Add "md5" detection macro.

[dxcommon.git] / m4 / md5.m4

diff --git a/m4/md5.m4 b/m4/md5.m4
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+++ b/m4/md5.m4
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+dnl Copyright © 2021 Nick Bowler
+dnl
+dnl License WTFPL2: Do What The Fuck You Want To Public License, version 2.
+dnl This is free software: you are free to do what the fuck you want to.
+dnl There is NO WARRANTY, to the extent permitted by law.
+
+dnl DX_PROG_MD5
+dnl
+dnl Search PATH for a command-line md5 digest utility, such as GNU md5sum,
+dnl FreeBSD md5 or openssl md5.  If found, the MD5 variable (which is
+dnl substituted by AC_SUBST) is set to the result and the cache variable
+dnl dx_cv_md5_works is set to "yes".  Otherwise, dx_cv_md5_works is set to
+dnl "no".
+dnl
+dnl The utilities that can be found have slightly different options and
+dnl output formats.  For example, GNU md5sum prints each line with the
+dnl digest followed by the filename, whereas openssl md5 prints the filename
+dnl followed by the digest.  The MD5 setting will include the -r option, when
+dnl supported, to prefer a command that prints the digest first as this is
+dnl easier to parse by shell code.  The cache variable dx_cv_md5_outpos will
+dnl be set to "front" if the digest appears at the beginning of the line,
+dnl and "back" if the digest appears at the end of the line.  Portable usage
+dnl should handle both scenarios.
+AC_DEFUN([DX_PROG_MD5], [AC_PREREQ([2.62])dnl
+AC_ARG_VAR([MD5], [MD5 digest command])dnl
+eval ': >conftest.in'
+AC_CACHE_CHECK([for utility to compute MD5 digests], [ac_cv_path_MD5],
+[dx_cv_md5_found=:
+AC_PATH_PROGS_FEATURE_CHECK([MD5], [md5sum md5 openssl],
+[DX_BASENAME([md5_relcmd], ["$ac_path_MD5"])
+set x '-r' ''; shift
+AS_CASE([$md5_relcmd], [openssl], [ac_path_MD5="$ac_path_MD5 md5"],
+                       [md5sum], [shift])
+eval ': >conftest.in'
+for md5_arg
+do
+_DX_MD5_DO_TEST([$ac_path_MD5 $md5_arg],
+  [ac_path_MD5="$ac_path_MD5 $md5_arg"; break])
+done
+AS_IF([test x"$dx_cv_md5_works" = x"yes"],
+[md5_bypath=`{ command -v "$md5_relcmd"; } 2>/dev/null` #''
+ac_cv_path_MD5=$ac_path_MD5
+set x $ac_path_MD5; shift
+if test x"$md5_bypath" = x"$[1]"; then
+  shift; set x $md5_relcmd "$[@]"; shift;
+  ac_cv_path_MD5=$[*]
+fi
+ac_path_MD5_found=:])], [ac_cv_path_MD5='none found' dx_cv_md5_found=false])])
+AS_IF([$dx_cv_md5_found],
+[MD5=$ac_cv_path_MD5
+AC_CACHE_CHECK([for $MD5 digest position], [dx_cv_md5_outpos],
+[_DX_MD5_DO_TEST([$MD5])])])
+rm -f conftest.in conftest.out])
+
+AC_DEFUN([_DX_MD5_DO_TEST],
+[AS_IF([$1 conftest.in >conftest.out],
+[read a b <conftest.out
+AS_IF([test x"$a" = x"d41d8cd98f00b204e9800998ecf8427e"],
+  [dx_cv_md5_works=yes dx_cv_md5_outpos=front
+$2],
+[set x $b; shift; eval "a=\$$[#]"
+AS_IF([test x"$a" = x"d41d8cd98f00b204e9800998ecf8427e"],
+  [dx_cv_md5_works=yes dx_cv_md5_outpos=back
+$2], [dx_cv_md5_works=no dx_cv_md5_outpos='not found'])])],
+[dx_cv_md5_works=no dx_cv_md5_outpos='not found'])])