SQLite
Class StringEncoder
public
class
StringEncoder
extends Object
String encoder/decoder for SQLite.
This module was kindly donated by Eric van der Maarel of Nedap N.V.
This encoder was implemented based on an original idea from an anonymous
author in the source code of the SQLite distribution.
I feel obliged to provide a quote from the original C-source code:
"The author disclaims copyright to this source code. In place of
a legal notice, here is a blessing:
May you do good and not evil.
May you find forgiveness for yourself and forgive others.
May you share freely, never taking more than you give."
Method Summary |
static byte[] | byteCopy(byte[] source, int offset, int count, byte[] target)
Copies count elements from source, starting at element with
index offset, to the given target. |
static byte[] | decode(String s)
Decodes the given string that is assumed to be a valid encoding
of a byte array. |
static String | encode(byte[] a)
Encodes the given byte array into a string that can be used by
the SQLite database. |
static String | encodeX(byte[] a)
Encodes the given byte array into SQLite3 blob notation, ie X'..' |
static final char[] xdigits
private static byte[] byteCopy(byte[] source, int offset, int count, byte[] target)
Copies count elements from source, starting at element with
index offset, to the given target.
Parameters: source the source. offset the offset. count the number of elements to be copied. target the target to be returned.
Returns: the target being copied to.
public static byte[] decode(String s)
Decodes the given string that is assumed to be a valid encoding
of a byte array. Typically the given string is generated by
this class'
encode
method.
Parameters: s the given string encoding.
Returns: the byte array obtained from the decoding.
Throws: IllegalArgumentException when the string given is not
a valid encoded string for this encoder.
public static String encode(byte[] a)
Encodes the given byte array into a string that can be used by
the SQLite database. The database cannot handle null (0x00) and
the character '\'' (0x27). The encoding consists of escaping
these characters with a reserved character (0x01). The escaping
is applied after determining and applying a shift that minimizes
the number of escapes required.
With this encoding the data of original size n is increased to a
maximum of 1+(n*257)/254.
For sufficiently large n the overhead is thus less than 1.2%.
Parameters: a the byte array to be encoded. A null reference is handled as
an empty array.
Returns: the encoded bytes as a string. When an empty array is
provided a string of length 1 is returned, the value of
which is bogus.
When decoded with this class' decode
method
a string of size 1 will return an empty byte array.
public static String encodeX(byte[] a)
Encodes the given byte array into SQLite3 blob notation, ie X'..'
Parameters: a the byte array to be encoded. A null reference is handled as
an empty array.
Returns: the encoded bytes as a string.