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Class type

All implementations of Path functionality have this module type.

type ustring

Type of strings used. In case of Path.OfRope it is Rope.t and in Path.OfString module it is string.

type uchar

Type of characters. It corresponds to ustring type.

module OperatorLift : sig ... end

Convenience operator for lifting primitive strings to ustring type.

type t = ustring list

A type for storing paths. It is reversed list of names. In case of absolute path, the last element of the list is empty string (Windows: empty or letter-colon; details below). Empty list represents empty relative path.

Examples: ["a";"b";"c"] is c/b/a (relative path); ["d";"e";""] stays for /e/d (absolute path).

All examples here and below are given for ustring=string case for clarity. To have the code working with other string types, one should prepend the !! operator (OperatorLift.(!!)) to all string literals.

There are two infix operators provided to allow to write expressions in natural order. For example, to build a path using PathType.Operators.(/:) one can write:

base_dir/:"bar" instead of "bar"::base_dir

However it may be sometimes inevitable to write components in reverse, for example:

let whose_readme = function "README"::app::"doc"::"share"::_ -> Some app | _ -> None

Windows: Windows absolute paths start with "\\" or with drive letter. Use following representation:

• Path.root/:"."/:"pipe" = ["pipe";".";""] for "\\.\pipe"
• ["C:"]/:"foo" = ["foo";"C:"] for "C:\foo"

In principle the first type of paths has broader range of allowed characters, but this implementation applies more strict rules to both (default_validator).

val is_relative : t -> bool
val is_absolute : t -> bool
Construction
val root : t

Root of the filesystem ([""]). It is minimal absolute path. Below it is called 'empty'. However it yields "/" or "\\" when converted to a string.

Windows: This path (root and nothing more) is meaningless, but for simplicity it is considered valid here. To create absolute path starting with drive letter, construct the list explicitly (as in ["C:"]/:"foo"). A path consisting of drive letter only is also called 'empty' here.

val append : t -> ustring -> t

Alternative name for Operators.(/:)

val concat : t -> t -> t

Alternative name for Operators.(//@)

module Operators : sig ... end

Infix operators for path construction. They are in separate module, so one can open Path.Operators to use them.

module Infix : sig ... end

As other Operators modules in batteries are named "Infix" we provide Infix as well. This is a mere copy of Operators.

exception Malformed_path
val normalize_filepath : t -> t

Consumes single dots where possible, e.g.:

normalize ([".."]/:"foo"/:"."/:"bar"/:"sub1"/:".."/:"sub2") = [".."]/:"foo"/:"bar"/:"sub1"/:".."/:"sub2"

When a directory structure contains links, it can be not pefectly pure tree. Then meaing of the ".." symbol depends on the real nature of parent of what is denoted by the name that preceded the ".." symbol. This symbol cannot be resolved for a graph traversal case when dealing with abstract paths only.

Windows: If single dot is next to root, it is preserved.

val normalize_in_graph : t -> t

Another name for normalize_filepath.

val normalize_in_tree : t -> t

Consumes single dots and applies double dots where possible, e.g.:

normalize ([".."]/:"foo"/:"."/:"bar"/:"sub1"/:".."/:"sub2") = [".."]/:"foo"/:"bar"/:"sub2"

This normalization is useful when dealing with paths that describe locations in a tree and the ".." symbol always points to the only parent of what precedes this symbol.

Windows: If single dot is next to root, it is preserved.

• raises Malformed_path

when absolute path is given that contains double dots that would be applied to the root.

val normalize : t -> t

Deprecated name for normalize_in_tree

val parent : t -> t

Returns parent path, i.e. immediate ancestor: parent (foo/:bar) = foo

• raises Invalid_argument

if empty path (relative [] or absolute [""]) is given

val belongs : t -> t -> bool

belongs base sub is true when sub descends from base, i.e. base is a prefix of sub. If base=sub the function returns true. It is otherwise false. Both arguments must be absolute paths or both relative.

If both arguments have a root portion with drive letter and these letters are different, belongs base sub returns false.

• raises Invalid_argument

if exactly one of given arguments is absolute path

val relative_to_any : t -> t -> t

relative_to_any base sub returns relative path rel such that normalize (base/:rel) = normalize sub, i.e. common base is stripped and ".." are added if necessary. Both arguments must be absolute paths or both relative.

This function normalizes base and sub before calculation of the relative path.

Windows: If base and sub are absolute, they must have the same root element: have the same drive letter or both starting with root (i.e. "" is the last element of the list). Exceptionally it is possible to get an absolute path as a result if drive letter is in sub but not as a root element (e .g. base = root/:"bar" and sub = root/:bar//@(["C:"]/:"foo").

• see relative_to_parent

may be sometimes more suitable

• raises Invalid_argument

if exactly one of given arguments is an absolute path

exception Not_parent
val relative_to_parent : t -> t -> t

relative_to_parent parent sub returns relative path rel such that (normalize parent)/:rel = normalize sub. It is checked if sub is really a descendant of parent. Both arguments must be absolute paths or both relative.

This function normalizes base and sub before calculation of the relative path.

Windows: Exceptionally it is possible to get an absolute path as a result if drive letter is in sub but not as a root element (e .g. base = root/:"bar" and sub = root/:bar//@(["C:"]/:"foo")).

• raises Not_parent

if sub is not descendant of parent

• raises Invalid_argument

if exactly one of given arguments is absolute path

Validation
exception Illegal_char
type validator = ustring -> bool

Validators should check if all characters of given string can be used in a name (path component). Return true if the name is valid. Return false if illegal character is found.

If a name should be rejected for some other reason, user defined validator may raise an exception.

val default_validator : validator ref

Forward slash and code zero are considered invalid.

Windows: Invalid characters are *?:\/<> and all with code <32. Exception: the function PathType.of_string doesn't use validator against drive letter with colon.

Conversions
val to_ustring : t -> ustring

Convert to the chosen ustring type. Empty relative path is converted to "." (single dot).

Windows: backslash is used as a separator and double backslash for root. If the path is only a drive letter (empty absolute path) trailing backslash is added (e.g. to_string ["C:"] = "C:\").

• see to_string

is likely to bo more useful "

val to_string : t -> string

Convert to type primitive string with UTF-8 content. The string is built in the same way as by to_ustring function.

val of_string : ustring -> t

Parse path in a given string. Any number of consecutive separators collapse ("a//b" becomes "a/b"). Path.default_validator is applied to each resulting name.

Windows: both slashes '\' and '/' are accepted as separators. Paths of the 'semi-relative' form "C:foo\bar" are not recognized. For example "C:" string is parsed as ["C:"] which has different meaning (see to_string).

• raises Illegal_char

when a character not allowed in paths is found.

Convenience aliases
val s : t -> string
val p : ustring -> t

These functions do not accept empty paths, i.e. [], [""] or ["C:"].

val name : t -> ustring

Returns name of the object the pathname points to, i.e. name (foo/:bar) = bar

• raises Invalid_argument

if empty path (relative [] or absolute [""]) is given

val map_name : (ustring -> ustring) -> t -> t

map_name fu path returns path with the name replaced by fu (PathType.name path).

Example: map_name (fun nn -> nn ^ ".backup") (["foo"]/:"bar") = ["foo"]/:"bar.backup"

PathType.default_validator is applied to new name.

• raises Illegal_char

(raised by validator if any bad character is found)

val ext : t -> ustring option

Returns extension of the name of the object the pathname points to. Examples:

ext ["aa.bb"] = Some "bb"

ext ["aa."] = Some ""

ext ["aa"] = None

ext [".hidden"] = Some "hidden" (!)

Extension begins where the rightmost dot in the name is found. If the name ends with a dot, the extension is empty and Some "" is returned. If there is no extension (no dot) the function returns None.

@example "Count unfinished music downloads (files ending with '.ogg.part')."

let count_music_parts download_dir =
let check file =
match Path.ext file with
| Some "part" -> ((Path.ext (Path.name_core file)) = "ogg")
| _ -> false
in
let music_parts = List.filter check files in
List.length music_parts
• raises Invalid_argument

if empty path (relative [] or absolute [""]) is given

val map_ext : (ustring option -> ustring option) -> t -> t

map_ext fu path returns path but with the name with extension given by fu (PathType.ext path). If fu returns Some _, the original extension may be replaced (when Some ext is passed to fu) or new added (when fu gets None). In case fu returns None, the extension is removed (if exists).

@example "A name for file being encoded in a new format."

let pngname file = map_ext (function Some _ | None -> Some "png") file
let new_bar = pngname (["foo"]/:"bar.jpeg") (* = ["foo"]/:"bar.png" *)

PathType.default_validator is applied to the resulting name.

The replacement string returned by the mapping function fu can contain dots. Consequently, this string doesn't need to be an extension as defined by the ext function. Consider for example:

let before = foo/:"bar.mli"
let replacement = "mli.off"
let ext_before = Path.ext before (* = Some "mli" *)
let after = Path.map_ext (fun _ -> Some replacement) before (* = foo/:"bar.mli.off" *)
let ext_after = Path.ext after (* = Some "off" *)

Note the difference between replacement and ext_after! (map_ext fu) is idempotent only if fu always returns Some _. Otherwise it can remove the extension, possibly exposing part of the name that becomes the new extension.

Windows: If fu returns Some "" (to make a name with trailing period) map_ext returns a path that shouldn't be passed to the operating system (it is invalid).

• raises Illegal_char

(raised by validator if any bad character is found)

• raises Invalid_argument

if empty path (relative [] or absolute [""]) is given

val name_core : t -> ustring

Returns part of the name to the left of rightmost dot. Returns empty string if the name starts with a dot.

@example "Label for a piece of GUI in which a file is edited."

let tab_label modified file =
let text = (if modified then "*" else "") ^ (Path.name_core file) in
GMisc.label ~text ()
• raises Invalid_argument

if empty path (relative [] or absolute [""]) is given

type components = t * ustring * ustring option

A path can be represented by the following triple: (Path.parent path, Path.name_core path, Path.ext path)

val split : t -> components

Dissect the path to its components (parent path, core part of name and possibly an extension).

Resulting name_core string can be empty. For example, Path.split (Path.root/:"home"/:"user"/:".bashrc") equals (Path.root/:"home"/:"user", "", Some "bashrc").

• raises Invalid_argument

if empty path (relative [] or absolute [""]) is given

val join : components -> t

Create a path from given components.

• raises Illegal_char

(raised by validator on any bad character)

@example "Creating paths for a series of numbered images."

let get_animation_frames working_dir count =
let frame_file num = Path.join
(working_dir/:"rendering"
,"frame"^(stirng_of_int num)
,Some "png"
)
in
BatEnum.map frame_file (1 -- count)
val map : (components -> components) -> t -> t

Map a path through a function that operates on separate components.

• raises Illegal_char

(raised by validator on any bad character)

• raises Invalid_argument

if empty path (relative [] or absolute [""]) is given

@example "Insert a string just before file extension."

let extract_first_page file =
let insert (parent, name_core, ext) = (parent, name_core ^ "_page1", ext) in
let result_file = Path.map insert file in
let code = Sys.command
(String.concat ' '
["psselect -p1 <"; P.s file
;" >"; P.s result_file
]
)
in
if code = 0 then result_file else failwith "psselect"
Supplementary functions
val drive_letter : t -> uchar option

Return drive letter of the given absolute path.

Windows: drive_letter abs returns None if abs is simple absolute path (i.e. begins with a separator), otherwise the root element of abs consists of a letter ch with a colon - in this case Some ch is returned.

Other systems: Returns None on all absolute paths.

@example "(Windows only) Are the locations on the same partition?"

let can_move_quickly ~path_from ~path_to =
(drive_letter path_from) = (drive_letter path_to)
• raises Invalid_argument

if relative path is given