node-wgdb

Bindings for WhiteDB for Node.JS.

This library is still a work in progress and might not work for everyone. Please report any and all issues.

Installing

You need to first install the WhiteDB library from their download page. The version developed against is 0.7.0.

Via Git

git clone git://github.com/brettlangdon/node-wgdb.git
cd ./node-wgdb
npm install

Via NPM

npm install wgdb

API

• wgdb
  • constants
  • new wgdb(db_name, [size])
  • wgdb.attach([callback])
  • wgdb.detach([callback])
  • wgdb.delete([callback])
  • wgdb.dump(filename, [callback])
  • wgdb.import(import, [callback])
  • wgdb.createRecord(num_fields, [callback])
  • wgdb.firstRecord([callback])
  • wgdb.findRecord(field, condition, value, [last_record], [callback])
  • wgdb.query(query, [callback])
• record
  • record.setField(field, value, [callback])
  • record.getField(field, [callback])
  • record.length([callback])
  • record.getFields([callback])
  • record.delete([callback)
• cursor
  • cursor.next([callback])

wgdb

When requiring the module you will end up with the wgdb class which is how you interact with WhiteDB

CONSTANTS

• wgdb.EQUAL - used to represent = condition for queries
• wgdb.NOT_EQUAL - used to represent != condition for queries
• wgdb.LESSTHAN - used to represent < condition for queries
• wgdb.GREATER - used to represent > condition for queries
• wgdb.LTEQUAL - used to represent <= condition for queries
• wgdb.GTEQUAL - used to represent >= condition for queries

new wgdb(db_name, [size])

Creates a new instance of wgdb.

• db_name - integer name of shared memory space (required)
• size - the size in bytes for the databae if it does not already exist (default: 10000000 - 10MB)

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);

wgdb.attach([callback])

Either attaches to or creates the shared space for the wgdb instance.

Calling attach is very important, this makes it so you can use the other methods.

• callback - function(error) to call when done attaching
  • error will be undefined if no error occurred.

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(error){
       console.log(error);
    }
 
    // do some cool stuff
});

wgdb.detach([callback])

Detaches an attached wgdb instance.

• callback - function(error) to call when done detaching
  • error will be undefined if no error occurred.

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        // do some cool stuff
        db.detach(console.log);
    }
});

wgdb.delete([callback])

Delete the shared memory space for the wgdb instance.

• callback - function(error) to call when done deleting
  • error will be undefined if no error occurred.

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.delete(console.log);
    }
});

wgdb.dump(filename, [callback])

Dump the wgdb database to filename.

• filename - string filename of where to dump the database (required)
• callback - function(error) to call when done dumping
  • error will be undefined if no error occurred.

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.dump("backup.db", console.log);
    }
});

wgdb.import(filename, [callback])

Import filename into the wgdb database.

• filename - string filename of where to load the database from (required)
• callback - function(error) to call when done importing
  • error will be undefined if no error occurred.

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.import("backup.db", console.log);
    }
});

wgdb.createRecord(num_fields, [callback])

Add a new record to the wgdb instance.

• num_fields - int number of fields for the record to have (required)
• callback - function(error, record) to call when done creating
  • error will be undefined if no error occurred
  • record will be undefined if an error occurred or else will be a record instance.

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.createRecord(2, function(error, record){
            if(error || !record){
                console.log(error);
                return;
            }
 
            // do some cool record stuff here
        });
    }
});

wgdb.firstRecord([callback])

Get the first record from the wgdb instance.

• callback - function(error, record) to call when done creating
  • error will be undefined if no error occurred
  • record will be undefined if an error occurred or else will be a record instance.

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.firstRecord(function(error, record){
            if(error || !record){
                console.log(error);
                return;
            }
 
            // do some cool record stuff here
        });
    }
});

wgdb.findRecord(field, condition, value [last_record], [callback])

Find the first record in the wgdb database which meets the condition and value requirements.

If last_record is given, then find the first record after last_record which meets the conditions.

• field - int of the field to search by (required)
• condition - one of the wgdb condition constants, e.g. wgdb.EQUAL (required)
• value - the value to match condition on (required)
• last_record - a record instance, find the next record after last_record which matches condition and value (optional)
• callback - function(error, record) to call when done searching
  • error will be undefined if no error occurred
  • record will be undefined if an error occurred or else will be a record instance.

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        // find the first record where field 1 = 5
        db.findRecord(1, wgdb.EQUAL, 5, function(error, first){
            if(error || !first){
                console.log(error);
                return;
            }
 
            // find the next record after `first` where field 1 == 5
            db.findRecord(1, wgdb.EQUAL, 5, first, function(error, second){
                // do cool stuff with `second`
            });
        });
    }
});

wgdb.query(query, [callback])

Query the wgdb instance for all records which meet the provided query.

query is similar to a list of parameters to wgdb.findRecord.

[
    [<field_num>, <condition>, <value>],
    ...
]

• query - array representing the query to make (required)
• callback - function(error, cursor) to call when done searching
  • error will be undefined if no error occurred
  • cursor will be undefined if an error occurred or else will be a cursor instance.

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.query([
            [1, wgdb.GTEQUAL, 5],
        ], function(error, cursor){
            if(error || !cursor){
                console.log(error);
                return;
            }
 
            cursor.next(function(error, record){
                // do someting with record
                cursor.next(function(error, record){
                    // do something with record
                });
            });
        });
    }
});

record

A record instance represents a single record in a wgdb database;

The only way to get a record is either by querying a wgdb instance or calling wgdb.createRecord

record.setField(field, value, [callback])

Set the value of a field in a record.

• field - int of the field to set value for
• value - the value to set the field to, please see notes on supported values
• callback - function(error) to call when done setting
  • error will be undefined if no error occurred

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.createRecord(2, function(error, record){
            // error checking here
 
            record.setField(0, "hello", function(error){
                record.setField(1, "world", function(error){
 
                });
            });
        });
    }
});

record.getField(field, [callback])

Get the value of a given field for the record instance

• field - int of the field to set value for
• callback - function(error, value) to call when done getting
  • error will be undefined if no error occurred
  • value will be the value stored in that field, please see notes on supported values

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.findRecord(0, wgdb.EQUAL, "hello", function(error, record){
            // error checking here
 
            record.getField(1, function(error, value){
                console.log(value);
            });
        });
    }
});

record.length([callback])

Get the number of fields in a given record instance.

• callback - function(error, value) to call when done getting
  • error will be undefined if no error occurred
  • length will be the length of the record, this is the value set when calling wgdb.createRecord

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.findRecord(0, wgdb.EQUAL, "hello", function(error, record){
            // error checking here
 
            record.length(function(error, length){
                console.log(length);
            });
        });
    }
});

record.getFields([callback])

Get the value of all fields for the record instance.

• callback - function(error, fields) to call when done getting
  • error will be undefined if no error occurred
  • fields will be an array of values for the fields in record

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.findRecord(0, wgdb.EQUAL, "hello", function(error, record){
            // error checking here
 
            record.getFields(function(error, fields){
                console.dir(fields);
            });
        });
    }
});

record.delete([callback])

Delete the record that the record instance points to.

• callback - function(error) to call when done deleting
  • error will be undefined if no error occurred

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.findRecord(0, wgdb.EQUAL, "hello", function(error, record){
            // error checking here
 
            record.delete(function(error){
                // it is gone, no going back
            });
        });
    }
});

cursor

A cursor is used to iterate over the results of a call to wgdb.query.

The only way to get an instance of cursor is by calling wgdb.query.

cursor.next([callback])

Get the next record in the query results.

• callback - function(error, record) to call when done fetching
  • error will be undefined if no error occurred
  • record will be undefined if an error has occurred or if there are no more records left in the query results, otherwise it will be a record instance

var wgdb = require("wgdb");
 
var db = new wgdb(1000, 2000000);
db.attach(function(error){
    if(!error){
        db.query([
            [1, wgdb.GTEQUAL, 5],
        ], function(error, cursor){
            if(error || !cursor){
                console.log(error);
                return;
            }
 
            cursor.next(function(error, record){
                if(error){
                    // something bad happend
                    return;
                }
                if(!record){
                    // no more records left in the results
                    return;
                }
 
                // do something with record
 
                // on to the next one
                cursor.next(function(error, record){
                    // do the same checking as above
                });
            });
        });
    }
});

License

The MIT License (MIT)

Copyright (c) 2013 Brett Langdon <brett@blangdon.com>

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.