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Fix unaligned 16-bit access in swap_regs() #130

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Fix unaligned 16-bit access in swap_regs() #130

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8 changes: 6 additions & 2 deletions nanomodbus.c
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Original file line number Diff line number Diff line change
Expand Up @@ -138,8 +138,12 @@ static void put_regs(nmbs_t* nmbs, const uint16_t* data, uint16_t n) {


static void swap_regs(uint16_t* data, uint16_t n) {
while (n--) {
data[n] = (data[n] << 8) | ((data[n] >> 8) & 0xFF);
// Swap bytes in place to avoid unaligned 16-bit access, which hardfaults on e.g. Cortex-M0/M0+
uint8_t* bytes = (uint8_t*) data;
for (uint16_t i = 0; i < n; i++) {
uint8_t tmp = bytes[2 * i];
bytes[2 * i] = bytes[2 * i + 1];
bytes[2 * i + 1] = tmp;
}
}

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