/*
 * channels.c: Channel handling
 *
 * See the main source file 'vdr.c' for copyright information and
 * how to reach the author.
 *
 * $Id: channels.c 1.21 2004/01/25 16:02:13 kls Exp $
 */

#include "channels.h"
#include <linux/dvb/frontend.h>
#include <ctype.h>

// IMPORTANT NOTE: in the 'sscanf()' calls there is a blank after the '%d'
// format characters in order to allow any number of blanks after a numeric
// value!

// -- Channel Parameter Maps -------------------------------------------------

const tChannelParameterMap InversionValues[] = {
  {   0, INVERSION_OFF },
  {   1, INVERSION_ON },
  { 999, INVERSION_AUTO },
  { -1 }
  };

const tChannelParameterMap BandwidthValues[] = {
  {   6, BANDWIDTH_6_MHZ },
  {   7, BANDWIDTH_7_MHZ },
  {   8, BANDWIDTH_8_MHZ },
  { 999, BANDWIDTH_AUTO },
  { -1 }
  };

const tChannelParameterMap CoderateValues[] = {
  {   0, FEC_NONE },
  {  12, FEC_1_2 },
  {  23, FEC_2_3 },
  {  34, FEC_3_4 },
  {  45, FEC_4_5 },
  {  56, FEC_5_6 },
  {  67, FEC_6_7 },
  {  78, FEC_7_8 },
  {  89, FEC_8_9 },
  { 999, FEC_AUTO },
  { -1 }
  };

const tChannelParameterMap ModulationValues[] = {
  {   0, QPSK },
  {  16, QAM_16 },
  {  32, QAM_32 },
  {  64, QAM_64 },
  { 128, QAM_128 },
  { 256, QAM_256 },
  { 999, QAM_AUTO },
  { -1 }
  };

const tChannelParameterMap TransmissionValues[] = {
  {   2, TRANSMISSION_MODE_2K },
  {   8, TRANSMISSION_MODE_8K },
  { 999, TRANSMISSION_MODE_AUTO },
  { -1 }
  };

const tChannelParameterMap GuardValues[] = {
  {   4, GUARD_INTERVAL_1_4 },
  {   8, GUARD_INTERVAL_1_8 },
  {  16, GUARD_INTERVAL_1_16 },
  {  32, GUARD_INTERVAL_1_32 },
  { 999, GUARD_INTERVAL_AUTO },
  { -1 }
  };

const tChannelParameterMap HierarchyValues[] = {
  {   0, HIERARCHY_NONE },
  {   1, HIERARCHY_1 },
  {   2, HIERARCHY_2 },
  {   4, HIERARCHY_4 },
  { 999, HIERARCHY_AUTO },
  { -1 }
  };

int UserIndex(int Value, const tChannelParameterMap *Map)
{
  const tChannelParameterMap *map = Map;
  while (map && map->userValue != -1) {
        if (map->userValue == Value)
           return map - Map;
        map++;
        }
  return -1;
}

int DriverIndex(int Value, const tChannelParameterMap *Map)
{
  const tChannelParameterMap *map = Map;
  while (map && map->userValue != -1) {
        if (map->driverValue == Value)
           return map - Map;
        map++;
        }
  return -1;
}

int MapToUser(int Value, const tChannelParameterMap *Map)
{
  int n = DriverIndex(Value, Map);
  if (n >= 0)
     return Map[n].userValue;
  return -1;
}

int MapToDriver(int Value, const tChannelParameterMap *Map)
{
  int n = UserIndex(Value, Map);
  if (n >= 0)
     return Map[n].driverValue;
  return -1;
}

// -- tChannelID -------------------------------------------------------------

const tChannelID tChannelID::InvalidID;

bool tChannelID::operator== (const tChannelID &arg) const
{
  return source == arg.source && nid == arg.nid && tid == arg.tid && sid == arg.sid && rid == arg.rid;
}

tChannelID tChannelID::FromString(const char *s)
{
  char *sourcebuf = NULL;
  int nid;
  int tid;
  int sid;
  int rid = 0;
  int fields = sscanf(s, "%a[^-]-%d-%d-%d-%d", &sourcebuf, &nid, &tid, &sid, &rid);
  if (fields == 4 || fields == 5) {
     int source = cSource::FromString(sourcebuf);
     free(sourcebuf);
     if (source >= 0)
        return tChannelID(source, nid, tid, sid, rid);
     }
  return tChannelID::InvalidID;
}

const char *tChannelID::ToString(void)
{
  static char buffer[256];
  snprintf(buffer, sizeof(buffer), rid ? "%s-%d-%d-%d-%d" : "%s-%d-%d-%d", cSource::ToString(source), nid, tid, sid, rid);
  return buffer;
}

// -- cChannel ---------------------------------------------------------------

char *cChannel::buffer = NULL;

cChannel::cChannel(void)
{
  memset(&__BeginData__, 0, (char *)&__EndData__ - (char *)&__BeginData__);
  inversion    = INVERSION_AUTO;
  bandwidth    = BANDWIDTH_AUTO;
  coderateH    = FEC_AUTO;
  coderateL    = FEC_AUTO;
  modulation   = QAM_AUTO;
  transmission = TRANSMISSION_MODE_AUTO;
  guard        = GUARD_INTERVAL_AUTO;
  hierarchy    = HIERARCHY_AUTO;
  modification = CHANNELMOD_NONE;
}

cChannel::cChannel(const cChannel *Channel)
{
  *this = *Channel;
  *name = 0;
  vpid         = 0;
  ppid         = 0;
  apids[0]     = 0;
  dpids[0]     = 0;
  tpid         = 0;
  caids[0]     = 0;
  nid          = 0;
  tid          = 0;
  sid          = 0;
  rid          = 0;
  number       = 0;
  groupSep     = false;
  modification = CHANNELMOD_NONE;
}

cChannel& cChannel::operator= (const cChannel &Channel)
{
  memcpy(&__BeginData__, &Channel.__BeginData__, (char *)&Channel.__EndData__ - (char *)&Channel.__BeginData__);
  return *this;
}

int cChannel::Transponder(void) const
{
  int tf = frequency;
  while (tf > 20000)
        tf /= 1000;
  return tf;
}

tChannelID cChannel::GetChannelID(void) const
{
  return tChannelID(source, nid, (nid || tid) ? tid : Transponder(), sid, rid);
}

int cChannel::Modification(int Mask)
{
  int Result = modification & Mask;
  modification = CHANNELMOD_NONE;
  return Result;
}

bool cChannel::SetSatTransponderData(int Source, int Frequency, char Polarization, int Srate, int CoderateH, bool Log)
{
  // Workarounds for broadcaster stupidity:
  // Some providers broadcast the transponder frequency of their channels with two different
  // values (like 12551 and 12552), so we need to allow for a little tolerance here
  if (abs(frequency - Frequency) <= 1)
     Frequency = frequency;
  // Sometimes the transponder frequency is set to 0, which is just wrong
  if (Frequency == 0)
     return false;

  if (source != Source || frequency != Frequency || polarization != Polarization || srate != Srate || coderateH != CoderateH) {
     if (Log)
        dsyslog("changing transponder data of channel %d from %s:%d:%c:%d:%d to %s:%d:%c:%d:%d", Number(), cSource::ToString(source), frequency, polarization, srate, coderateH, cSource::ToString(Source), Frequency, Polarization, Srate, CoderateH);
     source = Source;
     frequency = Frequency;
     polarization = Polarization;
     srate = Srate;
     coderateH = CoderateH;
     modulation = QPSK;
     modification |= CHANNELMOD_TRANSP;
     Channels.SetModified();
     }
  return true;
}

bool cChannel::SetCableTransponderData(int Source, int Frequency, int Modulation, int Srate, int CoderateH, bool Log)
{
  if (source != Source || frequency != Frequency || modulation != Modulation || srate != Srate || coderateH != CoderateH) {
     if (Log)
        dsyslog("changing transponder data of channel %d from %s:%d:%d:%d:%d to %s:%d:%d:%d:%d", Number(), cSource::ToString(source), frequency, modulation, srate, coderateH, cSource::ToString(Source), Frequency, Modulation, Srate, CoderateH);
     source = Source;
     frequency = Frequency;
     modulation = Modulation;
     srate = Srate;
     coderateH = CoderateH;
     modification |= CHANNELMOD_TRANSP;
     Channels.SetModified();
     }
  return true;
}

bool cChannel::SetTerrTransponderData(int Source, int Frequency, int Bandwidth, int Modulation, int Hierarchy, int CoderateH, int CoderateL, int Guard, int Transmission, bool Log)
{
  if (source != Source || frequency != Frequency || bandwidth != Bandwidth || modulation != Modulation || hierarchy != Hierarchy || coderateH != CoderateH || coderateL != CoderateL || guard != Guard || transmission != Transmission) {
     if (Log)
        dsyslog("changing transponder data of channel %d from %s:%d:%d:%d:%d:%d:%d:%d:%d to %s:%d:%d:%d:%d:%d:%d:%d:%d", Number(), cSource::ToString(source), frequency, bandwidth, modulation, hierarchy, coderateH, coderateL, guard, transmission, cSource::ToString(Source), Frequency, Bandwidth, Modulation, Hierarchy, CoderateH, CoderateL, Guard, Transmission);
     source = Source;
     frequency = Frequency;
     bandwidth = Bandwidth;
     modulation = Modulation;
     hierarchy = Hierarchy;
     coderateH = CoderateH;
     coderateL = CoderateL;
     guard = Guard;
     transmission = Transmission;
     modification |= CHANNELMOD_TRANSP;
     Channels.SetModified();
     }
  return true;
}

void cChannel::SetId(int Nid, int Tid, int Sid, int Rid, bool Log)
{
  if (nid != Nid || tid != Tid || sid != Sid || rid != Rid) {
     if (Log)
        dsyslog("changing id of channel %d from %d-%d-%d-%d to %d-%d-%d-%d", Number(), nid, tid, sid, rid, Nid, Tid, Sid, Rid);
     nid = Nid;
     tid = Tid;
     sid = Sid;
     rid = Rid;
     modification |= CHANNELMOD_ID;
     Channels.SetModified();
     }
}

void cChannel::SetName(const char *Name, bool Log)
{
  if (!isempty(Name) && strcmp(name, Name) != 0) {
     if (Log)
        dsyslog("changing name of channel %d from '%s' to '%s'", Number(), name, Name);
     strn0cpy(name, Name, MaxChannelName);
     modification |= CHANNELMOD_NAME;
     Channels.SetModified();
     }
}

static bool IntArraysDiffer(const int *a, const int *b, const char na[][4] = NULL, const char nb[][4] = NULL)
{
  int i = 0;
  while (a[i] && b[i]) {
        if (a[i] != b[i] || na && nb && strcmp(na[i], nb[i]) != 0)
           return true;
        i++;
        }
  return a[i] != b[i] || a[i] && na && nb && strcmp(na[i], nb[i]) != 0;
}

static int IntArrayToString(char *s, const int *a, int Base = 10, const char n[][4] = NULL)
{
  char *q = s;
  int i = 0;
  while (a[i] || i == 0) {
        q += sprintf(q, Base == 16 ? "%s%X" : "%s%d", i ? "," : "", a[i]);
        if (a[i] && n && *n[i])
           q += sprintf(q, "=%s", n[i]);
        i++;
        }
  *q = 0;
  return q - s;
}

void cChannel::SetPids(int Vpid, int Ppid, int *Apids, char ALangs[][4], int *Dpids, char DLangs[][4], int Tpid)
{
  bool modified = vpid != Vpid || ppid != Ppid || tpid != Tpid;
  if (!modified)
     modified = IntArraysDiffer(apids, Apids, alangs, ALangs) || IntArraysDiffer(dpids, Dpids, dlangs, DLangs);
  if (modified) {
     char OldApidsBuf[MAXAPIDS * 2 * 10 + 10]; // 2: Apids and Dpids, 10: 5 digits plus delimiting ',' or ';' plus optional '=cod', +10: paranoia
     char NewApidsBuf[MAXAPIDS * 2 * 10 + 10];
     char *q = OldApidsBuf;
     q += IntArrayToString(q, apids, 10, alangs);
     if (dpids[0]) {
        *q++ = ';';
        q += IntArrayToString(q, dpids, 10, dlangs);
        }
     *q = 0;
     q = NewApidsBuf;
     q += IntArrayToString(q, Apids, 10, ALangs);
     if (Dpids[0]) {
        *q++ = ';';
        q += IntArrayToString(q, Dpids, 10, DLangs);
        }
     *q = 0;
     dsyslog("changing pids of channel %d from %d+%d:%s:%d to %d+%d:%s:%d", Number(), vpid, ppid, OldApidsBuf, tpid, Vpid, Ppid, NewApidsBuf, Tpid);
     vpid = Vpid;
     ppid = Ppid;
     for (int i = 0; i <= MAXAPIDS; i++) { // <= to copy the terminating 0
         apids[i] = Apids[i];
         strn0cpy(alangs[i], ALangs[i], 4);
         dpids[i] = Dpids[i];
         strn0cpy(dlangs[i], DLangs[i], 4);
         }
     tpid = Tpid;
     modification |= CHANNELMOD_PIDS;
     Channels.SetModified();
     }
}

void cChannel::SetCaIds(const int *CaIds)
{
  if (caids[0] && caids[0] <= 0x00FF)
     return; // special values will not be overwritten
  if (IntArraysDiffer(caids, CaIds)) {
     char OldCaIdsBuf[MAXCAIDS * 5 + 10]; // 5: 4 digits plus delimiting ',', 10: paranoia
     char NewCaIdsBuf[MAXCAIDS * 5 + 10];
     IntArrayToString(OldCaIdsBuf, caids, 16);
     IntArrayToString(NewCaIdsBuf, CaIds, 16);
     dsyslog("changing caids of channel %d from %s to %s", Number(), OldCaIdsBuf, NewCaIdsBuf);
     for (int i = 0; i <= MAXCAIDS && CaIds[i]; i++) // <= to copy the terminating 0
         caids[i] = CaIds[i];
     modification |= CHANNELMOD_CA;
     Channels.SetModified();
     }
}

void cChannel::SetCaDescriptors(int Level)
{
  if (Level > 0) {
     modification |= CHANNELMOD_CA;
     Channels.SetModified();
     if (Level > 1)
        dsyslog("changing ca descriptors of channel %d", Number());
     }
}

static int PrintParameter(char *p, char Name, int Value)
{
  return Value >= 0 && Value != 999 ? sprintf(p, "%c%d", Name, Value) : 0;
}

const char *cChannel::ParametersToString(void)
{
  char type = *cSource::ToString(source);
  if (isdigit(type))
     type = 'S';
#define ST(s) if (strchr(s, type))
  static char buffer[64];
  char *q = buffer;
  *q = 0;
  ST(" S ")  q += sprintf(q, "%c", polarization);
  ST("CST")  q += PrintParameter(q, 'I', MapToUser(inversion, InversionValues));
  ST("CST")  q += PrintParameter(q, 'C', MapToUser(coderateH, CoderateValues));
  ST("  T")  q += PrintParameter(q, 'D', MapToUser(coderateL, CoderateValues));
  ST("C T")  q += PrintParameter(q, 'M', MapToUser(modulation, ModulationValues));
  ST("  T")  q += PrintParameter(q, 'B', MapToUser(bandwidth, BandwidthValues));
  ST("  T")  q += PrintParameter(q, 'T', MapToUser(transmission, TransmissionValues));
  ST("  T")  q += PrintParameter(q, 'G', MapToUser(guard, GuardValues));
  ST("  T")  q += PrintParameter(q, 'Y', MapToUser(hierarchy, HierarchyValues));
  return buffer;
}

static const char *ParseParameter(const char *s, int &Value, const tChannelParameterMap *Map)
{
  if (*++s) {
     char *p = NULL;
     errno = 0;
     int n = strtol(s, &p, 10);
     if (!errno && p != s) {
        Value = MapToDriver(n, Map);
        if (Value >= 0)
           return p;
        }
     }
  esyslog("ERROR: illegal value for parameter '%c'", *(s - 1));
  return NULL;
}

bool cChannel::StringToParameters(const char *s)
{
  while (s && *s) {
        switch (toupper(*s)) {
          case 'B': s = ParseParameter(s, bandwidth, BandwidthValues); break;
          case 'C': s = ParseParameter(s, coderateH, CoderateValues); break;
          case 'D': s = ParseParameter(s, coderateL, CoderateValues); break;
          case 'G': s = ParseParameter(s, guard, GuardValues); break;
          case 'H': polarization = *s++; break;
          case 'I': s = ParseParameter(s, inversion, InversionValues); break;
          case 'L': polarization = *s++; break;
          case 'M': s = ParseParameter(s, modulation, ModulationValues); break;
          case 'R': polarization = *s++; break;
          case 'T': s = ParseParameter(s, transmission, TransmissionValues); break;
          case 'V': polarization = *s++; break;
          case 'Y': s = ParseParameter(s, hierarchy, HierarchyValues); break;
          default: esyslog("ERROR: unknown parameter key '%c'", *s);
                   return false;
          }
        }
  return true;
}

const char *cChannel::ToText(cChannel *Channel)
{
  char buf[MaxChannelName * 2];
  char *s = Channel->name;
  if (strchr(s, ':')) {
     s = strcpy(buf, s);
     strreplace(s, ':', '|');
     }
  free(buffer);
  if (Channel->groupSep) {
     if (Channel->number)
        asprintf(&buffer, ":@%d %s\n", Channel->number, s);
     else
        asprintf(&buffer, ":%s\n", s);
     }
  else {
     char vpidbuf[32];
     char *q = vpidbuf;
     q += snprintf(q, sizeof(vpidbuf), "%d", Channel->vpid);
     if (Channel->ppid && Channel->ppid != Channel->vpid)
        q += snprintf(q, sizeof(vpidbuf) - (q - vpidbuf), "+%d", Channel->ppid);
     *q = 0;
     char apidbuf[MAXAPIDS * 2 * 10 + 10]; // 2: Apids and Dpids, 10: 5 digits plus delimiting ',' or ';' plus optional '=cod', +10: paranoia
     q = apidbuf;
     q += IntArrayToString(q, Channel->apids, 10, Channel->alangs);
     if (Channel->dpids[0]) {
        *q++ = ';';
        q += IntArrayToString(q, Channel->dpids, 10, Channel->dlangs);
        }
     *q = 0;
     char caidbuf[MAXCAIDS * 5 + 10]; // 5: 4 digits plus delimiting ',', 10: paranoia
     q = caidbuf;
     q += IntArrayToString(q, Channel->caids, 16);
     *q = 0;
     asprintf(&buffer, "%s:%d:%s:%s:%d:%s:%s:%d:%s:%d:%d:%d:%d\n", s, Channel->frequency, Channel->ParametersToString(), cSource::ToString(Channel->source), Channel->srate, vpidbuf, apidbuf, Channel->tpid, caidbuf, Channel->sid, Channel->nid, Channel->tid, Channel->rid);
     }
  return buffer;
}

const char *cChannel::ToText(void)
{
  return ToText(this);
}

bool cChannel::Parse(const char *s, bool AllowNonUniqueID)
{
  bool ok = true;
  if (*s == ':') {
     groupSep = true;
     if (*++s == '@' && *++s) {
        char *p = NULL;
        errno = 0;
        int n = strtol(s, &p, 10);
        if (!errno && p != s && n > 0) {
           number = n;
           s = p;
           }
        }
     strn0cpy(name, skipspace(s), MaxChannelName);
     }
  else {
     groupSep = false;
     char *namebuf = NULL;
     char *sourcebuf = NULL;
     char *parambuf = NULL;
     char *vpidbuf = NULL;
     char *apidbuf = NULL;
     char *caidbuf = NULL;
     int fields = sscanf(s, "%a[^:]:%d :%a[^:]:%a[^:] :%d :%a[^:]:%a[^:]:%d :%a[^:]:%d :%d :%d :%d ", &namebuf, &frequency, &parambuf, &sourcebuf, &srate, &vpidbuf, &apidbuf, &tpid, &caidbuf, &sid, &nid, &tid, &rid);
     if (fields >= 9) {
        if (fields == 9) {
           // allow reading of old format
           sid = atoi(caidbuf);
           delete caidbuf;
           caidbuf = NULL;
           caids[0] = tpid;
           caids[1] = 0;
           tpid = 0;
           }
        vpid = ppid = 0;
        apids[0] = 0;
        dpids[0] = 0;
        ok = false;
        if (parambuf && sourcebuf && vpidbuf && apidbuf) {
           ok = StringToParameters(parambuf) && (source = cSource::FromString(sourcebuf)) >= 0;

           char *p = strchr(vpidbuf, '+');
           if (p)
              *p++ = 0;
           sscanf(vpidbuf, "%d", &vpid);
           if (p)
              sscanf(p, "%d", &ppid);
           else
              ppid = vpid;

           char *dpidbuf = strchr(apidbuf, ';');
           if (dpidbuf)
              *dpidbuf++ = 0;
           p = apidbuf;
           char *q;
           int NumApids = 0;
           while ((q = strtok(p, ",")) != NULL) {
                 if (NumApids < MAXAPIDS) {
                    char *l = strchr(q, '=');
                    if (l) {
                       *l++ = 0;
                       strn0cpy(alangs[NumApids], l, 4);
                       }
                    else
                       *alangs[NumApids] = 0;
                    apids[NumApids++] = strtol(q, NULL, 10);
                    }
                 else
                    esyslog("ERROR: too many APIDs!"); // no need to set ok to 'false'
                 p = NULL;
                 }
           apids[NumApids] = 0;
           if (dpidbuf) {
              char *p = dpidbuf;
              char *q;
              int NumDpids = 0;
              while ((q = strtok(p, ",")) != NULL) {
                    if (NumDpids < MAXAPIDS) {
                       char *l = strchr(q, '=');
                       if (l) {
                          *l++ = 0;
                          strn0cpy(dlangs[NumDpids], l, 4);
                          }
                       else
                          *dlangs[NumDpids] = 0;
                       dpids[NumDpids++] = strtol(q, NULL, 10);
                       }
                    else
                       esyslog("ERROR: too many DPIDs!"); // no need to set ok to 'false'
                    p = NULL;
                    }
              dpids[NumDpids] = 0;
              }

           if (caidbuf) {
              char *p = caidbuf;
              char *q;
              int NumCaIds = 0;
              while ((q = strtok(p, ",")) != NULL) {
                    if (NumCaIds < MAXCAIDS) {
                       caids[NumCaIds++] = strtol(q, NULL, 16) & 0xFFFF;
                       if (NumCaIds == 1 && caids[0] <= 0x00FF)
                          break;
                       }
                    else
                       esyslog("ERROR: too many CA ids!"); // no need to set ok to 'false'
                    p = NULL;
                    }
              caids[NumCaIds] = 0;
              }
           }
        strn0cpy(name, namebuf, MaxChannelName);
        free(parambuf);
        free(sourcebuf);
        free(vpidbuf);
        free(apidbuf);
        free(caidbuf);
        free(namebuf);
        if (!GetChannelID().Valid()) {
           esyslog("ERROR: channel data results in invalid ID!");
           return false;
           }
        if (!AllowNonUniqueID && Channels.GetByChannelID(GetChannelID())) {
           esyslog("ERROR: channel data not unique!");
           return false;
           }
        }
     else
        return false;
     }
  strreplace(name, '|', ':');
  return ok;
}

bool cChannel::Save(FILE *f)
{
  return fprintf(f, ToText()) > 0;
}

// -- cChannels --------------------------------------------------------------

cChannels Channels;

cChannels::cChannels(void)
{
  maxNumber = 0;
  modified = false;
}

bool cChannels::Load(const char *FileName, bool AllowComments, bool MustExist)
{
  if (cConfig<cChannel>::Load(FileName, AllowComments, MustExist)) {
     ReNumber();
     return true;
     }
  return false;
}

int cChannels::GetNextGroup(int Idx)
{
  cChannel *channel = Get(++Idx);
  while (channel && !(channel->GroupSep() && *channel->Name()))
        channel = Get(++Idx);
  return channel ? Idx : -1;
}

int cChannels::GetPrevGroup(int Idx)
{
  cChannel *channel = Get(--Idx);
  while (channel && !(channel->GroupSep() && *channel->Name()))
        channel = Get(--Idx);
  return channel ? Idx : -1;
}

int cChannels::GetNextNormal(int Idx)
{
  cChannel *channel = Get(++Idx);
  while (channel && channel->GroupSep())
        channel = Get(++Idx);
  return channel ? Idx : -1;
}

void cChannels::ReNumber( void )
{
  int Number = 1;
  for (cChannel *channel = First(); channel; channel = Next(channel)) {
      if (channel->GroupSep()) {
         if (channel->Number() > Number)
            Number = channel->Number();
         }
      else {
         maxNumber = Number;
         channel->SetNumber(Number++);
         }
      }
}

cChannel *cChannels::GetByNumber(int Number, int SkipGap)
{
  cChannel *previous = NULL;
  for (cChannel *channel = First(); channel; channel = Next(channel)) {
      if (!channel->GroupSep()) {
         if (channel->Number() == Number)
            return channel;
         else if (SkipGap && channel->Number() > Number)
            return SkipGap > 0 ? channel : previous;
         previous = channel;
         }
      }
  return NULL;
}

cChannel *cChannels::GetByServiceID(int Source, int Transponder, unsigned short ServiceID)
{
  for (cChannel *channel = First(); channel; channel = Next(channel)) {
      if (!channel->GroupSep() && channel->Source() == Source && ISTRANSPONDER(channel->Transponder(), Transponder) && channel->Sid() == ServiceID)
         return channel;
      }
  return NULL;
}

cChannel *cChannels::GetByChannelID(tChannelID ChannelID, bool TryWithoutRid)
{
  for (cChannel *channel = First(); channel; channel = Next(channel)) {
      if (!channel->GroupSep() && channel->GetChannelID() == ChannelID)
         return channel;
      }
  if (TryWithoutRid) {
     ChannelID.ClrRid();
     for (cChannel *channel = First(); channel; channel = Next(channel)) {
         if (!channel->GroupSep() && channel->GetChannelID().ClrRid() == ChannelID)
            return channel;
         }
     }
  return NULL;
}

bool cChannels::HasUniqueChannelID(cChannel *NewChannel, cChannel *OldChannel)
{
  tChannelID NewChannelID = NewChannel->GetChannelID();
  for (cChannel *channel = First(); channel; channel = Next(channel)) {
      if (!channel->GroupSep() && channel != OldChannel && channel->GetChannelID() == NewChannelID)
         return false;
      }
  return true;
}

bool cChannels::SwitchTo(int Number)
{
  cChannel *channel = GetByNumber(Number);
  return channel && cDevice::PrimaryDevice()->SwitchChannel(channel, true);
}

void cChannels::SetModified(void)
{
  modified = true;
}

bool cChannels::Modified(void)
{
  bool Result = modified;
  modified = false;
  return Result;
}

cChannel *cChannels::NewChannel(const cChannel *Transponder, const char *Name, int Nid, int Tid, int Sid, int Rid)
{
  if (Transponder) {
     dsyslog("creating new channel '%s' on %s transponder %d with id %d-%d-%d-%d", Name, cSource::ToString(Transponder->Source()), Transponder->Transponder(), Nid, Tid, Sid, Rid);
     cChannel *NewChannel = new cChannel(Transponder);
     Add(NewChannel);
     ReNumber();
     NewChannel->SetId(Nid, Tid, Sid, Rid, false);
     NewChannel->SetName(Name, false);
     return NewChannel;
     }
  return NULL;
}