(Perl) S3 Resume Download

Suppose an S3 download of a very large file failed for some reason and you have a partial file on disk. Rather than restart the entire download, you wish to download the remaining portion. This example demonstrates how to finish a previously failed download.

Note: This example requires Chilkat v9.5.0.83 or above.

Chilkat Perl Downloads Perl Module for Windows, MacOS, Linux, Alpine Linux, Solaris

use chilkat();

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

$rest = chilkat::CkRest->new();

# Connect to the Amazon AWS REST server.
$bTls = 1;
$port = 443;
$bAutoReconnect = 1;
$success = $rest->Connect("s3.amazonaws.com",$port,$bTls,$bAutoReconnect);

# ---------------------------------------------------------------------------
# Important: For buckets created in regions outside us-east-1,
# there are three important changes that need to be made.
# See Working with S3 Buckets in Non-us-east-1 Regions for the details.
# ---------------------------------------------------------------------------

# Provide AWS credentials for the REST call.
$authAws = chilkat::CkAuthAws->new();
$authAws->put_AccessKey("AWS_ACCESS_KEY");
$authAws->put_SecretKey("AWS_SECRET_KEY");
$authAws->put_ServiceName("s3");
$success = $rest->SetAuthAws($authAws);

# Set the bucket name via the HOST header.
# In this case, the bucket name is "chilkat100".
$rest->put_Host("chilkat100.s3.amazonaws.com");

# We want to continue downloading a file.
# The relative local filepath of our previously partially downoaded file is: qa_output/hamlet.xml
# Let's find out how many bytes are already downloaded.
$fac = chilkat::CkFileAccess->new();
$localFilepath = "qa_output/hamlet.xml";
# Note: The FileSize method returns a signed 32-bit integer.  If the file is potentially larger than 2GB, call FileSizeStr instead to return
# the size of the file as a string, then convert to an integer value.
$sz = $fac->FileSize($localFilepath);
if ($sz > 0) {
    print "sz = " . $sz . "\r\n";

    # If the sz equals 42375 bytes, then we want to add a Range header that looks like this:
    # Range: bytes=42375-
    $sbRange = chilkat::CkStringBuilder->new();
    $sbRange->Append("bytes=");
    $sbRange->AppendInt($sz);
    $sbRange->Append("-");
    $rest->AddHeader("Range",$sbRange->getAsString());
    print "Added Range: " . $sbRange->getAsString() . "\r\n";
}

# Send the request to download the remainder of the file.
$success = $rest->SendReqNoBody("GET","/hamlet.xml");
if ($success != 1) {
    print $rest->lastErrorText() . "\r\n";
    exit;
}

# Read the response header.
$responseStatusCode = $rest->ReadResponseHeader();
if ($responseStatusCode < 0) {
    print $rest->lastErrorText() . "\r\n";
    exit;
}

print "Response status code = " . $responseStatusCode . "\r\n";

# We expect a 200 or 206 response status if the file data is coming.
# Otherwise, we'll get a string response body with an error message(or no response body).
if (($responseStatusCode == 200) or ($responseStatusCode == 206)) {

    $bodyStream = chilkat::CkStream->new();

    # The stream's sink will be a file.
    # We will append to the file..
    $bodyStream->put_SinkFile($localFilepath);

    # Indicate that we wish to append to the output file.
    # The SinkFileAppend property was added in Chilkat v9.50.83
    $bodyStream->put_SinkFileAppend(1);

    # Read the response body to the stream.  Given that we've
    # set the stream's sink to a file, it will stream directly
    # to the file.
    $success = $rest->ReadRespBodyStream($bodyStream,1);
    if ($success != 1) {
        print $rest->lastErrorText() . "\r\n";
        exit;
    }

    print "Successfully downloaded the file." . "\r\n";

}
else {
    $errResponse = $rest->readRespBodyString();
    if ($rest->get_LastMethodSuccess() != 1) {
        print $rest->lastErrorText() . "\r\n";
    }
    else {
        print $errResponse . "\r\n";
    }

}