80 lines
2.7 KiB
Swift
80 lines
2.7 KiB
Swift
//
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// Copyright 2023 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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//
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import Wire
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extension MessageBackup {
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public enum ProtoInputStreamReadResult<T> {
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case success(T, moreBytesAvailable: Bool)
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case invalidByteLengthDelimiter
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case protoDeserializationError(Swift.Error)
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}
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}
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/**
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* Input stream for reading and writing a backup file on disk.
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*
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* The backup file is just a sequence of serialized proto bytes, back to back, delimited by varint
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* byte sizes so we know how much to read into memory to deserialize the next proto.
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* The input stream abstracts over this, and allows callers to just think in terms of "frames",
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* the individual proto objects that we read one at a time.
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*/
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public protocol MessageBackupProtoInputStream {
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/// Read the single header object at the start of every backup file.
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/// If this header is missing or invalid, the backup should be discarded.
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func readHeader() -> MessageBackup.ProtoInputStreamReadResult<BackupProto.BackupInfo>
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/// Read a the next frame from the backup file.
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func readFrame() -> MessageBackup.ProtoInputStreamReadResult<BackupProto.Frame>
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/// Close the stream. Attempting to read after closing will result in failures.
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func closeFileStream()
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}
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internal class MessageBackupProtoInputStreamImpl: MessageBackupProtoInputStream {
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private var inputStream: InputStreamable
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private var inputStreamDelegate: StreamDelegate
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internal init(
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inputStream: InputStreamable,
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inputStreamDelegate: StreamDelegate
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) {
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self.inputStream = inputStream
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self.inputStreamDelegate = inputStreamDelegate
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}
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internal func readHeader() -> MessageBackup.ProtoInputStreamReadResult<BackupProto.BackupInfo> {
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return readProto { protoData in
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return try ProtoDecoder(enumDecodingStrategy: .returnNil)
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.decode(BackupProto.BackupInfo.self, from: protoData)
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}
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}
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internal func readFrame() -> MessageBackup.ProtoInputStreamReadResult<BackupProto.Frame> {
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return readProto { protoData in
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return try ProtoDecoder(enumDecodingStrategy: .returnNil)
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.decode(BackupProto.Frame.self, from: protoData)
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}
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}
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public func closeFileStream() {
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try? inputStream.close()
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}
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private func readProto<T>(
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_ initializer: (Data) throws -> T
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) -> MessageBackup.ProtoInputStreamReadResult<T> {
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do {
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let data = try inputStream.read(maxLength: 8192)
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let protoObject = try initializer(data)
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return .success(protoObject, moreBytesAvailable: inputStream.hasBytesAvailable)
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} catch {
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return .protoDeserializationError(error)
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}
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}
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}
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