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bug fix for gdl90_escape_message_for_tx() #1

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bug fix for gdl90_escape_message_for_tx() #1

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1d4974b
bug fix for gdl90_escape_message_for_tx()
aaknitt Dec 31, 2022
7693683
Fix missing trailing flag byte
aaknitt Jun 8, 2024
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14 changes: 8 additions & 6 deletions gdl90.c
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Original file line number Diff line number Diff line change
Expand Up @@ -734,24 +734,26 @@ void gdl90_escape_message_for_tx(gdl_message_t *rawMsg, gdl_message_escaped_t *e
break;
}

originalLen += 5; // Add (2) Frame bytes, (2) CRC bytes, and (1) msg ID byte
originalLen += 3; //One frame byte and msg ID byte are outside the data[] array. One frame byte and 2 byte CRC are inside data[]

// Init the escaped message
escapedMsg->length = 0;
memset(&(escapedMsg->data[0]), 0, sizeof(escapedMsg->data));
escapedMsg->data[0] = GDL90_FLAG_BYTE;
escapedMsg->data[1] = rawMsg->messageId;

// Start escaping! Start at index 1 and stop 1 byte short so we skip the true frame bytes
uint16_t paddedIndex = 1;
for(size_t i = 1; i < originalLen - 1; i++) {
// Start escaping! Stop 1 byte short so we skip the end frame byte that's inside data[]
uint16_t paddedIndex = 2;
for(size_t i = 0; i < originalLen - 1; i++) {
if ((rawMsg->data[i] == GDL90_FLAG_BYTE) || (rawMsg->data[i] == GDL90_CONTROL_ESCAPE)) {
escapedMsg->data[paddedIndex++] = GDL90_CONTROL_ESCAPE;
escapedMsg->data[paddedIndex++] = rawMsg->data[i] ^ GDL90_ESCAPE_BYTE;
} else {
escapedMsg->data[paddedIndex++] = rawMsg->data[i];
}
}

//Add the end flag byte back in since we skipped it in the loop (don't want to escape it)
escapedMsg->data[paddedIndex++] = GDL90_FLAG_BYTE;
// Update the length of our now escaped message
escapedMsg->length = paddedIndex - 1;
escapedMsg->length = paddedIndex;
}