File content as of revision 3:e8d2ebb7392e:

#include "mbed.h"
#include "Utils.h"
#include "hci.h"
#include "sdp_data.h"
#include "sdp.h"

SDPManager SDP; //instance
const unsigned char base_uuid[16] = { 0xfb, 0x34, 0x9b, 0x5f, 0x80, 0, 0x07, 0x70, 0, 0x10, 0, 0};
map<unsigned, serv_rec*> SDPManager::server;
int SDPManager::serverSock = 0;

void attribHandler(serv_rec *r) {
    printf("Service 0x%08X\n", (*r)[0x0000]->asUnsigned());
    map<unsigned short, sdp_data*>::iterator it = r->begin();
    for (;it != r->end();it++) {
        printf("   0x%04X: %s\n", (*it).first, (*it).second->asString());
    }
}

#define BROWSEROOT  0x1002
#define SERIALSERV  0x1101

SDPHandler::SDPHandler(): txid(1), tree(0) {
    ErrorResponse=errorhandler;
    ServiceSearchResponse=0;
    ServiceAttributeResponse=attribHandler;
    ServiceSearchAttributeResponse=0;
    buf = l2cap_buf+OFFSET;
    contBuf = 0;
    byteCount = 0;
    contState[0] = 0;
    _state = 0;
}

void SDPHandler::Clear() {
    for (index = services.begin(); index != services.end(); index++) {//for all services
        for (serv_rec::iterator it = index->second->begin(); it != index->second->end(); it++)//for all attributes
            delete it->second; //delete the attribute value tree
        delete (*index).second; //delete the attribute list
    }
    services.clear();//and empty the services list
}

//Called as: Socket_Open(SOCKET_SDP, addr, callback, userdata(this)) from SDPManager
//never called
int SDPHandler::Open(SocketInternal* sock, SocketAddrHdr* addr) {
    printf("Successfully opened SDP socket %d\n", sock->ID);
    sock->SetState(SocketState_Open);
    sdp_socket = sock->ID;
    return sdp_socket;
}

int SDPHandler::Send(SocketInternal* sock, const u8* data, int len) {
    printf("SDPHandler::Send should not be called directly\n");
//        return Socket_Send(_l2cap, data, len);
    BTDevice *l2cap = (BTDevice*)sock->userData;
    return l2cap->Send(sock, data, len);
}

int SDPHandler::Close(SocketInternal* sock) {
    printf("SDPHandler::Close(%d)\n", sock->ID);
    Clear();
//    printf("SDP socket %d and L2CAP socket %d closed, freemem=%d\n", sock->ID, _l2cap, AvailableMemory(1));
    int retval = 0;//Socket_Close(_l2cap);//could also keep it open for the next connection
    return retval;
}

//this function is called when the L2CAP layer receives SDP packets (see SDPHandler::Open), userdata is the sdpmanager instance
void SDPHandler::OnSdpRsp(int socket, SocketState state, const u8* data, int len, void* userData) {
    printf("\x1B[%dm", 35);
//        printf("OnSdpRsp(socket=%d, state=%d, len=%d)\n", socket, state, len);
    printf("SDPHandler::OnSdpRsp(socket=%d, state=%d, len=%d, freemem=%d\n", socket, state, len, AvailableMemory(1));
    SDPHandler *self = (SDPHandler*)userData;
    if (state == SocketState_Open) {
        self->sdp_socket = socket;
        self->OnSdpRsp(data, len);
    } else if (state == SocketState_Closed) {
        SDP.Destroy(socket);
    }
    printf("\x1B[%dm", 0);
}

//this function is called when the L2CAP layer receives SDP packets (see SDPHandler::Open), userdata is the sdpmanager instance
//void SDPHandler::OnSdpRsp(int socket, SocketState state, const u8* data, int len, void* userData) {
void SDPHandler::OnSdpRsp(const u8* data, int len) {
    static sdp_data list(sdp_data::SEQUENCE);
    static sdp_data all(0x0000ffffU,4);
    static sdp_data serviceID(0U, 2);
    static sdp_data name(0x100U, 2);
    static sdp_data root(sdp_data::UUID, BROWSEROOT);
    static sdp_data req(sdp_data::SEQUENCE);
    static bool once = true;
//    printf("_state=%d first=%d   ", _state, once);
    if (once) {
        list.add_element(&all);
        //list.add_element(&serviceID);
        //list.add_element(&name);
        req.add_element(&root);
        once = false;
    }
    if (data) {
        parseRsp(data, len);
    }
    switch (_state) {
        case 0: //closed
            if (len==0) { //socket just opened
                //'Open' cleared the services list
                ServiceSearchRequest(&req, 10);
                _state = 1; //wait for service handles
            }
            break;
        case 1: //service handles arriving
            if (contState[0]) {//continuation, repeat request
                ServiceSearchRequest(&req, 5);
            } else {
                if (data[0]==3) {
                    index = services.begin();
                    if (index != services.end()) {
                        unsigned handle = (*index).first;
                        //printf("req.: handle %#X\n", handle);
                        ServiceAttributeRequest(handle, 100, &list);//0x1001D
                    } else
                        printf(" - empty list - \n");//should not happen
                    _state = 2; //wait for attribute response
                } else
                    printf("Expected a ServiceSearchResponse 0x03, got %#x\n", data[0]);
            }
            break;
        case 2:
            if (contState[0])//repeat request
                ServiceAttributeRequest((*index).first, 100, &list);
            else {
                if (data[0]==5) {
                    index++; //move to next service
                    if (index != services.end()) {
                        //printf("req.: handle %#X\n", (*index).first);
                        ServiceAttributeRequest((*index).first, 100, &list);
                    } else {
                        printf(" - end of list - \n");
                        Socket_Close(sdp_socket); //Note: socket=L2CAP, sdp_socket=SDP !!!
                        _state = 0;
                    }
                } else
                    printf("Expected a ServiceAttributeResponse 0x05, got %#x\n", data[0]);
            }
            break;
    }
}

//this function is called when the SDP sockets receives data (see HCICallback in TestShell),
//currently does not happen because not forwarded from OnSdpRsp, can be used to handle multiple connections
void SDPHandler::OnSockCallback(int socket, SocketState state, const u8* data, int len, void* userData) {
    printf("SDPHandler::OnSockCallback(socket=%d, state=%d, len=%d)\n", socket, state, len);
    printfBytes("Got SDP Response from socket: ", data, len);
}

//void SDPHandler::errorhandler(unsigned err) {//default error handler
void errorhandler(unsigned err) {//default error handler
    switch (err) {
        case 1:
            printf("Unsupported version of SDP\n");
            break;
        case 2:
            printf("Invalid SDP ServiceRecordHandle\n");
            break;
        case 3:
            printf("SDP syntax error\n");
            break;
        case 4:
            printf("PDU size was invalid\n");
            break;
        case 5:
            printf("Continuation state was invalid\n");
            break;
        case 6:
            printf("SDP server has insufficient resources\n");
            break;
        default:
            printf("Unknown SDP error code\n");
            break;
    }
}

int SDPHandler::ServiceSearchRequest(sdp_data *sp, unsigned count, unsigned cs) {
    int parlen = sp->Size() + contState[0] + 3;
    buf[0] = 2; //pdu
    buf[1] = txid>>8;
    buf[2] = txid++;
    buf[4] = parlen;
    buf[3] = parlen>>8;
    int p = sp->build(buf+5, 100-10);
    buf[p+6] = count;
    buf[p+5] = count>>8;
    buf[p+7] = contState[0];
    for (int j = 1; j <= contState[0]; j++)
        buf[p+j+7] = contState[j];
    //printfBytes("SDP Send: ", buf, parlen+5);
    return Socket_Send(sdp_socket, l2cap_buf, parlen + 5 + OFFSET);
}

int SDPHandler::ServiceAttributeRequest(unsigned handle, unsigned count, sdp_data* al, unsigned cs) {
    int parlen = al->Size() + contState[0] + 7;
    buf[0] = 4; //pdu
    buf[1] = txid>>8;
    buf[2] = txid++;
    buf[4] = parlen;
    buf[3] = parlen>>8;
    for (int i = 0; i < 4; i++)
        buf[i+5] = ((char*)&handle)[3-i];
    buf[9] = count>>8;
    buf[10] = count;
    int p = al->build(buf+11, 100-26);
    buf[p+11] = contState[0];
    for (int j = 1; j <= contState[0]; j++)
        buf[p+j+11] = contState[j];
    //printfBytes("SDP Send: ", buf, parlen+5);
    return Socket_Send(sdp_socket, l2cap_buf, parlen + 5 + OFFSET);
}

int SDPHandler::ServiceSearchAttributeRequest(sdp_data *sp, unsigned count, sdp_data* al, unsigned cs) {
    int parlen = sp->Size() + al->Size() + contState[0] + 3; // count (2 bytes) + at least 1 cont
    buf[0] = 6; //pdu
    buf[1] = txid>>8;
    buf[2] = txid++;
    buf[4] = parlen;
    buf[3] = parlen>>8;
    int p = sp->build(buf+5, 30);
    buf[p+6] = count;
    buf[p+5] = count>>8;
    p += al->build(buf+11, 100-38);
    buf[p+7] = contState[0];
    for (int j = 1; j <= contState[0]; j++)
        buf[p+j+7] = contState[j];
    //printfBytes("SDP Send: ", buf, parlen+5);
    return Socket_Send(sdp_socket, l2cap_buf, parlen + 5 + OFFSET);
}

int SDPManager::ServiceSearchAttributeReply(unsigned rxid, sdp_data* al, unsigned count, unsigned cs) {
    unsigned size = al->Size();
    unsigned cont = 0;//outgoing continuation
    unsigned char *_buf = new unsigned char[OFFSET+5+2+size+3];
    unsigned char *buf = _buf+OFFSET;
    unsigned byteCount = size - cs; //remainder of data to send
    unsigned parlen = 2 + byteCount + 1 ;// attributelistbytecount+payload+no_continuation
    if (byteCount > count) {//still too large, need continuation
        byteCount = count; //limit at maximum
        cont = cs + count; //start for next iteration
        parlen = 2 + byteCount + 3; //adjusted for payload and continuation
        printf("Need continuation, sending bytes [%d, %d> of attributeList\n", cs, cont);
    } else {
     //   printf("Final or only block, sending bytes [%d, %d> of attributeList\n", cs, cs+byteCount);
    }
    buf[0] = 7; //pdu
    buf[1] = rxid>>8;
    buf[2] = rxid;
    buf[3] = parlen>>8;
    buf[4] = parlen;
    buf[5] = byteCount>>8;
    buf[6] = byteCount;
    int p = al->build(buf+7, size);//limited only by buffersize
    //printf("'build' added %d bytes to the buffer\n", p);
    if (cs == 0) { //this is not a continuation
        buf[byteCount+7] = 0;
    } else { //this is a continuation
        memcpy(buf+7, buf+7+cs, byteCount);//move part of interrest to beginning of buffer
        buf[byteCount+7] = 2;
        buf[byteCount+8] = cont>>8;
        buf[byteCount+9] = cont;
    }
    //printfBytes("SDP Send: ", buf, parlen+5);
    int retval = Socket_Send(serverSock, _buf, parlen + 5 + OFFSET);
    delete[] _buf;
    return retval;
}

//unsigned SDPHandler::getval(const unsigned char *p, int n) {
unsigned getval(const unsigned char *p, int n) {
    unsigned ret = 0;
    for (int i = 0; i < n; i++)
        ret = (ret<<8) + (unsigned)p[i];
    return ret;
}

//unsigned SDPHandler::length(const unsigned char *el, unsigned &p) {
unsigned length(const unsigned char *el, unsigned &p) {
    unsigned len = 0;
    switch (el[p++] & 7) {//length
        case 0:
            len = 1;
            break;
        case 1:
            len = 2;
            break;
        case 2:
            len = 4;
            break;
        case 3:
            len = 8;
            break;
        case 4:
            len = 16;
            break;
        case 7://4bytes
            len= el[p++]<<24;
            len += el[p++]<<16;
        case 6://2bytes
            len += el[p++]<<8;
        case 5://1byte
            len += el[p++];
            break;
    }
    return len;
}

extern "C" void HardFault_Handler() {
    printf("Hard Fault! %d bytes left\n", AvailableMemory(1));
    while (1);
}

unsigned SDPHandler::parseLight (const unsigned char *el, unsigned count, sdp_data* &result, serv_rec* &record) {
    unsigned p = 0;
    unsigned len = length(el, p);
    int end = p+len;//end is the index of the item just after the sequence
    sdp_data *item = 0;
    switch (el[0]>>3) {//type
        case sdp_data::NULL_:
            printf("NULL ");
            break;
        case sdp_data::UNSIGNED:
            printf("UINT%d=%u ", len, (unsigned)getval(el+p, len));
            break;
        case sdp_data::SIGNED:
            printf("INT%d=%d ", len, (unsigned)getval(el+p, len));
            break;
        case sdp_data::UUID:
            if (len==16) {
                printf("UUID16= ");
                for (int i = 0; i < 16; i++)
                    printf("%02x ", el[p+i]);
            } else
                printf("UUID%d=%u ", len, (unsigned)getval(el+p, len));
            break;
        case sdp_data::STRING:
            printf("STR%d='%s' ", len, (char*)el+p);
            break;
        case sdp_data::BOOL:
            printf("BOOL%d=%d ", len, (unsigned)getval(el+p, len));
            break;
        case sdp_data::SEQUENCE:
            goto skip;
        case sdp_data::ALTERNATIVE:
skip: {//p points just after the length indicator, hence at the first item IN the sequence
                printf("SEQ%d{%p ", len, item);
                int n = 0;
                unsigned short key;
                serv_rec *dummy = 0;
                while (p < end) {
                    sdp_data *elem = 0;
                    p += parseLight(el + p, len-p, elem, dummy);//parse each element in the sequence, the second arg is as yet unused
                    if (record) {
                        if (n & 1) { //value
                            record->insert(pair<unsigned short, sdp_data*>(key, elem));
                        } else //key
                            key = n;
                        n++;
                    }
                }
            }
            printf("}\n");
            break;
        case 8:
            printf("URL%d='%s' ", len, (char*)el+p);
            break;
        default:
            printf("Parse: Unknown type %d, len=%d (code=%#02X)\n", el[0]>>3, len, el[0]);
    }
    result = item;
    return end;
}

unsigned SDPHandler::parse (const unsigned char *el, unsigned count, sdp_data* &result, serv_rec* &record) {
    unsigned p = 0;
    unsigned len = length(el, p);
    int end = p+len;//end is the index of the item just after the sequence
    sdp_data *item = 0;
    switch (el[0]>>3) {//type
        case sdp_data::NULL_:
            item = new sdp_data();
            break;
        case sdp_data::UNSIGNED:
            item = new sdp_data((unsigned)getval(el+p, len), len);
            break;
        case sdp_data::SIGNED:
            item = new sdp_data((int)getval(el+p, len), len);
            break;
        case sdp_data::UUID:
            if (len==16) {
                char rev[16];
                for (int i = 0; i < 16; i++)
                    rev[i] = el[p+15-i];
                item = new sdp_data(sdp_data::UUID, rev, len);
            } else
                item = new sdp_data(sdp_data::UUID, getval(el+p, len), len);
            break;
        case sdp_data::STRING:
            item = new sdp_data((char*)el+p, len);
            break;
        case sdp_data::BOOL:
            item = new sdp_data((bool)getval(el+p, len), len);
            break;
        case sdp_data::SEQUENCE:
            item = new sdp_data(sdp_data::SEQUENCE);
            goto skip;
        case sdp_data::ALTERNATIVE:
            item = new sdp_data(sdp_data::ALTERNATIVE);
skip: {//p points just after the length indicator, hence at the first item IN the sequence
                //printf("SEQ%d{%p ", len, item);
                int n = 0;
                unsigned short key;
                serv_rec *dummy = 0;//means: there is no service record to fill in for deeper levels
                while (p < end) {
                    sdp_data *elem = 0; //this becomes the tree with attribute values
                    p += parse(el + p, len-p, elem, dummy);//parse each element in the sequence, the second arg is as yet unused
                    if (record) { //if at the level of attribute list, add elem to record as key/value pair
                        if (n & 1) { //value
                            record->insert(pair<unsigned short, sdp_data*>(key, elem));
                        } else //key
                            key = elem->asUnsigned();
                        n++;
                    } else //just add the elements to the value tree
                        item->add_element(elem);
                }
            }
            //printf("}\n");
            break;
        case 8:
            item = new sdp_data(sdp_data::URL, (char*)el+p, len);
            break;
        default:
            printf("Parse: Unknown type %d, len=%d (code=%#02X)\n", el[0]>>3, len, el[0]);
    }
    result = item;
    return end;
}

void SDPHandler::append(const unsigned char *payload, int len) {
    unsigned char *tmp = new unsigned char[byteCount + len];//append the payload to the previous continuation buffer
    if (contBuf && byteCount) {
        memcpy(tmp, contBuf, byteCount); //copy the existing part
        delete[] contBuf;//delete the old buffer
    }
    memcpy(tmp+byteCount, payload, len); //append the new part
    contBuf = tmp;
    byteCount += len;
}

void SDPHandler::freeBuf() {
    if (contBuf) {
        delete[] contBuf;
        contBuf = 0;
    }
    byteCount = 0;
}


//TODO: test case 7, add server support (cases 2, 4, 6)
//3 cases: cont==0 && contBuf==0 -> use rsp; cont!=0 -> append; cont==0 && contBuf!=0 -> append and use contBuf
int SDPHandler::parseRsp(const unsigned char*rsp, int len) {
    //unsigned tid = rsp[2] + ((unsigned)rsp[1]<<8);
    unsigned parlen = rsp[4] + ((unsigned)rsp[3]<<8);
    //printf("ParseRsp: tid=%04X, parlen=%d ", tid, parlen);
    unsigned cont = 0;
    switch (rsp[0]) {
        case 1: {//errorRsp
            unsigned errorcode = rsp[6] + ((unsigned)rsp[5]<<8);
            if (parlen > 2) {
                printf("ErrorInfo (%d bytes) for error %d is available\n", parlen-2, errorcode);
            }
            if (ErrorResponse)
                ErrorResponse(errorcode);
            return errorcode;
        }
        //break;
        case 3: { //servicesearchRsp
            unsigned total = rsp[6] + ((unsigned)rsp[5]<<8);
            unsigned current = rsp[8] + ((unsigned)rsp[7]<<8);
            cont = rsp[9+4*current];
            memcpy(contState, &rsp[9+4*current], cont+1);//copy the continuation state
            //printf("total=%d, current=%d, cont=%d\n", total, current, cont);
            if (cont) {
                //no special handling here, just append the servicerecordhandles
            }
            //linear list of 32bit service-handles
            for (int i = 0; i < current; i++) {
                unsigned result = 0;
                for (int j = 0; j< 4; j++)
                    result = (result<<8) + rsp[9 + 4*i + j];
                printf("SDP Search handle %08X\n", result);
                services.insert(pair<unsigned, serv_rec*>(result, 0));
            }
            if (ServiceSearchResponse)
                ServiceSearchResponse();
        }
        break;
        case 5: { //serviceattributeRsp
            unsigned count = rsp[6] + ((unsigned)rsp[5]<<8);//bytes in this part of the attribute list
//            append(rsp+7, count);
            cont = rsp[7+count];
            memcpy(contState, &rsp[7+count], cont+1);//copy the continuation state
            if (cont) {
                append(rsp+7, count);
                break;
            }
            //printf("count=%d parsing...\n", byteCount);
            serv_rec *serv = new serv_rec;
            if (contBuf) {
                append(rsp+7, count);
                parse(contBuf, byteCount, tree, serv);
            } else
                parse(rsp+7, count, tree, serv);
            //printf("...parsing done,  ");
            //get the AttributeID, make sure attribId 0 is always included in the request
            unsigned key = (*serv)[0]->asUnsigned();//AttributeID '0' always refers to the serviceID
            //printf("Key=%#X\n", key); //key will be 0 when not requested
            services[key] = serv; //Add the attribute list to the services
            freeBuf();
            if (ServiceAttributeResponse)
                ServiceAttributeResponse(serv);
        }
        break;
        //below is UNTESTED
        case 7: { //servicesearchattributeRsp
            unsigned count = rsp[6] + ((unsigned)rsp[5]<<8);
            append(rsp+7, count);
            cont = rsp[7+count];
            memcpy(contState, &rsp[7+count], cont+1);
            if (cont)
                break;
            unsigned pos = 0;
            if (contBuf[pos]>>3 != sdp_data::SEQUENCE) {
                printf("Expected a sequence of attribute lists\n");
                break;
            }
            unsigned len = length(contBuf, pos);//get the length of the list of lists and advance pos to the first list
            while (pos<len) {
                printf("pos=%d, count=%d, parsing...\n", pos, len);
                serv_rec *serv = new serv_rec;
                pos = parse(contBuf+pos, len, tree, serv);
                unsigned key = (*serv)[0]->asUnsigned();
                services[key] = serv;
            }
            freeBuf();
            printf("...parsing done, pos=%d\n", pos);
            if (ServiceSearchAttributeResponse)
                ServiceSearchAttributeResponse();
        }
        break;
        default:
            printf("Unknown SDP response type %02X\n", rsp[0]);
            break;
    }
    return 0;
}

//************************ SERVER related *******************************************//

//unsigned SDPHandler::parseUUID(const u8* data, int len, unsigned &p) {
unsigned parseUUID(const u8* data, int len, unsigned &p) {
    unsigned u = 0;
    if ((data[p]>>3) != sdp_data::UUID) {
        printf(" UUID expected, got %d ", data[p]>>3);
        return (unsigned)-1;
    }
    switch (data[p++] & 7) {
        case 1:
            u = getval(data+p, 2);
            p +=2;
            break;
        case 2:
            u = getval(data+p, 4);
            p += 4;
            break;
        case 4:
            u = getval(data+p, 4);
            p += 16;
            break;
        default:
            printf(" UUID must be 2, 4 or 16 bytes, got type %d\n", data[p-1]);
    }
    return u;
}

#define SVC_HANDLE  0x0001001DU  //serial service
void SDPManager::buildServer() {
    static sdp_data rfcomm(sdp_data::SEQUENCE);
    static sdp_data l2cap(sdp_data::SEQUENCE);
    static sdp_data protocol(sdp_data::SEQUENCE);
    static sdp_data serviceclass(sdp_data::SEQUENCE);
    static sdp_data browsegroup(sdp_data::SEQUENCE);
    static sdp_data root(sdp_data::UUID, BROWSEROOT);
    static sdp_data l2capuuid(sdp_data::UUID, 0x0100);
    static sdp_data rfcommuuid(sdp_data::UUID, 0x003);
    static sdp_data serial(sdp_data::UUID, 0x1101);
    static sdp_data chan(1U,1);
    static sdp_data handle(SVC_HANDLE,4);
    static sdp_data serviceID(0U, 2);
    static sdp_data name("MBED BlueUSB RFCOMM Serial");
    rfcomm.add_element(&rfcommuuid);
    rfcomm.add_element(&chan);
    l2cap.add_element(&l2capuuid);
    protocol.add_element(&l2cap);
    protocol.add_element(&rfcomm);
    serviceclass.add_element(&serial);
    browsegroup.add_element(&root);
    static serv_rec attr_list;
    attr_list[0] = &handle;
    attr_list[1] = &serviceclass;
    attr_list[4] = &protocol;
    attr_list[5] = &browsegroup;
    attr_list[0x100] = &name;
    server[SVC_HANDLE] = &attr_list;//server is static and this statement crashes the program when invoked from the constructor which is also invoked statically
}

int SDPManager::findUUID(unsigned h, unsigned uuid) {
    serv_rec *rec = server[h];
    for ( serv_rec::iterator it = rec->begin(); it != rec->end(); it++) {
        if (it->second->findUUID(uuid))
            return it->first;
    }
    printf("rejected %08X because of %04Xx\n", h, uuid);
    return -1;
}

void SDPManager::match(bool elig[], unsigned uuid) {
    map<unsigned, serv_rec*>::iterator idx;
    int i = 0;
    for (idx = server.begin(); idx != server.end(); idx++, i++)
        if (findUUID(idx->first, uuid) < 0)
            elig[i] = false;
}

bool SDPManager::isInList(unsigned short id, const unsigned char* list, int end) {
    int len;
    for (unsigned pos = 0; pos < end; pos += len) {
        len = length(list, pos);
        switch (len) {
            case 2: //single value
                if (getval(list+pos, 2) == id)
                    return true;
                break;
            case 4: //range
                if (getval(list+pos, 2) > id) break;
                if (getval(list+pos+2, 2) < id) break;
                return true;
            default:
                printf("Unexpected length %d\n", len);
        }
    }
    return false;
}

void SDPManager::addToReply(sdp_data *svc, serv_rec *list, const unsigned char* att, int end) {
    unsigned short len, low, high;
    serv_rec::iterator from, to, idx;
    for (unsigned pos = 0; pos < end; pos += len) {
        len = length(att, pos);
        switch (len) {
            case 2: //single value
                low = getval(att+pos, 2);
                svc->add_element(new sdp_data(low, 2));
                svc->add_element((*list)[low]);
                printf("Found attrib %d\n", low);
                break;
            case 4: //range
                low = getval(att+pos, 2);
                high = getval(att+pos+2, 2);
                from = list->lower_bound(low);
                to = list->upper_bound(high);
                for (idx = from; idx != to; idx++) {
                  svc->add_element(new sdp_data(idx->first, 2));
                  svc->add_element(idx->second);
                  printf("Found attrib %d\n", idx->first);
                }
                break;
            default:
                printf("Unexpected length %d\n", len);
        }
    }
}

//for continuations, just generate the entire list, truncate to desired length and append position of the remainder as continuation
//on the next iteration, generate the list again, use continuation to find remainder and reiterate
void SDPManager::SDPServer(int socket, SocketState state, const u8* data, int len, void* userData) {
    unsigned tid = data[2] + ((unsigned)data[1]<<8);
    unsigned parlen = data[4] + ((unsigned)data[3]<<8);
    //printf("ParseReq: PDU_ID=%d, tid=%04X, parlen=%d ", data[0], tid, parlen);
    unsigned pos = 5;
    switch (data[0]) {
        case 1: {//errorRsp
            unsigned errorcode = data[6] + ((unsigned)data[5]<<8);
            if (parlen > 2) {
                printf("ErrorInfo (%d bytes) for error %d is available\n", parlen-2, errorcode);
            }
            errorhandler(errorcode);
        }
        break;
        case 2: { //servicesearchReq
        }
        break;
        case 4: { //serviceattributeReq
        }
        break;
        case 6: { //servicesearchattributeReq
            sdp_data reply(sdp_data::SEQUENCE);//the attributelist of the reply

            unsigned pat[12];//the received search pattern
            int pn;//number of uuids in the pattern
            if (data[pos]>>3 != sdp_data::SEQUENCE) {//the uuids are wrapped in a sequence
                printf("Expected a sequence of UUIDs\n");
                break;
            }
            unsigned end = pos + length(data, pos);//get the length of the list of lists and advance pos to the first list
            bool *eligible = new bool[server.size()];//marks for the services identified by the search pattern
            for (int i = 0; i < server.size(); i++) eligible[i] = true;
            for (pn = 0; pn < 12 && pos < end; pn++) {
                pat[pn] = parseUUID(data,end, pos);//store uuid from the sequence in the pattern
                match(eligible, pat[pn]);//unmark a service when it does not contain the uuid
                //printf("pos=%d, count=%d, uuid=%#X\n", pos, len, pat[pn]);
            }

            unsigned count = getval(data+pos, 2); //maximum length of attribute list to return
            pos += 2;

            int len = length(data, pos); //get the length of the attributeID list
            int cont = pos + len;
            //printf("Count = %d pos=%d, data[pos]=%02x, len=%d, cont=%d\n", count, pos, data[pos], len, cont);
            int i = 0;
            for (map<unsigned, serv_rec*>::iterator idx = server.begin(); idx != server.end(); idx++, i++) {//foreach service
                //printf("testing service handle %08X\n", idx->first);
                if (!eligible[i]) continue; //skip services that don't match the pattern
                sdp_data *svc = new sdp_data(sdp_data::SEQUENCE); //create a sequence for the attributes of the present service
#if 0
                for (serv_rec::iterator attr = idx->second->begin(); attr != idx->second->end(); attr++) {//foreach attrib in the service
                    //printf("testing attribID %u\n", attr->first);
                    if (isInList(attr->first, data+pos, len)) {//check if it is requested
                        printf("Found attribID %d\n", attr->first);
                        sdp_data *p = attr->second; //the attribute
                        svc->add_element(new sdp_data(attr->first, 2)); //add the attribute ID as an unsigned short
                        svc->add_element(p);                            //add the attribute
                        //printf("appending %d bytes\n", p->Size());
                    }
                }
#else
//alternatively use map::lower/upper_bound and equal_range, needs only one pass over the range list for each service
                addToReply(svc, idx->second, data+pos, len);
#endif
                reply.add_element(svc); //append the new attribute list to the reply list
            }
            
            unsigned tail = data[cont];
            if (tail) {
                tail = getval(data+cont+1, tail);
                printf("requested continuation tailpos=%u, size=%u\n", tail, reply.Size());
            }
            else {
                //printf("No continuation requested\n");
            }
            ServiceSearchAttributeReply(tid, &reply, count, tail);
            
            for (int j = 0; j < reply.items(); j++) {
                sdp_data *al = reply.item(j);
                for (int k = 0; k < al->items(); k++) {
                    if ((k & 1) == 0) //even hence ID
                        delete al->item(k); //destroy the ID
                    al->remove(k);  //set all items to nil to prevent destruction of the DB
                }
                delete al; //destroy the list;
                reply.remove(j);
            }
            delete[] eligible;
        }
        break;
        default:
            printf("Unknown SDP request type %02X\n", data[0]);
            break;
    }
}