Base64 Encoding/Decoding

Robert Dickow <dickow@turbonet.com> Package base64 Version 1.0.0 - 2018-03-30

Description:

A simple lexicon to encode and decode strings or arbitrary data in base64 format using most common (e.g. MIME) character mapping and padding characters.

Top level words:

\ N.B. For flexibility, the buffers are not delimited. Store your own counts as needed.

\ Given an output buffer, a source buffer holding un-encoded data, and its length

\ in bytes, returns addr of the output buffer holding encoded data and its length.

>BASE64 ( c-addr-output c-addr-source-data n-len -- c-addr-output n-len )

\ Given an output buffer, a source buffer holding encoded data, and its length

\ in bytes, returns address of the decoded output buffer and its length.

BASE64> ( c-addr-output c-addr-source-data n-len -- c-addr-output n-len )

Helper words:

\ given buffer and its length, returns bytes needed for encoded data.

BASE64-ENCODE-LEN ( n-decoded-len -- n )

\ given buffer addr and its length, returns bytes needed for decoded data.

BASE64-DECODE-LEN ( c-addr-encoded n-len -- n )

\ given buffer addr and its length, returns buffer addr and new length

\ trimming the count of padding characters, if present. The buffer is not

\ touched.

TRIM-PADDING ( c-addr-encoded n -- c-addr-encoded n )

Configuration words:

PADDING? variable, TRUE|FALSE to use padding or not.

PADDING-CHR variable, defaulted to the usual '='

Include file

base64.f

Dependencies

none

Usage Example

\ *************************

\ Set up a buffer in heap memory based

\ on the storage needs of a string of

\ text to encode.

\ *************************

\ for storing the address of allocated memory:

VARIABLE output-buffer

\ the string to encode and later decode:

S" Hello World!!" DUP ( c-addr len len )

\ allocate len bytes, drop the Ior, and save address:

ALLOCATE DROP DUP output-buffer ! ( c-addr len c-addr-output )

\ set up the stack for encoding word:

ROT ROT ( c-addr-output c-addr len )

\ *********************

\ Encode:

\ *********************

BASE64 ( c-addr-output n-len )

2DUP CR TYPE ( c-addr-output n-len )

\ displays: "SGVsbG8gV29ybGQhIQ=="

\ *********************

\ Decode:

\ *********************

\ Note: PAD works fine for small buffers.

\ The same buffer won't work for both output and

\ input in the same operation, hence the allocated

\ memory buffer.

PAD ROT ROT ( addr-pad c-addr-output n-len )

BASE64> CR ( -- addr-pad n-len )

TYPE

\ displays: "Hello World!!"

output-buffer @ FREE DROP ( -- )

\ done

Tests

DECIMAL

\ set up oversized buffers for the encoded and decoded data:

CREATE EncodedOutput-Buffer 50 ALLOT

CREATE DecodedOutput-Buffer 50 ALLOT

T{ EncodedOutput-Buffer S" Man is distinguished" >BASE64 S" TWFuIGlzIGRpc3Rpbmd1aXNoZWQ=" COMPARE -> 0 }T

T{ DecodedOutput-Buffer S" TWFuIGlzIGRpc3Rpbmd1aXNoZWQ=" BASE64> S" Man is distinguished" COMPARE -> 0 }T

T{ S" Hello world!" 2DUP EncodedOutput-Buffer -ROT >BASE64 DecodedOutput-Buffer -ROT BASE64> COMPARE -> 0 }T

Changes

1.0.0 first version

Bug Reports

Please send suggestions, comments, or bug reports Bob Dickow <dickow@turbonet.com>

Compatibility

This lexicon was tested on SwiftForth 3.7.1