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Improved float serialization when -fsingle-precision-constant is used

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Benoit Blanchon
2018-07-04 12:07:03 +02:00
parent 7b229e4c38
commit 954428e341
2 changed files with 38 additions and 12 deletions
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5
CHANGELOG.md
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@@ -1,6 +1,11 @@
ArduinoJson: change log ArduinoJson: change log
======================= =======================
HEAD
----
* Improved float serialization when `-fsingle-precision-constant` is used
v5.13.2 v5.13.2
------- -------

45
src/ArduinoJson/TypeTraits/FloatTraits.hpp
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@@ -44,28 +44,46 @@ struct FloatTraits<T, 8 /*64bits*/> {
static T positiveBinaryPowerOfTen(int index) { static T positiveBinaryPowerOfTen(int index) {
static T factors[] = { static T factors[] = {
1e1, 1e2, 1e4, 1e8, 1e16, 1e32, 1e1,
// workaround to support platforms with single precision literals 1e2,
forge(0x4D384F03, 0xE93FF9F5), forge(0x5A827748, 0xF9301D32), 1e4,
forge(0x75154FDD, 0x7F73BF3C)}; 1e8,
1e16,
forge(0x4693B8B5, 0xB5056E17), // 1e32
forge(0x4D384F03, 0xE93FF9F5), // 1e64
forge(0x5A827748, 0xF9301D32), // 1e128
forge(0x75154FDD, 0x7F73BF3C) // 1e256
};
return factors[index]; return factors[index];
} }
static T negativeBinaryPowerOfTen(int index) { static T negativeBinaryPowerOfTen(int index) {
static T factors[] = { static T factors[] = {
1e-1, 1e-2, 1e-4, 1e-8, 1e-16, 1e-32, forge(0x3FB99999, 0x9999999A), // 1e-1
// workaround to support platforms with single precision literals forge(0x3F847AE1, 0x47AE147B), // 1e-2
forge(0x32A50FFD, 0x44F4A73D), forge(0x255BBA08, 0xCF8C979D), forge(0x3F1A36E2, 0xEB1C432D), // 1e-4
forge(0x0AC80628, 0x64AC6F43)}; forge(0x3E45798E, 0xE2308C3A), // 1e-8
forge(0x3C9CD2B2, 0x97D889BC), // 1e-16
forge(0x3949F623, 0xD5A8A733), // 1e-32
forge(0x32A50FFD, 0x44F4A73D), // 1e-64
forge(0x255BBA08, 0xCF8C979D), // 1e-128
forge(0x0AC80628, 0x64AC6F43) // 1e-256
};
return factors[index]; return factors[index];
} }
static T negativeBinaryPowerOfTenPlusOne(int index) { static T negativeBinaryPowerOfTenPlusOne(int index) {
static T factors[] = { static T factors[] = {
1e0, 1e-1, 1e-3, 1e-7, 1e-15, 1e-31, 1e0,
// workaround to support platforms with single precision literals forge(0x3FB99999, 0x9999999A), // 1e-1
forge(0x32DA53FC, 0x9631D10D), forge(0x25915445, 0x81B7DEC2), forge(0x3F50624D, 0xD2F1A9FC), // 1e-3
forge(0x0AFE07B2, 0x7DD78B14)}; forge(0x3E7AD7F2, 0x9ABCAF48), // 1e-7
forge(0x3CD203AF, 0x9EE75616), // 1e-15
forge(0x398039D6, 0x65896880), // 1e-31
forge(0x32DA53FC, 0x9631D10D), // 1e-63
forge(0x25915445, 0x81B7DEC2), // 1e-127
forge(0x0AFE07B2, 0x7DD78B14) // 1e-255
};
return factors[index]; return factors[index];
} }
@@ -77,6 +95,9 @@ struct FloatTraits<T, 8 /*64bits*/> {
return forge(0x7ff00000, 0x00000000); return forge(0x7ff00000, 0x00000000);
} }
// constructs a double floating point values from its binary representation
// we use this function to workaround platforms with single precision literals
// (for example, when -fsingle-precision-constant is passed to GCC)
static T forge(uint32_t msb, uint32_t lsb) { static T forge(uint32_t msb, uint32_t lsb) {
union { union {
uint64_t integerBits; uint64_t integerBits;