Module String.Escaping

Operations for escaping and unescaping strings, with parameterized escape and escapeworthy characters. Escaping/unescaping using this module is more efficient than using Pcre. Benchmark code can be found in core/benchmarks/string_escaping.ml.

val escape_gen_exn : escapeworthy_map:(char * char) list -> escape_char:char -> (string -> string) Staged.t

escape_gen_exn escapeworthy_map escape_char returns a function that will escape a string s as follows: if (c1,c2) is in escapeworthy_map, then all occurrences of c1 are replaced by escape_char concatenated to c2.

Raises an exception if escapeworthy_map is not one-to-one. If escape_char is not in escapeworthy_map, then it will be escaped to itself.

val escape_gen : escapeworthy_map:(char * char) list -> escape_char:char -> (string -> string) Or_error.t
val escape : escapeworthy:char list -> escape_char:char -> (string -> string) Staged.t

escape ~escapeworthy ~escape_char s is

escape_gen_exn ~escapeworthy_map:(List.zip_exn escapeworthy escapeworthy)
  ~escape_char

Duplicates and escape_char will be removed from escapeworthy. So, no exception will be raised

val unescape_gen_exn : escapeworthy_map:(char * char) list -> escape_char:char -> (string -> string) Staged.t

unescape_gen_exn is the inverse operation of escape_gen_exn. That is,

let escape = Staged.unstage (escape_gen_exn ~escapeworthy_map ~escape_char) in
let unescape = Staged.unstage (unescape_gen_exn ~escapeworthy_map ~escape_char) in
assert (s = unescape (escape s))

always succeed when ~escapeworthy_map is not causing exceptions.

val unescape_gen : escapeworthy_map:(char * char) list -> escape_char:char -> (string -> string) Or_error.t
val unescape : escape_char:char -> (string -> string) Staged.t

unescape ~escape_char is defined as unescape_gen_exn ~map:[] ~escape_char

val is_char_escaping : string -> escape_char:char -> int -> bool

Any char in an escaped string is either escaping, escaped, or literal. For example, for escaped string "0_a0__0" with escape_char as '_', pos 1 and 4 are escaping, 2 and 5 are escaped, and the rest are literal.

is_char_escaping s ~escape_char pos returns true if the char at pos is escaping, false otherwise.

val is_char_escaped : string -> escape_char:char -> int -> bool

is_char_escaped s ~escape_char pos returns true if the char at pos is escaped, false otherwise.

val is_char_literal : string -> escape_char:char -> int -> bool

is_char_literal s ~escape_char pos returns true if the char at pos is not escaped or escaping.

val index : string -> escape_char:char -> char -> int option

index s ~escape_char char finds the first literal (not escaped) instance of char in s starting from 0.

val index_exn : string -> escape_char:char -> char -> int
val rindex : string -> escape_char:char -> char -> int option

rindex s ~escape_char char finds the first literal (not escaped) instance of char in s starting from the end of s and proceeding towards 0.

val rindex_exn : string -> escape_char:char -> char -> int
val index_from : string -> escape_char:char -> int -> char -> int option

index_from s ~escape_char pos char finds the first literal (not escaped) instance of char in s starting from pos and proceeding towards the end of s.

val index_from_exn : string -> escape_char:char -> int -> char -> int
val rindex_from : string -> escape_char:char -> int -> char -> int option

rindex_from s ~escape_char pos char finds the first literal (not escaped) instance of char in s starting from pos and towards 0.

val rindex_from_exn : string -> escape_char:char -> int -> char -> int
val split : string -> on:char -> escape_char:char -> string list

split s ~escape_char ~on returns a list of substrings of s that are separated by literal versions of on. Consecutive on characters will cause multiple empty strings in the result. Splitting the empty string returns a list of the empty string, not the empty list.

E.g., split ~escape_char:'_' ~on:',' "foo,bar_,baz" = ["foo"; "bar_,baz"].

val split_on_chars : string -> on:char list -> escape_char:char -> string list

split_on_chars s ~on returns a list of all substrings of s that are separated by one of the literal chars from on. on are not grouped. So a grouping of on in the source string will produce multiple empty string splits in the result.

E.g., split_on_chars ~escape_char:'_' ~on:[',';'|'] "foo_|bar,baz|0" -> ["foo_|bar"; "baz"; "0"].

val lsplit2 : string -> on:char -> escape_char:char -> (string * string) option

lsplit2 s ~on ~escape_char splits s into a pair on the first literal instance of on (meaning the first unescaped instance) starting from the left.

val lsplit2_exn : string -> on:char -> escape_char:char -> string * string
val rsplit2 : string -> on:char -> escape_char:char -> (string * string) option

rsplit2 s ~on ~escape_char splits s into a pair on the first literal instance of on (meaning the first unescaped instance) starting from the right.

val rsplit2_exn : string -> on:char -> escape_char:char -> string * string
val lstrip_literal : ?drop:(char -> bool) -> t -> escape_char:char -> t

These are the same as lstrip, rstrip, and strip for generic strings, except that they only drop literal characters -- they do not drop characters that are escaping or escaped. This makes sense if you're trying to get rid of junk whitespace (for example), because escaped whitespace seems more likely to be deliberate and not junk.

val rstrip_literal : ?drop:(char -> bool) -> t -> escape_char:char -> t
val strip_literal : ?drop:(char -> bool) -> t -> escape_char:char -> t