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ofono
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Code Issues Releases Activity

Add support for wrapping of HDLC receive ring buffer

This commit is contained in:
Marcel Holtmann 2010-04-23 17:18:30 +02:00
parent fa5e8cf56b
commit a31870f542
1 changed files with 34 additions and 21 deletions
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55
gatchat/gathdlc.c
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@ -32,6 +32,15 @@
#define BUFFER_SIZE 2048
#define HDLC_FLAG 0x7e /* Flag sequence */
#define HDLC_ESCAPE 0x7d /* Asynchronous control escape */
#define HDLC_TRANS 0x20 /* Asynchronous transparency modifier */
#define HDLC_INITFCS 0xffff /* Initial FCS value */
#define HDLC_GOODFCS 0xf0b8 /* Good final FCS value */
#define HDLC_FCS(fcs, c) crc_ccitt_byte(fcs, c)
struct _GAtHDLC {
gint ref_count;
GIOChannel *channel;
@ -43,6 +52,7 @@ struct _GAtHDLC {
unsigned char *decode_buffer;
guint decode_offset;
guint16 decode_fcs;
gboolean decode_escape;
GAtReceiveFunc receive_func;
gpointer receive_data;
GAtDebugFunc debugf;
@ -52,38 +62,40 @@ struct _GAtHDLC {
static void new_bytes(GAtHDLC *hdlc)
{
unsigned int len = ring_buffer_len(hdlc->read_buffer);
unsigned int wrap = ring_buffer_len_no_wrap(hdlc->read_buffer);
unsigned char *buf = ring_buffer_read_ptr(hdlc->read_buffer, 0);
unsigned char val;
unsigned int pos = 0;
while (pos < len) {
if (buf[pos] == 0x7e) {
if (hdlc->decode_escape == TRUE) {
unsigned char val = *buf ^ HDLC_TRANS;
hdlc->decode_buffer[hdlc->decode_offset++] = val;
hdlc->decode_fcs = HDLC_FCS(hdlc->decode_fcs, val);
hdlc->decode_escape = FALSE;
} else if (*buf == HDLC_ESCAPE) {
hdlc->decode_escape = TRUE;
} else if (*buf == HDLC_FLAG) {
if (hdlc->receive_func && hdlc->decode_offset > 2 &&
hdlc->decode_fcs == 0xf0b8) {
hdlc->decode_fcs == HDLC_GOODFCS) {
hdlc->receive_func(hdlc->decode_buffer,
hdlc->decode_offset - 2,
hdlc->receive_data);
}
hdlc->decode_fcs = 0xffff;
hdlc->decode_fcs = HDLC_INITFCS;
hdlc->decode_offset = 0;
pos++;
continue;
} else {
hdlc->decode_buffer[hdlc->decode_offset++] = *buf;
hdlc->decode_fcs = HDLC_FCS(hdlc->decode_fcs, *buf);
}
if (buf[pos] == 0x7d) {
if (pos + 2 > len)
break;
pos++;
val = buf[pos] ^ 0x20;
} else
val = buf[pos];
hdlc->decode_buffer[hdlc->decode_offset] = val;
hdlc->decode_fcs = crc_ccitt_byte(hdlc->decode_fcs, val);
hdlc->decode_offset++;
buf++;
pos++;
if (pos == wrap)
buf = ring_buffer_read_ptr(hdlc->read_buffer, pos);
}
ring_buffer_drain(hdlc->read_buffer, pos);
@ -158,8 +170,9 @@ GAtHDLC *g_at_hdlc_new(GIOChannel *channel)
return NULL;
hdlc->ref_count = 1;
hdlc->decode_fcs = 0xffff;
hdlc->decode_fcs = HDLC_INITFCS;
hdlc->decode_offset = 0;
hdlc->decode_escape = FALSE;
hdlc->max_read_attempts = 8;
hdlc->read_buffer = ring_buffer_new(BUFFER_SIZE);
@ -319,7 +332,7 @@ gboolean g_at_hdlc_send(GAtHDLC *hdlc, const unsigned char *data, gsize size)
{
unsigned char *buf;
unsigned int space, i = 0;
guint16 fcs = 0xffff;
guint16 fcs = HDLC_INITFCS;
gsize pos;
do {
@ -335,7 +348,7 @@ gboolean g_at_hdlc_send(GAtHDLC *hdlc, const unsigned char *data, gsize size)
hdlc_put(hdlc, buf, &pos, data[i++]);
}
fcs ^= 0xffff;
fcs ^= HDLC_INITFCS;
hdlc_put(hdlc, buf, &pos, fcs & 0xff);
hdlc_put(hdlc, buf, &pos, fcs >> 8);