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[core] Add xor_bytes and sum16_bytes checksum helpers (#20921)

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This commit is contained in:
J. Nick Koston
2026-10-16 15:57:00 -10:00
committed by GitHub
parent 7671d4410c
commit a5a883fd19
2 changed files with 28 additions and 0 deletions
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esphome/core/helpers.h
+10
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@@ -887,6 +887,16 @@ constexpr uint8_t sum_bytes(const uint8_t *data, size_t len, uint8_t sum = 0) {
return std::accumulate(data, data + len, sum);
}
/// Add up the bytes of \p data with size \p len, truncated to 16 bits.
constexpr uint16_t sum16_bytes(const uint8_t *data, size_t len, uint16_t sum = 0) {
return std::accumulate(data, data + len, sum);
}
/// XOR the bytes of \p data with size \p len, starting from \p init.
constexpr uint8_t xor_bytes(const uint8_t *data, size_t len, uint8_t init = 0) {
return std::accumulate(data, data + len, init, std::bit_xor<>());
}
/// Calculate a CRC-8 checksum of \p data with size \p len.
uint8_t crc8(const uint8_t *data, uint8_t len, uint8_t crc = 0x00, uint8_t poly = 0x8C, bool msb_first = false);
tests/components/core/helpers_test.cpp
+18
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@@ -78,6 +78,24 @@ TEST(HelpersTest, SumBytes) {
static_assert(sum_bytes(FRAME, 2) == 0xEB, "usable in constant expressions");
}
TEST(HelpersTest, Sum16Bytes) {
static constexpr uint8_t FRAME[] = {0x42, 0x4D, 0xE1, 0x00, 0x01};
EXPECT_EQ(sum16_bytes(FRAME, sizeof(FRAME)), 0x0171); // the PMSx003 active mode command checksum
EXPECT_EQ(sum16_bytes(FRAME, 0), 0);
EXPECT_EQ(sum16_bytes(FRAME, sizeof(FRAME), 0x1234), 0x13A5);
EXPECT_EQ(sum16_bytes(FRAME, sizeof(FRAME), 0xFFFF), 0x0170); // wraps at 16 bits
static_assert(sum16_bytes(FRAME, 2) == 0x8F, "usable in constant expressions");
}
TEST(HelpersTest, XorBytes) {
static constexpr uint8_t FRAME[] = {0x01, 0x03, 0x00, 0x15, 0x00};
EXPECT_EQ(xor_bytes(FRAME + 1, 3, 0xFF), 0xE9); // the Z-Wave GetVersion frame checksum
EXPECT_EQ(xor_bytes(FRAME, 0), 0);
EXPECT_EQ(xor_bytes(FRAME, 0, 0x5A), 0x5A);
EXPECT_EQ(xor_bytes(FRAME, sizeof(FRAME)), 0x17);
static_assert(xor_bytes(FRAME, 2) == 0x02, "usable in constant expressions");
}
TEST(StaticVectorTest, ConvertingConstructorFromSmaller) {
StaticVector<uint8_t, 5> small{0x03, 0x00, 0x10, 0x00, 0x01};
StaticVector<uint8_t, 253> big = small;