Zig

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. Zig

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

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

    const sftp = try chilkat.SFtp.init();
    defer sftp.deinit();

    // Set some timeouts, in milliseconds:
    sftp.setConnectTimeoutMs(5000);
    sftp.setIdleTimeoutMs(10000);

    // Connect to the SSH server.
    // The standard SSH port = 22
    // The hostname may be a hostname or IP address.
    const hostname = "sftp.example.com";
    const port = 22;
    sftp.connect(hostname, port) catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        return;
    };

    // Authenticate with the SSH server.  Chilkat SFTP supports
    // both password-based authenication as well as public-key
    // authentication.  This example uses password authenication.
    sftp.authenticatePw("myLogin", "myPassword") catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        return;
    };

    // After authenticating, the SFTP subsystem must be initialized:
    sftp.initializeSftp() catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        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.)
    const handle = sftp.openFile(alloc, "big.zip", "writeOnly", "createTruncate") catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        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.
    const local_file_path = "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.
    const fac = try chilkat.FileAccess.init();
    defer fac.deinit();

    fac.openForRead(local_file_path) catch {
        sftp.closeHandle(handle) catch {};
        std.debug.print("{s}\n", .{try fac.getLastErrorText(alloc)});
        return;
    };

    // If we were to split the local file into 128K chunks, how many chunks (blocks) would
    // we have, including the last partial block?
    const block_size = 131072;
    const num_blocks = fac.getNumBlocks(block_size);
    std.debug.print("Number of blocks = {d}\n", .{num_blocks});

    const bd = try chilkat.BinData.init();
    defer bd.deinit();
    var i: i32 = 0;
    while (i < num_blocks) {
        // Read the Nth block, which gets appended to the bd.  (which means
        // we must clear the contents of bd before the next iteration)
        fac.readBlockBd(i, block_size, bd) catch {
            sftp.closeHandle(handle) catch {};
            std.debug.print("{s}\n", .{try fac.getLastErrorText(alloc)});
            return;
        };

        // Upload this block to the open remote file.
        sftp.writeFileBd(handle, bd) catch {
            std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
            return;
        };

        // Clear the contents for the next iteration.
        bd.clear() catch {};

        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.
    sftp.closeHandle(handle) catch {
        std.debug.print("{s}\n", .{try sftp.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("Success.\n", .{});
}