mirror of
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36 lines
1.9 KiB
Swift
36 lines
1.9 KiB
Swift
import Foundation
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private let tinyThumbnailHeaderPattern = Data(base64Encoded: "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")
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private let tinyThumbnailFooterPattern = Data(base64Encoded: "/9k=")
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public func decodeTinyThumbnail(data: Data) -> Data? {
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if data.count < 3 {
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return nil
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}
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guard let tinyThumbnailHeaderPattern = tinyThumbnailHeaderPattern, let tinyThumbnailFooterPattern = tinyThumbnailFooterPattern else {
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return nil
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}
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var version: UInt8 = 0
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data.copyBytes(to: &version, count: 1)
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if version != 1 {
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return nil
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}
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var width: UInt8 = 0
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var height: UInt8 = 0
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data.copyBytes(to: &width, from: 1 ..< 2)
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data.copyBytes(to: &height, from: 2 ..< 3)
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var resultData = Data()
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resultData.append(tinyThumbnailHeaderPattern)
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resultData.append(data.subdata(in: 3 ..< data.count))
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resultData.append(tinyThumbnailFooterPattern)
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resultData.withUnsafeMutableBytes { buffer -> Void in
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guard let resultBytes = buffer.baseAddress?.assumingMemoryBound(to: UInt8.self) else {
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return
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}
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resultBytes[164] = width
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resultBytes[166] = height
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}
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return resultData
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}
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