BOTA Sender tutorial

This short tutorial shows how to use the BOTA Sender API in order to start and manage a BOTA transfer. For the purpose of this tutorial we will assume that we want to write a functional OS thread, that initializes and handles the BOTA Sender service. It will also start and manage a single transfer.

The general scheme of the BOTA Sender thread

BOTA API follows an object-oriented style of programming. In order to use the BOTA Sender service we need its instance: BotaSender. First, the instance needs to be initialized through a call to BOTA_SENDER_Init. Next, the service is handled through a repeating call to BOTA_SENDER_Proc. Once the service is not needed, it can be deinitialized by a call to BOTA_SENDER_Deinit.

Let's start to write some thread code. In general the BOTA service thread will look like this:

#include "bota_sender.h" // the one and only header file needed to use the BOTA Sender service
 
// BOTA Sender instance
BotaSender botaSender;
 
// Time provider function needed for BOTA. This function should return the number of milliseconds passing.
static uint64_t botaTimeFunc(void) {
    return GetTickCount();
}
 
// The BOTA Sender thread
void BotaThread(void* arg) {
    // Initialize BOTA service
    BOTA_SENDER_Init(&botaSender, BOTA_DEFAULT_PORT, botaTimeFunc);
    while (1) {
        // Process the BOTA service
        BOTA_SENDER_Proc(&botaSender);
        // Add some delay - in general anywhere near 10ms-100ms is sufficient
        Sleep(10);
    }
    // Deinitialize the BOTA service
    BOTA_SENDER_Deinit(&botaSender);
}

The above code initializes and runs the service, but since there are no transfers defined it will mostly be IDLE code.

Starting a transfer

In order to start a BOTA transfer a call to BOTA_SENDER_StartTransfer is needed. But this call requires couple of things. We will discuss them one by one below:

Bulk memory

BOTA Sender accesses the data to send through a callback 'read' function. The user is expected to provide an implementation of such function, allowing to access the data that should be send. Let's look at a simple example:

static uint8_t bulkToSend[] = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod "
                              "tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim "
                              "veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea "
                              "commodo consequat. Duis aute irure dolor in reprehenderit in voluptate "
                              "velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint "
                              "occaecat cupidatat non proident, sunt in culpa qui officia deserunt "
                              "mollit anim id est laborum.";
 
static void readFunc(BotaMemoryAddr addr, void* dst, size_t size, BotaTransferId transferId) {
    memcpy(dst, bulkToSend + addr, size);
}

In the above example the 'botaSenderReadFunc' is the read function that reads from a static memory buffer 'bulkToSend'.

In order to define the Bulk Memory during the start of the transfer, the user code is expected to provide:

'readFunc' (as shown above)
'readAddr' - additional read offset in the bulk memory (for the above read function this address should be 0)
'size' - total size (in number of bytes) of the data to be sent

Recipient IPv6 address

The recipient(s) of the transfer are defined using IPv6 address. This can be an unicast address or group address. If unicast addressing is used, then there is only one expected recipient. In case of group addressing there might potentially be many recipients. The recipient address is provided as 'recipientAddr' in the call to BOTA_SENDER_StartTransfer.

Transfer information

When the transfer is started we can pass additional information describing it. This information is user-defined and can contain up to 32 bytes. In the above example we've used a simple string containing "testTransfer".

Transfer space

In order to handle multiple recipients the BOTA Sender instance needs additional operational memory called 'transfer space'. This memory is provided through the following arguments of the BOTA_SENDER_StartTransfer call:

transferSpace - pointer to the transfer space size
transferSpaceSize - size (in number of bytes) of the transfer space

You can use the BOTA_SENDER_GetRequiredTransferSpaceSize call to determine how much memory is needed in order to handle a given number of recipients. The code below illustrates this idea:

    // Get required transfer space assuming that we will handle 100 recipients
    size_t transferSpaceSize = BOTA_SENDER_GetRequiredTransferSpaceSize(100);
    // Allocate the necessary memory
    void* transferSpace = malloc(transferSpaceSize);

Callbacks

As an option we can define two additional callbacks, that will inform about some important events during the BOTA transfer:

onTransferAccepted - is a callback that will be called each time a new recipient accepts an incoming transfer
onTransferFinished - is a callback that will be called once the transfer is done

Some exemplary callback implementation is shown below:

static void onTransferAcceptedCallback(BotaTransferId transferId, const EMBENET_IPV6* recepientAddr) {
    printf("Transfer was accepted\n");
}
 
static void onTransferFinishedCallback(BotaTransferId transferId) {
    printf("Transfer was finished\n");
    // explicitly end the transfer removing it from the transfer list
    BOTA_SENDER_EndTransfer(&botaSender, transferId);
}

Ending the transfer

Note that we must explicitly end the transfer by a call to BOTA_SENDER_EndTransfer. In the above example this is done in the onTransferFinished callback.

The BOTA_SENDER_EndTransfer can also be called to end and ongoing transfer.

Putting it all together to manage a transfer

The example below merges all the above code into a thread that runs the BOTA Sender service and starts a single transfer.

#include "bota_sender.h" // the one and only header file needed to use the BOTA Sender service
 
// BOTA Sender instance
BotaSender botaSender;
 
// Time provider function needed for BOTA. This function should return the number of milliseconds passing.
static uint64_t botaTimeFunc(void) {
    return GetTickCount();
}
 
static uint8_t bulkToSend[] = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod "
                              "tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim "
                              "veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea "
                              "commodo consequat. Duis aute irure dolor in reprehenderit in voluptate "
                              "velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint "
                              "occaecat cupidatat non proident, sunt in culpa qui officia deserunt "
                              "mollit anim id est laborum.";
 
static void readFunc(BotaMemoryAddr addr, void* dst, size_t size, BotaTransferId transferId) {
    memcpy(dst, bulkToSend + addr, size);
}
 
 
static void onTransferAcceptedCallback(BotaTransferId transferId, const EMBENET_IPV6* recepientAddr) {
    printf("Transfer was accepted\n");
}
 
static void onTransferFinishedCallback(BotaTransferId transferId) {
    printf("Transfer was finished\n");
    // explicitly end the transfer removing it from the transfer list
    BOTA_SENDER_EndTransfer(&botaSender, transferId);
}
 
 
// The BOTA Sender thread
void BotaThread(void* arg) {
    // Initialize BOTA service
    BOTA_SENDER_Init(&botaSender, BOTA_DEFAULT_PORT, botaTimeFunc);
 
    // Get required transfer space assuming that we will handle 100 recipients
    size_t transferSpaceSize = BOTA_SENDER_GetRequiredTransferSpaceSize(100);
    // Allocate the necessary memory
    void* transferSpace = malloc(transferSpaceSize);
 
    // This variable will hold the transfer identifier
    BotaTransferId transferId;
    // Start the transfer
    BotaResult result;
    result = BOTA_SENDER_StartTransfer(&botaSender,                // sender instance
                                       readFunc,                   // read function
                                       0,                          // read address
                                       sizeof(bulkToSend),         // total size of the bulk data to send
                                       NULL,                       // recipient address
                                       BOTA_DEFAULT_PORT,          // recipient port
                                       "lorem ipsum",              // additional transfer information
                                                                   // (user defined)
                                       12,                         // size (in bytes) of the additional
                                                                   // transfer information (up to 32 bytes)
                                       transferSpace,              // transfer space
                                       transferSpaceSize,          // transfer space size
                                       onTransferAcceptedCallback, // on transfer accepted callback
                                       onTransferFinishedCallback, // on transfer finished callback
                                       &transferId                 // place to store the transfer identifier
    );
    if (result != BOTA_RESULT_OK) {
        printf("Unable to start BOTA transfer\n");
    }
 
    while (1) {
        // Process the BOTA service
        BOTA_SENDER_Proc(&botaSender);
        // Add some delay - in general anywhere near 10ms-100ms is sufficient
        Sleep(10);
    }
    // Deinitialize the BOTA service
    BOTA_SENDER_Deinit(&botaSender);
}

Monitoring the transfer

At any point after starting the transfer it is possible to poll the transfer status using BOTA_SENDER_GetTransferStatus function. Also it is possible to retrieve the current number of transfer recipients and basic information about each recipient using BOTA_SENDER_GetRecipientCount and BOTA_SENDER_GetRecipient functions. The example below illustrates the usage.

        // Get transfer status
        BotaTransferStatus status = BOTA_SENDER_GetTransferStatus(&botaSender, transferId);
        // Print out status based on the transfer state
        switch (status.transferState) {
            case BOTA_TRANSFER_STATE_FINISHED:
                // note that in this code this will not happen, if we end the transfer immediately
                // in the onTransferFinished callback
                printf("Transfer was finished");
                // get number of recipients
                size_t recipientCount = BOTA_SENDER_GetRecipientCount(&botaSender, transferId);
                // go through all recipients
                for (size_t i = 0; i < recipientCount; i++) {
                    // get information about the recipient 'i'
                    BotaTransferRecipient* recipient = BOTA_SENDER_GetRecipient(&botaSender, transferId, i);
                    printf("Transfer recipient with uid=%" PRIu64 "\n", recipient->uid);
                }
                // end the transfer since it was finished, removing it from the transfer list
                BOTA_SENDER_EndTransfer(&botaSender, transferId);
                break;
            case BOTA_TRANSFER_STATE_ERROR:
                printf("Transfer error\n"); // the transfer was unable to finish - better end it
                BOTA_SENDER_EndTransfer(&botaSender, transferId);
                break;
            case BOTA_TRANSFER_STATE_UNKNOWN:
                printf("Unknown transfer\n"); // whoops, something went really wrong
                break;
            default: printf("Transfer is ongoing. Bytes sent: %u of %u \n", (unsigned int)status.transferredBytes, (unsigned int)status.totalBytes); break;
        }

Note that once we end the transfer through a call to BOTA_SENDER_EndTransfer we no longer can poll its status.

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