dlm for Android

A full Android port of dlm, the C download manager (segmented/resumable downloads, a SQLite-backed queue with packages/priorities/linkgrabber, native archive.org extraction, yt-dlp delegation, MD5/SHA1 verification).

This is a true port: the proven C engine (libdlm) is compiled with the Android NDK and reused largely verbatim through a JNI bridge. The daemon, CLI and GTK GUI are replaced by an Android Foreground Service + Jetpack Compose UI, and the queue.c scheduler is re-implemented in Kotlin over the same persisted sqlite store.

Architecture

 Compose UI  ──▶ QueueViewModel ──▶ QueueRepository ──▶ QueueScheduler (Kotlin, ex-queue.c)
                                                              │
                          DownloadService (foreground, dataSync, wakelock)
                                                              │
        ┌─────────────────────────────────────────────┬──────┴───────────────┐
        ▼                                               ▼                      ▼
  NativeEngine (download.c)                     NativeStore (store.c)   YtdlpManager
  segmented + resume, via JNI                   sqlite queue, via JNI   (youtubedl-android,
        │                                                               auto-downloaded)
        └──▶ libdlmcore.so  =  libdlm/*.c (verbatim)  +  jni/*.c  +  prebuilt curl/openssl/jansson/pcre2

Module	Contents
core/	Android library: vendored libdlm C (core/src/main/cpp/libdlm), the JNI bridge (core/src/main/cpp/jni), and the Kotlin Native* wrappers + models. Builds libdlmcore.so.
app/	The application: QueueScheduler (port of queue.c), DownloadService, YtdlpManager, QueueRepository, and the Compose UI.
nativeDeps/	Prebuilt curl/openssl/jansson/pcre2 per ABI (produced by scripts/build-deps.sh).

What is reused verbatim from the C: the segmented engine + journal resume (download.c), the sqlite schema/migrations/ordering (store.c), the archive.org extractor (archiveorg.c), checksum verify (verify.c), the IA-auth store (iaauth.c), and the subtle yt-dlp JSON parser (dlm_ytdlp_parse). Only ytdlp.c's subprocess path is #ifdef'd out for Android (the JVM runs yt-dlp instead and feeds its JSON back into the verbatim parser). The only other change is the documented CA-bundle injection: libcurl on Android has no usable default trust store and ignores CURL_CA_BUNDLE, so the engine applies a shipped cacert.pem via CURLOPT_CAINFO (a small dlm_ca_bundle hook in util.c, set once from jni_init.c). XDG paths are handled by setenv.

Building

Prerequisites: Android Studio (Koala+) or the Android SDK + NDK r25+, and the host build tools used by the dependency script (autoconf/automake/libtool, cmake, make, perl, curl).

1. Build the native dependencies (one-time, per ABI). This cross-compiles OpenSSL, libcurl, jansson and pcre2 into nativeDeps/, and downloads the CA bundle into app/src/main/assets/cacert.pem:

   export ANDROID_NDK_HOME=~/Android/Sdk/ndk/26.1.10909125
   ./scripts/build-deps.sh
   # or a subset while iterating:  ABIS="arm64-v8a" ./scripts/build-deps.sh

2. Generate the Gradle wrapper jar if it isn't present (binary, not checked in here): gradle wrapper once, or just open the project in Android Studio.

3. Build / install the app:

   ./gradlew :app:assembleDebug
   ./gradlew :app:installDebug

   Per-ABI APKs are produced (plus a universal one) to keep size down.

The yt-dlp runtime (Python + yt-dlp + ffmpeg) is not bundled in the APK. It is downloaded and set up automatically on first use (or from Settings → "Set up now"), then yt-dlp self-updates in the background.

Features (parity with desktop dlm)

Segmented resumable downloads · global/per-download speed limits · queue with packages (group/folder/priority/collapse) · linkgrabber staging + confirm · priorities (−3..+3) · enable/disable · per-link & global autostart · force start · reorder (up/down/top/bottom) · clear finished · archive.org native extraction + sign-in (S3 keys / email+password / cookie) · yt-dlp delegation · MD5/SHA1 verification · live progress (in-app + ongoing notification).

Android specifics: shared/opened http(s) links are accepted via the system Share sheet; finished files can be exported to a user-chosen folder via the Storage Access Framework (auto-export optional).

Testing

• Host C tests (verify the vendored core on Linux CI, no Android needed):

  cmake -S core/src/main/cpp/host-tests -B build-host
  ctest --test-dir build-host --output-on-failure

  Covers util, store, ia, ytdlp (incl. the verbatim dlm_ytdlp_parse). Note: the daemon binds a listening socket and is intentionally not part of this port; its queue logic is re-verified by the Kotlin parity tests below.

• Scheduler parity tests (JVM, mirror upstream test_queue.c/test_package.c):

  ./gradlew :app:testDebugUnitTest

• NDK smoke + JNI round-trip (emulator/device):

  ./gradlew :core:connectedDebugAndroidTest

Security notes

• HTTPS only (usesCleartextTraffic=false + network-security-config); TLS peer verification stays on, pinned to a shipped CA bundle via CURLOPT_CAINFO.
• archive.org secrets live in app-private storage (iaauth.c, mode 0600); consider wrapping with EncryptedFile before shipping.
• Foreground service is dataSync and not exported; the engine caps response/ capture buffers (inherited from the C core).
• Build the host C tests and NDK build under ASan/UBSan in CI (the upstream supports -DDLM_ASAN=ON) and treat warnings as errors.

Status / known integration points

This repository is the complete port source. Two things must be provided in your environment before a release build runs end-to-end:

1. nativeDeps/ must be populated by scripts/build-deps.sh (needs the NDK).
2. app/src/main/assets/cacert.pem must be the real CA bundle (the script fetches it; a placeholder is committed so the tree is self-describing).

The youtubedl-android coordinates/version are pinned in gradle/libs.versions.toml; adjust if a newer release changes the API.

License

dlm for Android is free software licensed under the GNU General Public License, version 3, or (at your option) any later version (GPL-3.0-or-later). The full text is in LICENSE.

Copyright (C) 2026 the dlm authors

This program is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation, either version 3 of the License, or (at your option)
any later version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
more details.

First-party source files carry an SPDX-License-Identifier: GPL-3.0-or-later tag. Bundled third-party components keep their own licenses: SQLite (public domain) and the prebuilt OpenSSL, libcurl, jansson and pcre2 under nativeDeps/.