-spec at(Subject, Pos) -> byte() when Subject :: binary(), Pos :: non_neg_integer().

Returns the byte at position Pos (zero-based) in binary Subject as an integer.

If Pos >= byte_size(Subject), a badarg exception is raised.

Examples

1> binary:at(<<5,19,72,33>>, 0).
5
2> binary:at(<<5,19,72,33>>, 1).
19
3> binary:at(<<5,19,72,33>>, 4).
** exception error: bad argument
     in function  binary:at/2
        called as binary:at(<<5,19,72,33>>,4)

-spec bin_to_list(Subject) -> [byte()] when Subject :: binary().

Converts Subject to a list of byte()s, each representing the value of one byte.

Examples

1> binary:bin_to_list(<<"erlang",0>>).
[101,114,108,97,110,103,0]

-spec bin_to_list(Subject, PosLen) -> [byte()] when Subject :: binary(), PosLen :: part().

Equivalent to bin_to_list(Subject, Pos, Len).

-spec bin_to_list(Subject, Pos, Len) -> [byte()]
                     when Subject :: binary(), Pos :: non_neg_integer(), Len :: integer().

Converts part of Subject to a list of byte/0s, each representing the value of one byte.

Pos and Len denote which part of the Subject binary to convert.

Examples

1> binary:bin_to_list(<<"erlang">>, 1, 3).
"rla"
%% or [114,108,97] in list notation.
2> binary:bin_to_list(<<"erlang">>, 5, 3).
** exception error: bad argument
     in function  binary:bin_to_list/3
        called as binary:bin_to_list(<<"erlang">>,5,3)
        *** argument 3: out of range

If Pos and Len reference outside the binary in any way, a badarg exception is raised.

-spec compile_pattern(Pattern) -> cp()
                         when
                             Pattern :: PatternBinary | [PatternBinary, ...],
                             PatternBinary :: nonempty_binary().

Builds an internal structure representing a compilation of a search pattern, later to be used in functions match/3, matches/3, split/3, or replace/4.

The cp/0 returned is guaranteed to be a tuple/0 to allow programs to distinguish it from non-precompiled search patterns.

When a list of binaries is specified, it denotes a set of alternative binaries to search for. For example, if [<<"functional">>,<<"programming">>] is specified as Pattern, this means either <<"functional">> or <<"programming">>". The pattern is a set of alternatives; when only a single binary is specified, the set has only one element. The order of alternatives in a pattern is not significant.

The list of binaries used for search alternatives must be flat, proper, and non-empty.

If Pattern is not a binary or a flat proper non-empty list of binaries with length greater than 0, a badarg exception is raised.

Examples

1> Pat = binary:compile_pattern(~"rain").
2> binary:match(~"the rain in spain", Pat).
{4,4}

-spec copy(Subject) -> binary() when Subject :: binary().

Creates a copy of Subject.

Using copy/1 on a binary that references a larger binary can potentially free up the larger binary for garbage collection.

Examples

1> HugeBinary = <<0:100_000/unit:8>>.
2> byte_size(HugeBinary).
100000
3> Part = binary:part(HugeBinary, 0, 5).
<<0,0,0,0,0>>
4> Copy = binary:copy(Part).
<<0,0,0,0,0>>

-spec copy(Subject, N) -> binary() when Subject :: binary(), N :: non_neg_integer().

Creates a binary with the content of Subject duplicated N times.

This function always creates a new binary, even when N is 1.

Examples

1> binary:copy(~"-", 10).
<<"----------">>

-spec decode_hex(Bin) -> Bin2 when Bin :: <<_:_*16>>, Bin2 :: binary().

Decodes a hex-encoded binary into a binary.

An exception is raised if the size of the binary is not evenly divisble by two, or if the binary contains any characters that do not represent hex digits.

Examples

1> binary:decode_hex(<<"666f6f">>).
<<"foo">>
2> binary:decode_hex(<<"A">>).
** exception error: bad argument
     in function  binary:decode_hex/1
        called as binary:decode_hex(<<"A">>)
        *** argument 1: must contain an even number of bytes

-spec decode_unsigned(Subject) -> Unsigned when Subject :: binary(), Unsigned :: non_neg_integer().

Equivalent to decode_unsigned(Subject, big).

-spec decode_unsigned(Subject, Endianness) -> Unsigned
                         when
                             Subject :: binary(),
                             Endianness :: big | little,
                             Unsigned :: non_neg_integer().

Converts the binary digit representation, in big endian or little endian, of a positive integer in Subject to an Erlang integer/0.

Examples

1> binary:decode_unsigned(<<7>>).
7
2> binary:decode_unsigned(<<1,0>>).
256
3> binary:decode_unsigned(<<169,138,199>>).
11111111
4> binary:decode_unsigned(<<169,138,199>>, big).
11111111
5> binary:decode_unsigned(<<169,138,199>>, little).
13077161

-spec encode_hex(Bin) -> Bin2 when Bin :: binary(), Bin2 :: <<_:_*16>>.

Equivalent to encode_hex(Bin, uppercase).

-spec encode_hex(Bin, Case) -> Bin2
                    when Bin :: binary(), Case :: lowercase | uppercase, Bin2 :: <<_:_*16>>.

Encodes a binary into a hex-encoded binary using the specified case for the hexadecimal digits "a" to "f".

Examples

1> binary:encode_hex(<<"foo">>, uppercase).
<<"666F6F">>
2> binary:encode_hex(<<"/">>, uppercase).
<<"2F">>
3> binary:encode_hex(<<"/">>, lowercase).
<<"2f">>

-spec encode_unsigned(Unsigned) -> binary() when Unsigned :: non_neg_integer().

Equivalent to encode_unsigned(Unsigned, big).

-spec encode_unsigned(Unsigned, Endianness) -> binary()
                         when Unsigned :: non_neg_integer(), Endianness :: big | little.

Converts a non-negative integer into the smallest possible unsigned binary representation, using either big-endian or little-endian format.

If Unsigned is not a non-negative integer, a badarg exception is raised.

Examples

1> binary:encode_unsigned(0, big).
<<0>>
2> binary:encode_unsigned(255, big).
<<255>>
3> binary:encode_unsigned(256, big).
<<1,0>>
4> binary:encode_unsigned(256, little).
<<0,1>>
5> binary:encode_unsigned(11111111, big).
<<169,138,199>>
6> binary:encode_unsigned(11111111, little).
<<199,138,169>>

-spec first(Subject) -> byte() when Subject :: binary().

Returns the first byte of binary Subject as an integer.

If the size of Subject is zero, a badarg exception is raised.

Examples

1> binary:first(<<42,99,100>>).
42
2> binary:first(<<>>).
** exception error: bad argument
     in function  binary:first/1
        called as binary:first(<<>>)
        *** argument 1: a zero-sized binary is not allowed

-spec join([binary()], binary()) -> binary().

Joins a list of binaries together by a specified Separator.

Equivalent to iolist_to_binary(lists:join(Separator, Binaries)), but faster.

Examples

1> binary:join([<<"a">>, <<"b">>, <<"c">>], <<", ">>).
<<"a, b, c">>

-spec last(Subject) -> byte() when Subject :: binary().

Returns the last byte of binary Subject as an integer.

If the size of Subject is zero, a badarg exception is raised.

Examples

1> binary:last(<<42,99,100>>).
100
2> binary:last(<<>>).
** exception error: bad argument
     in function  binary:last/1
        called as binary:last(<<>>)
        *** argument 1: a zero-sized binary is not allowed

-spec list_to_bin(ByteList) -> binary() when ByteList :: iolist().

Works exactly as erlang:list_to_binary/1.

This function is provided for completeness.

-spec longest_common_prefix(Binaries) -> non_neg_integer() when Binaries :: [binary(), ...].

Returns the length of the longest common prefix of the binaries in list Binaries.

If Binaries is not a flat non-empty list of binaries, a badarg exception is raised.

Examples

1> binary:longest_common_prefix([<<"erlang">>, <<"ergonomy">>]).
2
2> binary:longest_common_prefix([<<"erlang">>, <<"perl">>]).
0

-spec longest_common_suffix(Binaries) -> non_neg_integer() when Binaries :: [binary(), ...].

Returns the length of the longest common suffix of the binaries in list Binaries.

If Binaries is not a flat non-empty list of binaries, a badarg exception is raised.

Examples

1> binary:longest_common_suffix([<<"erlang">>, <<"fang">>]).
3
2> binary:longest_common_suffix([<<"erlang">>, <<"perl">>]).
0

-spec match(Subject, Pattern) -> Found | nomatch
               when
                   Subject :: binary(),
                   Pattern :: PatternBinary | [PatternBinary, ...] | cp(),
                   PatternBinary :: nonempty_binary(),
                   Found :: part().

Equivalent to match(Subject, Pattern, []).

-spec match(Subject, Pattern, Options) -> Found | nomatch
               when
                   Subject :: binary(),
                   Pattern :: PatternBinary | [PatternBinary, ...] | cp(),
                   PatternBinary :: nonempty_binary(),
                   Found :: part(),
                   Options :: [Option],
                   Option :: {scope, part()}.

Searches for the first occurrence of Pattern in Subject and returns the position and length.

The function returns {Pos, Length} for the binary in Pattern, starting at the lowest position in Subject.

Summary of the options:

• {scope, {Start, Length}} - Only the specified part is searched. Return values still have offsets from the beginning of Subject. A negative Length is allowed as described in Types.

If none of the strings in Pattern is found, the atom nomatch is returned.

For a description of Pattern, see compile_pattern/1.

If {scope, {Start,Length}} is specified in the options such that Start > size of Subject, Start + Length < 0 or Start + Length > size of Subject, a badarg exception is raised.

Examples

1> binary:match(<<"abcde">>, [<<"bcde">>, <<"cd">>], []).
{1,4}

Even though <<"cd">> ends before <<"bcde">>, <<"bcde">> begins first and is therefore the first match. If two overlapping matches begin at the same position, the longest is returned.

1> binary:match(~"the rain in spain", ~"ain", []).
{5,3}

-spec matches(Subject, Pattern) -> Found
                 when
                     Subject :: binary(),
                     Pattern :: PatternBinary | [PatternBinary, ...] | cp(),
                     PatternBinary :: nonempty_binary(),
                     Found :: [part()].

Equivalent to matches(Subject, Pattern, []).

-spec matches(Subject, Pattern, Options) -> Found
                 when
                     Subject :: binary(),
                     Pattern :: PatternBinary | [PatternBinary, ...] | cp(),
                     PatternBinary :: nonempty_binary(),
                     Found :: [part()],
                     Options :: [Option],
                     Option :: {scope, part()}.

As match/2, but Subject is searched until exhausted and a list of all non-overlapping parts matching Pattern is returned (in order).

The first and longest match is preferred to a shorter, which is illustrated by the following example:

1> binary:matches(<<"abcde">>,
                  [<<"bcde">>,<<"bc">>,<<"de">>],
                  []).
[{1,4}]

The result shows that <<"bcde">> is selected instead of the shorter match <<"bc">> (which would have resulted in one more match, <<"de">>). This corresponds to the behavior of POSIX regular expressions (and programs such as awk), but is not consistent with alternative matches in re (and Perl), where lexical ordering in the search pattern determines which string matches.

If none of the strings in a pattern is found, an empty list is returned.

For a description of Pattern, see compile_pattern/1. For a description of available options, see match/3.

If {scope, {Start,Length}} is specified in the options such that Start > size of Subject, Start + Length < 0 or Start + Length is > size of Subject, a badarg exception is raised.

Examples

1> binary:matches(~"the rain in spain", ~"ai", []).
[{5,2},{14,2}]

-spec part(Subject, PosLen) -> binary() when Subject :: binary(), PosLen :: part().

Equivalent to part(Subject, Pos, Len).

-spec part(Subject, Pos, Len) -> binary()
              when Subject :: binary(), Pos :: non_neg_integer(), Len :: integer().

Extracts the part of binary Subject described by PosLen.

A negative length can be used to extract bytes at the end of a binary.

If Pos and Len in any way references outside the binary, a badarg exception is raised.

Examples

1> Bin = <<1,2,3,4,5,6,7,8,9,10>>.
2> binary:part(Bin, 1, 3).
<<2,3,4>>
3> binary:part(Bin, byte_size(Bin), -5).
<<6,7,8,9,10>>

-spec referenced_byte_size(Binary) -> non_neg_integer() when Binary :: binary().

Get the size of the underlying binary referenced by Binary.

If a binary references a larger binary (often called a subbinary), it can be useful to determine the size of the referenced binary. This function can be used to decide when to trigger copy/1. Copying a binary can help eliminate the reference to the original, potentially large, binary that the smaller binary depends on.

Examples

store(Binary, GBSet) ->
    NewBin =
        case binary:referenced_byte_size(Binary) of
            Large when Large > 2 * byte_size(Binary) ->
                binary:copy(Binary);
            _ ->
                Binary
        end,
    gb_sets:insert(NewBin, GBSet).

In this example, we choose to copy the binary content before inserting it into gb_sets:set() if it references a binary more than twice the size of the data we want to retain. Naturally, different rules apply when copying in different applications.

Binary sharing occurs whenever binaries are taken apart. This is the fundamental reason why binaries are efficient; decomposition always has O(1) complexity. However, in rare circumstances this data sharing is undesirable. In such situations, this function, along with copy/1 can be useful for optimizing memory usage.

1> A = binary:copy(<<1>>, 1000).
<<1,1,1,1,1,_/binary>>
2> byte_size(A).
1000
3> binary:referenced_byte_size(A).
1000
4> <<B:10/binary, C/binary>> = A.
5> {byte_size(B), binary:referenced_byte_size(B)}.
{10,10}
6> {byte_size(C), binary:referenced_byte_size(C)}.
{990,1000}

In the above example, the small binary B was copied, while the larger binary C still references binary A.

-spec replace(Subject, Pattern, Replacement) -> Result
                 when
                     Subject :: binary(),
                     Pattern :: PatternBinary | [PatternBinary, ...] | cp(),
                     PatternBinary :: nonempty_binary(),
                     Replacement :: binary() | fun((binary()) -> binary()),
                     Result :: binary().

Equivalent to replace(Subject, Pattern, Replacement, []).

-spec replace(Subject, Pattern, Replacement, Options) -> Result
                 when
                     Subject :: binary(),
                     Pattern :: PatternBinary | [PatternBinary, ...] | cp(),
                     PatternBinary :: nonempty_binary(),
                     Replacement :: binary() | fun((binary()) -> binary()),
                     Options :: [Option],
                     Option :: global | {scope, part()} | {insert_replaced, InsPos},
                     InsPos :: OnePos | [OnePos],
                     OnePos :: non_neg_integer(),
                     Result :: binary().

Constructs a new binary by replacing the parts in Subject matching Pattern with Replacement if given as a literal binary/0 or with the result of applying Replacement to a matching subpart if given as a fun.

If Replacement is given as a binary/0 and the matching subpart of Subject giving rise to the replacement is to be inserted in the result, option {insert_replaced, InsPos} inserts the matching part into Replacement at the specified position (or positions) before inserting Replacement into Subject. If Replacement is given as a fun instead, this option is ignored.

If any position specified in InsPos is greater than the size of the replacement binary, a badarg exception is raised.

Options global and {scope, part()} work as for split/3. The return type is always binary/0.

For a description of Pattern, see compile_pattern/1.

Examples

1> binary:replace(<<"abcde">>, [<<"b">>, <<"d">>], <<"X">>, []).
<<"aXcde">>

2> binary:replace(<<"abcde">>, [<<"b">>, <<"d">>], <<"X">>, [global]).
<<"aXcXe">>

3> binary:replace(<<"abcde">>, <<"b">>, <<"[]">>, [{insert_replaced, 1}]).
<<"a[b]cde">>

4> binary:replace(<<"abcde">>, [<<"b">>, <<"d">>], <<"[]">>, [global,{insert_replaced,1}]).
<<"a[b]c[d]e">>

5> binary:replace(<<"abcde">>, [<<"b">>, <<"d">>], <<"[]">>, [global,{insert_replaced,[1,1]}]).
<<"a[bb]c[dd]e">>

6> binary:replace(<<"abcde">>, [<<"b">>, <<"d">>], <<"[-]">>, [global,{insert_replaced,[1,2]}]).
<<"a[b-b]c[d-d]e">>

7> binary:replace(<<"abcde">>, [<<"b">>, <<"d">>], fun(M) -> <<$[, M/binary, $]>> end, []).
<<"a[b]cde">>

8> binary:replace(<<"abcde">>, [<<"b">>, <<"d">>], fun(M) -> <<$[, M/binary, $]>> end, [global]).
<<"a[b]c[d]e">>

-spec split(Subject, Pattern) -> Parts
               when
                   Subject :: binary(),
                   Pattern :: PatternBinary | [PatternBinary, ...] | cp(),
                   PatternBinary :: nonempty_binary(),
                   Parts :: [binary()].

Equivalent to split(Subject, Pattern, []).

-spec split(Subject, Pattern, Options) -> Parts
               when
                   Subject :: binary(),
                   Pattern :: PatternBinary | [PatternBinary, ...] | cp(),
                   PatternBinary :: nonempty_binary(),
                   Options :: [Option],
                   Option :: {scope, part()} | trim | global | trim_all,
                   Parts :: [binary()].

Splits Subject into a list of binaries based on Pattern.

If option global is not specified, only the first occurrence of Pattern in Subject gives rise to a split.

The parts of Pattern found in Subject are not included in the result.

Summary of options:

• {scope, part()} - Works as in match/3 and matches/3. Note that this only defines the scope of the search for matching strings; it does not cut the binary before splitting. The bytes before and after the scope are kept in the result. See the example below.

• trim - Removes trailing empty parts of the result (as does trim in re:split/3).

• trim_all - Removes all empty parts of the result.

• global - Repeats the split until Subject is exhausted. Conceptually option global makes split work on the positions returned by matches/3, while it normally works on the position returned by match/3.

Example of the difference between a scope and taking the binary apart before splitting:

1> binary:split(<<"banana">>, [<<"a">>], [{scope,{2,3}}]).
[<<"ban">>,<<"na">>]
2> binary:split(binary:part(<<"banana">>,{2,3}), [<<"a">>], []).
[<<"n">>,<<"n">>]

The return type is always a list of binaries that are all referencing Subject. This means that the data in Subject is not copied to new binaries, and that Subject cannot be garbage collected until the results of the split are no longer referenced.

For a description of Pattern, see compile_pattern/1.

Examples

1> binary:split(~"the quick brown fox", ~" ", []).
[<<"the">>,<<"quick brown fox">>]
2> binary:split(~"the quick brown fox", ~" ", [global]).
[<<"the">>,<<"quick">>,<<"brown">>,<<"fox">>]
3> binary:split(<<1,255,4,0,0,0,2,3>>, [<<0,0,0>>,<<2>>], []).
[<<1,255,4>>, <<2,3>>]
4> binary:split(<<0,1,0,0,4,255,255,9>>, [<<0,0>>, <<255,255>>], [global]).
[<<0,1>>,<<4>>,<<9>>]