scarica un oggetto utilizzando un intervallo di byte

Scarica un oggetto utilizzando un intervallo di byte da un bucket Cloud Storage.

Per saperne di più

Per la documentazione dettagliata che include questo esempio di codice, vedi quanto segue:

Scaricare oggetti

Esempio di codice

C++

Per maggiori informazioni, consulta la documentazione di riferimento dell'API C++ di Cloud Storage.

Per eseguire l'autenticazione in Cloud Storage, configura Credenziali predefinite dell'applicazione. Per maggiori informazioni, consulta Configurare l'autenticazione per un ambiente di sviluppo locale.

namespace gcs = ::google::cloud::storage;
[](gcs::Client client, std::string const& bucket_name,
   std::string const& object_name, std::int64_t start, std::int64_t end) {
  gcs::ObjectReadStream stream =
      client.ReadObject(bucket_name, object_name, gcs::ReadRange(start, end));

  int count = 0;
  std::string line;
  while (std::getline(stream, line, '\n')) {
    std::cout << line << "\n";
    ++count;
  }
  if (stream.bad()) throw google::cloud::Status(stream.status());

  std::cout << "The requested range has " << count << " lines\n";
}

C#

Per maggiori informazioni, consulta la documentazione di riferimento dell'API C# di Cloud Storage.


using Google.Apis.Storage.v1;
using Google.Cloud.Storage.V1;
using System;
using System.IO;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;

public class DownloadByteRangeAsyncSample
{
    public async Task DownloadByteRangeAsync(
        string bucketName = "your-unique-bucket-name",
        string objectName = "my-file-name",
        long firstByte = 0,
        long lastByte = 20,
        string localPath = "my-local-path/my-file-name")
    {
        var storageClient = StorageClient.Create();

        // Create an HTTP request for the media, for a limited byte range.
        StorageService storage = storageClient.Service;
        var uri = new Uri($"{storage.BaseUri}b/{bucketName}/o/{objectName}?alt=media");

        var request = new HttpRequestMessage { RequestUri = uri };
        request.Headers.Range = new RangeHeaderValue(firstByte, lastByte);

        using var outputFile = File.OpenWrite(localPath);
        // Use the HttpClient in the storage object because it supplies
        // all the authentication headers we need.
        var response = await storage.HttpClient.SendAsync(request);
        await response.Content.CopyToAsync(outputFile, null);
        Console.WriteLine($"Downloaded {objectName} to {localPath}.");
    }
}

Go

Per maggiori informazioni, consulta la documentazione di riferimento dell'API Go di Cloud Storage.

import (
	"context"
	"fmt"
	"io"
	"os"
	"time"

	"cloud.google.com/go/storage"
)

// downloadByteRange downloads a specific byte range of an object to a file.
func downloadByteRange(w io.Writer, bucket, object string, startByte int64, endByte int64, destFileName string) error {
	// bucket := "bucket-name"
	// object := "object-name"
	// startByte := 0
	// endByte := 20
	// destFileName := "file.txt"
	ctx := context.Background()
	client, err := storage.NewClient(ctx)
	if err != nil {
		return fmt.Errorf("storage.NewClient: %w", err)
	}
	defer client.Close()

	ctx, cancel := context.WithTimeout(ctx, time.Second*50)
	defer cancel()

	f, err := os.Create(destFileName)
	if err != nil {
		return fmt.Errorf("os.Create: %w", err)
	}

	length := endByte - startByte
	rc, err := client.Bucket(bucket).Object(object).NewRangeReader(ctx, startByte, length)
	if err != nil {
		return fmt.Errorf("Object(%q).NewReader: %w", object, err)
	}
	defer rc.Close()

	if _, err := io.Copy(f, rc); err != nil {
		return fmt.Errorf("io.Copy: %w", err)
	}

	if err = f.Close(); err != nil {
		return fmt.Errorf("f.Close: %w", err)
	}

	fmt.Fprintf(w, "Bytes %v to %v of blob %v downloaded to local file %v\n", startByte, startByte+length, object, destFileName)

	return nil

}

Java

Per maggiori informazioni, consulta la documentazione di riferimento dell'API Java di Cloud Storage.


import com.google.cloud.ReadChannel;
import com.google.cloud.storage.BlobId;
import com.google.cloud.storage.Storage;
import com.google.cloud.storage.StorageOptions;
import com.google.common.io.ByteStreams;
import java.io.IOException;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;

public class DownloadByteRange {

  public static void downloadByteRange(
      String projectId,
      String bucketName,
      String blobName,
      long startByte,
      long endBytes,
      String destFileName)
      throws IOException {
    // The ID of your GCP project
    // String projectId = "your-project-id";

    // The ID of your GCS bucket
    // String bucketName = "your-unique-bucket-name";

    // The name of the blob/file that you wish to modify permissions on
    // String blobName = "your-blob-name";

    // The starting byte at which to begin the download
    // long startByte = 0;

    // The ending byte at which to end the download
    // long endByte = 20;

    // The path to which the file should be downloaded
    // String destFileName = '/local/path/to/file.txt';

    Storage storage = StorageOptions.newBuilder().setProjectId(projectId).build().getService();
    BlobId blobId = BlobId.of(bucketName, blobName);
    try (ReadChannel from = storage.reader(blobId);
        FileChannel to = FileChannel.open(Paths.get(destFileName), StandardOpenOption.WRITE)) {
      from.seek(startByte);
      from.limit(endBytes);

      ByteStreams.copy(from, to);

      System.out.printf(
          "%s downloaded to %s from byte %d to byte %d",
          blobId.toGsUtilUri(), destFileName, startByte, endBytes);
    }
  }
}

Node.js

Per maggiori informazioni, consulta la documentazione di riferimento dell'API Node.js di Cloud Storage.

/**
 * TODO(developer): Uncomment the following lines before running the sample.
 */
// The ID of your GCS bucket
// const bucketName = 'your-unique-bucket-name';

// The ID of your GCS file
// const fileName = 'your-file-name';

// The starting byte at which to begin the download
// const startByte = 0;

// The ending byte at which to end the download
// const endByte = 20;

// The path to which the file should be downloaded
// const destFileName = '/local/path/to/file.txt';

// Imports the Google Cloud client library
const {Storage} = require('@google-cloud/storage');

// Creates a client
const storage = new Storage();

async function downloadByteRange() {
  const options = {
    destination: destFileName,
    start: startByte,
    end: endByte,
  };

  // Downloads the file from the starting byte to the ending byte specified in options
  await storage.bucket(bucketName).file(fileName).download(options);

  console.log(
    `gs://${bucketName}/${fileName} downloaded to ${destFileName} from byte ${startByte} to byte ${endByte}.`
  );
}

downloadByteRange();

PHP

Per maggiori informazioni, consulta la documentazione di riferimento dell'API PHP di Cloud Storage.

use Google\Cloud\Storage\StorageClient;

/**
 * Download a byte range from Cloud Storage and save it as a local file.
 *
 * @param string $bucketName The name of your Cloud Storage bucket.
 *        (e.g. 'my-bucket')
 * @param string $objectName The name of your Cloud Storage object.
 *        (e.g. 'my-object')
 * @param int $startByte The starting byte at which to begin the download.
 *        (e.g. 1)
 * @param int $endByte The ending byte at which to end the download. (e.g. 5)
 * @param string $destination The local destination to save the object.
 *        (e.g. '/path/to/your/file')
 */
function download_byte_range(
    string $bucketName,
    string $objectName,
    int $startByte,
    int $endByte,
    string $destination
): void {
    $storage = new StorageClient();
    $bucket = $storage->bucket($bucketName);
    $object = $bucket->object($objectName);
    $object->downloadToFile($destination, [
        'restOptions' => [
            'headers' => [
                'Range' => "bytes=$startByte-$endByte",
            ],
        ],
    ]);
    printf(
        'Downloaded gs://%s/%s to %s' . PHP_EOL,
        $bucketName,
        $objectName,
        basename($destination)
    );
}

Python

Per maggiori informazioni, consulta la documentazione di riferimento dell'API Python di Cloud Storage.

from google.cloud import storage

def download_byte_range(
    bucket_name, source_blob_name, start_byte, end_byte, destination_file_name
):
    """Downloads a blob from the bucket."""
    # The ID of your GCS bucket
    # bucket_name = "your-bucket-name"

    # The ID of your GCS object
    # source_blob_name = "storage-object-name"

    # The starting byte at which to begin the download
    # start_byte = 0

    # The ending byte at which to end the download
    # end_byte = 20

    # The path to which the file should be downloaded
    # destination_file_name = "local/path/to/file"

    storage_client = storage.Client()

    bucket = storage_client.bucket(bucket_name)

    # Construct a client side representation of a blob.
    # Note `Bucket.blob` differs from `Bucket.get_blob` as it doesn't retrieve
    # any content from Google Cloud Storage. As we don't need additional data,
    # using `Bucket.blob` is preferred here.
    blob = bucket.blob(source_blob_name)
    blob.download_to_filename(destination_file_name, start=start_byte, end=end_byte)

    print(
        "Downloaded bytes {} to {} of object {} from bucket {} to local file {}.".format(
            start_byte, end_byte, source_blob_name, bucket_name, destination_file_name
        )
    )

Ruby

Per maggiori informazioni, consulta la documentazione di riferimento dell'API Ruby di Cloud Storage.

# The ID of your GCS bucket
# bucket_name = "your-unique-bucket-name"

# file_name = "Name of a file in the Storage bucket"

# The starting byte at which to begin the download
# start_byte = 0

# The ending byte at which to end the download
# end_byte = 20

# The path to which the file should be downloaded
# local_file_path = "/local/path/to/file.txt"

require "google/cloud/storage"

storage = Google::Cloud::Storage.new
bucket  = storage.bucket bucket_name
file    = bucket.file file_name

file.download local_file_path, range: start_byte..end_byte

puts "Downloaded bytes #{start_byte} to #{end_byte} of object #{file_name} from bucket #{bucket_name}" \
     + " to local file #{local_file_path}."

Passaggi successivi

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