod bytebuffer;
 mod values;
 mod varint;
 mod record;
-
+mod builder;
 
 
 #[cfg(test)]

src/page.rs

@@ -1,6 +1,7 @@
 use crate::bytebuffer::ByteBuffer;
 use crate::database;
-const POSITION_CELL_COUNT: u32 = 3;
+
+pub const POSITION_CELL_COUNT: u16 = 3;
 const START_OF_CONTENT_AREA: u32 = 5;
 
 pub enum PageType {
@@ -11,16 +12,16 @@ pub enum PageType {
 /// Represents an SQLite page
 pub struct Page {
     data: ByteBuffer,
-    key: i64,
+    pub key: u64,
     children: Vec<Page>,
     number: u32,
     page_type: PageType,
 }
 
 impl Page {
-    fn with_capacity(size: u16, page_type: PageType) -> Self {
+    pub fn with_capacity(size: u16, page_type: PageType) -> Self {
         Self {
-            data: ByteBuffer::new(size as usize),
+            data: ByteBuffer::new(size as u16),
             key: 0,
             children: Vec::new(),
             number: 0,
@@ -28,13 +29,13 @@ impl Page {
         }
     }
 
-    fn new_leaf() -> Self {
+    pub fn new_leaf() -> Self {
         let mut page = Page::with_capacity(database::DEFAULT_PAGE_SIZE, PageType::Leaf);
         page.put_u8(database::TABLE_LEAF_PAGE);
         page
     }
 
-    fn new_interior() -> Self {
+    pub fn new_interior() -> Self {
         let mut page = Page::with_capacity(database::DEFAULT_PAGE_SIZE, PageType::Interior);
         page.put_u8(database::TABLE_LEAF_PAGE);
         page
@@ -44,22 +45,41 @@ impl Page {
         self.children.push(child);
     }
 
-    pub fn fw_position(&mut self, new_position: usize) {
+    pub fn set_fw_position(&mut self, new_position: u16) {
         self.data.fw_position = new_position;
     }
 
-    pub fn bw_position(&mut self, new_position: usize) {
+    pub fn get_fw_position(&self) -> u16 {
+        self.data.fw_position
+    }
+    pub fn set_bw_position(&mut self, new_position: u16) {
         self.data.bw_position = new_position;
     }
 
+    pub fn get_bw_position(&self) -> u16 {
+        self.data.bw_position
+    }
+
     pub fn put_u8a(&mut self, value: &[u8]) {
         self.data.put_u8a(value);
     }
 
+    pub fn put_u8a_bw(&mut self, value: &[u8]) {
+        self.data.put_u8a_bw(value);
+    }
+
+    pub fn put_vec_u8_bw(&mut self, value: Vec<u8>) {
+        self.data.put_vec_u8_bw(value);
+    }
+
     pub fn put_u8(&mut self, value: u8) {
         self.data.put_u8(value);
     }
 
+    pub fn put_u8_bw(&mut self, value: u8) {
+        self.data.put_u8_bw(value);
+    }
+
     pub fn put_u16(&mut self, value: u16) {
         self.data.put_u16(value);
     }
@@ -70,6 +90,6 @@ impl Page {
 
     // may panic
     pub fn get_page_nr_last_child(self) -> u32 {
-        self.children[self.children.len()-1].number
+        self.children[self.children.len() - 1].number
     }
 }

src/record.rs

@@ -2,8 +2,8 @@ use crate::bytebuffer::ByteBuffer;
 use crate::values::*;
 use crate::varint;
 
-struct Record {
+pub struct Record {
-    rowid: u64,
+    pub rowid: u64,
     //or should it be i64??
     values: Vec<Value>,
 }
@@ -20,14 +20,12 @@ impl Record {
         self.values.push(value);
     }
 
-    fn to_bytes(&self) -> Vec<u8> {
+    pub fn to_bytes(&self) -> Vec<u8> {
-        let record_length: usize = self.values.iter()
+        let record_length = self.get_length();
-            .map(|v| v.get_length())
-            .sum();
         let length_bytes = varint::write(record_length as u64);
         let rowid_bytes = varint::write(self.rowid);
 
-        let mut buffer = ByteBuffer::new(length_bytes.len() + rowid_bytes.len() + record_length);
+        let mut buffer = ByteBuffer::new(length_bytes.len() as u16 + rowid_bytes.len() as u16 + record_length);
         buffer.put_u8v(&length_bytes);
         buffer.put_u8v(&rowid_bytes);
 
@@ -48,6 +46,13 @@ impl Record {
         }
         buffer.data
     }
+
+    pub fn get_length(&self) -> u16 {
+        let record_length: u16 = self.values.iter()
+            .map(|v| v.get_length())
+            .sum();
+        record_length
+    }
 }
 
 #[cfg(test)]

src/values.rs

@@ -8,8 +8,8 @@ pub struct Value {
 
 
 impl Value {
-    pub fn get_length(&self) -> usize {
+    pub fn get_length(&self) -> u16 {
-        self.datatype.len() + self.data.len()
+        (self.datatype.len() + self.data.len()) as u16
     }
 }