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SML: fix incomplete sign extension for abbreviated transmissions (#5544)

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Fabian Bläse 2023-10-17 20:39:05 +02:00 committed by GitHub
parent 6839de69c1
commit b0ac729a8e
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1 changed files with 8 additions and 17 deletions
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25
esphome/components/sml/sml_parser.cpp
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@ -88,11 +88,6 @@ uint64_t bytes_to_uint(const bytes &buffer) {
for (auto const value : buffer) {
val = (val << 8) + value;
}
// Some smart meters send 24 bit signed integers. Sign extend to 64 bit if the
// 24 bit value is negative.
if (buffer.size() == 3 && buffer[0] & 0x80) {
val |= 0xFFFFFFFFFF000000;
}
return val;
}
@ -100,19 +95,15 @@ int64_t bytes_to_int(const bytes &buffer) {
uint64_t tmp = bytes_to_uint(buffer);
int64_t val;
switch (buffer.size()) {
case 1: // int8
val = (int8_t) tmp;
break;
case 2: // int16
val = (int16_t) tmp;
break;
case 4: // int32
val = (int32_t) tmp;
break;
default: // int64
val = (int64_t) tmp;
// sign extension for abbreviations of leading ones (e.g. 3 byte transmissions, see 6.2.2 of SML protocol definition)
// see https://stackoverflow.com/questions/42534749/signed-extension-from-24-bit-to-32-bit-in-c
if (buffer.size() < 8) {
const int bits = buffer.size() * 8;
const uint64_t m = 1u << (bits - 1);
tmp = (tmp ^ m) - m;
}
val = (int64_t) tmp;
return val;
}