@adguard/diff-builder

AdGuard Diff Builder

A tool for generating differential updates for filter lists.

• How to install
• How to use
  • Use as CLI
  • Use as API
• Algorithm

How to install

yarn add @adguard/diff-builder

How to Use

CLI

diff-builder build [-c] [-d <seconds>] [-r <resolution>] [-v] -n <name> -t <expirationPeriod> <old_filter> <new_filter> <path_to_patches>

Where:

• <old_filter> — the relative path to the old filter.
• <new_filter> — the relative path to the new filter.
• <path_to_patches> — the relative path to the directory where the patch should be saved.
• -n <name> or --name=<name> — name of the patch file, an arbitrary string to identify the patch. Must be a string of length 1-64 with no spaces or other special characters.
• -r <timestampResolution> or --resolution=<timestampResolution> — is an optional flag, that specifies the resolution for both expirationPeriod and epochTimestamp (timestamp when the patch was generated). Possible values:
  • h — hours (used if resolution is not specified)
  • m — minutes
  • s — seconds
• -t <expirationPeriod> or --time=<expirationPeriod> — expiration time for the diff update (the unit depends on resolution parameter).
• -d <seconds> or --delete-older-than-sec=<seconds> — an optional parameter, this time in seconds will be used when scanning the <path_to_patches> folder to remove patches whose mtime is older than the specified time. By default, it will be 604800 (7 days).
• -v or --verbose — verbose mode.
• -c or --checksum — an optional flag, indicating whether it should calculate the SHA sum for the filter and add it to the diff directive with the filter name and the number of changed lines, following this format: diff name:[name] checksum:[checksum] lines:[lines]:
  • name — the name of the corresponding filter list. This key-value pair is optional — it will be included only if there is a Diff-Name tag in the <old_filter>.
  • checksum — the expected SHA1 checksum of the file after the patch is applied. This is used to validate the patch.
  • lines — the number of lines that follow, making up the RCS diff block. Note that lines are counted using the same algorithm as used by wc -l, essentially counting \n.

Algorithm

1. Logging and File Path Resolution

- Create a logger for verbose output if `verbose` is `true`.
- Resolve the absolute paths for `oldFilterPath`, `newFilterPath`, and `patchesPath`.

2. Read and Split Filter Contents

- Read the contents of `oldFilterPath` and `newFilterPath` into `oldFile` and `newFile`.
- Determine the line endings for `oldFile` and `newFile`.
- Split the contents of `oldFile` and `newFile` into arrays of lines (`oldFileSplitted` and `newFileSplitted`).

3. Parse Diff-Path Tag

- Parse the `Diff-Path` tag from `oldFileSplitted` and store it in `oldFileDiffName`.

4. Create Patches Folder

- Create the `patchesPath` directory recursively if it doesn't exist. Log if it's created.

5. Delete Outdated Patches

- Scan `patchesPath` and delete outdated patches older than `deleteOlderThanSec`. Log the number of deleted patches.

6. Check for File Sameness

• Compare the checksums of oldFile and newFile. If they match, log and exit.

7. Generate and Save the Diff

- Generate a new patch name based on parameters.
- Create an empty patch file for the new version if it doesn't exist.
- Update the `Diff-Path` tag in `newFileSplitted`.
- Calculate and save the difference between `oldFile` and `newFile` as a patch file.

8. Log Patch File Path and Completion

- Log the path where the patch file is saved.
- The process is completed.

Important

The oldFilterPath is expected to already contain a Diff-Path tag.

API

CJS

const { DiffBuilder } = require('@adguard/diff-builder');
const { DiffUpdater } = require('@adguard/diff-builder/diff-updater');

await DiffBuilder.buildDiff({
   oldFilterPath,
   newFilterPath,
   patchesPath,
   name,
   time,
   resolution,
   verbose: true,
});

const updatedFilter = await DiffUpdater.applyPatch({
    filterUrl,
    filterContent,
    verbose: true,
});

ESM

import { DiffBuilder } from '@adguard/diff-builder/es';
import { DiffUpdater } from '@adguard/diff-builder/diff-updater/es';

await DiffBuilder.buildDiff({
   oldFilterPath,
   newFilterPath,
   patchesPath,
   name,
   time,
   resolution,
   verbose: true,
});

const updatedFilter = await DiffUpdater.applyPatch({
    filterUrl,
    filterContent,
    verbose: true,
});