kaspad/util/btcmath.go
stasatdaglabs 3ace16ad23 [DEV-134] Implement Continuous Integration (#105)
* [DEV-134] Implement Continuous Integration

Squashed commit:

[5e41d830] Dev 223 fix txindex (#100)

* [DEV-201] In handleGetBlockDAGInfo calculate difficulty by the tip with the lowest bits

* [DEV-202] Move VirtualBlock.GetUTXOEntry to BlockDAG

* [DEV-203] Move VirtualBlock.SelectedTip() to BlockDAG

* [DEV-203] Move VirtualBlock.SelectedTip() to BlockDAG

* [DEV-204] Unexport VirtualBlock() and add CalcMedianTime method for DAG

* [DEV-204] add explanation about difficulty in CurrentBits() comment

* [DEV-204] unexport VirtualBlock type

* [DEV-223] make applyUTXOChanges return pastUTXOResults

* [DEV-223] add bluestxdata for current block as well

* [DEV-223] re-design tx index

* [DEV-223] edit txindex comments

* [DEV-223] rename BluesTxData -> AcceptedTxData, and return from applyUTXOChanges only transactions that got accepted

* [DEV-223] add unit test for txindex

* [DEV-223] fix comments and unite blueTransaction and AcceptedTxData to one type

* [DEV-223] use bucket cursor for dbFetchFirstTxRegion

* [DEV-223] use the same cursor instance for dbFetchFirstTxRegion

* [DEV-223] write in dbFetchFirstTxRegion's comment that it returns the first block region

* [DEV-223] rename type BlueBlockTransaction to TxWithBlockHash

* [DEV-223] add named returned value for applyUTXOChanges

[4c95e293] [DEV-134] Made golint ignore the vendor directory.

[21736dbc] [DEV-134] Renamed ExampleBlockChain_ProcessBlock to ExampleBlockDAG_ProcessBlock to satisfy go vet.

[beea6486] [DEV-134] Removed pushing the built docker to a remove repository. That's unnecessary at this stage.

[bee911ed] [DEV-134] Made all precompilation checks run on everything instead of only the root dir.

[585f92ae] [DEV-134] Added "github.com/pkg/errors" to dep.

[5f02f570] [DEV-134] -vendor-only is written with only one hyphen.

[3eee7f95] [DEV-134] go vet instead of go tool vet.

[0c2d4343] [DEV-134] Split all the pre-compile checks to separate lines to be able to tell which of them is failing.

[780519c8] [DEV-134] Ran gofmt on everything.

[8247146b] Dev 223 fix txindex (#100)

* [DEV-201] In handleGetBlockDAGInfo calculate difficulty by the tip with the lowest bits

* [DEV-202] Move VirtualBlock.GetUTXOEntry to BlockDAG

* [DEV-203] Move VirtualBlock.SelectedTip() to BlockDAG

* [DEV-203] Move VirtualBlock.SelectedTip() to BlockDAG

* [DEV-204] Unexport VirtualBlock() and add CalcMedianTime method for DAG

* [DEV-204] add explanation about difficulty in CurrentBits() comment

* [DEV-204] unexport VirtualBlock type

* [DEV-223] make applyUTXOChanges return pastUTXOResults

* [DEV-223] add bluestxdata for current block as well

* [DEV-223] re-design tx index

* [DEV-223] edit txindex comments

* [DEV-223] rename BluesTxData -> AcceptedTxData, and return from applyUTXOChanges only transactions that got accepted

* [DEV-223] add unit test for txindex

* [DEV-223] fix comments and unite blueTransaction and AcceptedTxData to one type

* [DEV-223] use bucket cursor for dbFetchFirstTxRegion

* [DEV-223] use the same cursor instance for dbFetchFirstTxRegion

* [DEV-223] write in dbFetchFirstTxRegion's comment that it returns the first block region

* [DEV-223] rename type BlueBlockTransaction to TxWithBlockHash

* [DEV-223] add named returned value for applyUTXOChanges

[bff68aa3] [DEV-134] Gave executable permission to deploy.sh

[638a99d9] [DEV-134] Added jenkinsfile and deploy script.

* [DEV-134] Added a robust testing script.

* [DEV-134] Fixed a bash-ism.

* [DEV-134] Disabled testing with coverage for now.

* [DEV-134] Disabled golint and removed removing debug symbols.

* [DEV-134] Disabled aligncheck.

* [DEV-134] Disabled structcheck and varcheck.

* [DEV-134] Added "don't inline functions" to compiler flags for testing.

* [DEV-134] Made build fail if gofmt prints out anything.

* [DEV-134] Fixed misleading comment.

* [DEV-134] Added comments to test.sh.

* [DEV-134] Renamed tm to measure_runtime and removed do_ prefixes from functions.

* [DEV-134] Fixed gofmt line in build script.

* [DEV-134] Fixed gofmt some more.

* [DEV-134]  Fixed gofmt not actually failing due to logical or.
2018-10-25 18:58:41 +03:00

21 lines
589 B
Go

package util
// log2FloorMasks defines the masks to use when quickly calculating
// floor(log2(x)) in a constant log2(32) = 5 steps, where x is a uint32, using
// shifts. They are derived from (2^(2^x) - 1) * (2^(2^x)), for x in 4..0.
var log2FloorMasks = []uint32{0xffff0000, 0xff00, 0xf0, 0xc, 0x2}
// FastLog2Floor calculates and returns floor(log2(x)) in a constant 5 steps.
func FastLog2Floor(n uint32) uint8 {
rv := uint8(0)
exponent := uint8(16)
for i := 0; i < 5; i++ {
if n&log2FloorMasks[i] != 0 {
rv += exponent
n >>= exponent
}
exponent >>= 1
}
return rv
}