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Diffstat (limited to 'lib/system/bitmasks.nim')
| -rw-r--r-- | lib/system/bitmasks.nim | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/lib/system/bitmasks.nim b/lib/system/bitmasks.nim new file mode 100644 index 000000000..0663247c2 --- /dev/null +++ b/lib/system/bitmasks.nim @@ -0,0 +1,39 @@ +# +# +# Nim's Runtime Library +# (c) Copyright 2015 Andreas Rumpf +# +# See the file "copying.txt", included in this +# distribution, for details about the copyright. +# + +# Page size of the system; in most cases 4096 bytes. For exotic OS or +# CPU this needs to be changed: +const + PageShift = when defined(nimPage256) or defined(cpu16): 3 + elif defined(nimPage512): 9 + elif defined(nimPage1k): 10 + else: 12 # \ # my tests showed no improvements for using larger page sizes. + + PageSize = 1 shl PageShift + PageMask = PageSize-1 + + + MemAlign = # also minimal allocatable memory block + when defined(nimMemAlignTiny): 4 + elif defined(useMalloc): + when defined(amd64): 16 + else: 8 + else: 16 + + BitsPerPage = PageSize div MemAlign + UnitsPerPage = BitsPerPage div (sizeof(int)*8) + # how many ints do we need to describe a page: + # on 32 bit systems this is only 16 (!) + + TrunkShift = 9 + BitsPerTrunk = 1 shl TrunkShift # needs to be power of 2 and divisible by 64 + TrunkMask = BitsPerTrunk - 1 + IntsPerTrunk = BitsPerTrunk div (sizeof(int)*8) + IntShift = 5 + ord(sizeof(int) == 8) # 5 or 6, depending on int width + IntMask = 1 shl IntShift - 1 |