70 lines
2.0 KiB
Swift
70 lines
2.0 KiB
Swift
//
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// Copyright 2019 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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//
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// Some parts Copyright (c) 2014 - 2016 Apple Inc. and the project authors
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// Those parts Licensed under Apache License v2.0 with Runtime Library Exception
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import Foundation
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enum ChunkedInputStreamError: Error {
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case truncated, malformed
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}
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struct ChunkedInputStream {
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private var remainingData: Data
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init(forReadingFrom dataValue: Data) {
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self.remainingData = dataValue
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}
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mutating func decodeData(count: Int) throws -> Data {
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let result = self.remainingData.prefix(count)
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try consume(length: count)
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return result
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}
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/// Based on SwiftProtobuf.BinaryDecoder.decodeSingularUInt32Field
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mutating func decodeSingularUInt32Field() throws -> UInt32 {
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guard let result = UInt32(exactly: try decodeVarint()) else {
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throw ChunkedInputStreamError.malformed
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}
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return result
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}
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var isEmpty: Bool {
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return self.remainingData.isEmpty
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}
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/// Advance the current position.
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private mutating func consume(length: Int) throws {
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guard self.remainingData.count >= length else {
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throw ChunkedInputStreamError.truncated
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}
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self.remainingData = self.remainingData.dropFirst(length)
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}
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/// Private: Parse the next raw varint from the input.
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///
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/// Based on SwiftProtobuf.BinaryDecoder.decodeVarint()
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private mutating func decodeVarint() throws -> UInt64 {
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var value = 0 as UInt64
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var shift = 0 as UInt64
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while true {
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if shift > 63 {
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throw ChunkedInputStreamError.malformed
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}
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if self.remainingData.isEmpty {
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throw ChunkedInputStreamError.truncated
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}
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let c = self.remainingData.removeFirst()
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value |= UInt64(c & 0x7f) << shift
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if c & 0x80 == 0 {
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return value
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}
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shift += 7
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}
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}
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}
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