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#!/usr/bin/env python
""" Calculate the sectorsize for various keysizes.
See the conditions in btr.c:
if ((info.sectorSize < sizeof(bNode))
|| (info.sectorSize % 4)
|| (info.sectorSize > MAX_SECTOR_SIZE))
return bErrSectorSize;
/* ensure that there are at least 3 children/parent for gather/scatter */
maxCt = info.sectorSize - (sizeof(bNode) - sizeof(bKey));
maxCt /= sizeof(bIdxAddr) + info.keySize + sizeof(bRecAddr);
if (maxCt < 6) return bErrSectorSize;
MAX_SECTOR_SIZE is 1024.
For keysize = 25 on a 64-bit platform:
(gdb) print maxCt
$4 = 5
(gdb) print info.sectorSize
$5 = 256
(gdb) print sizeof(bNode)
$6 = 40
(gdb) print sizeof(bKey)
$7 = 1
(gdb) print sizeof(bIdxAddr)
$8 = 8
(gdb) print info.keySize
$9 = 26
(gdb) print sizeof(bRecAddr)
$10 = 8
(gdb) print sizeof(bIdxAddr) + info.keySize + sizeof(bRecAddr)
$11 = 42
(gdb) print info.sectorSize - (sizeof(bNode) - sizeof(bKey))
$12 = 217
"""
from mx.BeeBase import BeeIndex
### Globals
# Debug level
_debug = 0
# Allowed sector sizes; these have to be == 0 mod 4 and should ideally
# be multiples of disk sector sizes for better performance
SECTOR_SIZES = (
256,
512,
1024,
2048,
4096,
)
###
def calc_maxCt(sectorSize,
keySize,
sizeof_bNode=BeeIndex.sizeof_bNode,
sizeof_bKey=BeeIndex.sizeof_bKey,
sizeof_bRecAddr=BeeIndex.sizeof_bRecAddr,
sizeof_bIdxAddr=BeeIndex.sizeof_bIdxAddr):
maxCt = sectorSize - (sizeof_bNode - sizeof_bKey)
maxCt /= sizeof_bIdxAddr + keySize + sizeof_bRecAddr
return maxCt
def find_sectorsizes():
l = []
# Sanity check
for sectorsize in SECTOR_SIZES:
assert sectorsize % 4 == 0, 'invalid sectorsize %i' % sectorsize
# Find keysizes
for keysize in range(1, SECTOR_SIZES[-1]):
# The keysize used in mxBeeBase's Python interface does
# not include the terminating 0-byte, so add one to the
# keysize
bytesize = keysize + 1
for sectorsize in SECTOR_SIZES:
maxct = calc_maxCt(sectorsize,
bytesize)
if maxct < 6:
continue
else:
l.append((keysize, sectorsize))
break
else:
# Max. sectorsize reached, stop searching
if _debug:
print ('WARNING: no sectorsize found for keysize=%i' % keysize)
break
return l
###
if __name__ == '__main__':
print ('mxBeeBase BeeIndex - Valid sectorsizes for various keysizes')
print ('')
print ('keysize : sectorsize')
print ('--------------------')
for (keysize, sectorsize) in find_sectorsizes():
print ('%-8i: %i' % (keysize, sectorsize))
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