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Conversion Functions

This module contains functions to convert data between different formats.

Conventions

All functions and errors in this module are assigned to the http://basex.org/modules/convert namespace, which is statically bound to the convert prefix.

Strings

`convert:string-to-base64`

Signature

convert:string-to-base64(
  $string    as xs:string,
  $encoding  as xs:string?  := ()
) as xs:base64Binary

Summary Converts the specified $string to an xs:base64Binary item. If the default encoding is chosen, conversion will be cheap, as strings and binaries are both internally represented as byte arrays. The UTF-8 default encoding can be overwritten with the optional $encoding argument.

Errors

`binary`	The input cannot be converted to a binary representation.
`encoding`	The specified encoding is invalid or not supported.

Examples

string(convert:string-to-base64('HelloWorld'))

Result: 'SGVsbG9Xb3JsZA=='

`convert:string-to-hex`

Signature

convert:string-to-hex(
  $string    as xs:string,
  $encoding  as xs:string?  := ()
) as xs:hexBinary

Summary Converts the specified $string to an xs:hexBinary item. If the default encoding is chosen, conversion will be cheap, as strings and binaries are both internally represented as byte arrays. The UTF-8 default encoding can be overwritten with the optional $encoding argument.

Errors

`binary`	The input cannot be converted to a binary representation.
`encoding`	The specified encoding is invalid or not supported.

Examples

string(convert:string-to-hex('HelloWorld'))

Result: '48656C6C6F576F726C64'

Binary Data

`convert:integers-to-base64`

Signature	convert:integers-to-base64( $integers as xs:integer* ) as xs:base64Binary
Summary	Converts the specified `$integers` to an item of type `xs:base64Binary`: Only the first 8 bits of the supplied integers will be considered. Conversion of byte sequences is very efficient, as items of binary type are internally represented as byte arrays.
Examples	`convert:integers-to-base64(Q{java:java.lang.String}get-bytes('abc'))` Converts a byte sequence to a `xs:base64Binary` item.

`convert:integers-to-hex`

Signature	convert:integers-to-hex( $integers as xs:integer* ) as xs:hexBinary
Summary	Converts the specified `$integers` to an item of type `xs:hexBinary`: Only the first 8 bits of the supplied integers will be considered. Conversion of byte sequences is very efficient, as items of binary type are internally represented as byte arrays.

`convert:binary-to-integers`

Signature	convert:binary-to-integers( $binary as (xs:base64Binary\|xs:hexBinary) ) as xs:integer*
Summary	Returns the specified `$binary` as a sequence of unsigned integers (octets).
Examples	`convert:binary-to-integers(xs:hexBinary('FF'))` Result: `255`

`convert:binary-to-bytes`

Signature

Signature	convert:binary-to-bytes( $binary as (xs:base64Binary\|xs:hexBinary) ) as xs:byte*
Summary	Returns the specified `$binary` as a sequence of bytes. The conversion is very cheap and takes no additional memory, as items of binary type are internally represented as byte arrays.
Examples	`convert:binary-to-bytes(xs:base64Binary('QmFzZVggaXMgY29vbA=='))` Yields the sequence `(66, 97, 115, 101, 88, 32, 105, 115, 32, 99, 111, 111, 108)`. `convert:binary-to-bytes(xs:hexBinary("4261736558"))` Yields the sequence `(66 97 115 101 88)`.

convert:binary-to-bytes(
  $binary  as (xs:base64Binary|xs:hexBinary)
) as xs:byte*

Summary Returns the specified $binary as a sequence of bytes. The conversion is very cheap and takes no additional memory, as items of binary type are internally represented as byte arrays.

Examples

convert:binary-to-bytes(xs:base64Binary('QmFzZVggaXMgY29vbA=='))

Yields the sequence (66, 97, 115, 101, 88, 32, 105, 115, 32, 99, 111, 111, 108).

convert:binary-to-bytes(xs:hexBinary("4261736558"))

Yields the sequence (66 97 115 101 88).

Number

`convert:integer-to-base`

Signature

convert:integer-to-base(
  $number  as xs:integer,
  $base    as xs:integer
) as xs:string

Summary Converts $number to a string, using the specified $base, interpreting it as a 64-bit unsigned integer. The first base elements of the sequence '0',..,'9','a',..,'z' are used as digits. Valid bases are 2, .., 36.

Errors

base The specified base is not in the range 2-36.

Examples

convert:integer-to-base(-1, 16)

Result: 'ffffffffffffffff'

convert:integer-to-base(22, 5)

Result: '42'

`convert:integer-from-base`

Signature

convert:integer-from-base(
  $string  as xs:string,
  $base    as xs:integer
) as xs:integer

Summary Decodes an integer from $string, using the specified $base. The first base elements of the sequence '0',..,'9','a',..,'z' are allowed as digits; case does not matter. Valid bases are 2 - 36. If the supplied string contains more than 64 bits of information, the result will be truncated.

Errors

`base`	The specified base is not in the range 2-36.
`integer`	The specified digit is not valid for the given range.

Examples

convert:integer-from-base('ffffffffffffffff', 16)

Result: -1

convert:integer-from-base('CAFEBABE', 16)

Result: 3405691582

convert:integer-from-base('42', 5)

Result: 22

convert:integer-from-base(convert:integer-to-base(123, 7), 7)

Result: 123

Dates and Durations

`convert:integer-to-dateTime`

Signature

Signature	convert:integer-to-dateTime( $milliseconds as xs:integer ) as xs:dateTime
Summary	Converts the specified number of `$milliseconds` since 1 Jan 1970 to an item of type xs:dateTime.
Examples	`convert:integer-to-dateTime(0)` Result: `xs:dateTime('1970-01-01T00:00:00Z')` `convert:integer-to-dateTime(1234567890123)` Result: `xs:dateTime('2009-02-13T23:31:30.123Z')` `convert:integer-to-dateTime(prof:current-ms())` Returns the current miliseconds in the `xs:dateTime` format.

convert:integer-to-dateTime(
  $milliseconds  as xs:integer
) as xs:dateTime

Summary Converts the specified number of $milliseconds since 1 Jan 1970 to an item of type xs:dateTime.

Examples

convert:integer-to-dateTime(0)

Result: xs:dateTime('1970-01-01T00:00:00Z')

convert:integer-to-dateTime(1234567890123)

Result: xs:dateTime('2009-02-13T23:31:30.123Z')

convert:integer-to-dateTime(prof:current-ms())

Returns the current miliseconds in the xs:dateTime format.

`convert:dateTime-to-integer`

Signature	convert:dateTime-to-integer( $dateTime as xs:dateTime ) as xs:integer
Summary	Converts the specified `$dateTime` item to the number of milliseconds since 1 Jan 1970.
Examples	`convert:dateTime-to-integer(xs:dateTime('1970-01-01T00:00:00Z'))` Result: `0`

`convert:integer-to-dayTime`

Signature	convert:integer-to-dayTime( $milliseconds as xs:integer ) as xs:dayTimeDuration
Summary	Converts the specified number of `$milliseconds` to an item of type xs:dayTimeDuration.
Examples	`convert:integer-to-dayTime(1234)` Result: `xs:dayTimeDuration('PT1.234S')`

`convert:dayTime-to-integer`

Signature	convert:dayTime-to-integer( $dayTime as xs:dayTimeDuration ) as xs:integer
Summary	Converts the specified `$dayTime` duration to milliseconds represented by an integer.
Examples	`convert:dayTime-to-integer(xs:dayTimeDuration('PT1S'))` Result: `1000`

Keys

The key conversion is employed by the JSON Functions and the CSV Functions to encode strings to valid element names and back to the original representation:

If lax conversion is disabled, invalid characters are replaced with underscores or (when invalid as first character of an element name) prefixed with an underscore. The resulting string may be better readable, but it cannot necessarily be converted back to the original form.
With lax conversion enabled, a string is encoded to a valid NCName representation:
- An empty string is converted to a single underscore (_).
- Existing underscores are rewritten to two underscores (__).
- Characters that are no valid NCName characters are rewritten to an underscore and the character’s four-digit Unicode. For example, the exclamation mark ? is transformed to _003f.

`convert:encode-key`

Signature	convert:encode-key( $key as xs:string, $lax as xs:boolean? := false() ) as xs:string
Summary	Encodes the specified `$key` (with the optional `$lax` conversion method) to a valid NCName representation, which can be used to create an element node. This encoding is employed by the JSON Functions and the CSV Functions.
Examples	`element { convert:encode-key("!") } { }` Creates a new element with an encoded name: `<_0021/>`.

`convert:decode-key`

Signature

convert:decode-key(
  $key  as xs:string,
  $lax  as xs:boolean?  := false()
) as xs:string

Summary Decodes the specified $key (with the optional $lax conversion method) to the original string representation. Keys supplied to this function can be element names that have been created by the JSON Functions or CSV Functions.

Errors

key The specified key cannot be decoded to its original representation.

Examples

convert:decode-key(name(<_0021/>))

Result: '!'

json:doc("doc.json")//* ! convert:decode-key(name())

Yields the original string representation of all names of a JSON document.

Errors

Code	Description
`base`	The specified base is not in the range 2-36.
`binary`	The input cannot be converted to a binary representation.
`encoding`	The specified encoding is invalid or not supported.
`integer`	The specified digit is not valid for the given range.
`key`	The specified key cannot be decoded to its original representation.
`string`	The input is an invalid XML string, or the wrong encoding has been specified.

Changelog

Version 9.4

Added: convert:encode-key, convert:decode-key.

Version 9.0

Added: convert:binary-to-integers.
Updated: convert:integers-to-base64, convert:integers-to-hex: Renamed from convert:bytes-to-base64; argument type relaxed from xs:byte to xs:integer.
Updated: error codes updated; errors now use the module namespace

Version 8.5

Updated: convert:binary-to-string: $fallback argument added.

Version 7.5

Added: convert:integer-to-dateTime, convert:dateTime-to-integer, convert:integer-to-dayTime, convert:dayTime-to-integer.

Version 7.3

Added: New module added. Some of the functions have been adopted from the obsolete Utility Functions.

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