Author Archives: DISAM Support

D-ISAM Python module

This Python module imports D-ISAM as a shared library, and exports three classes.

d7 class exports the D-ISAM library itself, and adds “constant” values for the standard ISAM defines – for example d7.isOpen( "myfile", d7.ISINOUT + d7.ISAUTOLOCK )

d7error is a python Exception class, for example raise d7error( isam, "message text" )

d7key is a ctypes Structure class, and provides an instance of an ISAM key descriptor.

An example of usage can be found here

An overview is available here

Download the module here

#!/bin/python

from ctypes import CDLL, Structure, c_void_p, c_char_p, c_int, c_short, c_uint

d7 = CDLL( "libdisam72.so" )

# disam 'constant' values

d7.ISMAXPARTS = 20
d7.ISINPUT = 0x00
d7.ISOUTPUT = 0x01
d7.ISINOUT = 0x02
d7.ISTRANS = 0x04
d7.ISNOLOG = 0x08
d7.ISFIXLEN = 0x00
d7.ISVARLEN = 0x10
d7.ISVARCMP = 0x30
d7.ISSYNCWR = 0x40
d7.ISMASKED = 0x80
d7.ISNOCARE = 0x8000
d7.ISRDONLY = 0x100
d7.ISAUTOLOCK = 0x200
d7.ISMANULOCK = 0x400
d7.ISEXCLLOCK = 0x800
d7.ISSEMILOCK = 0x1000
d7.ISFIRST = 0
d7.ISLAST = 1
d7.ISNEXT = 2
d7.ISPREV = 3
d7.ISCURR = 4
d7.ISEQUAL = 5
d7.ISGREAT = 6
d7.ISGTEQ = 7
d7.CHARTYPE = 0
d7.DECIMALTYPE = 0
d7.INTTYPE = 1
d7.LONGTYPE = 2
d7.DOUBLETYPE = 3
d7.FLOATTYPE = 4
d7.MINTTYPE = 5
d7.MLONGTYPE = 6
d7.STRINGTYPE = 7
d7.ISDESC = 0x80
d7.CHARSIZE = 1
d7.INTSIZE = 2
d7.LONGSIZE = 4
d7.DOUBLESIZE = 8
d7.FLOATSIZE = 4
d7.MINTSIZE = 2
d7.MLONGSIZE = 4
d7.STRINGSIZE = 1
d7.ISNODUPS = 0x00
d7.ISDUPS = 0x01
d7.DCOMPRESS = 0x02
d7.LCOMPRESS = 0x04
d7.TCOMPRESS = 0x08
d7.COMPRESS = 0x0E
d7.TNULL = 0x10
d7.NULLKEY = 0x20
d7.ISLOCK = 0x100
d7.ISSKIPLOCK = 0x200
d7.ISWAIT = 0x400
d7.ISLCKW = 0x500
d7.ISKEEPLOCK = 0x800
d7.AUDSETNAME = 0
d7.AUDGETNAME = 1
d7.AUDSTART = 2
d7.AUDSTOP = 3
d7.AUDINFO = 4
d7.USERINFOSIZE = 10

# disam functions return and argument definitions

d7.isIndexInfo.restype = c_int
d7.isIndexInfo.argtypes = [ c_void_p, c_void_p, c_int ]

d7.isIsamInfo.restype = c_int
d7.isIsamInfo.argtypes = [ c_void_p, c_void_p ]

d7.isErase.restype = c_int
d7.isErase.argtypes = [ c_char_p ]

d7.isRename.restype = c_int
d7.isRename.argtypes = [ c_char_p, c_char_p ]

d7.isCluster.restype = c_void_p
d7.isCluster.argtypes = [ c_void_p, c_void_p ]

d7.isClone.restype = c_void_p
d7.isClone.argtypes = [ c_void_p, c_char_p ]

d7.isCopy.restype = c_int
d7.isCopy.argtypes = [ c_void_p, c_void_p, c_void_p ]

d7.isBuild.restype = c_void_p
d7.isBuild.argtypes = [ c_char_p, c_int, c_int, c_void_p, c_int ]

d7.isPrecious.restype = c_int
d7.isPrecious.argtypes = [ c_void_p, c_int ]

d7.isAddIndex.restype = c_int
d7.isAddIndex.argtypes = [ c_void_p, c_void_p ]

d7.isDelIndex.restype = c_int
d7.isDelIndex.argtypes = [ c_void_p, c_void_p ]

d7.isUserInfo.restype = c_int
d7.isUserInfo.argtypes = [ c_void_p, c_int, c_char_p ]

d7.isOpen.restype = c_void_p
d7.isOpen.argtypes = [ c_char_p, c_int ]

d7.isClose.restype = c_int
d7.isClose.argtypes = [ c_void_p ]

d7.isLockCheck.restype = c_int
d7.isLockCheck.argtypes = [ c_void_p, c_int ]

d7.isSetMode.restype = c_int
d7.isSetMode.argtypes = [ c_void_p, c_int ]

d7.isWrite.restype = c_int
d7.isWrite.argtypes = [ c_void_p, c_void_p ]

d7.isWrLock.restype = c_int
d7.isWrLock.argtypes = [ c_void_p, c_void_p ]

d7.isWrCurr.restype = c_int
d7.isWrCurr.argtypes = [ c_void_p, c_void_p ]

d7.isRewrite.restype = c_int
d7.isRewrite.argtypes = [ c_void_p, c_void_p ]

d7.isRewCurr.restype = c_int
d7.isRewCurr.argtypes = [ c_void_p, c_void_p ]

d7.isRewRec.restype = c_int
d7.isRewRec.argtypes = [ c_void_p, c_uint, c_void_p ]

d7.isRewNxt.restype = c_int
d7.isRewNxt.argtypes = [ c_void_p, c_void_p ]

d7.isRead.restype = c_int
d7.isRead.argtypes = [ c_void_p, c_void_p, c_int ]

d7.isStart.restype = c_int
d7.isStart.argtypes = [ c_void_p, c_void_p, c_int, c_void_p, c_int ]

d7.isIndex.restype = c_int
d7.isIndex.argtypes = [ c_void_p, c_int ]

d7.isGoto.restype = c_int
d7.isGoto.argtypes = [ c_void_p, c_uint ]

d7.isPush.restype = c_int
d7.isPush.argtypes = [ c_void_p, c_void_p, c_void_p ]

d7.isPop.restype = c_int
d7.isPop.argtypes = [ c_void_p, c_int, c_uint ]

d7.isData.restype = c_int
d7.isData.argtypes = [ c_void_p, c_void_p, c_uint ]

d7.isLock.restype = c_int
d7.isLock.argtypes = [ c_void_p ]

d7.isUnLock.restype = c_int
d7.isUnLock.argtypes = [ c_void_p ]

d7.isRelease.restype = c_int
d7.isRelease.argtypes = [ c_void_p ]

d7.isRelRec.restype = c_int
d7.isRelRec.argtypes = [ c_void_p, c_uint ]

d7.isRelCurr.restype = c_int
d7.isRelCurr.argtypes = [ c_void_p ]

d7.isDelete.restype = c_int
d7.isDelete.argtypes = [ c_void_p, c_void_p ]

d7.isDelCurr.restype = c_int
d7.isDelCurr.argtypes = [ c_void_p ]

d7.isDelRec.restype = c_int
d7.isDelRec.argtypes = [ c_void_p, c_uint ]

d7.isErrno.restype = c_int
d7.isErrno.argtypes = [ c_void_p ]

d7.isErrio.restype = c_int
d7.isErrio.argtypes = [ c_void_p ]

d7.isCount.restype = c_int
d7.isCount.argtypes = [ c_void_p ]

d7.isRecnum.restype = c_int
d7.isRecnum.argtypes = [ c_void_p ]

d7.isReclen.restype = c_int
d7.isReclen.argtypes = [ c_void_p ]

d7.isSetrec.restype = c_int
d7.isSetrec.argtypes = [ c_void_p, c_uint ]

d7.isSetlen.restype = c_int
d7.isSetlen.argtypes = [ c_void_p, c_short ]

d7.isLdSchema.restype = c_int
d7.isLdSchema.argtypes = [ c_void_p, c_char_p ]

d7.isDpSchema.restype = c_int
d7.isDpSchema.argtypes = [ c_void_p ]

d7.isStSchema.restype = c_int
d7.isStSchema.argtypes = [ c_void_p, c_char_p ]

d7.isRmSchema.restype = c_int
d7.isRmSchema.argtypes = [ c_void_p ]

d7.isSetUnique.restype = c_int
d7.isSetUnique.argtypes = [ c_void_p, c_uint ]

d7.isUniqueId.restype = c_int
d7.isUniqueId.argtypes = [ c_void_p, c_void_p ]

d7.isGetLastRec.restype = c_int
d7.isGetLastRec.argtypes = [ c_void_p, c_void_p ]

d7.isSetLastRec.restype = c_int
d7.isSetLastRec.argtypes = [ c_void_p, c_uint ]

d7.isLastRec.restype = c_int
d7.isLastRec.argtypes = [ c_void_p, c_void_p ]

d7.isAmSane.restype = c_int
d7.isAmSane.argtypes = [ ]

d7.isCheckData.restype = c_int
d7.isCheckData.argtypes = [ c_void_p ]

d7.isCheckIndex.restype = c_int
d7.isCheckIndex.argtypes = [ c_void_p, c_int ]

d7.isRebuildFree.restype = c_int
d7.isRebuildFree.argtypes = [ c_void_p, c_int ]

d7.isRebuildIdx.restype = c_int
d7.isRebuildIdx.argtypes = [ c_void_p, c_int ]

d7.isCheckVarlen.restype = c_int
d7.isCheckVarlen.argtypes = [ c_void_p, c_void_p ]

class d7error(Exception):

  def __init__ ( self, isam, string ):
    self.value = d7.isErrno( isam ) 
    self.string = string;

  def __str__ ( self ):
    return repr( "[%s] %s" % ( self.value, self.string ) )


class _d7_key_part(Structure):
  _fields_ = [ ("kp_start", c_short),
               ("kp_leng", c_short),
               ("kp_type", c_short) ]

class d7key(Structure):
  _fields_ = [ ("k_flags", c_short),
               ("k_nparts", c_short),
               ("k_part", _d7_key_part * d7.ISMAXPARTS) ]

D-ISAM example in Python

The following example code demonstrates the basic principles of using D-ISAM in Python, by means of the standard ctypes library.

The required disam72 class module is here

An overview is available here

Download the example here

#!/usr/bin/python

from ctypes import *
from disam72 import d7, d7key, d7error

name = "example_isam_file"

class RECORD(Structure):
  _fields_ = [ ( "code", c_int ),
               ( "name", c_char * 31 ) ]

key1 = d7key( d7.ISNODUPS, 1, ( ( 0, 4, d7.LONGTYPE ), ) )

key2 = d7key( d7.COMPRESS + d7.TNULL, 1, ( ( 4, 31, d7.STRINGTYPE ), ) )

d7.iserase( name )

isam = d7.isBuild( name, 35, 0, byref(key1), d7.ISINOUT + d7.ISMANULOCK )
if isam is None:
  raise d7error( None, "build %s failed" % name )

if d7.isAddIndex( isam, byref(key2) ) == 0:
  raise d7error( isam, "add second index failed" );

pad = RECORD( 0, "" )

pad.code = 1
pad.name = "banana, junior"
if d7.isWrite( isam, byref(pad) ) == 0:
  raise d7error( isam, "add %d %s failed" % ( pad.code, pad.name ) )

pad.code = 2
pad.name = "apple, macintosh"
if d7.isWrite( isam, byref(pad) ) == 0:
  raise d7error( isam, "add %d %s failed" % ( pad.code, pad.name ) )

pad.code = 999
pad.name = "error, read failed"

if d7.isRead( isam, byref(pad), d7.ISFIRST ) == 0:
  raise d7error( isam, "read first on primary index failed" )
else:
  print "%d: %s" % ( pad.code, pad.name )

if d7.isStart( isam, byref(key2), 1, isam, d7.ISFIRST ) == 0:
  raise d7error( isam, "switch to secondary index failed" );

if d7.isRead( isam, byref(pad), d7.ISFIRST ) == 0:
  raise d7error( isam, "read first on secondary index failed" )
else:
  print "%d: %s" % ( pad.code, pad.name )

result:

1: banana, junior
2: apple, macintosh