---
title: "mova-modules-torrent — Mova code model"
description: "Mova code model of tools/modules/src/torrent.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/tools/modules/src/torrent.rs.groupant/"
---
Elamur: [Mova](https://md.mova.elamur.ai/free/en/) · [Dictionary](https://md.dictionary.elamur.ai/free/en/) · [Research](https://md.research.elamur.ai/free/en/) · **Groupants**

This page as HTML: <https://groupants.elamur.ai/free/en/mova/tools/modules/src/torrent.rs.groupant/>

# mova-modules-torrent

The groupant beside tools/modules/src/torrent.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.

## Facts

- **kind:** groupant
- **status:** partial source bound model
- **source:** [`tools/modules/src/torrent.rs`](https://github.com/ElamurAI/mova-free/blob/main/tools/modules/src/torrent.rs)
- **source SHA-256:** `08b43c232a4d8bce…`
- **repository folder:** [`tools/modules/src/torrent.rs.groupant`](https://github.com/ElamurAI/mova-free/tree/main/tools/modules/src/torrent.rs.groupant)
- **repository commit:** `855da7bd4a7b`

> **Implementation material.** A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.

## Components

| component | label | where |
|---|---|---|
| **approximant** | partial source model | [forward](#forward) |
| **ast** | partial | `syntax.json` |
| **composition** | partial source model | [composition](#composition) |
| **cost** | partial source model | [cost](#cost) |
| **descriptant** | partial source model | [epoch-memory](#epoch-memory) |
| **invariant** | partial source model | [invariant](#invariant) |
| **tests** | partial source model | [checks](#checks) |

## Obernants

The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.

| id | type | label | where |
|---|---|---|---|
| `mova-modules-torrent-behavior-complement` | behavior_complement | partial source model | [behavior-complement](#behavior-complement) |
| `mova-modules-torrent-reverse-reconstruction` | reverse_reconstruction | partial source model | [reverse-reconstruction](#reverse-reconstruction) |
| `mova-modules-torrent-canonical-bencode` | constraint_relation | partial source model | [invariant](#invariant) |

## Model text


### forward

`Value` is a bencode tree whose dictionaries are `BTreeMap<Vec<u8>, _>` (byte-ordered keys); `encode` writes BEP 3
bencode. `decode` parses one value, refusing non-canonical integers, unordered keys and truncation. `make(dir,
trackers, web_seeds)` parses and verifies the module folder, checks URLs (web seeds `https://` folders ending in `/`),
orders module.json and the listed files by path, concatenates their bytes into pieces of `piece_length(total)` (power
of two, 256 KiB..16 MiB, at most about 2 000 pieces), SHA-1s each piece, builds `info` {files [{length, path}], name
`<name>-<version>`, piece length, pieces}, hashes the bencoded info (the info hash), adds a comment with licence and
attribution, optional `announce`/`announce-list` and `url-list`, and a magnet link with `dn`, `tr`, `ws`.

### invariant

- Same folder and options ⇒ same bytes and info hash (no dates, sorted keys and paths).
- The torrent covers exactly module.json and the listed files, all verified first.
- `decode(encode(v)) = v` for canonical values.

### cost

B bytes: one SHA-1 pass O(B) plus the module's SHA-256 verification O(B); memory holds all files (modules are read
whole), pieces 20 bytes each.

### composition

Called by `main_args` (`make-torrent`); reads through `crate::Manifest::parse`, `verify_dir`, `read_verified`.

### behavior-complement

Does not: transfer data, contact trackers or DHT, make BitTorrent v2 or hybrid torrents, stream files larger than
memory, set a private flag, verify that a web seed actually serves the files.

### reverse-reconstruction

From the info dictionary, file names, lengths and order are recoverable exactly; file contents only up to SHA-1
piece collisions (search); the module's licence and attribution only from the outer comment, which is not covered by
the info hash.

### checks

`cargo test --release -p mova-modules torrent` (bencode_round_trip_and_canonical_form,
a_module_torrent_is_deterministic_and_hashes_its_pieces, piece_length_grows_with_size). Negative controls: unordered
keys, a leading zero, a truncated string, an HTTP or non-folder web seed, a changed file.

### epoch-memory

2026-11-04, first epoch. No external client was available to load the produced torrent; correctness rests on the
recomputed info hash and pieces in the tests. A multi-file web seed is fetched as `<seed><name>-<version>/<path>`
(BEP 19), so a server must expose a `<name>-<version>/` folder.