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Introduce byteswap helpers (#2661)

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* Backport std::byteswap() in helpers.h

* Introduce convert_big_endian() function

* Use convert_big_endian() in i2c byte swap functions
This commit is contained in:
Oxan van Leeuwen 2021-11-10 19:40:18 +01:00 committed by GitHub
parent 8aa72f4c1e
commit c422b2fb0b
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2 changed files with 28 additions and 10 deletions
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13
esphome/components/i2c/i2c.h
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@ -1,6 +1,7 @@
#pragma once
#include "i2c_bus.h"
#include "esphome/core/helpers.h"
#include "esphome/core/optional.h"
#include <array>
#include <vector>
@ -32,16 +33,8 @@ class I2CRegister {
// like ntohs/htons but without including networking headers.
// ("i2c" byte order is big-endian)
inline uint16_t i2ctohs(uint16_t i2cshort) {
union {
uint16_t x;
uint8_t y[2];
} conv;
conv.x = i2cshort;
return ((uint16_t) conv.y[0] << 8) | ((uint16_t) conv.y[1] << 0);
}
inline uint16_t htoi2cs(uint16_t hostshort) { return i2ctohs(hostshort); }
inline uint16_t i2ctohs(uint16_t i2cshort) { return convert_big_endian(i2cshort); }
inline uint16_t htoi2cs(uint16_t hostshort) { return convert_big_endian(hostshort); }
class I2CDevice {
public:

25
esphome/core/helpers.h
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@ -306,6 +306,31 @@ template<typename T> T *new_buffer(size_t length) {
// ---------------------------------------------------------------------------------------------------------------------
/// @name STL backports
///@{
// std::byteswap is from C++23 and technically should be a template, but this will do for now.
constexpr uint8_t byteswap(uint8_t n) { return n; }
constexpr uint16_t byteswap(uint16_t n) { return __builtin_bswap16(n); }
constexpr uint32_t byteswap(uint32_t n) { return __builtin_bswap32(n); }
constexpr uint64_t byteswap(uint64_t n) { return __builtin_bswap64(n); }
///@}
/// @name Bit manipulation
///@{
/// Convert a value between host byte order and big endian (most significant byte first) order.
template<typename T, enable_if_t<std::is_unsigned<T>::value, int> = 0> constexpr T convert_big_endian(T val) {
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
return byteswap(val);
#else
return val;
#endif
}
///@}
/// @name Parsing & formatting
///@{