Implementing SimpleFTPSample in swift

Question

I am trying to convert an Objective-C app to swift. I am reaching the part where I need to send a file through FTP to a distant server. I was able to to that in Objective-C but only because I had the SimpleFTPSample project that apple made to help the developers. Right now I have almost complete the conversion between the two language but I am stuck.

I need to convert that code (from SimpleFTPSample+personal):

- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
    // An NSStream delegate callback that's called when events happen on our 
    // network stream.
{
    #pragma unused(aStream)
    assert(aStream == self.networkStream);

    switch (eventCode) {
        case NSStreamEventOpenCompleted: {
            [self updateStatus:@"Opened connection"];
        } break;
        case NSStreamEventHasBytesAvailable: {
            assert(NO);     // should never happen for the output stream
        } break;
        case NSStreamEventHasSpaceAvailable: {
            [self updateStatus:@"Sending"];

            // If we don't have any data buffered, go read the next chunk of data.

            if (self.bufferOffset == self.bufferLimit) {
                NSInteger   bytesRead;

                bytesRead = [self.fileStream read:self.buffer maxLength:kSendBufferSize];

                if (bytesRead == -1) {
                    [self stopSendWithStatus:@"File read error"];
                } else if (bytesRead == 0) {
                    [self stopSendWithStatus:nil];
                } else {
                    self.bufferOffset = 0;
                    self.bufferLimit  = bytesRead;
                }
            }

            // If we're not out of data completely, send the next chunk.

            if (self.bufferOffset != self.bufferLimit) {
                NSInteger   bytesWritten;
                bytesWritten = [self.networkStream write:&self.buffer[self.bufferOffset] maxLength:self.bufferLimit - self.bufferOffset];
                assert(bytesWritten != 0);
                if (bytesWritten == -1) {
                    [self stopSendWithStatus:@"Network write error"];
                } else {
                    self.bufferOffset += bytesWritten;
                }
            }
        } break;
        case NSStreamEventErrorOccurred: {
            [self stopSendWithStatus:@"Stream open error"];
        } break;
        case NSStreamEventEndEncountered: {
            // ignore
        } break;
        default: {
            assert(NO);
        } break;
    }
}

For now I managed to do that :

// An NSStream delegate callback that's called when events happen on our
// network stream.
func stream(theStream: NSStream!, handleEvent streamEvent: NSStreamEvent) {
    switch (streamEvent) {
    case NSStreamEvent.OpenCompleted:
        println("Opened connection")
    case NSStreamEvent.HasBytesAvailable:
        println("Not suposed to happend")
    case NSStreamEvent.HasSpaceAvailable:
        println("Sending")

        // If we don't have any data buffered, go read the next chunk of data.
        if self.bufferOffset == self.bufferLimit {
            var bytesRead: Int
            bytesRead = self.fileStream.read(self.buffer, maxLength: 32768)

            if bytesRead == -1 { self.stopSendWithStatus("File read error") }
            else if bytesRead == 0 { self.stopSendWithStatus(nil) }
            else {
                self.bufferOffset = 0
                self.bufferLimit  = size_t(bytesRead)
            }
        }

        // If we're not out of data completely, send the next chunk.
        if self.bufferOffset != self.bufferLimit {
            var bytesWritten: Int

            bytesWritten = self.networkStream.write(&self.buffer[self.bufferOffset], maxLength: self.bufferLimit - self.bufferOffset)

            if bytesWritten == -1 { self.stopSendWithStatus("Network write error") }
            else { self.bufferOffset += size_t(bytesWritten) }
        }
    case NSStreamEvent.ErrorOccurred:
        self.stopSendWithStatus("Stream open error")
    case NSStreamEvent.EndEncountered:
        println("ignore")
    default:
        println("default")
    }
}

The kind of the used variables is :

var isSending = Bool()
var networkStream: NSOutputStream! = NSOutputStream()
var fileStream: NSInputStream! = NSInputStream()
var buffer: CConstPointer<UInt8>
var bufferOffset = size_t()
var bufferLimit = size_t()

I am stuck for the if self.bufferOffset != self.bufferLimit part.

Apparently &self.buffer[self.bufferOffset] is not correct (does not have a member name subscript), as well as self.bufferLimit - self.bufferOffset (could not find an overload '-' that accepts the supplied arguments)

To be honest I am not even sure to get what &self.buffer[self.bufferOffset] means. (not the variable but the notation.

So if someone has an idea on how to fixe that, he will be very welcomed !

You can find the SimpleFTPSample project here.

Sorry if my english is not perfect.

Answer 1

Here is my plagiarism of apple's SimpleFTPExample to solve my problem of uploading a csv file from an iOS app to a ftp server. I took the PutController objective-c file, cut lots and lots (too much?) out of it an included it into my swift application. I modified the parameters passed to the main PutController function, to pass in the data I wanted to send, the URL it has to go to and the username and password to get onto the server.

The cut down PutController.m

#import "PutController.h"
#include <CFNetwork/CFNetwork.h>

enum {
    kSendBufferSize = 32768
};

@interface PutController () <NSStreamDelegate>

@property (nonatomic, strong, readwrite) NSOutputStream *  networkStream;
@property (nonatomic, strong, readwrite) NSInputStream *   fileStream;
@property (nonatomic, assign, readonly ) uint8_t *         buffer;
@property (nonatomic, assign, readwrite) size_t            bufferOffset;
@property (nonatomic, assign, readwrite) size_t            bufferLimit;

@end

@implementation PutController
{
    uint8_t _buffer[kSendBufferSize];
}

// Because buffer is declared as an array, you have to use a custom getter.  
// A synthesised getter doesn't compile.

- (uint8_t *)buffer
{
    return self->_buffer;
}


- (void)startSend:(NSData *)dataToUpload withURL:(NSURL *)toURL withUsername:(NSString *)username andPassword:(NSString *)password
{
    printf(__FUNCTION__);

    self.fileStream = [NSInputStream inputStreamWithData:dataToUpload];

    [self.fileStream open];

    // Open a CFFTPStream for the URL.

    self.networkStream = CFBridgingRelease(
        CFWriteStreamCreateWithFTPURL(NULL, (__bridge CFURLRef) toURL)
    );

    [self.networkStream setProperty:username forKey:(id)kCFStreamPropertyFTPUserName];
    [self.networkStream setProperty:password forKey:(id)kCFStreamPropertyFTPPassword];

    self.networkStream.delegate = self;
    [self.networkStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.networkStream open];

}

- (void)stopSendWithStatus:(NSString *)statusString
{
    printf(__FUNCTION__);

    if (self.networkStream != nil) {
        [self.networkStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
        self.networkStream.delegate = nil;
        [self.networkStream close];
        self.networkStream = nil;
    }
    if (self.fileStream != nil) {
        [self.fileStream close];
        self.fileStream = nil;
    }
}

- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
    // An NSStream delegate callback that's called when events happen on our 
    // network stream.
{
    printf(__FUNCTION__);

    switch (eventCode) {
        case NSStreamEventOpenCompleted: {
            printf("Opened connection");
        } break;
        case NSStreamEventHasBytesAvailable: {
            printf("should never happen for the output stream");
        } break;
        case NSStreamEventHasSpaceAvailable: {
            printf("Sending");

            // If we don't have any data buffered, go read the next chunk of data.

            if (self.bufferOffset == self.bufferLimit) {
                NSInteger   bytesRead;

                bytesRead = [self.fileStream read:self.buffer maxLength:kSendBufferSize];

                if (bytesRead == -1) {
                    [self stopSendWithStatus:@"File read error"];
                } else if (bytesRead == 0) {
                    [self stopSendWithStatus:nil];
                } else {
                    self.bufferOffset = 0;
                    self.bufferLimit  = bytesRead;
                }
            }

            // If we're not out of data completely, send the next chunk.

            if (self.bufferOffset != self.bufferLimit) {
                NSInteger   bytesWritten;
                bytesWritten = [self.networkStream write:&self.buffer[self.bufferOffset] maxLength:self.bufferLimit - self.bufferOffset];
                assert(bytesWritten != 0);
                if (bytesWritten == -1) {
                    [self stopSendWithStatus:@"Network write error"];
                } else {
                    self.bufferOffset += bytesWritten;
                }
            }
        } break;
        case NSStreamEventErrorOccurred: {
            [self stopSendWithStatus:@"Stream open error"];
        } break;
        case NSStreamEventEndEncountered: {
            // ignore
        } break;
        default: {
            assert(NO);
        } break;
    }
}

@end

Then the PutController.h

#import <UIKit/UIKit.h>

@interface PutController : NSObject

- (void)startSend:(NSData *)dataToUpload withURL:(NSURL *)toURL withUsername:(NSString *)username andPassword:(NSString *)password;
@end

This is the bridging file, that is project wide, to allow the swift application to pick up the objective-C header files. The objective-C code detail can then be mostly ignored. It really is one line.

// PlantRoomChecks-Bridging-Header.h
//
//  Use this file to import your target's public headers that you would like to expose to Swift.
//
#import "PutController.h"

This is my project file that call the PutController. I have cut it to show just the relevant parts.

// Showing that I am not including any networking libraries import UIKit import CoreGraphics

class GraphVC: UIViewController {

var sendFile : PutController = PutController()

let username = "arthur_dent"
let password = "six_times_seven"


func saveData(){

    var filename = "ftp://www.domain.co.uk/subdirectory/datafile"

    // Converting the messing filename into one that can be used as a URL
    let convertedStringForURL = filename.stringByAddingPercentEscapesUsingEncoding(NSUTF8StringEncoding)
    let uploadUrl = NSURL(string: convertedStringForURL!)

    Let dataForFile : NSData = dataFromElseWhere
    let dataToUpload = dataForFile.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)

    // USE THE OBJECTIVE-C VARIABLE
    sendFile.startSend(dataToUpload, withURL: uploadUrl, withUsername: username, andPassword: password)

}

Answer 2

Can't you just compile SimpleFTP into a framework and use its methods directly from swift? No need to rewrite everything, Xcode does that for you. I use that for many custom libraries and it works like a charm. Just add target, and put in the required frameworks, include the framework and you're all set!