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remove a condition that table size must be passed as power of 2 (#14926)

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* remove a condition that table size must be passed as power of 2
* remove power-of-2 condition from sets and sharedtables
* remove power-of-2 condition from deques
* use 'correctSize' for both branches
* prettify changelog.md and fix typos
* add a changelog entry
* fix double-call of 'right-size'
* fix the same thing in sets.nim
* introduce a new internal proc `slotsNeeded`

Deprecate the public proc `rightSize`, which is not needed anymore.
Now it is an identity function, allowing the old code to work
correctly and without extra allocations.
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Miran 2020-07-08 15:01:47 +02:00 • committed by GitHub
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10 changed files with 83 additions and 120 deletions
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14
lib/pure/collections/hashcommon.nim
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@ -30,17 +30,23 @@ proc nextTry(h, maxHash: Hash): Hash {.inline.} =
result = (h + 1) and maxHash
proc mustRehash[T](t: T): bool {.inline.} =
# If this is changed, make sure to synchronize it with `slotsNeeded` below
assert(t.dataLen > t.counter)
result = (t.dataLen * 2 < t.counter * 3) or (t.dataLen - t.counter < 4)
proc rightSize*(count: Natural): int {.inline.} =
proc slotsNeeded(count: Natural): int {.inline.} =
# Make sure to synchronize with `mustRehash` above
result = nextPowerOfTwo(count * 3 div 2 + 4)
proc rightSize*(count: Natural): int {.inline, deprecated: "Deprecated since 1.4.0".} =
## **Deprecated since Nim v1.4.0**, it is not needed anymore
## because picking the correct size is done internally.
##
## Return the value of ``initialSize`` to support ``count`` items.
##
## If more items are expected to be added, simply add that
## expected extra amount to the parameter before calling this.
#
# Make sure to synchronize with `mustRehash`
result = nextPowerOfTwo(count * 3 div 2 + 4)
result = count
template rawGetKnownHCImpl() {.dirty.} =
if t.dataLen == 0: