Base64 Encoding and Decoding
This library provides support for Base64 encoding and decoding, similar to net/base64 but with more options.
| (require base64) | package: base64-lib |
procedure
(base64-encode src [ #:endcodes endcodes #:line line #:line-end line-end #:pad? pad?]) → bytes? src : (or/c bytes? string? input-port?) endcodes : (or/c #f 'url bytes?) = #f line : (or/c #f exact-positive-integer?) = #f line-end : bytes? = #"\r\n" pad? : boolean? = (and line #t)
If endcodes is #f, the standard characters for the last two codes are used: #"+/". If endcodes is 'url, the alternate endcodes for URLs and filenames are used: #"-_" (see [RFC4648], section 5). Otherwise, endcodes must be a byte string containing two bytes, and these are used as the last two codes for the encoding.
If line is a number, it must be a positive multiple of 4. In that case, the output is broken into segments whose length is line bytes (except possibly the final segment), and line-end is added to the end of each segment.
If pad? is #t, then the output is padded, using = characters, to a multiple of 4 bytes (disregarding line separators). If pad? is #f, the padding is omitted.
> (base64-encode #"apple") #"YXBwbGU"
> (base64-encode #"apple" #:pad? #t) #"YXBwbGU="
> (base64-encode #"apple" #:line 8) #"YXBwbGU=\r\n"
> (base64-encode "orange") #"b3Jhbmdl"
> (base64-encode "orange" #:pad? #t) #"b3Jhbmdl"
> (base64-encode "orange" #:line 8) #"b3Jhbmdl\r\n"
> (base64-encode "apples or oranges") #"YXBwbGVzIG9yIG9yYW5nZXM"
> (base64-encode "apples or oranges" #:line 8) #"YXBwbGVz\r\nIG9yIG9y\r\nYW5nZXM=\r\n"
procedure
(base64-decode src [ #:endcodes endcodes #:mode mode]) → bytes? src : (or/c bytes? string? input-port?) endcodes : (or/c #f 'url bytes?) = #f mode : (or/c 'strict 'whitespace 'padding) = 'whitespace
If mode is 'strict, then the entire input must consist of Base64-encoded data, without padding and without whitespace or other extra characters.
If mode is 'whitespace, then the input is divided into segments separated by whitespace and padding = characters; each segment is decoded independently, and the results are concatenated. This correctly handles the concatenation of padded encodings, but it is not equivalent to deleting padding and whitespace characters and then decoding what remains as a single segment.
If mode is 'padding, then the input is divided into segments separated by padding = characters, whitespace within each segment is discarded, each segment is decoded independently, and the results are concatenated.
If src contains any content that is not valid
Base64-encodings, padding, or whitespace, then exn:fail:read is raised,
with the location of the first illegal byte. If the length of a segment (not
including whitespace or padding) is 1 (mod 4), then exn:fail:read is
raised, with the location of the segment’s end. If the length of a segment is 2
or 3 (mod 4), then the unused bits in the final byte are ignored —
> (base64-decode "YXBwbGU") #"apple"
> (base64-decode "YXBw = \n=bGU") #"apple"
> (base64-decode "YXB wbGU") ; different! #"ap\301\261\224"
> (base64-decode "YXB wbGU" #:mode 'padding) #"apple"
Changed in version 1.1 of package base64-lib: Added the 'padding mode.
procedure
(base64-encode-stream src dest [ #:endcodes endcodes #:line line #:line-end line-end #:pad? pad?]) → void? src : (or/c bytes? string? input-port?) dest : output-port? endcodes : (or/c #f 'url bytes?) = #f line : (or/c #f exact-positive-integer?) = #f line-end : bytes? = #"\r\n" pad? : boolean? = (and line #t)
procedure
(base64-decode-stream src [ #:endcodes endcodes #:mode mode]) → bytes? src : (or/c bytes? string? input-port?) endcodes : (or/c #f 'url bytes?) = #f mode : (or/c 'strict 'whitespace 'padding) = 'whitespace
Changed in version 1.1 of package base64-lib: Added the 'padding mode.
Bibliography
| [RFC4648] | “RFC 4648: The Base16, Base32, and Base64 Data Encodings.” https://tools.ietf.org/html/rfc4648 |