[thin_restore (rust)] rewrite the btree_builder

Now copes with adding shared leaves.

src/thin/restore.rs

@@ -1,9 +1,62 @@
 use anyhow::Result;
+
+use std::collections::{BTreeMap, BTreeSet};
+use std::fs::OpenOptions;
 use std::path::Path;
 use std::sync::Arc;
 
 use crate::report::*;
 
+use crate::thin::block_time::*;
+use crate::thin::device_detail::*;
+use crate::thin::superblock::*;
+use crate::thin::xml::{self, *};
+
+//------------------------------------------
+
+#[derive(Default)]
+struct Pass1 {
+    //
+}
+
+impl MetadataVisitor for Pass1 {
+    fn superblock_b(&mut self, sb: &xml::Superblock) -> Result<Visit> {
+        todo!();
+    }
+
+    fn superblock_e(&mut self) -> Result<Visit> {
+        todo!();
+    }
+
+    fn def_shared_b(&mut self, name: &str) -> Result<Visit> {
+        todo!();
+    }
+
+    fn def_shared_e(&mut self) -> Result<Visit> {
+        todo!();
+    }
+
+    fn device_b(&mut self, d: &Device) -> Result<Visit> {
+        todo!();
+    }
+
+    fn device_e(&mut self) -> Result<Visit> {
+        todo!();
+    }
+
+    fn map(&mut self, m: &Map) -> Result<Visit> {
+        todo!();
+    }
+
+    fn ref_shared(&mut self, name: &str) -> Result<Visit> {
+        todo!();
+    }
+
+    fn eof(&mut self) -> Result<Visit> {
+        todo!();
+    }
+}
+
 //------------------------------------------
 
 pub struct ThinRestoreOptions<'a> {
@@ -15,8 +68,16 @@ pub struct ThinRestoreOptions<'a> {
 
 //------------------------------------------
 
-pub fn restore(_opts: ThinRestoreOptions) -> Result<()> {
-    todo!();
+pub fn restore(opts: ThinRestoreOptions) -> Result<()> {
+    let input = OpenOptions::new()
+        .read(true)
+        .write(false)
+        .open(opts.input)?;
+
+    let mut pass = Pass1::default();
+    xml::read(input, &mut pass)?;
+
+    Ok(())
 }
 
 //------------------------------------------