Support building with the Perl XS bindings disabled

Since the Perl bindings require shared libraries, this is required on
platforms such as Cygwin where we do a static build.

configure.ac

@@ -71,7 +71,7 @@ fi
 AC_PROG_CC
 AC_PROG_CXX
 
-# To build programs to be run in the build machine
+# To build programs to be run in the build machine.
 if test "$CC_FOR_BUILD" = ""; then
     if test "$cross_compiling" = "yes"; then
         AC_CHECK_PROGS(CC_FOR_BUILD, gcc cc)
@@ -86,13 +86,6 @@ AC_DISABLE_STATIC
 AC_ENABLE_SHARED
 AC_PROG_LIBTOOL
 
-if test "$enable_shared" = yes; then
-   SUB_CONFIGURE_FLAGS="--enable-shared --disable-static"
-else
-   SUB_CONFIGURE_FLAGS="--enable-static --disable-shared"
-fi
-AC_SUBST(SUB_CONFIGURE_FLAGS)
-
 
 # Use 64-bit file system calls so that we can support files > 2 GiB.
 AC_SYS_LARGEFILE
@@ -247,7 +240,7 @@ PKG_CHECK_MODULES([SQLITE3], [sqlite3 >= 3.6.19], [CXXFLAGS="$SQLITE3_CFLAGS $CX
 
 # Whether to use the Boehm garbage collector.
 AC_ARG_ENABLE(gc, AC_HELP_STRING([--enable-gc],
-  [enable garbage collection in the Nix expression evaluator (requires Boehm GC)]),
+  [enable garbage collection in the Nix expression evaluator (requires Boehm GC) [default=no]]),
   gc=$enableval, gc=no)
 if test "$gc" = yes; then
   PKG_CHECK_MODULES([BDW_GC], [bdw-gc])
@@ -277,6 +270,20 @@ AC_MSG_RESULT(yes)
 AC_SUBST(perlFlags)
 
 
+# Whether to build the Perl bindings
+AC_MSG_CHECKING([whether to build the Perl bindings])
+AC_ARG_ENABLE(perl-bindings, AC_HELP_STRING([--enable-perl-bindings],
+  [whether to build the Perl bindings (recommended) [default=yes]]),
+  perlbindings=$enableval, perlbindings=yes)
+if test "$enable_shared" = no; then
+   # Perl bindings require shared libraries.
+   perlbindings=no
+fi
+AM_CONDITIONAL(PERL_BINDINGS, test "$perlbindings" = "yes")
+AC_SUBST(perlbindings)
+AC_MSG_RESULT($perlbindings)
+
+
 AC_ARG_ENABLE(init-state, AC_HELP_STRING([--disable-init-state],
   [do not initialise DB etc. in `make install']),
   init_state=$enableval, init_state=yes)

perl/Makefile.am

@@ -2,9 +2,12 @@ PERL_MODULES = lib/Nix/Store.pm lib/Nix/Manifest.pm lib/Nix/GeneratePatches.pm l
 
 all: $(PERL_MODULES:.in=)
 
-install-exec-local: $(PERL_MODULES:.in=)
+install-exec-local: $(PERL_MODULES:.in=) install-perl-xs
 	$(INSTALL) -d $(DESTDIR)$(perllibdir)/Nix
 	$(INSTALL_DATA) $(PERL_MODULES:.in=) $(DESTDIR)$(perllibdir)/Nix
+
+if PERL_BINDINGS
+install-perl-xs:
 	$(INSTALL) -d $(DESTDIR)$(perllibdir)/auto/Nix/Store
 	ln -sfn $(pkglibdir)/libNixStore$(dynlib_suffix) $(DESTDIR)$(perllibdir)/auto/Nix/Store/Store$(dynlib_suffix)
 
@@ -25,6 +28,10 @@ AM_CXXFLAGS = \
 lib/Nix/Store.cc: lib/Nix/Store.xs
 	xsubpp $^ -output $@
 
+else
+install-perl-xs:
+endif
+
 EXTRA_DIST = $(PERL_MODULES) lib/Nix/Store.xs
 
 include ../substitute.mk

perl/lib/Nix/Config.pm.in

@@ -10,6 +10,8 @@ $confDir = $ENV{"NIX_CONF_DIR"} || "@sysconfdir@/nix";
 $bzip2 = $ENV{"NIX_BZIP2"} || "@bzip2@";
 $curl = "@curl@";
 
+$useBindings = "@perlbindings@" eq "yes";
+
 sub readConfig {
     my %config;
     my $config = "@sysconfdir@/nix/nix.conf";

perl/lib/Nix/Store.pm

@@ -2,6 +2,7 @@ package Nix::Store;
 
 use strict;
 use warnings;
+use Nix::Config;
 
 require Exporter;
 
@@ -21,8 +22,70 @@ our @EXPORT = qw(
 
 our $VERSION = '0.15';
 
-require XSLoader;
-XSLoader::load('Nix::Store', $VERSION);
+sub backtick {
+    open(RES, "-|", @_) or die;
+    local $/;
+    my $res = <RES> || "";
+    close RES or die;
+    return $res;
+}
+
+if ($Nix::Config::useBindings) {
+    require XSLoader;
+    XSLoader::load('Nix::Store', $VERSION);
+} else {
+
+    # Provide slow fallbacks of some functions on platforms that don't
+    # support the Perl bindings.
+
+    use File::Temp;
+    use Fcntl qw/F_SETFD/;
+
+    sub hashFile {
+        my ($algo, $base32, $path) = @_;
+        my $res = backtick("$Nix::Config::binDir/nix-hash", "--flat", $path, "--type", $algo, $base32 ? "--base32" : ());
+        chomp $res;
+        return $res;
+    }
+
+    sub hashPath {
+        my ($algo, $base32, $path) = @_;
+        my $res = backtick("$Nix::Config::binDir/nix-hash", $path, "--type", $algo, $base32 ? "--base32" : ());
+        chomp $res;
+        return $res;
+    }
+
+    sub hashString {
+        my ($algo, $base32, $s) = @_;
+        my $fh = File::Temp->new();
+        print $fh $s;
+        my $res = backtick("$Nix::Config::binDir/nix-hash", $fh->filename, "--type", $algo, $base32 ? "--base32" : ());
+        chomp $res;
+        return $res;
+    }
+
+    sub addToStore {
+        my ($srcPath, $recursive, $algo) = @_;
+        die "not implemented" if $recursive || $algo ne "sha256";
+        my $res = backtick("$Nix::Config::binDir/nix-store", "--add", $srcPath);
+        chomp $res;
+        return $res;
+    }
+
+    sub isValidPath {
+        my ($path) = @_;
+        my $res = backtick("$Nix::Config::binDir/nix-store", "--check-validity", "--print-invalid", $path);
+        chomp $res;
+        return $res ne $path;
+    }
+
+    sub queryPathHash {
+        my ($path) = @_;
+        my $res = backtick("$Nix::Config::binDir/nix-store", "--query", "--hash", $path);
+        chomp $res;
+        return $res;
+    }
+}
 
 1;
 __END__

substitute.mk

@@ -30,6 +30,7 @@
 	 -e "s^@xsltproc\@^$(xsltproc)^g" \
 	 -e "s^@sqlite_bin\@^$(sqlite_bin)^g" \
 	 -e "s^@version\@^$(VERSION)^g" \
+	 -e "s^@perlbindings\@^$(perlbindings)^g" \
 	 -e "s^@testPath\@^$(coreutils):$$(dirname $$(type -p expr))^g" \
 	 < $< > $@ || rm $@
 	if test -x $<; then chmod +x $@; fi