From 9317538667e6f54661949fee1c1f300ba89d185c Mon Sep 17 00:00:00 2001
From: Joshua Allen <axlecrusher@gmail.com>
Date: Fri, 10 Feb 2017 20:09:33 -0500
Subject: don't write to buffer until preamble is found

---
 tools/ootx_decode/ootx_decoder.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

(limited to 'tools')

diff --git a/tools/ootx_decode/ootx_decoder.c b/tools/ootx_decode/ootx_decoder.c
index f5ab7e5..5a14113 100644
--- a/tools/ootx_decode/ootx_decoder.c
+++ b/tools/ootx_decode/ootx_decoder.c
@@ -62,11 +62,15 @@ void ootx_reset_buffer(ootx_decoder_context *ctx) {
 
 void ootx_inc_buffer_offset(ootx_decoder_context *ctx) {
 	++(ctx->buf_offset);
-//	if (buf_offset>=MAX_BUFF_SIZE) buf_offset = 0;
+
+//	assert(ctx->buf_offset<MAX_BUFF_SIZE);
+
+	/* the buffer is going to overflow, wrap the buffer and don't write more data until the preamble is found again */
 	if(ctx->buf_offset>=MAX_BUFF_SIZE) {
+		ctx->buf_offset = 0;
 		ctx->found_preamble = 0;
 	}
-	assert(ctx->buf_offset<MAX_BUFF_SIZE);
+
 	ctx->buffer[ctx->buf_offset] = 0;
 }
 
@@ -99,12 +103,17 @@ void ootx_process_bit(ootx_decoder_context *ctx, uint32_t length) {
 		ctx->found_preamble = 1;
 	}
 	else if(ctx->bits_processed>16) {
-		//every 17th bit needs to be dropped
+		//every 17th bit needs to be dropped (sync bit)
 //		printf("drop %d\n", dbit);
 		ctx->bits_processed = 0;
 	}
-	else
+	else if (ctx->found_preamble > 0)
 	{
+		/*	only write to buffer if the preamble is found.
+			if the buffer overflows, found_preamble will be cleared
+			and writing will stop. data would be corrupted, so there is no point in continuing
+		*/
+
 		ootx_write_to_buffer(ctx, dbit);
 
 		if (ctx->buf_offset >= (*(ctx->payload_size)+6)) {
-- 
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