package b0

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Module B0_base64Source

base64 and base64url codecs.

As defined in RFC 4684, with or without padding. Decoding errors on non-canonical encodings to ensure that no two different encodings decode to the same byte sequence (see this paper).

Encoding and padding specification

Sourcetype encoding = [
  1. | `Base64
    (*

    base64

    *)
  2. | `Base64url
    (*

    base64url

    *)
]

The type for encodings.

Sourcetype padding = [
  1. | `Padded
    (*

    Padded with '=' characters.

    *)
  2. | `Unpadded
    (*

    Not padded.

    *)
]

The type for specifing padding.

Decoding errors

Sourcetype error =
  1. | Invalid_length of int
    (*

    Invalid input length

    *)
  2. | Invalid_letter of char * int
    (*

    Invalid letter at index.

    *)
  3. | Non_canonical_encoding
    (*

    Non-canonical encoding.

    *)

The type for decoding errors.

Sourceval error_message : encoding -> error -> string

error_message enc e is an error message for error e while decoding encoding enc.

base64

Sourceval encode : padding -> string -> string

encode p s is the base64 encoding of s padded according to p.

Sourceval decode' : padding -> string -> (string, error) result

decode' p s is the base64 decode of s. If p is:

  • `Padding the decode expects a padded encoding. The decode errors with Invalid_length if the padding is missing.
  • `Unpadded the decode expect no padding. The decode errors with Invalid_letter if there is a padding.

All decodes error with Non_canonical_encoding if a padding letter has a non-zero padding.

Sourceval decode : padding -> string -> (string, string) result

decode is like decode' with errors mapped by error_message `Base64.

base64url

Sourceval encode_base64url : padding -> string -> string

encode_base64url is like encode but for the base64url encoding.

Sourceval decode_base64url' : padding -> string -> (string, error) result

decode_base64url' is like decode but for the base64url encoding.

Sourceval decode_base64url : padding -> string -> (string, string) result

decode_base64url is like decode_base64url' with errors mapped by error_message `Base64url.