This module contains functions for manipulating byte-oriented binaries. Although the majority of functions could be provided using bit-syntax, the functions in this library are highly optimized and are expected to either execute faster or consume less memory, or both, than a counterpart written in pure Erlang.
The module is provided according to Erlang Enhancement Proposal (EEP) 31.
The library handles byte-oriented data. For bitstrings that are not
binaries (does not contain whole octets of bits) a
Opaque data type representing a compiled
search pattern. Guaranteed to be a
A representaion of a part (or range) in a binary.
Returns the byte at position
Same as
Converts
Example:
1> binary:bin_to_list(<<"erlang">>, {1,3}).
"rla"
%% or [114,108,97] in list notation.
If
Same as
Builds an internal structure representing a compilation of a
search pattern, later to be used in functions
When a list of binaries is specified, it denotes a set of
alternative binaries to search for. For example, if
The list of binaries used for search alternatives must be flat and proper.
If
Same as
Creates a binary with the content of
This function always creates a new binary, even if
By deliberately copying a single binary to avoid referencing a larger binary, one can, instead of freeing up the larger binary for later garbage collection, create much more binary data than needed. Sharing binary data is usually good. Only in special cases, when small parts reference large binaries and the large binaries are no longer used in any process, deliberate copying can be a good idea.
If
Same as
Converts the binary digit representation, in big endian or little
endian, of a positive integer in
Example:
1> binary:decode_unsigned(<<169,138,199>>,big).
11111111
Same as
Converts a positive integer to the smallest possible representation in a binary digit representation, either big endian or little endian.
Example:
1> binary:encode_unsigned(11111111, big).
<<169,138,199>>
Returns the first byte of binary
Returns the last byte of binary
Works exactly as
Returns the length of the longest common prefix of the
binaries in list
Example:
1> binary:longest_common_prefix([<<"erlang">>, <<"ergonomy">>]).
2
2> binary:longest_common_prefix([<<"erlang">>, <<"perl">>]).
0
If
Returns the length of the longest common suffix of the
binaries in list
Example:
1> binary:longest_common_suffix([<<"erlang">>, <<"fang">>]).
3
2> binary:longest_common_suffix([<<"erlang">>, <<"perl">>]).
0
If
Same as
Searches for the first occurrence of
The function returns
Example:
1> binary:match(<<"abcde">>, [<<"bcde">>, <<"cd">>],[]).
{1,4}
Even though
Summary of the options:
Only the specified part is searched. Return values still have
offsets from the beginning of
If none of the strings in
For a description of
If
Same as
As
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 given raise to
one more match, <<"de">>).
This corresponds to the behavior of
POSIX regular expressions (and programs like awk), but is not
consistent with alternative matches in
If none of the strings in a pattern is found, an empty list is returned.
For a description of
If
Extracts the part of binary
A negative length can be used to extract bytes at the end of a binary:
1> Bin = <<1,2,3,4,5,6,7,8,9,10>>.
2> binary:part(Bin, {byte_size(Bin), -5}).
<<6,7,8,9,10>>
If
Same as
If a binary references a larger binary (often described as
being a subbinary), it can be useful to get the size of the
referenced binary. This function can be used in a program to trigger the
use of
Example:
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 chose to copy the binary content before
inserting it in
Binary sharing occurs whenever binaries are taken apart.
This is the fundamental reason why binaries are fast,
decomposition can always be done with O(1) complexity. In rare
circumstances this data sharing is however undesirable, why this
function together with
Example of binary sharing:
1> A = binary:copy(<<1>>, 100).
<<1,1,1,1,1 ...
2> byte_size(A).
100
3> binary:referenced_byte_size(A)
100
4> <<_:10/binary,B:10/binary,_/binary>> = A.
<<1,1,1,1,1 ...
5> byte_size(B).
10
6> binary:referenced_byte_size(B)
100
Binary data is shared among processes. If another process still references the larger binary, copying the part this process uses only consumes more memory and does not free up the larger binary for garbage collection. Use this kind of intrusive functions with extreme care and only if a real problem is detected.
Same as
Constructs a new binary by replacing the parts in
If the matching subpart of
Example:
1> binary:replace(<<"abcde">>,<<"b">>,<<"[]">>, [{insert_replaced,1}]).
<<"a[b]cde">>
2> binary:replace(<<"abcde">>,[<<"b">>,<<"d">>],<<"[]">>,[global,{insert_replaced,1}]).
<<"a[b]c[d]e">>
3> binary:replace(<<"abcde">>,[<<"b">>,<<"d">>],<<"[]">>,[global,{insert_replaced,[1,1]}]).
<<"a[bb]c[dd]e">>
4> binary:replace(<<"abcde">>,[<<"b">>,<<"d">>],<<"[-]">>,[global,{insert_replaced,[1,2]}]).
<<"a[b-b]c[d-d]e">>
If any position specified in
Options
For a description of
Same as
Splits
The parts of
Example:
1> binary:split(<<1,255,4,0,0,0,2,3>>, [<<0,0,0>>,<<2>>],[]).
[<<1,255,4>>, <<2,3>>]
2> binary:split(<<0,1,0,0,4,255,255,9>>, [<<0,0>>, <<255,255>>],[global]).
[<<0,1>>,<<4>>,<<9>>]
Summary of options:
Works as in
Removes trailing empty parts of the result (as does
Removes all empty parts of the result.
Repeats the split until
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
For a description of