freetdm: add code to troubleshoot crash on tone generation

libs/freetdm/src/ftdm_io.c

@@ -2743,10 +2743,9 @@ static ftdm_status_t ftdmchan_activate_dtmf_buffer(ftdm_channel_t *ftdmchan)
 	if (!ftdmchan->dtmf_buffer) {
 		if (ftdm_buffer_create(&ftdmchan->dtmf_buffer, 1024, 3192, 0) != FTDM_SUCCESS) {
 			ftdm_log(FTDM_LOG_ERROR, "Failed to allocate DTMF Buffer!\n");
-			snprintf(ftdmchan->last_error, sizeof(ftdmchan->last_error), "buffer error");
 			return FTDM_FAIL;
 		} else {
-			ftdm_log(FTDM_LOG_DEBUG, "Created DTMF Buffer!\n");
+			ftdm_log_chan_msg(ftdmchan, FTDM_LOG_DEBUG, "Created DTMF buffer\n");
 		}
 	}
 
@@ -3588,8 +3587,17 @@ static FIO_READ_FUNCTION(ftdm_raw_read)
 	return status;
 }
 
-static ftdm_status_t handle_dtmf(ftdm_channel_t *ftdmchan, ftdm_size_t datalen)
+/* This function takes care of automatically generating DTMF or FSK tones when needed */
+static ftdm_status_t handle_tone_generation(ftdm_channel_t *ftdmchan, ftdm_size_t datalen)
 {
+	/*
+	 * datalen: size in bytes of the chunk of data the user requested to read (this function 
+	 *          is called from the ftdm_channel_read function)
+	 * dblen: size currently in use in any of the tone generation buffers (data available in the buffer)
+	 * gen_dtmf_buffer: buffer holding the raw ASCII digits that the user requested to generate
+	 * dtmf_buffer: raw linear tone data generated by teletone to be written to the devices
+	 * fsk_buffer: raw linear FSK modulated data for caller id
+	 */
 	ftdm_buffer_t *buffer = NULL;
 	ftdm_size_t dblen = 0;
 	int wrote = 0;
@@ -3604,7 +3612,7 @@ static ftdm_status_t handle_dtmf(ftdm_channel_t *ftdmchan, ftdm_size_t datalen)
 		}
 
 		if (ftdm_buffer_read(ftdmchan->gen_dtmf_buffer, digits, dblen) && !ftdm_strlen_zero_buf(digits)) {
-			ftdm_log_chan(ftdmchan, FTDM_LOG_DEBUG, "Generating DTMF [%s]\n", digits);	
+			ftdm_log_chan(ftdmchan, FTDM_LOG_DEBUG, "Generating DTMF [%s]\n", digits);
 		
 			cur = digits;
 
@@ -3618,7 +3626,7 @@ static ftdm_status_t handle_dtmf(ftdm_channel_t *ftdmchan, ftdm_size_t datalen)
 					ftdm_buffer_write(ftdmchan->dtmf_buffer, ftdmchan->tone_session.buffer, wrote * 2);
 					x++;
 				} else {
-					ftdm_log(FTDM_LOG_ERROR, "%d:%d Problem Adding DTMF SEQ [%s]\n", ftdmchan->span_id, ftdmchan->chan_id, digits);
+					ftdm_log_chan(ftdmchan, FTDM_LOG_ERROR, "Problem adding DTMF sequence [%s]\n", digits);
 					return FTDM_FAIL;
 				}
 			}
@@ -3631,6 +3639,7 @@ static ftdm_status_t handle_dtmf(ftdm_channel_t *ftdmchan, ftdm_size_t datalen)
 	
 
 	if (!ftdmchan->buffer_delay || --ftdmchan->buffer_delay == 0) {
+		/* time to pick a buffer, either the dtmf or fsk buffer */
 		if (ftdmchan->dtmf_buffer && (dblen = ftdm_buffer_inuse(ftdmchan->dtmf_buffer))) {
 			buffer = ftdmchan->dtmf_buffer;
 		} else if (ftdmchan->fsk_buffer && (dblen = ftdm_buffer_inuse(ftdmchan->fsk_buffer))) {
@@ -3638,22 +3647,41 @@ static ftdm_status_t handle_dtmf(ftdm_channel_t *ftdmchan, ftdm_size_t datalen)
 		}
 	}
 
+	/* if we picked a buffer, time to read from it and write the linear data to the device */
 	if (buffer) {
-		ftdm_size_t dlen = datalen;
 		uint8_t auxbuf[1024];
+		/* we initialize dlen to datalen, which is the size in bytes the 
+		 * user wants to read (typically chunks of 160 bytes, 20ms G.711) */
+		ftdm_size_t dlen = datalen;
 		ftdm_size_t len, br, max = sizeof(auxbuf);
 		
+		/* if the codec is not linear, then data is really twice as much cuz
+		   tone generation is done in linear (we assume anything different than linear is G.711) */
 		if (ftdmchan->native_codec != FTDM_CODEC_SLIN) {
 			dlen *= 2;
 		}
-		
+
+		/* we do not expect the user chunks to be bigger than auxbuf */
+		ftdm_assert(dlen <= sizeof(auxbuf), "Unexpected size for user data chunk size\n");
+
+		/* dblen is the size in use for dtmf_buffer or fsk_buffer, and dlen is the size
+		 * of the read chunks of the user, we pick the smaller one */
 		len = dblen > dlen ? dlen : dblen;
 
+		/* we can't read more than the size of our auxiliary buffer */
+		ftdm_assert((len <= sizeof(auxbuf)), "Unexpected size to read into auxbuf\n");
+
 		br = ftdm_buffer_read(buffer, auxbuf, len);		
+
+		/* the amount read can't possibly be bigger than what we requested */
+		ftdm_assert((br <= len), "Unexpected size read from tone generation buffer\n");
+
+		/* if we read less than the chunk size, we must fill in with silence the rest */
 		if (br < dlen) {
 			memset(auxbuf + br, 0, dlen - br);
 		}
 
+		/* finally we convert to the native format for the channel if necessary */
 		if (ftdmchan->native_codec != FTDM_CODEC_SLIN) {
 			if (ftdmchan->native_codec == FTDM_CODEC_ULAW) {
 				fio_slin2ulaw(auxbuf, max, &dlen);
@@ -3662,6 +3690,7 @@ static ftdm_status_t handle_dtmf(ftdm_channel_t *ftdmchan, ftdm_size_t datalen)
 			}
 		}
 		
+		/* write the tone to the channel */
 		return ftdm_raw_write(ftdmchan, auxbuf, &dlen);
 	} 
 
@@ -3741,7 +3770,7 @@ FT_DECLARE(ftdm_status_t) ftdm_channel_read(ftdm_channel_t *ftdmchan, void *data
 			rdata[i] = ftdmchan->rxgain_table[rdata[i]];
 		}
 	}
-	handle_dtmf(ftdmchan, *datalen);
+	handle_tone_generation(ftdmchan, *datalen);
 
 	if (ftdm_test_flag(ftdmchan, FTDM_CHANNEL_TRANSCODE) && ftdmchan->effective_codec != ftdmchan->native_codec) {
 		if (ftdmchan->native_codec == FTDM_CODEC_ULAW && ftdmchan->effective_codec == FTDM_CODEC_SLIN) {
@@ -3938,7 +3967,8 @@ FT_DECLARE(ftdm_status_t) ftdm_channel_write(ftdm_channel_t *ftdmchan, void *dat
 	if (!ftdmchan->buffer_delay && 
 		((ftdmchan->dtmf_buffer && ftdm_buffer_inuse(ftdmchan->dtmf_buffer)) ||
 		 (ftdmchan->fsk_buffer && ftdm_buffer_inuse(ftdmchan->fsk_buffer)))) {
-		/* read size writing DTMF ATM */
+		/* generating some kind of tone at the moment (see handle_tone_generation), 
+		 * we ignore user data ... */
 		goto done;
 	}