#### Android...

#

# See NOTES.ANDROID for details, and don't miss platform-specific

# comments below...

{

    use File::Spec::Functions;

    my $android_ndk = {};

    my %triplet = (

        arm    => "arm-linux-androideabi",

        arm64  => "aarch64-linux-android",

        mips   => "mipsel-linux-android",

        mips64 => "mips64el-linux-android",

        x86    => "i686-linux-android",

        x86_64 => "x86_64-linux-android",

    );

    sub android_ndk {

        unless (%$android_ndk) {

            if ($now_printing =~ m|^android|) {

                return $android_ndk = { bn_ops => "BN_AUTO" };

            }

            my $ndk_var;

            my $ndk;

            foreach (qw(ANDROID_NDK_HOME ANDROID_NDK)) {

                $ndk_var = $_;

                $ndk = $ENV{$ndk_var};

                last if defined $ndk;

            }

            die "\$ANDROID_NDK_HOME is not defined"  if (!$ndk);

            if (!-d "$ndk/platforms" && !-f "$ndk/AndroidVersion.txt") {

                # $ndk/platforms is traditional "all-inclusive" NDK, while

                # $ndk/AndroidVersion.txt is so-called standalone toolchain

                # tailored for specific target down to API level.

                die "\$ANDROID_NDK_HOME=$ndk is invalid";

            }

            $ndk = canonpath($ndk);

            my $ndkver = undef;

            if (open my $fh, "<$ndk/source.properties") {

                local $_;

                while(<$fh>) {

                    if (m|Pkg\.Revision\s*=\s*([0-9]+)|) {

                        $ndkver = $1;

                        last;

                    }

                }

                close $fh;

            }

            my ($sysroot, $api, $arch);

            $config{target} =~ m|[^-]+-([^-]+)$|;	# split on dash

            $arch = $1;

            if ($sysroot = $ENV{CROSS_SYSROOT}) {

                $sysroot =~ m|/android-([0-9]+)/arch-(\w+)/?$|;

                ($api, $arch) = ($1, $2);

            } elsif (-f "$ndk/AndroidVersion.txt") {

                $sysroot = "$ndk/sysroot";

            } else {

                $api = "*";

                # see if user passed -D__ANDROID_API__=N

                foreach (@{$useradd{CPPDEFINES}}, @{$user{CPPFLAGS}}) {

                    if (m|__ANDROID_API__=([0-9]+)|) {

                        $api = $1;

                        last;

                    }

                }

                # list available platforms (numerically)

                my @platforms = sort { $a =~ m/-([0-9]+)$/; my $aa = $1;

                                       $b =~ m/-([0-9]+)$/; $aa <=> $1;

                                     } glob("$ndk/platforms/android-$api");

                die "no $ndk/platforms/android-$api" if ($#platforms < 0);

                $sysroot = "@platforms[$#platforms]/arch-$arch";

                $sysroot =~ m|/android-([0-9]+)/arch-$arch|;

                $api = $1;

            }

            die "no sysroot=$sysroot"   if (!-d $sysroot);

            my $triarch = $triplet{$arch};

            my $cflags;

            my $cppflags;

            # see if there is NDK clang on $PATH, "universal" or "standalone"

            if (which("clang") =~ m|^$ndk/.*/prebuilt/([^/]+)/|) {

                my $host=$1;

                # harmonize with gcc default

                my $arm = $ndkver > 16 ? "armv7a" : "armv5te";

                (my $tridefault = $triarch) =~ s/^arm-/$arm-/;

                (my $tritools   = $triarch) =~ s/(?:x|i6)86(_64)?-.*/x86$1/;

                $cflags .= " -target $tridefault "

                        .  "-gcc-toolchain \$($ndk_var)/toolchains"

                        .  "/$tritools-4.9/prebuilt/$host";

                $user{CC} = "clang" if ($user{CC} !~ m|clang|);

                $user{CROSS_COMPILE} = undef;

                if (which("llvm-ar") =~ m|^$ndk/.*/prebuilt/([^/]+)/|) {

                    $user{AR} = "llvm-ar";

                    $user{ARFLAGS} = [ "rs" ];

                    $user{RANLIB} = ":";

                }

            } elsif (-f "$ndk/AndroidVersion.txt") {    #"standalone toolchain"

                my $cc = $user{CC} // "clang";

                # One can probably argue that both clang and gcc should be

                # probed, but support for "standalone toolchain" was added

                # *after* announcement that gcc is being phased out, so

                # favouring clang is considered adequate. Those who insist

                # have option to enforce test for gcc with CC=gcc.

                if (which("$triarch-$cc") !~ m|^$ndk|) {

                    die "no NDK $triarch-$cc on \$PATH";

                }

                $user{CC} = $cc;

                $user{CROSS_COMPILE} = "$triarch-";

            } elsif ($user{CC} eq "clang") {

                die "no NDK clang on \$PATH";

            } else {

                if (which("$triarch-gcc") !~ m|^$ndk/.*/prebuilt/([^/]+)/|) {

                    die "no NDK $triarch-gcc on \$PATH";

                }

                $cflags .= " -mandroid";

                $user{CROSS_COMPILE} = "$triarch-";

            }

            if (!-d "$sysroot/usr/include") {

                my $incroot = "$ndk/sysroot/usr/include";

                die "no $incroot"          if (!-d $incroot);

                die "no $incroot/$triarch" if (!-d "$incroot/$triarch");

                $incroot =~ s|^$ndk/||;

                $cppflags  = "-D__ANDROID_API__=$api";

                $cppflags .= " -isystem \$($ndk_var)/$incroot/$triarch";

                $cppflags .= " -isystem \$($ndk_var)/$incroot";

            }

            $sysroot =~ s|^$ndk/||;

            $android_ndk = {

                cflags   => "$cflags --sysroot=\$($ndk_var)/$sysroot",

                cppflags => $cppflags,

                bn_ops   => $arch =~ m/64$/ ? "SIXTY_FOUR_BIT_LONG"

                                            : "BN_LLONG",

            };

        }

        return $android_ndk;

    }

}

my %targets = (

    "android" => {

        inherit_from     => [ "linux-generic32" ],

        template         => 1,

        ################################################################

        # Special note about -pie. The underlying reason is that

        # Lollipop refuses to run non-PIE. But what about older systems

        # and NDKs? -fPIC was never problem, so the only concern is -pie.

        # Older toolchains, e.g. r4, appear to handle it and binaries

        # turn out mostly functional. "Mostly" means that oldest

        # Androids, such as Froyo, fail to handle executable, but newer

        # systems are perfectly capable of executing binaries targeting

        # Froyo. Keep in mind that in the nutshell Android builds are

        # about JNI, i.e. shared libraries, not applications.

        cflags           => add(sub { android_ndk()->{cflags} }),

        cppflags         => add(sub { android_ndk()->{cppflags} }),

        cxxflags         => add(sub { android_ndk()->{cflags} }),

        bn_ops           => sub { android_ndk()->{bn_ops} },

        bin_cflags       => "-pie",

        enable           => [ ],

    },

    "android-arm" => {

        ################################################################

        # Contemporary Android applications can provide multiple JNI

        # providers in .apk, targeting multiple architectures. Among

        # them there is "place" for two ARM flavours: generic eabi and

        # armv7-a/hard-float. However, it should be noted that OpenSSL's

        # ability to engage NEON is not constrained by ABI choice, nor

        # is your ability to call OpenSSL from your application code

        # compiled with floating-point ABI other than default 'soft'.

        # (Latter thanks to __attribute__((pcs("aapcs"))) declaration.)

        # This means that choice of ARM libraries you provide in .apk

        # is driven by application needs. For example if application

        # itself benefits from NEON or is floating-point intensive, then

        # it might be appropriate to provide both libraries. Otherwise

        # just generic eabi would do. But in latter case it would be

        # appropriate to

        #

        #   ./Configure android-arm -D__ARM_MAX_ARCH__=8

        #

        # in order to build "universal" binary and allow OpenSSL take

        # advantage of NEON when it's available.

        #

        # Keep in mind that (just like with linux-armv4) we rely on

        # compiler defaults, which is not necessarily what you had

        # in mind, in which case you would have to pass additional

        # -march and/or -mfloat-abi flags. NDK defaults to armv5te.

        # Newer NDK versions reportedly require additional -latomic.

        #

        inherit_from     => [ "android", asm("armv4_asm") ],

        bn_ops           => add("RC4_CHAR"),

    },

    "android-arm64" => {

        inherit_from     => [ "android", asm("aarch64_asm") ],

        bn_ops           => add("RC4_CHAR"),

        perlasm_scheme   => "linux64",

    },

    "android-mips" => {

        inherit_from     => [ "android", asm("mips32_asm") ],

        bn_ops           => add("RC4_CHAR"),

        perlasm_scheme   => "o32",

    },

    "android-mips64" => {

        ################################################################

        # You are more than likely have to specify target processor

        # on ./Configure command line. Trouble is that toolchain's

        # default is MIPS64r6 (at least in r10d), but there are no

        # such processors around (or they are too rare to spot one).

        # Actual problem is that MIPS64r6 is binary incompatible

        # with previous MIPS ISA versions, in sense that unlike

        # prior versions original MIPS binary code will fail.

        #

        inherit_from     => [ "android", asm("mips64_asm") ],

        bn_ops           => add("RC4_CHAR"),

        perlasm_scheme   => "64",

    },

    "android-x86" => {

        inherit_from     => [ "android", asm("x86_asm") ],

        CFLAGS           => add(picker(release => "-fomit-frame-pointer")),

        bn_ops           => add("RC4_INT"),

        perlasm_scheme   => "android",

    },

    "android-x86_64" => {

        inherit_from     => [ "android", asm("x86_64_asm") ],

        bn_ops           => add("RC4_INT"),

        perlasm_scheme   => "elf",

    },

    ####################################################################

    # Backward compatible targets, (might) require $CROSS_SYSROOT

    #

    "android-armeabi" => {

        inherit_from     => [ "android-arm" ],

    },

    "android64" => {

        inherit_from     => [ "android" ],

    },

    "android64-aarch64" => {

        inherit_from     => [ "android-arm64" ],

    },

    "android64-x86_64" => {

        inherit_from     => [ "android-x86_64" ],

    },

    "android64-mips64" => {

        inherit_from     => [ "android-mips64" ],

    },

);