Yet (another urlencode compatible) encoding scheme

Encode and decode using an encoding scheme that is a superset of the utils::URLencode() encoding. With default settings, yencode() and ydecode() produce strings that are fully compatible with urlencode encoded strings. However, these functions allow a custom whitelist of symbols that should not be escaped by the encoding process, and a configurable escape character to use in place of the % symbol, for example to work with storage layers that do not like the % symbol.

The yencoder() and ydecoder() functions are convenience function, which return the corresponding a function with the escape and whitelist already set, allowing easy use in contexts that expect a single-argument function.

Usage

yencode(string, escape = "%", whitelist = c("._~-", "][!$&'()*+,;=:/?@#"))

yencoder(escape = "%", whitelist = c("._~-", "][!$&'()*+,;=:/?@#"))

ydecode(string, escape = "%")

ydecoder(escape = "%")

Arguments

string

The string to process.

escape

The escape character to use.

whitelist

Any characters that should not be escaped. See details.

Value

The processed (encoded or decoded) string.

Details

In addition to the supplied white-list, A-Z, a-z, and 0-9 are always white-listed. There are no restrictions on the white-list, except that the escape character must not be part of it (and will be removed from it with a warning). Of course, it is important that the underlying storage layer handles all white-listed characters gracefully.

Note that any ascii letter or number will work perfectly fine as an escape character, the output will be well-formed and decoded correctly, even if some of them, such as 1 will result in escape sequences that contain the letter itself.

In particular, yencoder("Z", whitelist="") returns a encoder that will encode any string to a pure A-Z, a-z, and 0-9 representation, suitable for extremely limited storage layers (it will encode Z as Z5A).