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Streamed binary downloading example for Swift
Added an example showing streaming binary downloads using the Swift SDK. Also made minor adjustments to the upload streaming example, including moving files a bit to build both examples in one package.
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165 changes: 165 additions & 0 deletions
165
swift/example_code/s3/binary-streaming/Sources/streamdown/streamdown.swift
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,165 @@ | ||
| // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved. | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
| // | ||
| /// A simple example that shows how to use the AWS SDK for Swift to | ||
| /// upload files using binary streaming. | ||
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| // snippet-start:[swift.s3.streaming-down.imports] | ||
| import ArgumentParser | ||
| import AWSClientRuntime | ||
| import AWSS3 | ||
| import Foundation | ||
| import Smithy | ||
| import SmithyHTTPAPI | ||
| import SmithyStreams | ||
|
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| // snippet-end:[swift.s3.streaming-down.imports] | ||
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| // -MARK: - Async command line tool | ||
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| struct ExampleCommand: ParsableCommand { | ||
| // -MARK: Command arguments | ||
| @Option(help: "Name of the Amazon S3 bucket to download from") | ||
| var bucket: String | ||
| @Option(help: "Key of the file on Amazon S3 to download") | ||
| var key: String | ||
| @Option(help: "Local path to download the file to") | ||
| var dest: String? | ||
| @Option(help: "Name of the Amazon S3 Region to use (default: us-east-1)") | ||
| var region = "us-east-1" | ||
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| static var configuration = CommandConfiguration( | ||
| commandName: "streamdown", | ||
| abstract: """ | ||
| This example shows how to use binary data streaming to download a file | ||
| from Amazon S3. | ||
| """, | ||
| discussion: """ | ||
| """ | ||
| ) | ||
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| // snippet-start:[swift.s3.streaming-down] | ||
| /// Download a file from the specified bucket. | ||
| /// | ||
| /// - Parameters: | ||
| /// - bucket: The Amazon S3 bucket name to get the file from. | ||
| /// - key: The name (or path) of the file to download from the bucket. | ||
| /// - destPath: The pathname on the local filesystem at which to store | ||
| /// the downloaded file. | ||
| func downloadFile(bucket: String, key: String, destPath: String?) async throws { | ||
| let fileURL: URL | ||
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| // If no destination path was provided, use the key as the name to use | ||
| // for the file in the downloads folder. | ||
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| if destPath == nil { | ||
| do { | ||
| try fileURL = FileManager.default.url( | ||
| for: .downloadsDirectory, | ||
| in: .userDomainMask, | ||
| appropriateFor: URL(string: key), | ||
| create: true | ||
| ).appendingPathComponent(key) | ||
| } catch { | ||
| throw TransferError.directoryError | ||
| } | ||
| } else { | ||
| fileURL = URL(fileURLWithPath: destPath!) | ||
| } | ||
|
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| let config = try await S3Client.S3ClientConfiguration(region: region) | ||
| let s3Client = S3Client(config: config) | ||
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| // Create a `FileHandle` referencing the local destination. Then | ||
| // create a `ByteStream` from that. | ||
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| FileManager.default.createFile(atPath: fileURL.path, contents: nil, attributes: nil) | ||
| let fileHandle = try FileHandle(forWritingTo: fileURL) | ||
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| // Download the file using `GetObject`. | ||
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| let getInput = GetObjectInput( | ||
| bucket: bucket, | ||
| key: key | ||
| ) | ||
|
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| do { | ||
| let getOutput = try await s3Client.getObject(input: getInput) | ||
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| guard let body = getOutput.body else { | ||
| throw TransferError.downloadError("Error: No data returned for download") | ||
| } | ||
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| // If the body is returned as a `Data` object, write that to the | ||
| // file. If it's a stream, read the stream chunk by chunk, | ||
| // appending each chunk to the destination file. | ||
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| switch body { | ||
| case .data: | ||
| guard let data = try await body.readData() else { | ||
| throw TransferError.downloadError("Download error") | ||
| } | ||
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| // Write the `Data` to the file. | ||
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| do { | ||
| try data.write(to: fileURL) | ||
| } catch { | ||
| throw TransferError.writeError | ||
| } | ||
| break | ||
|
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| case .stream(let stream as ReadableStream): | ||
| while (true) { | ||
| let chunk = try await stream.readAsync(upToCount: 5 * 1024 * 1024) | ||
| guard let chunk = chunk else { | ||
| break | ||
| } | ||
|
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| // Write the chunk to the destination file. | ||
|
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| do { | ||
| try fileHandle.write(contentsOf: chunk) | ||
| } catch { | ||
| throw TransferError.writeError | ||
| } | ||
| } | ||
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| break | ||
| default: | ||
| throw TransferError.downloadError("Received data is unknown object type") | ||
| } | ||
| } catch { | ||
| throw TransferError.downloadError("Error downloading the file: \(error)") | ||
| } | ||
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| print("File downloaded to \(fileURL.path).") | ||
| } | ||
| // snippet-end:[swift.s3.streaming-down] | ||
|
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| // -MARK: - Asynchronous main code | ||
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| /// Called by ``main()`` to run the bulk of the example. | ||
| func runAsync() async throws { | ||
| try await downloadFile(bucket: bucket, key: key, destPath: dest) | ||
| } | ||
| } | ||
|
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| // -MARK: - Entry point | ||
|
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| /// The program's asynchronous entry point. | ||
| @main | ||
| struct Main { | ||
| static func main() async { | ||
| let args = Array(CommandLine.arguments.dropFirst()) | ||
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| do { | ||
| let command = try ExampleCommand.parse(args) | ||
| try await command.runAsync() | ||
| } catch let error as TransferError { | ||
| print("ERROR: \(error.errorDescription ?? "Unknown error")") | ||
| } catch { | ||
| ExampleCommand.exit(withError: error) | ||
| } | ||
| } | ||
| } |
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swift/example_code/s3/binary-streaming/Sources/streamup/TransferError.swift
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,19 @@ | ||
| // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved. | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
|
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| /// Errors thrown by the example's functions. | ||
| enum TransferError: Error { | ||
| /// An error occurred while reading the file's contents. | ||
| case readError | ||
| /// An error occurred while uploading a file to Amazon S3. | ||
| case uploadError(_ message: String = "") | ||
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| var errorDescription: String? { | ||
| switch self { | ||
| case .readError: | ||
| return "An error occurred while reading the file data" | ||
| case .uploadError(message: let message): | ||
| return "An error occurred attempting to upload the file: \(message)" | ||
| } | ||
| } | ||
| } |
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