static int
readBytes (unsigned char *buffer, int size, size_t *length) {
*length = 0;
while (*length < size) {
unsigned char byte;
if (!serialReadChunk(serialDevice, buffer, length, 1, 0, 100)) {
return 0;
}
byte = buffer[*length - 1];
if ((*length == 1) && (byte == ACK)) {
*length = 0;
continue;
}
if (byte == CR) {
logBytes(LOG_DEBUG, "Read", buffer, *length);
return 1;
}
}
return 0;
}
/* "+" packets are silently discarded, since they are only disturbing us */
static ssize_t brl_readPacket(BrailleDisplay *brl, void *p, size_t size)
{
size_t offset = 0;
static unsigned char ack = 04;
static unsigned char nack = 05;
static int apacket = 0;
static unsigned char prefix, checksum;
unsigned char ch;
static unsigned char buf[MAXPACKETSIZE];
static unsigned char *q;
if ((p==NULL) || (size<2) || (size>MAXPACKETSIZE)) return 0;
while (serialReadChunk(serialDevice,&ch,&offset,1,0,1000)) {
if (ch==0x02) {
apacket = 1;
prefix = 0xff;
checksum = 0;
q = &buf[0];
} else if (apacket) {
if (ch==0x01) {
prefix &= ~(0x40);
} else if (ch==0x03) {
if (checksum==0) {
serialWriteData(serialDevice,&ack,1);
apacket = 0; q--;
if (buf[0]!='+') {
memcpy(p,buf,(q-buf));
return q-&buf[0];
}
} else {
serialWriteData(serialDevice,&nack,1);
apacket = 0;
return 0;
}
} else {
if ((q-&buf[0])>=size) {
logMessage(LOG_WARNING,"Packet too long: discarded");
apacket = 0;
return 0;
}
ch &= prefix; prefix |= 0x40;
checksum ^= ch;
(*q) = ch; q++;
}
}
offset = 0;
}
return 0;
}
static int
readPacket (BrailleDisplay *brl, unsigned char *packet, int length) {
size_t offset = 0;
int size = -1;
while (offset < length) {
const unsigned char *byte = &packet[offset];
if (!serialReadChunk(serialDevice, packet, &offset, 1, 0, 1000)) {
if (errno == EAGAIN) {
if (!offset) return 0;
logPartialPacket(packet, offset);
}
return -1;
}
if (offset == 1) {
if (*byte) {
logDiscardedByte(packet[0]);
offset = 0;
}
} else {
if (offset == 2) {
switch (*byte) {
default:
size = 1;
break;
}
size += offset;
}
if (offset == size) {
logInputPacket(packet, offset);
return offset;
}
}
}
logTruncatedPacket(packet, offset);
return 0;
}