Src/Modules/db_gdbm.c

/*
 * db_gdbm.c - bindings for gdbm
 *
 * This file is part of zsh, the Z shell.
 *
 * Copyright (c) 2008 Clint Adams
 * All rights reserved.
 *
 * Modifications copyright (c) 2017 Sebastian Gniazdowski
 * 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 software provided 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"

#ifndef PM_UPTODATE
#define PM_UPTODATE     (1<<19) /* Parameter has up-to-date data (e.g. loaded from DB) */
#endif

static Param createhash( char *name, int flags );
static int append_tied_name( const char *name );
static int remove_tied_name( const char *name );
static char *unmetafy_zalloc(const char *to_copy, int *new_len);
static void myfreeparamnode(HashNode hn);

static int no_database_action = 0;

/*
 * 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 char *backtype = "db/gdbm";

/*
 * Longer GSU structure, to carry GDBM_FILE of owning
 * database. Every parameter (hash value) receives GSU
 * pointer and thus also receives GDBM_FILE - this way
 * parameters can access proper database.
 *
 * Main HashTable parameter has the same instance of
 * the custom GSU struct in u.hash->tmpdata field.
 * When database is closed, `dbf` field is set to NULL
 * and hash values know to not access database when
 * being unset (total purge at zuntie).
 *
 * When database closing is ended, custom GSU struct
 * is freed. Only new ztie creates new custom GSU
 * struct instance.
 */

struct gsu_scalar_ext {
    struct gsu_scalar std; /* Size of three pointers */
    GDBM_FILE dbf;
    char *dbfile_path;
};

/* Source structure - will be copied to allocated one,
 * with `dbf` filled. `dbf` allocation <-> gsu allocation. */
static const struct gsu_scalar_ext gdbm_gsu_ext =
{ { gdbmgetfn, gdbmsetfn, gdbmunsetfn }, 0, 0 };

/**/
static const struct gsu_hash gdbm_hash_gsu =
{ hashgetfn, gdbmhashsetfn, gdbmhashunsetfn };

static struct builtin bintab[] = {
    BUILTIN("ztie", 0, bin_ztie, 1, -1, 0, "d:f:r", NULL),
    BUILTIN("zuntie", 0, bin_zuntie, 1, -1, 0, "u", NULL),
    BUILTIN("zgdbmpath", 0, bin_zgdbmpath, 1, -1, 0, "", NULL),
};

#define ROARRPARAMDEF(name, var) \
    { name, PM_ARRAY | PM_READONLY, (void *) var, NULL,  NULL, NULL, NULL }

/* Holds names of all tied parameters */
static char **zgdbm_tied;

static struct paramdef patab[] = {
    ROARRPARAMDEF( "zgdbm_tied", &zgdbm_tied ),
};

/**/
static int
bin_ztie(char *nam, char **args, Options ops, UNUSED(int func))
{
    struct gsu_scalar_ext *dbf_carrier;
    char *resource_name, *pmname;
    GDBM_FILE dbf = NULL;
    int read_write = GDBM_SYNC, pmflags = PM_REMOVABLE;
    Param tied_param;

    if(!OPT_ISSET(ops,'d')) {
        zwarnnam(nam, "you must pass `-d %s'", backtype);
	return 1;
    }
    if(!OPT_ISSET(ops,'f')) {
        zwarnnam(nam, "you must pass `-f' with a filename", NULL);
	return 1;
    }
    if (OPT_ISSET(ops,'r')) {
	read_write |= GDBM_READER;
	pmflags |= PM_READONLY;
    } else {
	read_write |= GDBM_WRCREAT;
    }

    /* Here should be a lookup of the backend type against
     * a registry, if generam DB mechanism is to be added */
    if (strcmp(OPT_ARG(ops, 'd'), backtype) != 0) {
        zwarnnam(nam, "unsupported backend type `%s'", OPT_ARG(ops, 'd'));
	return 1;
    }

    resource_name = OPT_ARG(ops, 'f');
    pmname = *args;

    if ((tied_param = (Param)paramtab->getnode(paramtab, pmname)) &&
	!(tied_param->node.flags & PM_UNSET)) {
	/*
	 * Unset any existing parameter.  Note there's no implicit
	 * "local" here, but if the existing parameter is local
	 * then new parameter will be also local without following
         * unset.
	 *
	 * We need to do this before attempting to open the DB
	 * in case this variable is already tied to a DB.
	 *
	 * This can fail if the variable is readonly or restricted.
	 * We could call unsetparam() and check errflag instead
	 * of the return status.
	 */
	if (unsetparam_pm(tied_param, 0, 1))
	    return 1;
    }

    gdbm_errno=0;
    dbf = gdbm_open(resource_name, 0, read_write, 0666, 0);
    if(dbf == NULL) {
	zwarnnam(nam, "error opening database file %s (%s)", resource_name, gdbm_strerror(gdbm_errno));
	return 1;
    }

    if (!(tied_param = createhash(pmname, pmflags))) {
        zwarnnam(nam, "cannot create the requested parameter %s", pmname);
	gdbm_close(dbf);
	return 1;
    }

    tied_param->gsu.h = &gdbm_hash_gsu;

    /* Allocate parameter sub-gsu, fill dbf field.
     * dbf allocation is 1 to 1 accompanied by
     * gsu_scalar_ext allocation. */

    dbf_carrier = (struct gsu_scalar_ext *) zalloc(sizeof(struct gsu_scalar_ext));
    dbf_carrier->std = gdbm_gsu_ext.std;
    dbf_carrier->dbf = dbf;
    tied_param->u.hash->tmpdata = (void *)dbf_carrier;

    /* Fill also file path field */
    if (*resource_name != '/') {
        /* Code copied from check_autoload() */
        resource_name = zhtricat(metafy(zgetcwd(), -1, META_HEAPDUP), "/", resource_name);
        resource_name = xsymlink(resource_name, 1);
    }
    dbf_carrier->dbfile_path = ztrdup(resource_name);

    addmodulefd(gdbm_fdesc(dbf), FDT_INTERNAL);
    append_tied_name(pmname);

    return 0;
}

/**/
static int
bin_zuntie(char *nam, char **args, Options ops, UNUSED(int func))
{
    Param pm;
    char *pmname;
    int ret = 0;

    for (pmname = *args; *args++; pmname = *args) {
	pm = (Param) paramtab->getnode(paramtab, pmname);
	if(!pm) {
	    zwarnnam(nam, "cannot untie %s", pmname);
	    ret = 1;
	    continue;
	}
	if (pm->gsu.h != &gdbm_hash_gsu) {
	    zwarnnam(nam, "not a tied gdbm hash: %s", pmname);
	    ret = 1;
	    continue;
	}

	queue_signals();
	if (OPT_ISSET(ops,'u')) {
            pm->node.flags &= ~PM_READONLY;
        }
	if (unsetparam_pm(pm, 0, 1)) {
	    /* assume already reported */
	    ret = 1;
	}
	unqueue_signals();
    }

    return ret;
}

/**/
static int
bin_zgdbmpath(char *nam, char **args, Options ops, UNUSED(int func))
{
    Param pm;
    char *pmname;

    pmname = *args;

    if (!pmname) {
        zwarnnam(nam, "parameter name (whose path is to be written to $REPLY) is required");
        return 1;
    }

    pm = (Param) paramtab->getnode(paramtab, pmname);
    if(!pm) {
        zwarnnam(nam, "no such parameter: %s", pmname);
        return 1;
    }

    if (pm->gsu.h != &gdbm_hash_gsu) {
        zwarnnam(nam, "not a tied gdbm parameter: %s", pmname);
        return 1;
    }

    /* Paranoia, it *will* be always set */
    if (((struct gsu_scalar_ext *)pm->u.hash->tmpdata)->dbfile_path) {
        setsparam("REPLY", ztrdup(((struct gsu_scalar_ext *)pm->u.hash->tmpdata)->dbfile_path));
    } else {
        setsparam("REPLY", ztrdup(""));
    }

    return 0;
}

/*
 * The param is actual param in hash – always, because
 * getgdbmnode creates every new key seen. However, it
 * might be not PM_UPTODATE - which means that database
 * wasn't yet queried.
 *
 * It will be left in this state if database doesn't
 * contain such key. That might be a drawback, maybe
 * setting to empty value has sense.
 */

/**/
static char *
gdbmgetfn(Param pm)
{
    datum key, content;
    int ret, umlen;
    char *umkey;
    GDBM_FILE dbf;

    /* Key already retrieved? There is no sense of asking the
     * database again, because:
     * - there can be only multiple readers
     * - so, no writer + reader use is allowed
     *
     * Thus:
     * - if we are writers, we for sure have newest copy of data
     * - if we are readers, we for sure have newest copy of data
     */
    if ( pm->node.flags & PM_UPTODATE ) {
        return pm->u.str ? pm->u.str : "";
    }

    /* Unmetafy key. GDBM fits nice into this
     * process, as it uses length of data */
    umlen = 0;
    umkey = unmetafy_zalloc(pm->node.nam,&umlen);

    key.dptr = umkey;
    key.dsize = umlen;

    dbf = ((struct gsu_scalar_ext *)pm->gsu.s)->dbf;

    if((ret = gdbm_exists(dbf, key))) {
        /* We have data – store it, return it */
        pm->node.flags |= PM_UPTODATE;

        content = gdbm_fetch(dbf, key);

        /* Ensure there's no leak */
        if (pm->u.str) {
            zsfree(pm->u.str);
            pm->u.str = NULL;
        }

        /* Metafy returned data. All fits - metafy
         * can obtain data length to avoid using \0 */
        pm->u.str = metafy(content.dptr, content.dsize, META_DUP);
        /* gdbm allocates with malloc */
        free(content.dptr);

        /* Free key */
        zfree(umkey, umlen+1);

        /* Can return pointer, correctly saved inside hash */
        return pm->u.str;
    }

    /* Free key */
    zfree(umkey, umlen+1);

    return "";
}

/**/
static void
gdbmsetfn(Param pm, char *val)
{
    datum key, content;
    GDBM_FILE dbf;

    /* Set is done on parameter and on database.
     * See the allowed workers / readers comment
     * at gdbmgetfn() */

    /* Parameter */
    if (pm->u.str) {
        zsfree(pm->u.str);
        pm->u.str = NULL;
        pm->node.flags &= ~(PM_UPTODATE);
    }

    if (val) {
        pm->u.str = val;
        pm->node.flags |= PM_UPTODATE;
    }

    /* Database */
    dbf = ((struct gsu_scalar_ext *)pm->gsu.s)->dbf;
    if (dbf && no_database_action == 0) {
        int umlen = 0;
        char *umkey = unmetafy_zalloc(pm->node.nam,&umlen);

        key.dptr = umkey;
        key.dsize = umlen;

        if (val) {
            /* Unmetafy with exact zalloc size */
            char *umval = unmetafy_zalloc(val,&umlen);

            /* Store */
            content.dptr = umval;
            content.dsize = umlen;
            (void)gdbm_store(dbf, key, content, GDBM_REPLACE);

            /* Free */
            zfree(umval, umlen+1);
        } else {
            (void)gdbm_delete(dbf, key);
        }

        /* Free key */
        zfree(umkey, key.dsize+1);
    }
}

/**/
static void
gdbmunsetfn(Param pm, UNUSED(int um))
{
    /* Set with NULL */
    gdbmsetfn(pm, NULL);
}

/**/
static HashNode
getgdbmnode(HashTable ht, const char *name)
{
    HashNode hn = gethashnode2( ht, name );
    Param val_pm = (Param) hn;

    /* Entry for key doesn't exist? Create it now,
     * it will be interfacing between the database
     * and Zsh - through special gdbm_gsu. So, any
     * seen key results in new interfacing parameter.
     *
     * Previous code was returning heap arena Param
     * that wasn't actually added to the hash. It was
     * plainly name / database-key holder. Here we
     * add the Param to its hash, it is not PM_UPTODATE.
     * It will be loaded from database *and filled*
     * or left in that state if the database doesn't
     * contain it.
     *
     * No heap arena memory is used, memory usage is
     * now limited - by number of distinct keys seen,
     * not by number of key *uses*.
     * */

    if ( ! val_pm ) {
        val_pm = (Param) zshcalloc( sizeof (*val_pm) );
        val_pm->node.flags = PM_SCALAR | PM_HASHELEM; /* no PM_UPTODATE */
        val_pm->gsu.s = (GsuScalar) ht->tmpdata;
        ht->addnode( ht, ztrdup( name ), val_pm ); /* sets pm->node.nam */
    }

    return (HashNode) val_pm;
}

/**/
static void
scangdbmkeys(HashTable ht, ScanFunc func, int flags)
{
    datum key, prev_key;
    GDBM_FILE dbf = ((struct gsu_scalar_ext *)ht->tmpdata)->dbf;

    /* Iterate keys adding them to hash, so
     * we have Param to use in `func` */
    key = gdbm_firstkey(dbf);

    while(key.dptr) {
        /* This returns database-interfacing Param,
         * it will return u.str or first fetch data
         * if not PM_UPTODATE (newly created) */
        char *zkey = metafy(key.dptr, key.dsize, META_DUP);
        HashNode hn = getgdbmnode(ht, zkey);
        zsfree( zkey );

	func(hn, flags);

        /* Iterate - no problem as interfacing Param
         * will do at most only fetches, not stores */
        prev_key = key;
        key = gdbm_nextkey(dbf, key);
        free(prev_key.dptr);
    }

}

/*
 * Replace database with new hash
 */

/**/
static void
gdbmhashsetfn(Param pm, HashTable ht)
{
    int i;
    HashNode hn;
    GDBM_FILE dbf;
    datum key, content;

    if (!pm->u.hash || pm->u.hash == ht)
	return;

    if (!(dbf = ((struct gsu_scalar_ext *)pm->u.hash->tmpdata)->dbf))
	return;

    key = gdbm_firstkey(dbf);
    while (key.dptr) {
	queue_signals();
	(void)gdbm_delete(dbf, key);
	free(key.dptr);
	unqueue_signals();
	key = gdbm_firstkey(dbf);
    }

    /* Just deleted everything, clean up if no new data.
     * User can also reorganize via gdbmtool. */
    if (!ht || ht->hsize == 0) {
        (void)gdbm_reorganize(dbf);
    }

    no_database_action = 1;
    emptyhashtable(pm->u.hash);
    no_database_action = 0;

    if (!ht)
	return;

     /* Put new strings into database, waiting
      * for their interfacing-Params to be created */

    for (i = 0; i < ht->hsize; i++) {
	for (hn = ht->nodes[i]; hn; hn = hn->next) {
	    struct value v;
            int umlen = 0;
            char *umkey, *umval;

	    v.isarr = v.flags = v.start = 0;
	    v.end = -1;
	    v.arr = NULL;
	    v.pm = (Param) hn;

            /* Unmetafy key */
            umkey = unmetafy_zalloc(v.pm->node.nam,&umlen);

	    key.dptr = umkey;
	    key.dsize = umlen;

	    queue_signals();

            /* Unmetafy */
            umval = unmetafy_zalloc(getstrvalue(&v),&umlen);

            /* Store */
	    content.dptr = umval;
	    content.dsize = umlen;
	    (void)gdbm_store(dbf, key, content, GDBM_REPLACE);

            /* Free - unmetafy_zalloc allocates
             * exact required space + 1 null byte */
            zfree(umval, content.dsize+1);
            zfree(umkey, key.dsize+1);

	    unqueue_signals();
	}
    }
    /* We reuse our hash, the input is to be deleted */
    deleteparamtable(ht);
}

/**/
static void
gdbmuntie(Param pm)
{
    GDBM_FILE dbf = ((struct gsu_scalar_ext *)pm->u.hash->tmpdata)->dbf;
    HashTable ht = pm->u.hash;

    if (dbf) { /* paranoia */
	fdtable[gdbm_fdesc(dbf)] = FDT_UNUSED;
        gdbm_close(dbf);

        /* Let hash fields know there's no backend */
        ((struct gsu_scalar_ext *)ht->tmpdata)->dbf = NULL;

        /* Remove from list of tied parameters */
        remove_tied_name(pm->node.nam);
    }

    /* for completeness ... createspecialhash() should have an inverse */
    ht->getnode = ht->getnode2 = gethashnode2;
    ht->scantab = NULL;

    pm->node.flags &= ~(PM_SPECIAL|PM_READONLY);
    pm->gsu.h = &stdhash_gsu;
}

/**/
static void
gdbmhashunsetfn(Param pm, UNUSED(int exp))
{
    struct gsu_scalar_ext * gsu_ext;

    gdbmuntie(pm);

    /* Remember custom GSU structure assigned to
     * u.hash->tmpdata before hash gets deleted */
    gsu_ext = pm->u.hash->tmpdata;

    /* Uses normal unsetter (because gdbmuntie is called above).
     * Will delete all owned field-parameters and also hashtable. */
    pm->gsu.h->setfn(pm, NULL);

    /* Don't need custom GSU structure with its
     * GDBM_FILE pointer anymore */
    zsfree( gsu_ext->dbfile_path );
    zfree( gsu_ext, sizeof(struct gsu_scalar_ext));

    pm->node.flags |= PM_UNSET;
}

static struct features module_features = {
    bintab, sizeof(bintab)/sizeof(*bintab),
    NULL, 0,
    NULL, 0,
    patab, sizeof(patab)/sizeof(*patab),
    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))
{
    zgdbm_tied = zshcalloc((1) * sizeof(char *));
    return 0;
}

/**/
int
cleanup_(Module m)
{
    /* This frees `zgdbm_tied` */
    return setfeatureenables(m, &module_features, NULL);
}

/**/
int
finish_(UNUSED(Module m))
{
    return 0;
}

/*********************
 * Utility functions *
 *********************/

static Param createhash( char *name, int flags ) {
    Param pm;
    HashTable ht;

    pm = createparam(name, flags | PM_SPECIAL | PM_HASHED);
    if (!pm) {
        return NULL;
    }

    if (pm->old)
	pm->level = locallevel;

    /* This creates standard hash. */
    ht = pm->u.hash = newparamtable(17, name);
    if (!pm->u.hash) {
        paramtab->removenode(paramtab, name);
        paramtab->freenode(&pm->node);
        zwarnnam(name, "out of memory when allocating hash");
        return NULL;
    }

    /* Does free Param (unsetfn is called) */
    ht->freenode = myfreeparamnode;

    /* These provide special features */
    ht->getnode = ht->getnode2 = getgdbmnode;
    ht->scantab = scangdbmkeys;

    return pm;
}

/*
 * Adds parameter name to `zgdbm_tied`
 */

static int append_tied_name( const char *name ) {
    int old_len = arrlen(zgdbm_tied);
    char **new_zgdbm_tied = zshcalloc( (old_len+2) * sizeof(char *));

    /* Copy */
    char **p = zgdbm_tied;
    char **dst = new_zgdbm_tied;
    while (*p) {
        *dst++ = *p++;
    }

    /* Append new one */
    *dst = ztrdup(name);

    /* Substitute, free old one */
    zfree(zgdbm_tied, sizeof(char *) * (old_len + 1));
    zgdbm_tied = new_zgdbm_tied;

    return 0;
}

/*
 * Removes parameter name from `zgdbm_tied`
 */

static int remove_tied_name( const char *name ) {
    int old_len = arrlen(zgdbm_tied);
    int new_len;

    /* Two stage, to always have arrlen() == zfree-size - 1.
     * Could do allocation and revert when `not found`, but
     * what would be better about that. */

    /* Find one to remove */
    char **p = zgdbm_tied;
    while (*p) {
        if (0==strcmp(name,*p)) {
            break;
        }
        p++;
    }

    if (*p)
	zsfree(*p);

    /* Copy x+1 to x */
    while (*p) {
        *p=*(p+1);
        p++;
    }

    /* Second stage. Size changed? Only old_size-1
     * change is possible, but.. paranoia way */
    new_len = arrlen(zgdbm_tied);
    if (new_len != old_len) {
        char **dst;
        char **new_zgdbm_tied = zshcalloc((new_len+1) * sizeof(char *));

        /* Copy */
        p = zgdbm_tied;
        dst = new_zgdbm_tied;
        while (*p) {
            *dst++ = *p++;
        }
        *dst = NULL;

        /* Substitute, free old one */
        zfree(zgdbm_tied, sizeof(char *) * (old_len + 1));
        zgdbm_tied = new_zgdbm_tied;
    }

    return 0;
}

/*
 * Unmetafy that:
 * - duplicates buffer to work on it,
 * - does zalloc of exact size for the new string,
 * - restores work buffer to original content, to restore strlen
 */
static char *
unmetafy_zalloc(const char *to_copy, int *new_len) {
    char *work, *to_return;
    int my_new_len = 0;

    work = ztrdup(to_copy);
    work = unmetafy(work,&my_new_len);

    if (new_len)
        *new_len = my_new_len;

    /* This string can be correctly zsfree()-d */
    to_return = (char *) zalloc((my_new_len+1)*sizeof(char));
    memcpy(to_return, work, sizeof(char)*my_new_len); /* memcpy handles $'\0' */
    to_return[my_new_len]='\0';

    /* Restore original strlen and correctly free */
    strcpy(work, to_copy);
    zsfree(work);

    return to_return;
}

static void
myfreeparamnode(HashNode hn)
{
    Param pm = (Param) hn;

    /* Upstream: The second argument of unsetfn() is used by modules to
     * differentiate "exp"licit unset from implicit unset, as when
     * a parameter is going out of scope.  It's not clear which
     * of these applies here, but passing 1 has always worked.
     */

    /* if (delunset) */
    pm->gsu.s->unsetfn(pm, 1);

    zsfree(pm->node.nam);
    /* If this variable was tied by the user, ename was ztrdup'd */
    if (!(pm->node.flags & PM_SPECIAL) && pm->ename) {
        zsfree(pm->ename);
        pm->ename = NULL;
    }
    zfree(pm, sizeof(struct param));
}

#else
# error no gdbm
#endif /* have gdbm */