(Objective-C) SFTP Upload Large File in Parts

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Demonstrates how to split a large file into N parts and then upload each part separately. This technique can be used to potentially avoid limits a SFTP server might impose on upload file size.

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#import <CkoSFtp.h>
#import <NSString.h>
#import <CkoFileAccess.h>
#import <CkoBinData.h>

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

CkoSFtp *sftp = [[CkoSFtp alloc] init];

// Set some timeouts, in milliseconds:
sftp.ConnectTimeoutMs = [NSNumber numberWithInt:5000];
sftp.IdleTimeoutMs = [NSNumber numberWithInt:10000];

// Connect to the SSH server.  
// The standard SSH port = 22
// The hostname may be a hostname or IP address.
NSString *hostname = @"sftp.example.com";
int port = 22;
BOOL success = [sftp Connect: hostname port: [NSNumber numberWithInt: port]];
if (success != YES) {
    NSLog(@"%@",sftp.LastErrorText);
    return;
}

// Authenticate with the SSH server.  Chilkat SFTP supports
// both password-based authenication as well as public-key
// authentication.  This example uses password authenication.
success = [sftp AuthenticatePw: @"myLogin" password: @"myPassword"];
if (success != YES) {
    NSLog(@"%@",sftp.LastErrorText);
    return;
}

// After authenticating, the SFTP subsystem must be initialized:
success = [sftp InitializeSftp];
if (success != YES) {
    NSLog(@"%@",sftp.LastErrorText);
    return;
}

// Open a remote file for writing on the SSH server.
// If the file already exists, it is overwritten.
// (Specify "createNew" instead of "createTruncate" to
// prevent overwriting existing files.)
NSString *handle = [sftp OpenFile: @"big.zip" access: @"writeOnly" createDisp: @"createTruncate"];
if (sftp.LastMethodSuccess != YES) {
    NSLog(@"%@",sftp.LastErrorText);
    return;
}

// We're going to upload the local file "qa_data/zips/big.zip" (a relative local path from our current working directory)
// to the SFTP server.
NSString *localFilePath = @"qa_data/zips/big.zip";

// Rather than uploading in one shot, we'll read the local file in chunks
// and upload a chunk at a time.
CkoFileAccess *fac = [[CkoFileAccess alloc] init];

success = [fac OpenForRead: localFilePath];
if (success == NO) {
    [sftp CloseHandle: handle];
    NSLog(@"%@",fac.LastErrorText);
    return;
}

// If we were to split the local file into 128K chunks, how many chunks (blocks) would
// we have, including the last partial block?
int blockSize = 131072;
int numBlocks = [[fac GetNumBlocks: [NSNumber numberWithInt: blockSize]] intValue];
NSLog(@"%@%d",@"Number of blocks = ",numBlocks);

CkoBinData *bd = [[CkoBinData alloc] init];
int i = 0;
while (i < numBlocks) {
    // Read the Nth block, which gets appended to the bd.  (which means
    // we must clear the contents of bd before the next iteration)
    success = [fac ReadBlockBd: [NSNumber numberWithInt: i] blockSize: [NSNumber numberWithInt: blockSize] bd: bd];
    if (success == NO) {
        [sftp CloseHandle: handle];
        NSLog(@"%@",fac.LastErrorText);
        return;
    }

    // Upload this block to the open remote file.
    success = [sftp WriteFileBd: handle bd: bd];
    if (success == NO) {
        NSLog(@"%@",sftp.LastErrorText);
        return;
    }

    // Clear the contents for the next iteration.
    [bd Clear];

    i = i + 1;
}

// Close the local file.
[fac FileClose];

// -----------------------------------------------------------------------------
// This is important.  You must close the handle on the server.
// Otherwise open handles will accumulate on the server until eventually a limit
// is reached and the server will fail on a call to OpenFile.
// -----------------------------------------------------------------------------

// Close the remote file handle on the server.
success = [sftp CloseHandle: handle];
if (success != YES) {
    NSLog(@"%@",sftp.LastErrorText);
    return;
}

NSLog(@"%@",@"Success.");