Heuristic detection of text vs. binary data.
Terra Perl6
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t Initial commit of Data::TextOrBinary. Jan 16, 2017
README.md Update README.md Jan 18, 2017



Implements a heuristic algorithm, very much like the one used by Git, to decide if some data is most likely to be text or binary.


# Test a Buf/Blob
say is-text('Vánoční stromek'.encode('utf-8'));         # True
say is-text(Buf.new(0x02, 0xFF, 0x00, 0x38));           # False

# Test a file
say is-text('/bin/bash'.IO);                            # False
say is-text('/usr/share/dict/words'.IO);                # True


The module exports a single subroutine is-text, which has candidates for Blob and IO::Path, enabling it to be used on data that has already been read into memory as well as data in a file.

On a Blob

my $text = is-text($the-blob, test-bytes => 8192);

When called on a Blob, is-text will test the first test-bytes bytes of it to decide if it contains text or binary data. The test-bytes named parameter is optional, and its default value is 4096.

On an IO::Path

my $text = is-text($filename.IO, test-bytes => 8192);

When called on an IO::Path, is-text will read the first test-bytes bytes from the file it points to. It will then test these to decide if the file is text or binary. The test-bytes named parameter is optional, and its default value is 4096.


The algorithm will flag a file as binary if it encounters a NULL byte or a lone carriage return (\r). Otherwise, it considers the ratio of printable to ASCII-range control characters, with newline sequences excluded. If there is less than one byte representing an unprintable ASCII character per 128 bytes representing printable ASCII characters, then the data is considered to be text.

Thread safety

The function exported by this module is safe to call from multiple threads at the same time.