CODEWITHSUNDEEP
perlbytereverseswap
user3623221
user3623221

Reputation: 43

Swapping two bytes in perl

I am trying to swap two bytes at a time in a file. So I was thinking I could read in two bytes at a time and use reverse to switch the bytes around. However I am not sure how to read two bytes at a time in perl. Can someone make a suggestion

Upvotes: 0

Views: 219

Answers (2)

ikegami
ikegami

Reputation: 385839

Reading two bytes at a time is hugely inefficient. You should continue to read larger blocks at a time and process the bytes in the buffer.

$buf =~ s/(.)(.)/$2$1/sg;

or

$buf = pack 'S<*, unpack 'S>*', $buf;

Upvotes: 1

jordan
jordan

Reputation: 1017

Use "read" (http://perldoc.perl.org/functions/read.html) to read and pass "2" for the LENGTH parameter to read 2 bytes (by default) of data.

For performance reasons, if you have a large file, you might want to consider reading more (or perhaps all) of the file once, instead of calling read ((filesize in bytes)/2) times.

Upvotes: 0

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