From df9581271823debfaee1ba459036d5ca6b4be2b1 Mon Sep 17 00:00:00 2001
From: arvidn <arvid@libtorrent.org>
Date: Thu, 26 Dec 2024 14:26:52 +0100
Subject: [PATCH] implement the one-shot serialize with backrefs in terms of
 the incremental serializer

---
 src/serde/mod.rs    |  2 +-
 src/serde/ser_br.rs | 94 +++------------------------------------------
 2 files changed, 6 insertions(+), 90 deletions(-)

diff --git a/src/serde/mod.rs b/src/serde/mod.rs
index f7ebe823..2458c22e 100644
--- a/src/serde/mod.rs
+++ b/src/serde/mod.rs
@@ -22,7 +22,7 @@ pub use de_tree::{parse_triples, ParsedTriple};
 pub use incremental::{Serializer, UndoState};
 pub use object_cache::{serialized_length, treehash, ObjectCache};
 pub use ser::{node_to_bytes, node_to_bytes_limit};
-pub use ser_br::{node_to_bytes_backrefs, node_to_bytes_backrefs_limit};
+pub use ser_br::node_to_bytes_backrefs;
 pub use tools::{
     serialized_length_from_bytes, serialized_length_from_bytes_trusted, tree_hash_from_stream,
 };
diff --git a/src/serde/ser_br.rs b/src/serde/ser_br.rs
index fe5f244a..72a231e8 100644
--- a/src/serde/ser_br.rs
+++ b/src/serde/ser_br.rs
@@ -1,93 +1,14 @@
 // Serialization with "back-references"
 
 use std::io;
-use std::io::Cursor;
 
-use super::object_cache::{serialized_length, treehash, ObjectCache};
-use super::read_cache_lookup::ReadCacheLookup;
-use super::write_atom::write_atom;
-use crate::allocator::{Allocator, NodePtr, SExp};
-use crate::serde::ser::LimitedWriter;
-
-const BACK_REFERENCE: u8 = 0xfe;
-const CONS_BOX_MARKER: u8 = 0xff;
-
-#[derive(PartialEq, Eq)]
-enum ReadOp {
-    Parse,
-    Cons,
-}
-
-pub fn node_to_stream_backrefs<W: io::Write>(
-    allocator: &Allocator,
-    node: NodePtr,
-    f: &mut W,
-) -> io::Result<()> {
-    let mut read_op_stack: Vec<ReadOp> = vec![ReadOp::Parse];
-    let mut write_stack: Vec<NodePtr> = vec![node];
-
-    let mut read_cache_lookup = ReadCacheLookup::new();
-
-    let mut thc = ObjectCache::new(treehash);
-    let mut slc = ObjectCache::new(serialized_length);
-
-    while let Some(node_to_write) = write_stack.pop() {
-        let op = read_op_stack.pop();
-        assert!(op == Some(ReadOp::Parse));
-
-        let node_serialized_length = *slc
-            .get_or_calculate(allocator, &node_to_write, None)
-            .expect("couldn't calculate serialized length");
-        let node_tree_hash = thc
-            .get_or_calculate(allocator, &node_to_write, None)
-            .expect("can't get treehash");
-        match read_cache_lookup.find_path(node_tree_hash, node_serialized_length) {
-            Some(path) => {
-                f.write_all(&[BACK_REFERENCE])?;
-                write_atom(f, &path)?;
-                read_cache_lookup.push(*node_tree_hash);
-            }
-            None => match allocator.sexp(node_to_write) {
-                SExp::Pair(left, right) => {
-                    f.write_all(&[CONS_BOX_MARKER])?;
-                    write_stack.push(right);
-                    write_stack.push(left);
-                    read_op_stack.push(ReadOp::Cons);
-                    read_op_stack.push(ReadOp::Parse);
-                    read_op_stack.push(ReadOp::Parse);
-                }
-                SExp::Atom => {
-                    let atom = allocator.atom(node_to_write);
-                    write_atom(f, atom.as_ref())?;
-                    read_cache_lookup.push(*node_tree_hash);
-                }
-            },
-        }
-        while !read_op_stack.is_empty() && read_op_stack[read_op_stack.len() - 1] == ReadOp::Cons {
-            read_op_stack.pop();
-            read_cache_lookup.pop2_and_cons();
-        }
-    }
-    Ok(())
-}
-
-pub fn node_to_bytes_backrefs_limit(
-    a: &Allocator,
-    node: NodePtr,
-    limit: usize,
-) -> io::Result<Vec<u8>> {
-    let buffer = Cursor::new(Vec::new());
-    let mut writer = LimitedWriter::new(buffer, limit);
-    node_to_stream_backrefs(a, node, &mut writer)?;
-    let vec = writer.into_inner().into_inner();
-    Ok(vec)
-}
+use crate::allocator::{Allocator, NodePtr};
+use crate::serde::incremental::Serializer;
 
 pub fn node_to_bytes_backrefs(a: &Allocator, node: NodePtr) -> io::Result<Vec<u8>> {
-    let mut buffer = Cursor::new(Vec::new());
-    node_to_stream_backrefs(a, node, &mut buffer)?;
-    let vec = buffer.into_inner();
-    Ok(vec)
+    let mut ser = Serializer::new();
+    ser.add(a, node, None)?;
+    Ok(ser.into_inner())
 }
 
 #[cfg(test)]
@@ -107,10 +28,5 @@ mod tests {
         let expected = &[255, 255, 255, 133, 1, 2, 3, 4, 5, 254, 2, 254, 2, 254, 2];
 
         assert_eq!(node_to_bytes_backrefs(&a, l3).unwrap(), expected);
-        assert_eq!(node_to_bytes_backrefs_limit(&a, l3, 15).unwrap(), expected);
-        assert_eq!(
-            node_to_bytes_backrefs_limit(&a, l3, 14).unwrap_err().kind(),
-            io::ErrorKind::OutOfMemory
-        );
     }
 }