eZ\Publish\Core\FieldType\BinaryBase\BinaryBaseStorage::getFieldData PHP Method

    public function getFieldData(VersionInfo $versionInfo, Field $field, array $context)
    {
        $field->value->externalData = $this->getGateway($context)->getFileReferenceData($field->id, $versionInfo->versionNo);
        if ($field->value->externalData !== null) {
            $binaryFile = $this->IOService->loadBinaryFile($field->value->externalData['id']);
            $field->value->externalData['fileSize'] = $binaryFile->size;
            $field->value->externalData['uri'] = isset($this->downloadUrlGenerator) ? $this->downloadUrlGenerator->getStoragePathForField($field, $versionInfo) : $binaryFile->uri;
        }
    }