vimrc/pylibs/logilab/common/dbf.py

# -*- coding: utf-8 -*-
# copyright 2003-2011 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of logilab-common.
#
# logilab-common is free software: you can redistribute it and/or modify it under
# the terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option) any
# later version.
#
# logilab-common is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with logilab-common.  If not, see <http://www.gnu.org/licenses/>.
"""This is a DBF reader which reads Visual Fox Pro DBF format with Memo field

Usage:

>>> rec = readDbf('test.dbf')
>>> for line in rec:
>>>     print line['name']


:date: 13/07/2007

http://www.physics.ox.ac.uk/users/santoso/Software.Repository.html
page says code is "available as is without any warranty or support".
"""

import struct
import os, os.path
import sys
import csv
import tempfile
import ConfigParser

class Dbase:
    def __init__(self):
        self.fdb = None
        self.fmemo = None
        self.db_data = None
        self.memo_data = None
        self.fields = None
        self.num_records = 0
        self.header = None
        self.memo_file = ''
        self.memo_header = None
        self.memo_block_size = 0
        self.memo_header_len = 0

    def _drop_after_NULL(self, txt):
        for i in range(0, len(txt)):
            if ord(struct.unpack('c', txt[i])[0])==0:
                return txt[:i]
        return txt

    def _reverse_endian(self, num):
        if not len(num):
            return 0
        val = struct.unpack('<L', num)
        val = struct.pack('>L', val[0])
        val = struct.unpack('>L', val)
        return val[0]

    def _assign_ids(self, lst, ids):
        result = {}
        idx = 0
        for item in lst:
            id = ids[idx]
            result[id] = item
            idx += 1
        return result

    def open(self, db_name):
        filesize = os.path.getsize(db_name)
        if filesize <= 68:
            raise IOError, 'The file is not large enough to be a dbf file'

        self.fdb = open(db_name, 'rb')

        self.memo_file = ''
        if os.path.isfile(db_name[0:-1] + 't'):
            self.memo_file = db_name[0:-1] + 't'
        elif os.path.isfile(db_name[0:-3] + 'fpt'):
            self.memo_file = db_name[0:-3] + 'fpt'

        if self.memo_file:
            #Read memo file
            self.fmemo = open(self.memo_file, 'rb')
            self.memo_data = self.fmemo.read()
            self.memo_header = self._assign_ids(struct.unpack('>6x1H', self.memo_data[:8]), ['Block size'])
            block_size = self.memo_header['Block size']
            if not block_size:
                block_size = 512
            self.memo_block_size = block_size
            self.memo_header_len = block_size
            memo_size = os.path.getsize(self.memo_file)

        #Start reading data file
        data = self.fdb.read(32)
        self.header = self._assign_ids(struct.unpack('<B 3B L 2H 20x', data), ['id', 'Year', 'Month', 'Day', '# of Records', 'Header Size', 'Record Size'])
        self.header['id'] = hex(self.header['id'])

        self.num_records = self.header['# of Records']
        data = self.fdb.read(self.header['Header Size']-34)
        self.fields = {}
        x = 0
        header_pattern = '<11s c 4x B B 14x'
        ids = ['Field Name', 'Field Type', 'Field Length', 'Field Precision']
        pattern_len = 32
        for offset in range(0, len(data), 32):
            if ord(data[offset])==0x0d:
                break
            x += 1
            data_subset = data[offset: offset+pattern_len]
            if len(data_subset) < pattern_len:
                data_subset += ' '*(pattern_len-len(data_subset))
            self.fields[x] = self._assign_ids(struct.unpack(header_pattern, data_subset), ids)
            self.fields[x]['Field Name'] = self._drop_after_NULL(self.fields[x]['Field Name'])

        self.fdb.read(3)
        if self.header['# of Records']:
            data_size = (self.header['# of Records'] * self.header['Record Size']) - 1
            self.db_data = self.fdb.read(data_size)
        else:
            self.db_data = ''
        self.row_format = '<'
        self.row_ids = []
        self.row_len = 0
        for key in self.fields:
            field = self.fields[key]
            self.row_format += '%ds ' % (field['Field Length'])
            self.row_ids.append(field['Field Name'])
            self.row_len += field['Field Length']

    def close(self):
        if self.fdb:
            self.fdb.close()
        if self.fmemo:
            self.fmemo.close()

    def get_numrecords(self):
        return self.num_records

    def get_record_with_names(self, rec_no):
        """
        This function accept record number from 0 to N-1
        """
        if rec_no < 0 or rec_no > self.num_records:
            raise Exception, 'Unable to extract data outside the range'

        offset = self.header['Record Size'] * rec_no
        data = self.db_data[offset:offset+self.row_len]
        record = self._assign_ids(struct.unpack(self.row_format, data), self.row_ids)

        if self.memo_file:
            for key in self.fields:
                field = self.fields[key]
                f_type = field['Field Type']
                f_name = field['Field Name']
                c_data = record[f_name]

                if f_type=='M' or f_type=='G' or f_type=='B' or f_type=='P':
                    c_data = self._reverse_endian(c_data)
                    if c_data:
                        record[f_name] = self.read_memo(c_data-1).strip()
                else:
                    record[f_name] = c_data.strip()
        return record

    def read_memo_record(self, num, in_length):
        """
        Read the record of given number. The second parameter is the length of
        the record to read. It can be undefined, meaning read the whole record,
        and it can be negative, meaning at most the length
        """
        if in_length < 0:
            in_length = -self.memo_block_size

        offset = self.memo_header_len + num * self.memo_block_size
        self.fmemo.seek(offset)
        if in_length<0:
            in_length = -in_length
        if in_length==0:
            return ''
        return self.fmemo.read(in_length)

    def read_memo(self, num):
        result = ''
        buffer = self.read_memo_record(num, -1)
        if len(buffer)<=0:
            return ''
        length = struct.unpack('>L', buffer[4:4+4])[0] + 8

        block_size = self.memo_block_size
        if length < block_size:
            return buffer[8:length]
        rest_length = length - block_size
        rest_data = self.read_memo_record(num+1, rest_length)
        if len(rest_data)<=0:
            return ''
        return buffer[8:] + rest_data

def readDbf(filename):
    """
    Read the DBF file specified by the filename and
    return the records as a list of dictionary.

    :param: filename File name of the DBF
    :return: List of rows
    """
    db = Dbase()
    db.open(filename)
    num = db.get_numrecords()
    rec = []
    for i in range(0, num):
        record = db.get_record_with_names(i)
        rec.append(record)
    db.close()
    return  rec

if __name__=='__main__':
    rec = readDbf('dbf/sptable.dbf')
    for line in rec:
        print '%s %s' % (line['GENUS'].strip(), line['SPECIES'].strip())