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Added some comment to cDevice::GetDevice()

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This commit is contained in:
Klaus Schmidinger
2006-06-15 10:00:40 +02:00
parent 4a98f33782
commit 3644347545
3 changed files with 21 additions and 11 deletions
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2
HISTORY
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@@ -4788,3 +4788,5 @@ Video Disk Recorder Revision History
- Added "-fPIC" to the compiler options in Make.config.template when compiling
plugins (thanks to Udo Richter). If you use your own Make.config file, you may
want to add these lines there, too.
- Added some comment to cDevice::GetDevice() to explain how the individual
conditions are put together to make a decision on which device to use.

25
device.c
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@@ -4,7 +4,7 @@
* See the main source file 'vdr.c' for copyright information and
* how to reach the author.
*
* $Id: device.c 1.130 2006/05/27 11:14:42 kls Exp $
* $Id: device.c 1.131 2006/06/15 09:59:40 kls Exp $
*/
#include "device.h"
@@ -281,19 +281,26 @@ cDevice *cDevice::GetDevice(int Index)
cDevice *cDevice::GetDevice(const cChannel *Channel, int Priority, bool *NeedsDetachReceivers)
{
cDevice *d = NULL;
uint Impact = 0xFFFFFFFF;
uint Impact = 0xFFFFFFFF; // we're looking for a device with the least impact
for (int i = 0; i < numDevices; i++) {
bool ndr;
if (device[i]->ProvidesChannel(Channel, Priority, &ndr)) { // this device is basicly able to do the job
// Put together an integer number that reflects the "impact" using
// this device would have on the overall system. Each condition is represented
// by one bit in the number (or several bits, if the condition is actually
// a numeric value). The sequence in which the conditions are listed corresponds
// to their individual severity, where the one listed first will make the most
// difference, because it results in the most significant bit of the result.
uint imp = 0;
imp <<= 1; imp |= !device[i]->Receiving() || ndr;
imp <<= 1; imp |= device[i]->Receiving();
imp <<= 1; imp |= device[i] == ActualDevice();
imp <<= 1; imp |= device[i]->IsPrimaryDevice();
imp <<= 1; imp |= device[i]->HasDecoder();
imp <<= 8; imp |= min(max(device[i]->Priority() + MAXPRIORITY, 0), 0xFF);
imp <<= 8; imp |= min(max(device[i]->ProvidesCa(Channel), 0), 0xFF);
imp <<= 1; imp |= !device[i]->Receiving() || ndr; // use receiving devices if we don't need to detach existing receivers
imp <<= 1; imp |= device[i]->Receiving(); // avoid devices that are receiving
imp <<= 1; imp |= device[i] == ActualDevice(); // avoid the actual device (in case of Transfer Mode)
imp <<= 1; imp |= device[i]->IsPrimaryDevice(); // avoid the primary device
imp <<= 1; imp |= device[i]->HasDecoder(); // avoid full featured cards
imp <<= 8; imp |= min(max(device[i]->Priority() + MAXPRIORITY, 0), 0xFF); // use the device with the lowest priority (+MAXPRIORITY to assure that values -99..99 can be used)
imp <<= 8; imp |= min(max(device[i]->ProvidesCa(Channel), 0), 0xFF); // use the device that provides the lowest number of conditional access methods
if (imp < Impact) {
// This device has less impact than any previous one, so we take it.
Impact = imp;
d = device[i];
if (NeedsDetachReceivers)

5
device.h
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@@ -4,7 +4,7 @@
* See the main source file 'vdr.c' for copyright information and
* how to reach the author.
*
* $Id: device.h 1.78 2006/05/28 15:04:24 kls Exp $
* $Id: device.h 1.79 2006/06/15 09:32:48 kls Exp $
*/
#ifndef __DEVICE_H
@@ -130,7 +130,8 @@ public:
///< \return A pointer to the device, or NULL if the Index was invalid.
static cDevice *GetDevice(const cChannel *Channel, int Priority = -1, bool *NeedsDetachReceivers = NULL);
///< Returns a device that is able to receive the given Channel at the
///< given Priority.
///< given Priority, with the least impact on active recordings and
///< live viewing.
///< See ProvidesChannel() for more information on how
///< priorities are handled, and the meaning of NeedsDetachReceivers.
static void Shutdown(void);