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defmodule Regex do
@moduledoc ~S"""
Provides regular expressions for Elixir.
Regex is based on PCRE (Perl Compatible Regular Expressions) and
built on top of Erlang's `:re` module. More information can be found
in the [`:re` module documentation](http://www.erlang.org/doc/man/re.html).
Regular expressions in Elixir can be created using the sigils
[`~r`](`Kernel.sigil_r/2`) or [`~R`](`Kernel.sigil_R/2`):
# A simple regular expression that matches foo anywhere in the string
~r/foo/
# A regular expression with case insensitive and Unicode options
~r/foo/iu
Regular expressions created via sigils are pre-compiled and stored
in the `.beam` file. Notice this may be a problem if you are precompiling
Elixir, see the "Precompilation" section for more information.
A Regex is represented internally as the `Regex` struct. Therefore,
`%Regex{}` can be used whenever there is a need to match on them.
Keep in mind it is not guaranteed two regular expressions from the
same source are equal, for example:
~r/(?<foo>.)(?<bar>.)/ == ~r/(?<foo>.)(?<bar>.)/
may return `true` or `false` depending on your machine, endianness,
available optimizations and others. You can, however, retrieve the source
of a compiled regular expression by accessing the `source` field, and then
compare those directly:
~r/(?<foo>.)(?<bar>.)/.source == ~r/(?<foo>.)(?<bar>.)/.source
## Precompilation
Regular expressions built with sigil are precompiled and stored in `.beam`
files. This may be a problem if you are precompiling Elixir to run in
different OTP releases, as OTP releases may update the underlying regular
expression engine at any time.
For such reasons, we always recommend precompiling Elixir projects using
the Erlang/OTP version meant to run in production. In case cross-compilation is
really necessary, you can manually invoke `Regex.recompile/1` or
`Regex.recompile!/1` to perform a runtime version check and recompile the
regex if necessary.
## Modifiers
The modifiers available when creating a Regex are:
* `unicode` (u) - enables Unicode specific patterns like `\p` and change
modifiers like `\w`, `\W`, `\s` and friends to also match on Unicode.
It expects valid Unicode strings to be given on match
* `caseless` (i) - adds case insensitivity
* `dotall` (s) - causes dot to match newlines and also set newline to
anycrlf; the new line setting can be overridden by setting `(*CR)` or
`(*LF)` or `(*CRLF)` or `(*ANY)` according to `:re` documentation
* `multiline` (m) - causes `^` and `$` to mark the beginning and end of
each line; use `\A` and `\z` to match the end or beginning of the string
* `extended` (x) - whitespace characters are ignored except when escaped
and allow `#` to delimit comments
* `firstline` (f) - forces the unanchored pattern to match before or at the
first newline, though the matched text may continue over the newline
* `ungreedy` (U) - inverts the "greediness" of the regexp
(the previous `r` option is deprecated in favor of `U`)
The options not available are:
* `anchored` - not available, use `^` or `\A` instead
* `dollar_endonly` - not available, use `\z` instead
* `no_auto_capture` - not available, use `?:` instead
* `newline` - not available, use `(*CR)` or `(*LF)` or `(*CRLF)` or
`(*ANYCRLF)` or `(*ANY)` at the beginning of the regexp according to the
`:re` documentation
## Captures
Many functions in this module handle what to capture in a regex
match via the `:capture` option. The supported values are:
* `:all` - all captured subpatterns including the complete matching string
(this is the default)
* `:first` - only the first captured subpattern, which is always the
complete matching part of the string; all explicitly captured subpatterns
are discarded
* `:all_but_first` - all but the first matching subpattern, i.e. all
explicitly captured subpatterns, but not the complete matching part of
the string
* `:none` - does not return matching subpatterns at all
* `:all_names` - captures all names in the Regex
* `list(binary)` - a list of named captures to capture
"""
defstruct re_pattern: nil, source: "", opts: "", re_version: ""
@type t :: %__MODULE__{re_pattern: term, source: binary, opts: binary}
defmodule CompileError do
defexception message: "regex could not be compiled"
end
@doc """
Compiles the regular expression.
The given options can either be a binary with the characters
representing the same regex options given to the
[`~r`](`Kernel.sigil_r/2`) sigil, or a list of options, as
expected by the Erlang's `:re` module.
It returns `{:ok, regex}` in case of success,
`{:error, reason}` otherwise.
## Examples
iex> Regex.compile("foo")
{:ok, ~r/foo/}
iex> Regex.compile("*foo")
{:error, {'nothing to repeat', 0}}
"""
@spec compile(binary, binary | [term]) :: {:ok, t} | {:error, any}
def compile(source, options \\ "") do
compile(source, options, version())
end
defp compile(source, options, version) when is_binary(options) do
case translate_options(options, []) do
{:error, rest} ->
{:error, {:invalid_option, rest}}
translated_options ->
compile(source, translated_options, options, version)
end
end
defp compile(source, options, version) when is_list(options) do
compile(source, options, "", version)
end
defp compile(source, opts, doc_opts, version) when is_binary(source) do
case :re.compile(source, opts) do
{:ok, re_pattern} ->
{:ok, %Regex{re_pattern: re_pattern, re_version: version, source: source, opts: doc_opts}}
error ->
error
end
end
@doc """
Compiles the regular expression and raises `Regex.CompileError` in case of errors.
"""
@spec compile!(binary, binary | [term]) :: t
def compile!(source, options \\ "") do
case compile(source, options) do
{:ok, regex} -> regex
{:error, {reason, at}} -> raise Regex.CompileError, "#{reason} at position #{at}"
end
end
@doc """
Recompiles the existing regular expression if necessary.
This checks the version stored in the regular expression
and recompiles the regex in case of version mismatch.
"""
@doc since: "1.4.0"
@spec recompile(t) :: t
def recompile(%Regex{} = regex) do
version = version()
case regex do
%{re_version: ^version} ->
{:ok, regex}
_ ->
%{source: source, opts: opts} = regex
compile(source, opts, version)
end
end
@doc """
Recompiles the existing regular expression and raises `Regex.CompileError` in case of errors.
"""
@doc since: "1.4.0"
@spec recompile!(t) :: t
def recompile!(regex) do
case recompile(regex) do
{:ok, regex} -> regex
{:error, {reason, at}} -> raise Regex.CompileError, "#{reason} at position #{at}"
end
end
@doc """
Returns the version of the underlying Regex engine.
"""
@doc since: "1.4.0"
@spec version :: term()
def version do
{:re.version(), :erlang.system_info(:endian)}
end
@doc """
Returns a boolean indicating whether there was a match or not.
## Examples
iex> Regex.match?(~r/foo/, "foo")
true
iex> Regex.match?(~r/foo/, "bar")
false
"""
@spec match?(t, String.t()) :: boolean
def match?(%Regex{re_pattern: compiled}, string) when is_binary(string) do
:re.run(string, compiled, [{:capture, :none}]) == :match
end
@doc """
Returns `true` if the given `term` is a regex.
Otherwise returns `false`.
## Examples
iex> Regex.regex?(~r/foo/)
true
iex> Regex.regex?(0)
false
"""
@spec regex?(any) :: boolean
def regex?(term)
def regex?(%Regex{}), do: true
def regex?(_), do: false
@doc """
Runs the regular expression against the given string until the first match.
It returns a list with all captures or `nil` if no match occurred.
## Options
* `:return` - set to `:index` to return byte index and match length.
Defaults to `:binary`.
* `:capture` - what to capture in the result. Check the moduledoc for `Regex`
to see the possible capture values.
## Examples
iex> Regex.run(~r/c(d)/, "abcd")
["cd", "d"]
iex> Regex.run(~r/e/, "abcd")
nil
iex> Regex.run(~r/c(d)/, "abcd", return: :index)
[{2, 2}, {3, 1}]
"""
@spec run(t, binary, [term]) :: nil | [binary] | [{integer, integer}]
def run(regex, string, options \\ [])
def run(%Regex{re_pattern: compiled}, string, options) when is_binary(string) do
return = Keyword.get(options, :return, :binary)
captures = Keyword.get(options, :capture, :all)
case :re.run(string, compiled, [{:capture, captures, return}]) do
:nomatch -> nil
:match -> []
{:match, results} -> results
end
end
@doc """
Returns the given captures as a map or `nil` if no captures are found.
## Options
* `:return` - set to `:index` to return byte index and match length.
Defaults to `:binary`.
## Examples
iex> Regex.named_captures(~r/c(?<foo>d)/, "abcd")
%{"foo" => "d"}
iex> Regex.named_captures(~r/a(?<foo>b)c(?<bar>d)/, "abcd")
%{"bar" => "d", "foo" => "b"}
iex> Regex.named_captures(~r/a(?<foo>b)c(?<bar>d)/, "efgh")
nil
"""
@spec named_captures(t, String.t(), [term]) :: map | nil
def named_captures(regex, string, options \\ []) when is_binary(string) do
names = names(regex)
options = Keyword.put(options, :capture, names)
results = run(regex, string, options)
if results, do: Enum.zip(names, results) |> Enum.into(%{})
end
@doc """
Returns the underlying `re_pattern` in the regular expression.
"""
@spec re_pattern(t) :: term
def re_pattern(%Regex{re_pattern: compiled}) do
compiled
end
@doc """
Returns the regex source as a binary.
## Examples
iex> Regex.source(~r(foo))
"foo"
"""
@spec source(t) :: String.t()
def source(%Regex{source: source}) do
source
end
@doc """
Returns the regex options as a string.
## Examples
iex> Regex.opts(~r(foo)m)
"m"
"""
@spec opts(t) :: String.t()
def opts(%Regex{opts: opts}) do
opts
end
@doc """
Returns a list of names in the regex.
## Examples
iex> Regex.names(~r/(?<foo>bar)/)
["foo"]
"""
@spec names(t) :: [String.t()]
def names(%Regex{re_pattern: re_pattern}) do
{:namelist, names} = :re.inspect(re_pattern, :namelist)
names
end
@doc ~S"""
Same as `run/3`, but scans the target several times collecting all
matches of the regular expression.
A list of lists is returned, where each entry in the primary list represents a
match and each entry in the secondary list represents the captured contents.
## Options
* `:return` - set to `:index` to return byte index and match length.
Defaults to `:binary`.
* `:capture` - what to capture in the result. Check the moduledoc for `Regex`
to see the possible capture values.
## Examples
iex> Regex.scan(~r/c(d|e)/, "abcd abce")
[["cd", "d"], ["ce", "e"]]
iex> Regex.scan(~r/c(?:d|e)/, "abcd abce")
[["cd"], ["ce"]]
iex> Regex.scan(~r/e/, "abcd")
[]
iex> Regex.scan(~r/\p{Sc}/u, "$, £, and €")
[["$"], ["£"], ["€"]]
iex> Regex.scan(~r/=+/, "=ü†ƒ8===", return: :index)
[[{0, 1}], [{9, 3}]]
"""
@spec scan(t, String.t(), [term]) :: [[String.t()]]
def scan(regex, string, options \\ [])
def scan(%Regex{re_pattern: compiled}, string, options) when is_binary(string) do
return = Keyword.get(options, :return, :binary)
captures = Keyword.get(options, :capture, :all)
options = [{:capture, captures, return}, :global]
case :re.run(string, compiled, options) do
:match -> []
:nomatch -> []
{:match, results} -> results
end
end
@doc """
Splits the given target based on the given pattern and in the given number of
parts.
## Options
* `:parts` - when specified, splits the string into the given number of
parts. If not specified, `:parts` defaults to `:infinity`, which will
split the string into the maximum number of parts possible based on the
given pattern.
* `:trim` - when `true`, removes empty strings (`""`) from the result.
Defaults to `false`.
* `:on` - specifies which captures to split the string on, and in what
order. Defaults to `:first` which means captures inside the regex do not
affect the splitting process.
* `:include_captures` - when `true`, includes in the result the matches of
the regular expression. Defaults to `false`.
## Examples
iex> Regex.split(~r{-}, "a-b-c")
["a", "b", "c"]
iex> Regex.split(~r{-}, "a-b-c", parts: 2)
["a", "b-c"]
iex> Regex.split(~r{-}, "abc")
["abc"]
iex> Regex.split(~r{}, "abc")
["", "a", "b", "c", ""]
iex> Regex.split(~r{a(?<second>b)c}, "abc")
["", ""]
iex> Regex.split(~r{a(?<second>b)c}, "abc", on: [:second])
["a", "c"]
iex> Regex.split(~r{(x)}, "Elixir", include_captures: true)
["Eli", "x", "ir"]
iex> Regex.split(~r{a(?<second>b)c}, "abc", on: [:second], include_captures: true)
["a", "b", "c"]
"""
@spec split(t, String.t(), [term]) :: [String.t()]
def split(regex, string, options \\ [])
def split(%Regex{}, "", opts) do
if Keyword.get(opts, :trim, false) do
[]
else
[""]
end
end
def split(%Regex{re_pattern: compiled}, string, opts)
when is_binary(string) and is_list(opts) do
on = Keyword.get(opts, :on, :first)
case :re.run(string, compiled, [:global, capture: on]) do
{:match, matches} ->
index = parts_to_index(Keyword.get(opts, :parts, :infinity))
trim = Keyword.get(opts, :trim, false)
include_captures = Keyword.get(opts, :include_captures, false)
do_split(matches, string, 0, index, trim, include_captures)
:match ->
[string]
:nomatch ->
[string]
end
end
defp parts_to_index(:infinity), do: 0
defp parts_to_index(n) when is_integer(n) and n > 0, do: n
defp do_split(_, string, offset, _counter, true, _with_captures)
when byte_size(string) <= offset do
[]
end
defp do_split(_, string, offset, 1, _trim, _with_captures),
do: [binary_part(string, offset, byte_size(string) - offset)]
defp do_split([], string, offset, _counter, _trim, _with_captures),
do: [binary_part(string, offset, byte_size(string) - offset)]
defp do_split([[{pos, _} | h] | t], string, offset, counter, trim, with_captures)
when pos - offset < 0 do
do_split([h | t], string, offset, counter, trim, with_captures)
end
defp do_split([[] | t], string, offset, counter, trim, with_captures),
do: do_split(t, string, offset, counter, trim, with_captures)
defp do_split([[{pos, length} | h] | t], string, offset, counter, trim, true) do
new_offset = pos + length
keep = pos - offset
<<_::binary-size(offset), part::binary-size(keep), match::binary-size(length), _::binary>> =
string
if keep == 0 and trim do
[match | do_split([h | t], string, new_offset, counter - 1, trim, true)]
else
[part, match | do_split([h | t], string, new_offset, counter - 1, trim, true)]
end
end
defp do_split([[{pos, length} | h] | t], string, offset, counter, trim, false) do
new_offset = pos + length
keep = pos - offset
if keep == 0 and trim do
do_split([h | t], string, new_offset, counter, trim, false)
else
<<_::binary-size(offset), part::binary-size(keep), _::binary>> = string
[part | do_split([h | t], string, new_offset, counter - 1, trim, false)]
end
end
@doc ~S"""
Receives a regex, a binary and a replacement, returns a new
binary where all matches are replaced by the replacement.
The replacement can be either a string or a function. The string
is used as a replacement for every match and it allows specific
captures to be accessed via `\N` or `\g{N}`, where `N` is the
capture. In case `\0` is used, the whole match is inserted. Note
that in regexes the backslash needs to be escaped, hence in practice
you'll need to use `\\N` and `\\g{N}`.
When the replacement is a function, the function may have arity
N where each argument maps to a capture, with the first argument
being the whole match. If the function expects more arguments
than captures found, the remaining arguments will receive `""`.
## Options
* `:global` - when `false`, replaces only the first occurrence
(defaults to `true`)
## Examples
iex> Regex.replace(~r/d/, "abc", "d")
"abc"
iex> Regex.replace(~r/b/, "abc", "d")
"adc"
iex> Regex.replace(~r/b/, "abc", "[\\0]")
"a[b]c"
iex> Regex.replace(~r/a(b|d)c/, "abcadc", "[\\1]")
"[b][d]"
iex> Regex.replace(~r/\.(\d)$/, "500.5", ".\\g{1}0")
"500.50"
iex> Regex.replace(~r/a(b|d)c/, "abcadc", fn _, x -> "[#{x}]" end)
"[b][d]"
iex> Regex.replace(~r/a/, "abcadc", "A", global: false)
"Abcadc"
"""
@spec replace(t, String.t(), String.t() | (... -> String.t()), [term]) :: String.t()
def replace(regex, string, replacement, options \\ [])
def replace(regex, string, replacement, options)
when is_binary(string) and is_binary(replacement) and is_list(options) do
do_replace(regex, string, precompile_replacement(replacement), options)
end
def replace(regex, string, replacement, options)
when is_binary(string) and is_function(replacement) and is_list(options) do
{:arity, arity} = Function.info(replacement, :arity)
do_replace(regex, string, {replacement, arity}, options)
end
defp do_replace(%Regex{re_pattern: compiled}, string, replacement, options) do
opts = if Keyword.get(options, :global) != false, do: [:global], else: []
opts = [{:capture, :all, :index} | opts]
case :re.run(string, compiled, opts) do
:nomatch ->
string
{:match, [mlist | t]} when is_list(mlist) ->
apply_list(string, replacement, [mlist | t]) |> IO.iodata_to_binary()
{:match, slist} ->
apply_list(string, replacement, [slist]) |> IO.iodata_to_binary()
end
end
defp precompile_replacement(""), do: []
defp precompile_replacement(<<?\\, ?g, ?{, rest::binary>>) when byte_size(rest) > 0 do
{ns, <<?}, rest::binary>>} = pick_int(rest)
[List.to_integer(ns) | precompile_replacement(rest)]
end
defp precompile_replacement(<<?\\, ?\\, rest::binary>>) do
[<<?\\>> | precompile_replacement(rest)]
end
defp precompile_replacement(<<?\\, x, rest::binary>>) when x in ?0..?9 do
{ns, rest} = pick_int(rest)
[List.to_integer([x | ns]) | precompile_replacement(rest)]
end
defp precompile_replacement(<<x, rest::binary>>) do
case precompile_replacement(rest) do
[head | t] when is_binary(head) ->
[<<x, head::binary>> | t]
other ->
[<<x>> | other]
end
end
defp pick_int(<<x, rest::binary>>) when x in ?0..?9 do
{found, rest} = pick_int(rest)
{[x | found], rest}
end
defp pick_int(bin) do
{[], bin}
end
defp apply_list(string, replacement, list) do
apply_list(string, string, 0, replacement, list)
end
defp apply_list(_, "", _, _, []) do
[]
end
defp apply_list(_, string, _, _, []) do
string
end
defp apply_list(whole, string, pos, replacement, [[{mpos, _} | _] | _] = list)
when mpos > pos do
length = mpos - pos
<<untouched::binary-size(length), rest::binary>> = string
[untouched | apply_list(whole, rest, mpos, replacement, list)]
end
defp apply_list(whole, string, pos, replacement, [[{pos, length} | _] = head | tail]) do
<<_::size(length)-binary, rest::binary>> = string
new_data = apply_replace(whole, replacement, head)
[new_data | apply_list(whole, rest, pos + length, replacement, tail)]
end
defp apply_replace(string, {fun, arity}, indexes) do
apply(fun, get_indexes(string, indexes, arity))
end
defp apply_replace(_, [bin], _) when is_binary(bin) do
bin
end
defp apply_replace(string, repl, indexes) do
indexes = List.to_tuple(indexes)
for part <- repl do
cond do
is_binary(part) ->
part
part >= tuple_size(indexes) ->
""
true ->
get_index(string, elem(indexes, part))
end
end
end
defp get_index(_string, {pos, _len}) when pos < 0 do
""
end
defp get_index(string, {pos, len}) do
<<_::size(pos)-binary, res::size(len)-binary, _::binary>> = string
res
end
defp get_indexes(_string, _, 0) do
[]
end
defp get_indexes(string, [], arity) do
["" | get_indexes(string, [], arity - 1)]
end
defp get_indexes(string, [h | t], arity) do
[get_index(string, h) | get_indexes(string, t, arity - 1)]
end
@doc ~S"""
Escapes a string to be literally matched in a regex.
## Examples
iex> Regex.escape(".")
"\\."
iex> Regex.escape("\\what if")
"\\\\what\\ if"
"""
@spec escape(String.t()) :: String.t()
def escape(string) when is_binary(string) do
string
|> escape(_length = 0, string)
|> IO.iodata_to_binary()
end
@escapable '.^$*+?()[]{}|#-\\\t\n\v\f\r\s'
defp escape(<<char, rest::binary>>, length, original) when char in @escapable do
escape_char(rest, length, original, char)
end
defp escape(<<_, rest::binary>>, length, original) do
escape(rest, length + 1, original)
end
defp escape(<<>>, _length, original) do
original
end
defp escape_char(<<rest::binary>>, 0, _original, char) do
[?\\, char | escape(rest, 0, rest)]
end
defp escape_char(<<rest::binary>>, length, original, char) do
[binary_part(original, 0, length), ?\\, char | escape(rest, 0, rest)]
end
# Helpers
@doc false
# Unescape map function used by Macro.unescape_string.
def unescape_map(?f), do: ?\f
def unescape_map(?n), do: ?\n
def unescape_map(?r), do: ?\r
def unescape_map(?t), do: ?\t
def unescape_map(?v), do: ?\v
def unescape_map(?a), do: ?\a
def unescape_map(_), do: false
# Private Helpers
defp translate_options(<<?u, t::binary>>, acc), do: translate_options(t, [:unicode, :ucp | acc])
defp translate_options(<<?i, t::binary>>, acc), do: translate_options(t, [:caseless | acc])
defp translate_options(<<?x, t::binary>>, acc), do: translate_options(t, [:extended | acc])
defp translate_options(<<?f, t::binary>>, acc), do: translate_options(t, [:firstline | acc])
defp translate_options(<<?U, t::binary>>, acc), do: translate_options(t, [:ungreedy | acc])
defp translate_options(<<?s, t::binary>>, acc),
do: translate_options(t, [:dotall, {:newline, :anycrlf} | acc])
defp translate_options(<<?m, t::binary>>, acc), do: translate_options(t, [:multiline | acc])
# TODO: Remove on 2.0
defp translate_options(<<?r, t::binary>>, acc) do
IO.warn("the /r modifier in regular expressions is deprecated, please use /U instead")
translate_options(t, [:ungreedy | acc])
end
defp translate_options(<<>>, acc), do: acc
defp translate_options(rest, _acc), do: {:error, rest}
end