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-//! This module defines functions to turn a forest of forest labels
-//! into a sequence of bytes.
-//!
-//! To be more specific, a forest consists of two parts: a vector of
-//! node labels and a graph specifying the relations between nodes.
-//!
-//! # Number format (endianness)
-//!
-//! Every number mentionned in this format is an unsigned integer of
-//! 64 bits, or 8 bytes. Every such number is specified in the big
-//! endian format.
-//!
-//! # Parts of the sequence of bytes
-//!
-//! The sequence of bytes has three parts:
-//!
-//! ## Header
-//!
-//! The header specifies metadata of this forest.
-//!
-//! ### Special mark
-//!
-//! The first three bytes form the string "rep", as a special mark.
-//!
-//! ### Number of nodes
-//!
-//! The next 8 bytes specifies the number of nodes of this forest.
-//!
-//! ## Graph
-//!
-//! Next comes the underlying graph for this forest. This part
-//! consists of a vector of vectors of numbers. Each vector of
-//! numbers represents the list of children of a node. So the number
-//! of vectors of numbers is equal to the number of nodes.
-//!
-//! ### Vector of vectors of numbers
-//!
-//! The vectors are not simply concatenated one after another, as that
-//! way one cannot read a random node in a constant amount of time.
-//!
-//! Instead, we first specify the number of children of each node
-//! first, along with the offset for that node of the vector of
-//! children.
-//!
-//! As an example, if a graph has three nodes, represented as the
-//! adjacency list: `[[1, 2], [2], []]`, then its representation as a
-//! sequence of bytes is as follows:
-//! ```text
-//! 2, x, 1, y, 0, z, 1, 2, 2,
-//! ^ ^ ^
-//! x y z
-//! ```
-//!
-//! This has the advantage that we can read the children of the `n`-th
-//! node in constant time.
-//!
-//! ## Vector of labels
-//!
-//! Each label occupies a fixed number of bytes, so we simply put the
-//! labels one after another. The only thing to note here is the
-//! format of the labels.
-//!
-//! ### Labels
-//!
-//! Each label has 3 parts:
-//!
-//! 1. Status: either Packed, Cloned, or Plain. If the node is
-//! cloned, it has a clone index. So in total this part occupies 1
-//! byte for the status and 8 bytes for the clone index.
-//! 2. Start and end: the range in the input sentence. We just store
-//! two numbers here. Hence this part occupies 16 bytes.
-//! 3. Grammar label: either a terminal, a non-terminal, or a rule.
-//! Each variant needs a number to speify its index. So in total this
-//! part occupies 1 byte for the variant discriminant and 8 bytes for
-//! the number.
-//!
-//! To sum up, each label occupies 34 bytes.
-
-use chain::item::{default::DefaultForest, ForestLabel};
-use grammar::{GrammarLabel, GrammarLabelType, TNT};
-use graph::{Graph, LabelGraph};
-
-pub(super) fn forest_to_bytes(forest: &DefaultForest<ForestLabel<GrammarLabel>>) -> Vec<u8> {
- // First calculate the total number of bytes.
- let nodes_len = forest.nodes_len();
-
- let degrees: Vec<_> = forest
- .nodes()
- .map(|node| forest.degree(node).unwrap_or(0))
- .collect();
-
- let total_degree: usize = degrees.iter().copied().sum();
-
- let len: usize = 8 // total number of bytes at the start
- + 3 // special mark
- + 8 // number of nodes
- + 8 // offset of labels
- + 16 * nodes_len // degree & offset for each node
- + 8 * total_degree // children of each node
- + 34 * nodes_len // labels
- ;
-
- // Then fill in the bytes.
-
- let mut bytes: Vec<u8> = Vec::with_capacity(len);
-
- // First the headers
-
- bytes.extend(len.to_be_bytes());
- bytes.extend([114, 101, 112]); // rep
- bytes.extend(nodes_len.to_be_bytes());
- bytes.extend((len - 34 * nodes_len).to_be_bytes());
-
- let mut accumulated: usize = 0;
-
- // Then degrees and offsets
-
- for degree in degrees.iter().copied() {
- bytes.extend(degree.to_be_bytes());
- bytes.extend((8 + 3 + 8 + 8 + 16 * nodes_len + 8 * accumulated).to_be_bytes());
-
- accumulated += degree;
- }
-
- // Then the children
-
- bytes.extend(forest.nodes().flat_map(|node| {
- forest
- .children_of(node)
- .unwrap_or_default()
- .flat_map(|child| child.to_be_bytes())
- }));
-
- // Finally the labels
-
- 'nodes_loop: for node in forest.nodes() {
- let label = match forest.vertex_label(node) {
- Ok(Some(label)) => label,
- _ => continue 'nodes_loop,
- };
-
- if label.is_plain() {
- bytes.extend(std::iter::repeat(0).take(9));
- } else if label.is_packed() {
- bytes.extend(std::iter::once(1).chain(std::iter::repeat(0).take(8)));
- } else if let Some(index) = label.clone_index() {
- bytes.extend(std::iter::once(2).chain(index.to_be_bytes()));
- }
-
- let label = label.label();
-
- bytes.extend(label.start().to_be_bytes());
- bytes.extend(label.end().unwrap_or(0).to_be_bytes());
-
- let label = label.label();
-
- match label {
- GrammarLabelType::TNT(TNT::Ter(t)) => {
- bytes.extend(std::iter::once(0).chain(t.to_be_bytes()));
- }
- GrammarLabelType::TNT(TNT::Non(n)) => {
- bytes.extend(std::iter::once(1).chain(n.to_be_bytes()));
- }
- GrammarLabelType::Rule(r) => {
- bytes.extend(std::iter::once(2).chain(r.to_be_bytes()));
- }
- }
- }
-
- if bytes.len() != len {
- dbg!();
- }
-
- bytes
-}