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@0x/contracts-utils: Add auto-scaling and zero-value optimizations to LibFractions.

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Lawrence Forman
2019-09-17 13:09:11 -04:00
committed by Lawrence Forman
parent e267a0e855
commit 527ec28915
2 changed files with 17 additions and 1 deletions
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4
contracts/utils/CHANGELOG.json
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@@ -57,6 +57,10 @@
{
"note": "Added LibFractions",
"pr": 2118
},
{
"note": "Introduce automatic normalization and some zero-value shortcuts in `LibFractions`.",
"pr": 2155
}
]
},

14
contracts/utils/contracts/src/LibFractions.sol
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@@ -7,6 +7,11 @@ library LibFractions {
using LibSafeMath for uint256;
/// @dev Maximum value for addition result components.
uint256 constant internal RESCALE_THRESHOLD = 10 ** 27;
/// @dev Rescale factor for addition.
uint256 constant internal RESCALE_BASE = 10 ** 9;
/// @dev Safely adds two fractions `n1/d1 + n2/d2`
/// @param n1 numerator of `1`
/// @param d1 denominator of `1`
@@ -37,6 +42,13 @@ library LibFractions {
.safeMul(d2)
.safeAdd(n2.safeMul(d1));
denominator = d1.safeMul(d2);
// If either the numerator or the denominator are > RESCALE_THRESHOLD,
// re-scale them to prevent overflows in future operations.
if (numerator > RESCALE_THRESHOLD || denominator > RESCALE_THRESHOLD) {
numerator = numerator.safeDiv(RESCALE_BASE);
denominator = denominator.safeDiv(RESCALE_BASE);
}
}
/// @dev Safely scales the difference between two fractions.
@@ -57,7 +69,7 @@ library LibFractions {
pure
returns (uint256 result)
{
if (s == 0 || d1 == 0) {
if (s == 0) {
return 0;
}
if (n2 == 0) {