PATCH: gdbm bindings

[Clint Adams <clint@xxxxxxx>]

I don't know how many years I've been talking about this and not doing
anything about it, so I am going to commit this mostly-useless patch
and talk about it some more instead of fixing it.

At present you can put the right sort of gdbm database file as
/tmp/db_test, then load the module and run

  ztie -d db/gdbm hokeypokey
  print ${hokeypokey}

and it will print the contents of the database.  That's about all it
does.  Printing the keys, writing to the database, all that stuff is
missing.

Moving on to the stuff which is not immediately relevant to my laziness:

ztie and zuntie should be moved somewhere more general, and each backend
module should be able to register its availability dynamically.  I
vaguely recall that there was some concern about referring to "tie" for
this purpose since there is already a variable-tying meaning.  So,
better ideas?

Probing for gdbm_open twice seems silly.  If I don't do it the second
time, HAVE_GDBM_OPEN isn't set.

I forget what else.

diff --git a/Src/Modules/db_gdbm.c b/Src/Modules/db_gdbm.c
new file mode 100644
index 0000000..9672123
--- /dev/null
+++ b/Src/Modules/db_gdbm.c
@@ -0,0 +1,236 @@
+/*
+ * db_gdbm.c - bindings for gdbm
+ *
+ * This file is part of zsh, the Z shell.
+ *
+ * Copyright (c) 2008 Clint Adams
+ * All rights reserved.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and to distribute modified versions of this software for any
+ * purpose, provided that the above copyright notice and the following
+ * two paragraphs appear in all copies of this software.
+ *
+ * In no event shall Clint Adams or the Zsh Development
+ * Group be liable to any party for direct, indirect, special, incidental, or
+ * consequential damages arising out of the use of this software and its
+ * documentation, even if Peter Stephenson, Sven Wischnowsky and the Zsh
+ * Development Group have been advised of the possibility of such damage.
+ *
+ * Clint Adams and the Zsh Development Group
+ * specifically disclaim any warranties, including, but not limited to, the
+ * implied warranties of merchantability and fitness for a particular purpose.
+ * The softwareprovided hereunder is on an "as is" basis, and Peter
+ * Stephenson, Sven Wischnowsky and the Zsh Development Group have no
+ * obligation to provide maintenance, support, updates, enhancements, or
+ * modifications.
+ *
+ */
+
+#include "db_gdbm.mdh"
+#include "db_gdbm.pro"
+
+/*
+ * Make sure we have all the bits I'm using for memory mapping, otherwise
+ * I don't know what I'm doing.
+ */
+#if defined(HAVE_GDBM_H) && defined(HAVE_GDBM_OPEN)
+
+#include <gdbm.h>
+
+static const struct gsu_hash gdbm_gsu =
+{ gdbmgetfn, gdbmsetfn, gdbmunsetfn };
+
+static struct builtin bintab[] = {
+    BUILTIN("ztie", 0, bin_ztie, 1, -1, 0, "d:", NULL),
+    BUILTIN("zuntie", 0, bin_zuntie, 1, -1, 0, NULL, NULL),
+};
+
+static char resource_name[] = "/tmp/db_test";
+GDBM_FILE dbf = NULL;
+Param tied_param;
+
+/**/
+static int
+bin_ztie(char *nam, char **args, Options ops, UNUSED(int func))
+{
+    if(!OPT_ISSET(ops,'d')) {
+        zwarnnam(nam, "you must pass `-d db/gdbm' to ztie", NULL);
+	return 1;
+    }
+
+    /* Here should be a lookup of the backend type against
+     * a registry.
+     */
+
+    /* Here should be an assignment of a resource name
+     * for the backend.
+     */
+
+    if(dbf) {
+        zwarnnam(nam, "something is already ztied and this implementation is flawed", NULL);
+	return 1;
+    }
+
+    char *pmname = ztrdup(*args);
+
+    if (!(tied_param = createspecialhash(pmname, &getgdbmnode, &scangdbmkeys, PM_SPECIAL | PM_HASHED))) {
+        zwarnnam(nam, "cannot create the requested parameter name", NULL);
+	return 1;
+    }
+
+    dbf = gdbm_open(resource_name, 0, GDBM_WRCREAT | GDBM_SYNC, 0666, 0);
+    if(!dbf) {
+        zwarnnam(nam, "error opening database file", NULL);
+	return 1;
+    }
+
+    return 0;
+}
+
+/**/
+static int
+bin_zuntie(char *nam, char **args, Options ops, UNUSED(int func))
+{
+    /* should untie the argument */
+
+    paramtab->removenode(paramtab, tied_param->node.nam);
+    gdbm_close(dbf);
+
+    return 0;
+}
+
+
+/**/
+static char *
+gdbmgetfn(Param pm)
+{
+return;
+}
+
+/**/
+static void
+gdbmsetfn(Param pm, char **key)
+{
+return;
+}
+
+/**/
+static void
+gdbmunsetfn(Param pm, int um)
+{
+return;
+}
+
+/**/
+static HashNode
+getgdbmnode(UNUSED(HashTable ht), const char *name)
+{
+    int len, ret;
+    char *nameu;
+    datum content, key;
+    Param pm = NULL;
+
+    nameu = dupstring(name);
+    unmetafy(nameu, &len);
+    key.dptr = nameu;
+
+    pm = (Param) hcalloc(sizeof(struct param));
+    pm->node.nam = nameu;
+    pm->node.flags = PM_SCALAR;
+
+    ret = gdbm_exists(dbf, key);
+    if(!ret) {
+	pm->u.str = dupstring("");
+	pm->node.flags |= PM_UNSET;
+    } else {
+	content = gdbm_fetch(dbf, key);
+
+	pm->u.str = content.dptr;
+	pm->gsu.s = &nullsetscalar_gsu;
+    }
+    return &pm->node;
+}
+
+/**/
+static void
+scangdbmkeys(UNUSED(HashTable ht), ScanFunc func, int flags)
+{
+    Param pm = NULL;
+    datum key, content;
+
+    pm = (Param) hcalloc(sizeof(struct param));
+
+    pm->node.flags = PM_SCALAR;
+    pm->gsu.s = &nullsetscalar_gsu;
+
+    key = gdbm_firstkey(dbf);
+
+    while(key.dptr) {
+	content = gdbm_fetch(dbf, key);
+
+	pm->u.str = content.dptr;
+	pm->gsu.s = &nullsetscalar_gsu;
+
+	func(&pm->node, flags);
+
+        key = gdbm_nextkey(dbf, key);
+    }
+
+}
+
+#else
+# error no gdbm
+#endif /* have gdbm */
+
+static struct features module_features = {
+    bintab, sizeof(bintab)/sizeof(*bintab),
+    NULL, 0,
+    NULL, 0,
+    NULL, 0,
+    0
+};
+
+/**/
+int
+setup_(UNUSED(Module m))
+{
+    return 0;
+}
+
+/**/
+int
+features_(Module m, char ***features)
+{
+    *features = featuresarray(m, &module_features);
+    return 0;
+}
+
+/**/
+int
+enables_(Module m, int **enables)
+{
+    return handlefeatures(m, &module_features, enables);
+}
+
+/**/
+int
+boot_(UNUSED(Module m))
+{
+    return 0;
+}
+
+/**/
+int
+cleanup_(UNUSED(Module m))
+{
+    return setfeatureenables(m, &module_features, NULL);
+}
+
+/**/
+int
+finish_(UNUSED(Module m))
+{
+    return 0;
+}
diff --git a/Src/Modules/db_gdbm.mdd b/Src/Modules/db_gdbm.mdd
new file mode 100644
index 0000000..ce7926b
--- /dev/null
+++ b/Src/Modules/db_gdbm.mdd
@@ -0,0 +1,12 @@
+name=zsh/db/gdbm
+link='if test "x$ac_cv_lib_gdbm_gdbm_open" = xyes && test "x$ac_cv_header_gdbm_h" = xyes; then
+  echo dynamic
+else
+  echo no
+fi
+'
+load=no
+
+autofeatures="b:ztie b:zuntie"
+
+objects="db_gdbm.o"
diff --git a/configure.ac b/configure.ac
index c4b4243..c8ccee5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -563,7 +563,7 @@ AC_CHECK_HEADERS(sys/time.h sys/times.h sys/select.h termcap.h termio.h \
 		 utmp.h utmpx.h sys/types.h pwd.h grp.h poll.h sys/mman.h \
 		 netinet/in_systm.h pcre.h langinfo.h wchar.h stddef.h \
 		 sys/stropts.h iconv.h ncurses.h ncursesw/ncurses.h \
-		 ncurses/ncurses.h)
+		 ncurses/ncurses.h gdbm.h)
 if test x$dynamic = xyes; then
   AC_CHECK_HEADERS(dlfcn.h)
   AC_CHECK_HEADERS(dl.h)
@@ -834,6 +834,8 @@ elif test x$zsh_cv_decl_ospeed_must_define = xyes; then
   AC_DEFINE(MUST_DEFINE_OSPEED)
 fi
 
+AC_CHECK_LIB(gdbm, gdbm_open)
+
 dnl --------------
 dnl CHECK TYPEDEFS
 dnl --------------
@@ -1130,7 +1132,8 @@ AC_CHECK_FUNCS(strftime strptime mktime timelocal \
 	       wctomb iconv \
 	       grantpt unlockpt ptsname \
 	       htons ntohs \
-	       regcomp regexec regerror regfree)
+	       regcomp regexec regerror regfree \
+	       gdbm_open)
 AC_FUNC_STRCOLL
 
 if test x$enable_cap = xyes; then