/*
* QBufPipe_Wait
*/
void QBufPipe_Wait( qbufPipe_t *pipe, int (*read)( qbufPipe_t *, unsigned( ** )(const void *), bool ),
unsigned (**cmdHandlers)( const void * ), unsigned timeout_msec )
{
while( !pipe->terminated ) {
int res;
bool result = false;
while( Sys_Atomic_CAS( &pipe->cmdbuf_len, 0, 0, pipe->cmdbuf_mutex ) == true ) {
QMutex_Lock( pipe->nonempty_mutex );
result = QCondVar_Wait( pipe->nonempty_condvar, pipe->nonempty_mutex, timeout_msec );
// don't hold the mutex, changes to cmdbuf_len are atomic anyway
QMutex_Unlock( pipe->nonempty_mutex );
break;
}
// we're guaranteed at this point that either cmdbuf_len is > 0
// or that waiting on the condition variable has timed out
res = read( pipe, cmdHandlers, result );
if( res < 0 ) {
// done
return;
}
}
}
/*
* QBufPipe_Finish
*
* Blocks until the reader thread handles all commands
* or terminates with an error.
*/
void QBufPipe_Finish( qbufPipe_t *pipe ) {
while( Sys_Atomic_CAS( &pipe->cmdbuf_len, 0, 0, pipe->cmdbuf_mutex ) == false && !pipe->terminated ) {
QMutex_Lock( pipe->nonempty_mutex );
QBufPipe_Wake( pipe );
QMutex_Unlock( pipe->nonempty_mutex );
QThread_Yield();
}
}
/*
* QBufPipe_ReadCmds
*/
int QBufPipe_ReadCmds( qbufPipe_t *pipe, unsigned (**cmdHandlers)( const void * ) )
{
int read = 0;
if( !pipe ) {
return -1;
}
while( Sys_Atomic_CAS( &pipe->cmdbuf_len, 0, 0, pipe->cmdbuf_mutex ) == false && !pipe->terminated ) {
int cmd;
int cmd_size;
int read_remains;
assert( pipe->bufSize >= pipe->read_pos );
if( pipe->bufSize < pipe->read_pos ) {
pipe->read_pos = 0;
}
read_remains = pipe->bufSize - pipe->read_pos;
if( sizeof( int ) > read_remains ) {
// implicit reset
pipe->read_pos = 0;
QBufPipe_BufLenAdd( pipe, -read_remains );
}
cmd = *((int *)(pipe->buf + pipe->read_pos));
if( cmd == -1 ) {
// this cmd is special
pipe->read_pos = 0;
QBufPipe_BufLenAdd( pipe, -((int)(sizeof(int) + read_remains)) ); // atomic
continue;
}
cmd_size = cmdHandlers[cmd](pipe->buf + pipe->read_pos);
read++;
if( !cmd_size ) {
pipe->terminated = 1;
return -1;
}
if( cmd_size > pipe->cmdbuf_len ) {
assert( 0 );
pipe->terminated = 1;
return -1;
}
pipe->read_pos += cmd_size;
QBufPipe_BufLenAdd( pipe, -cmd_size ); // atomic
break;
}
return read;
}
/*
* QBufPipe_WriteCmd
*
* Add new command to buffer. Never allow the distance between the reader
* and the writer to grow beyond the size of the buffer.
*
* Note that there are race conditions here but in the worst case we're going
* to erroneously drop cmd's instead of stepping on the reader's toes.
*/
void QBufPipe_WriteCmd( qbufPipe_t *pipe, const void *cmd, unsigned cmd_size )
{
void *buf;
unsigned write_remains;
bool was_empty;
if( !pipe ) {
return;
}
if( pipe->terminated ) {
return;
}
assert( pipe->bufSize >= pipe->write_pos );
if( pipe->bufSize < pipe->write_pos ) {
pipe->write_pos = 0;
}
was_empty = Sys_Atomic_CAS( &pipe->cmdbuf_len, 0, 0, pipe->cmdbuf_mutex ) == true;
write_remains = pipe->bufSize - pipe->write_pos;
if( sizeof( int ) > write_remains ) {
while( pipe->cmdbuf_len + cmd_size + write_remains > pipe->bufSize ) {
if( pipe->blockWrite ) {
QThread_Yield();
continue;
}
return;
}
// not enough space to enpipe even the reset cmd, rewind
QBufPipe_BufLenAdd( pipe, write_remains ); // atomic
pipe->write_pos = 0;
} else if( cmd_size > write_remains ) {
int *cmd;
while( pipe->cmdbuf_len + sizeof( int ) + cmd_size + write_remains > pipe->bufSize ) {
if( pipe->blockWrite ) {
QThread_Yield();
continue;
}
return;
}
// explicit pointer reset cmd
cmd = QBufPipe_AllocCmd( pipe, sizeof( int ) );
*cmd = -1;
QBufPipe_BufLenAdd( pipe, sizeof( *cmd ) + write_remains ); // atomic
pipe->write_pos = 0;
}
else
{
while( pipe->cmdbuf_len + cmd_size > pipe->bufSize ) {
if( pipe->blockWrite ) {
QThread_Yield();
continue;
}
return;
}
}
buf = QBufPipe_AllocCmd( pipe, cmd_size );
memcpy( buf, cmd, cmd_size );
QBufPipe_BufLenAdd( pipe, cmd_size ); // atomic
// wake the other thread waiting for signal
if( was_empty ) {
QMutex_Lock( pipe->nonempty_mutex );
QBufPipe_Wake( pipe );
QMutex_Unlock( pipe->nonempty_mutex );
}
}
/*
* QAtomic_CAS
*/
bool QAtomic_CAS( volatile int *value, int oldval, int newval, qmutex_t *mutex ) {
return Sys_Atomic_CAS( value, oldval, newval, mutex );
}
