ChecksumValidator

class ChecksumValidator

Validates file checksums using SHA256.

Constructors

ChecksumValidator()

ChecksumValidator({dynamic client})

Implementation

dart

ChecksumValidator({http.Client? client}) : _client = client;

Properties

client no setter

dynamic get client

Implementation

dart

http.Client get client => _client ?? http.Client();

hashCode no setter inherited

int get hashCode

The hash code for this object.

A hash code is a single integer which represents the state of the object that affects operator == comparisons.

All objects have hash codes. The default hash code implemented by Object represents only the identity of the object, the same way as the default operator == implementation only considers objects equal if they are identical (see identityHashCode).

If operator == is overridden to use the object state instead, the hash code must also be changed to represent that state, otherwise the object cannot be used in hash based data structures like the default Set and Map implementations.

Hash codes must be the same for objects that are equal to each other according to operator ==. The hash code of an object should only change if the object changes in a way that affects equality. There are no further requirements for the hash codes. They need not be consistent between executions of the same program and there are no distribution guarantees.

Objects that are not equal are allowed to have the same hash code. It is even technically allowed that all instances have the same hash code, but if clashes happen too often, it may reduce the efficiency of hash-based data structures like HashSet or HashMap.

If a subclass overrides hashCode, it should override the operator == operator as well to maintain consistency.

Inherited from Object.

Implementation

dart

external int get hashCode;

runtimeType no setter inherited

Type get runtimeType

A representation of the runtime type of the object.

Inherited from Object.

Implementation

dart

external Type get runtimeType;

Methods

computeFileChecksum()

Future<String> computeFileChecksum(String filePath)

Computes SHA256 checksum of a file.

Returns the checksum as a lowercase hexadecimal string.

Implementation

dart

Future<String> computeFileChecksum(String filePath) async {
  final file = File(filePath);
  if (!await file.exists()) {
    throw ChecksumValidationException('File not found: $filePath');
  }

  try {
    final bytes = await file.readAsBytes();
    final digest = sha256.convert(bytes);
    return digest.toString();
  } catch (e) {
    throw ChecksumValidationException(
      'Failed to compute checksum for $filePath: $e',
    );
  }
}

downloadChecksumFile()

Future<String> downloadChecksumFile(String checksumUrl)

Downloads checksum file from URL.

Many GitHub releases include .sha256 files alongside binaries. This method downloads such a file and extracts the checksum.

Expected format:

Single line with checksum: abc123...
Or with filename: abc123... filename.tar.gz

Implementation

dart

Future<String> downloadChecksumFile(String checksumUrl) async {
  try {
    final response = await client.get(Uri.parse(checksumUrl)).timeout(
      const Duration(seconds: 30),
      onTimeout: () {
        throw ChecksumValidationException(
          'Timeout downloading checksum from $checksumUrl',
        );
      },
    );

    if (response.statusCode != 200) {
      throw ChecksumValidationException(
        'Failed to download checksum: ${response.statusCode} ${response.reasonPhrase}',
      );
    }

    &#47;&#47; Parse checksum from response
    final content = response.body.trim();

    &#47;&#47; Handle empty response
    if (content.isEmpty) {
      throw ChecksumValidationException(
        'Empty checksum file from $checksumUrl',
      );
    }

    &#47;&#47; Extract checksum (handle both "checksum" and "checksum  filename" formats)
    final parts = content.split(RegExp(r'\s+'));
    final checksum = parts[0].toLowerCase();

    &#47;&#47; Validate checksum format (SHA256 is 64 hex characters)
    if (!RegExp(r'^[a-f0-9]{64}$').hasMatch(checksum)) {
      throw ChecksumValidationException(
        'Invalid checksum format: $checksum',
      );
    }

    return checksum;
  } catch (e) {
    if (e is ChecksumValidationException) rethrow;
    throw ChecksumValidationException(
      'Failed to download or parse checksum from $checksumUrl: $e',
    );
  }
}

noSuchMethod() inherited

dynamic noSuchMethod(Invocation invocation)

Invoked when a nonexistent method or property is accessed.

A dynamic member invocation can attempt to call a member which doesn't exist on the receiving object. Example:

dart

dynamic object = 1;
object.add(42); // Statically allowed, run-time error

This invalid code will invoke the noSuchMethod method of the integer 1 with an Invocation representing the .add(42) call and arguments (which then throws).

Classes can override noSuchMethod to provide custom behavior for such invalid dynamic invocations.

A class with a non-default noSuchMethod invocation can also omit implementations for members of its interface. Example:

dart

class MockList<T> implements List<T> {
  noSuchMethod(Invocation invocation) {
    log(invocation);
    super.noSuchMethod(invocation); // Will throw.
  }
}
void main() {
  MockList().add(42);
}

This code has no compile-time warnings or errors even though the MockList class has no concrete implementation of any of the List interface methods. Calls to List methods are forwarded to noSuchMethod, so this code will log an invocation similar to Invocation.method(#add, [42]) and then throw.

If a value is returned from noSuchMethod, it becomes the result of the original invocation. If the value is not of a type that can be returned by the original invocation, a type error occurs at the invocation.

The default behavior is to throw a NoSuchMethodError.

Inherited from Object.

Implementation

dart

@pragma("vm:entry-point")
@pragma("wasm:entry-point")
external dynamic noSuchMethod(Invocation invocation);

toString() inherited

String toString()

A string representation of this object.

Some classes have a default textual representation, often paired with a static parse function (like int.parse). These classes will provide the textual representation as their string representation.

Other classes have no meaningful textual representation that a program will care about. Such classes will typically override toString to provide useful information when inspecting the object, mainly for debugging or logging.

Inherited from Object.

Implementation

dart

external String toString();

tryValidateFromGitHubAssets()

Future<bool> tryValidateFromGitHubAssets(
  String filePath,
  String archiveUrl,
  List<String> availableAssetUrls,
)

Tries to find and validate checksum from GitHub release assets.

Looks for common checksum file patterns:

filename.sha256
filename.tar.gz.sha256
SHA256SUMS

Returns true if checksum found and valid, false if checksum not found. Throws if checksum found but validation fails.

Implementation

dart

Future<bool> tryValidateFromGitHubAssets(
  String filePath,
  String archiveUrl,
  List<String> availableAssetUrls,
) async {
  final archiveName = p.basename(Uri.parse(archiveUrl).path);

  String? findByBasename(Set<String> basenames) {
    for (final u in availableAssetUrls) {
      final bn = p.basename(Uri.parse(u).path);
      if (basenames.contains(bn)) return u;
    }
    return null;
  }

  &#47;&#47; Common patterns for per-asset checksum files.
  final directChecksumUrl = findByBasename({
    '$archiveName.sha256',
    '$archiveName.sha256.txt',
    '${archiveName.replaceAll('.tar.gz', '')}.sha256',
    '${archiveName.replaceAll('.zip', '')}.sha256',
  });

  if (directChecksumUrl != null) {
    final ok = await validateFileFromUrl(filePath, directChecksumUrl);
    if (!ok) {
      throw ChecksumValidationException(
        'Checksum validation failed for $archiveName',
      );
    }
    return true;
  }

  &#47;&#47; Fallback: consolidated checksum files.
  final sumsUrl = findByBasename({
    'SHA256SUMS',
    'SHA256SUMS.txt',
    'checksums.sha256',
  });
  if (sumsUrl == null) return false;

  final sums = await _downloadText(sumsUrl);
  final expected = _parseChecksumFromSums(sums, archiveName);
  if (expected == null) return false;

  final ok = await validateFile(filePath, expected);
  if (!ok) {
    throw ChecksumValidationException(
      'Checksum validation failed for $archiveName',
    );
  }
  return true;
}

validateFile()

Future<bool> validateFile(String filePath, String expectedChecksum)

Validates file checksum against expected value.

Returns true if checksums match, false otherwise.

Implementation

dart

Future<bool> validateFile(String filePath, String expectedChecksum) async {
  final actualChecksum = await computeFileChecksum(filePath);
  final expected = expectedChecksum.trim().toLowerCase();
  return actualChecksum == expected;
}

validateFileFromUrl()

Future<bool> validateFileFromUrl(String filePath, String checksumUrl)

Validates file against checksum URL.

Convenience method that downloads the checksum file and validates.

Implementation

dart

Future<bool> validateFileFromUrl(
  String filePath,
  String checksumUrl,
) async {
  final expectedChecksum = await downloadChecksumFile(checksumUrl);
  return validateFile(filePath, expectedChecksum);
}

Operators

operator ==() inherited

bool operator ==(Object other)

The equality operator.

The default behavior for all Objects is to return true if and only if this object and other are the same object.

Override this method to specify a different equality relation on a class. The overriding method must still be an equivalence relation. That is, it must be:

Total: It must return a boolean for all arguments. It should never throw.
Reflexive: For all objects o, o == o must be true.
Symmetric: For all objects o1 and o2, o1 == o2 and o2 == o1 must either both be true, or both be false.
Transitive: For all objects o1, o2, and o3, if o1 == o2 and o2 == o3 are true, then o1 == o3 must be true.

The method should also be consistent over time, so whether two objects are equal should only change if at least one of the objects was modified.

If a subclass overrides the equality operator, it should override the hashCode method as well to maintain consistency.

Inherited from Object.

Implementation

dart

external bool operator ==(Object other);

ChecksumValidator ​

Constructors ​