File: CDB_File.xs

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libcdb-file-perl 0.99-1
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/*

Most of this is reasonably straightforward.  The complications arise
when we are "iterating" over the CDB file, that is to say, using `keys'
or `values' or `each' to retrieve all the data in the file in order.
This interface stores extra data to allow us to track iterations: end
is a pointer to the end of data in the CDB file, and also a flag which
indicates whether we are iterating or not (note that the end of data
occurs at a position >= 2048); curkey is a copy of the current key;
curpos is the file offset of curkey; and fetch_advance is 0 for

    FIRSTKEY, fetch, NEXTKEY, fetch, NEXTKEY, fetch, ...

but 1 for

    FIRSTKEY, NEXTKEY, NEXTKEY, ..., fetch, fetch, fetch, ...

Don't tell the OO Police, but there are actually two different objects
called CDB_File.  One is created by TIEHASH, and accessed by the usual
tied hash methods (FETCH, FIRSTKEY, etc.).  The other is created by new,
and accessed by insert and finish.

In both cases, the object is a blessed reference to a scalar.  The
scalar contains either a struct cdbobj or a struct cdbmakeobj.

It gets a little messy in DESTROY: since this method will automatically
be called for both sorts of object, it distinguishes them by their
different sizes.

*/

#ifdef __cplusplus
extern "C" {
#endif

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"
#include "ppport.h"

#include <sys/stat.h>
#include <sys/types.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

#ifdef WIN32
#define fsync _commit
#endif

#ifdef HASMMAP
#include <sys/mman.h>
#endif

/* We need to whistle up an error number for a file that is not a CDB
file.  The BSDish EFTYPE probably gives the most useful error message;
failing that we'll settle for the Single Unix Specification v2 EPROTO;
and finally the rather inappropriate, but universally(?) implemented,
EINVAL. */
#ifdef EFTYPE
#else
#ifdef EPROTO
#define EFTYPE EPROTO
#else
#define EFTYPE EINVAL
#endif
#endif

#ifdef __cplusplus
}
#endif

struct t_cdb {
	PerlIO *fh;   /* */

#ifdef HASMMAP
	char *map;
#endif

	U32 end;    /* If non zero, the file offset of the first byte of hash tables. */
	SV *curkey; /* While iterating: a copy of the current key; */
	U32 curpos; /*                  the file offset of the current record. */
	int fetch_advance; /* the kludge */
	U32 size; /* initialized if map is nonzero */
	U32 loop; /* number of hash slots searched under this key */
	U32 khash; /* initialized if loop is nonzero */
	U32 kpos; /* initialized if loop is nonzero */
	U32 hpos; /* initialized if loop is nonzero */
	U32 hslots; /* initialized if loop is nonzero */
	U32 dpos; /* initialized if cdb_findnext() returns 1 */
	U32 dlen; /* initialized if cdb_findnext() returns 1 */
} ;

typedef struct t_cdb  cdb;

#define CDB_HPLIST 1000

struct cdb_hp { U32 h; U32 p; } ;

struct cdb_hplist {
	struct cdb_hp hp[CDB_HPLIST];
	struct cdb_hplist *next;
	int num;
} ;

struct t_cdb_make {
	PerlIO *f;            /* Handle of file being created. */
	char *fn;             /* Final name of file. */
	char *fntemp;         /* Temporary name of file. */
	char final[2048];
	char bspace[1024];
	U32 count[256];
	U32 start[256];
	struct cdb_hplist *head;
	struct cdb_hp *split; /* includes space for hash */
	struct cdb_hp *hash;
	U32 numentries;
	U32 pos;
	int fd;
} ;

typedef struct t_cdb_make cdb_make;

static void writeerror() { croak("Write to CDB_File failed: %s", Strerror(errno)); }

static void readerror() { croak("Read of CDB_File failed: %s", Strerror(errno)); }

static void seekerror() { croak("Seek in CDB_File failed: %s", Strerror(errno)); }

static void nomem() { croak("Out of memory!"); }

static int cdb_make_start(cdb_make *c) {
	c->head = 0;
	c->split = 0;
	c->hash = 0;
	c->numentries = 0;
	c->pos = sizeof c->final;
	return PerlIO_seek(c->f, c->pos, SEEK_SET);
}

static int posplus(cdb_make *c, U32 len) {
	U32 newpos = c->pos + len;
	if (newpos < len) { errno = ENOMEM; return -1; }
	c->pos = newpos;
	return 0;
}

static int cdb_make_addend(cdb_make *c, unsigned int keylen, unsigned int datalen, U32 h) {
	struct cdb_hplist *head;

	head = c->head;
	if (!head || (head->num >= CDB_HPLIST)) {
		New(0xCDB, head, 1, struct cdb_hplist);
		head->num = 0;
		head->next = c->head;
		c->head = head;
	}
	head->hp[head->num].h = h;
	head->hp[head->num].p = c->pos;
	++head->num;
	++c->numentries;
	if (posplus(c, 8) == -1) return -1;
	if (posplus(c, keylen) == -1) return -1;
	if (posplus(c, datalen) == -1) return -1;
	return 0;
}

#define CDB_HASHSTART 5381

static U32 cdb_hashadd(U32 h, unsigned char c) {
	h += (h << 5);
	return h ^ c;
}

static U32 cdb_hash(char *buf, unsigned int len) {
	U32 h;

	h = CDB_HASHSTART;
	while (len) {
		h = cdb_hashadd(h,*buf++);
		--len;
	}
	return h;
}

static void uint32_pack(char s[4], U32 u) {
	s[0] = u & 255;
	u >>= 8;
	s[1] = u & 255;
	u >>= 8;
	s[2] = u & 255;
	s[3] = u >> 8;
}

static void uint32_unpack(char s[4], U32 *u) {
	U32 result;

	result = (unsigned char) s[3];
	result <<= 8;
	result += (unsigned char) s[2];
	result <<= 8;
	result += (unsigned char) s[1];
	result <<= 8;
	result += (unsigned char) s[0];

	*u = result;
}

static void cdb_findstart(cdb *c) {
	c->loop = 0;
}

static int cdb_read(cdb *c, char *buf, unsigned int len, U32 pos) {

#ifdef HASMMAP
	if (c->map) {
		if ((pos > c->size) || (c->size - pos < len)) {
			errno = EFTYPE;
			return -1;
		}
		memcpy(buf, c->map + pos, len);
		return 0;
	}
#endif

	if (PerlIO_seek(c->fh, pos, SEEK_SET) == -1) return -1;
	while (len > 0) {
		int r;
		do
			r = PerlIO_read(c->fh, buf, len);
		while ((r == -1) && (errno == EINTR));
		if (r == -1) return -1;
		if (r == 0) {
			errno = EFTYPE;
			return -1;
		}
		buf += r;
		len -= r;
	}
	return 0;
}

static int match(cdb *c,char *key,unsigned int len, U32 pos) {
	char buf[32];
	int n;

	while (len > 0) {
		n = sizeof buf;
		if (n > len) n = len;
		if (cdb_read(c, buf, n, pos) == -1) return -1;
		if (memcmp(buf, key, n)) return 0;
		pos += n;
		key += n;
		len -= n;
	}
	return 1;
}

static int cdb_findnext(cdb *c,char *key,unsigned int len) {
	char buf[8];
	U32 pos;
	U32 u;

  /* Matt: reset these so if a search fails they are zero'd */
  c->dpos = 0;
  c->dlen = 0;
  if (!c->loop) {
    u = cdb_hash(key,len);
    if (cdb_read(c,buf,8,(u << 3) & 2047) == -1) return -1;
    uint32_unpack(buf + 4,&c->hslots);
    if (!c->hslots) return 0;
    uint32_unpack(buf,&c->hpos);
    c->khash = u;
    u >>= 8;
    u %= c->hslots;
    u <<= 3;
    c->kpos = c->hpos + u;
  }

  while (c->loop < c->hslots) {
    if (cdb_read(c,buf,8,c->kpos) == -1) return -1;
    uint32_unpack(buf + 4,&pos);
    if (!pos) return 0;
    c->loop += 1;
    c->kpos += 8;
    if (c->kpos == c->hpos + (c->hslots << 3)) c->kpos = c->hpos;
    uint32_unpack(buf,&u);
    if (u == c->khash) {
      if (cdb_read(c,buf,8,pos) == -1) return -1;
      uint32_unpack(buf,&u);
      if (u == len)
	switch(match(c,key,len,pos + 8)) {
	  case -1:
	    return -1;
	  case 1:
	    uint32_unpack(buf + 4,&c->dlen);
	    c->dpos = pos + 8 + len;
	    return 1;
	}
    }
  }

  return 0;
}

static int cdb_find(cdb *c, char *key, unsigned int len) {
  cdb_findstart(c);
  return cdb_findnext(c,key,len);
}

static void iter_start(cdb *c) {
	char buf[4];

	c->curpos = 2048;
	if (cdb_read(c, buf, 4, 0) == -1) readerror();
	uint32_unpack(buf, &c->end);
	c->curkey = NEWSV(0xcdb, 1);
	c->fetch_advance = 0;
}

static int iter_key(cdb *c) {
	char buf[8];
	U32 klen;

	if (c->curpos < c->end) {
		if (cdb_read(c, buf, 8, c->curpos) == -1) readerror();
		uint32_unpack(buf, &klen);
		(void)SvPOK_only(c->curkey);
		SvGROW(c->curkey, klen); SvCUR_set(c->curkey, klen);
		if (cdb_read(c, SvPVX(c->curkey), klen, c->curpos + 8) == -1) readerror();
		return 1;
	}
	return 0;
}

static void iter_advance(cdb *c) {
	char buf[8];
	U32 klen, dlen;

	if (cdb_read(c, buf, 8, c->curpos) == -1) readerror();
	uint32_unpack(buf, &klen);
	uint32_unpack(buf + 4, &dlen);
	c->curpos += 8 + klen + dlen;
}

static void iter_end(cdb *c) {
	if (c->end != 0) {
		c->end = 0;
		SvREFCNT_dec(c->curkey);
	}
}

#define cdb_datapos(c) ((c)->dpos)
#define cdb_datalen(c) ((c)->dlen)

typedef PerlIO * InputStream;

MODULE = CDB_File		PACKAGE = CDB_File	PREFIX = cdb_

PROTOTYPES: DISABLED

 # Some accessor methods.

 # WARNING: I don't really understand enough about Perl's guts (file
 # handles / globs, etc.) to write this code.  I think this is right, and
 # it seems to work, but input from anybody with a deeper
 # understanding would be most welcome.

 # Additional: fixed by someone with a deeper understanding ;-) (Matt Sergeant)

InputStream
cdb_handle(this)
	cdb *		this
	
	PREINIT:
        GV *gv;
        char *packname;

	CODE:
        /* here we dup the filehandle, because perl space will try and close
           it when it goes out of scope */
        RETVAL = PerlIO_fdopen(PerlIO_fileno(this->fh), "r");
        OUTPUT:
            RETVAL
        
U32
cdb_datalen(db)
	cdb *		db

	CODE:
	RETVAL = cdb_datalen(db);

	OUTPUT:
	RETVAL

U32
cdb_datapos(db)
	cdb *		db

	CODE:
	RETVAL = cdb_datapos(db);

	OUTPUT:
	RETVAL

cdb *
cdb_TIEHASH(CLASS, filename)
	char *		CLASS
	char *		filename

        PREINIT:
	PerlIO *f;
	IO *io;
	SV *cdbp;

	CODE:
        New(0, RETVAL, 1, cdb);
	RETVAL->fh = f = PerlIO_open(filename, "rb");
	if (!f) XSRETURN_NO;
	RETVAL->end = 0;
#ifdef HASMMAP
	{
		struct stat st;
		int fd = PerlIO_fileno(f);

		RETVAL->map = 0;
		if (fstat(fd, &st) == 0) {
			if (st.st_size <= 0xffffffff) {
				char *x;

				x = mmap(0, st.st_size, PROT_READ, MAP_SHARED, fd, 0);
				if (x != (char *)-1) {
					RETVAL->size = st.st_size;
					RETVAL->map = x;
				}
			}
		}
	}
#endif
	OUTPUT:
		RETVAL

SV *
cdb_FETCH(this, k)
	cdb *		this
	SV *		k

	PREINIT:
	PerlIO *f;
	char buf[8];
	int found;
	off_t pos;
	STRLEN klen, x;
	U32 klen0;
	char *kp;

	CODE:
	if (!SvOK(k)) {
		XSRETURN_UNDEF;
	}
	kp = SvPV(k, klen);
	if (this->end && sv_eq(this->curkey, k)) {
		if (cdb_read(this, buf, 8, this->curpos) == -1) readerror();
		uint32_unpack(buf + 4, &this->dlen);
		this->dpos = this->curpos + 8 + klen;
		if (this->fetch_advance) {
			iter_advance(this);
			if (!iter_key(this)) iter_end(this);
		}
		found = 1;
	} else {
		cdb_findstart(this);
		found = cdb_findnext(this, kp, klen);
		if ((found != 0) && (found != 1)) readerror();
	}
	ST(0) = sv_newmortal();
	if (found) {
		U32 dlen;
		SvUPGRADE(ST(0), SVt_PV);
		dlen = cdb_datalen(this);

		(void)SvPOK_only(ST(0));
		SvGROW(ST(0), dlen + 1); SvCUR_set(ST(0),  dlen);
		if (cdb_read(this, SvPVX(ST(0)), dlen, cdb_datapos(this)) == -1) readerror();
		SvPV(ST(0), PL_na)[dlen] = '\0';
	}


HV *
cdb_fetch_all(this)
	cdb *		this

	PREINIT:
	U32 dlen;
	SV *keyvalue;
  int found;
	STRLEN klen;
	char *kp;

	CODE:
  RETVAL = newHV();
	sv_2mortal((SV *)RETVAL);
  iter_start(this);
	while(iter_key(this)) {
    cdb_findstart(this);
	  kp = SvPV(this->curkey, klen);
		found = cdb_findnext(this, kp, klen);
		if ((found != 0) && (found != 1)) readerror();

		keyvalue = newSVpvn("", 0);
		dlen = cdb_datalen(this);
		SvGROW(keyvalue, dlen + 1); SvCUR_set(keyvalue,  dlen);
		if (cdb_read(this, SvPVX(keyvalue), dlen, cdb_datapos(this)) == -1) readerror();
		SvPV(keyvalue, PL_na)[dlen] = '\0';
		if (! hv_store_ent(RETVAL, this->curkey, keyvalue, 0)) {
        SvREFCNT_dec(keyvalue);
    };
		iter_advance(this);
	}
  iter_end(this);

	OUTPUT:
		RETVAL


AV *
cdb_multi_get(this, k)
	cdb *		this
	SV *		k
	
	PREINIT:
	PerlIO *f;
	char buf[8];
	int found;
	off_t pos;
	STRLEN klen;
	U32 dlen, klen0;
	char *kp;
	SV *x;

	CODE:
	if (!SvOK(k)) {
		XSRETURN_UNDEF;
	}
	cdb_findstart(this);
	RETVAL = newAV();
	sv_2mortal((SV *)RETVAL);
	kp = SvPV(k, klen);
	for (;;) {
		found = cdb_findnext(this, kp, klen);
		if ((found != 0) && (found != 1)) readerror();
		if (!found) break;
		x = newSVpvn("", 0);
		dlen = cdb_datalen(this);
		SvGROW(x, dlen + 1); SvCUR_set(x,  dlen);
		if (cdb_read(this, SvPVX(x), dlen, cdb_datapos(this)) == -1) readerror();
		SvPV(x, PL_na)[dlen] = '\0';
		av_push(RETVAL, x);
	}

	OUTPUT:
		RETVAL

int
cdb_EXISTS(this, k)
	cdb *		this
	SV *		k

        PREINIT:
	STRLEN klen;
	char *kp;

	CODE:
	if (!SvOK(k)) {
		XSRETURN_NO;
	}
	kp = SvPV(k, klen);
	RETVAL = cdb_find(this, kp, klen);
	if (RETVAL != 0 && RETVAL != 1) readerror();

	OUTPUT:
		RETVAL

void
cdb_DESTROY(db)
        SV *    db

        PREINIT:
	cdb *		this;
        IO *io;

        CODE:
        if (sv_isobject(db) && (SvTYPE(SvRV(db)) == SVt_PVMG) ) {
          this = (cdb*)SvIV(SvRV(db));

          iter_end(this);
#ifdef HASMMAP
          if (this->map) {
            munmap(this->map, this->size);
            this->map = 0;
          }
#endif
          PerlIO_close(this->fh); /* close() on O_RDONLY cannot fail */
          Safefree(this);
        }

SV *
cdb_FIRSTKEY(this)
	cdb *		this

        PREINIT:
	char buf[8];
	U32 klen;

	CODE:
	iter_start(this);
	if (iter_key(this))
		ST(0) = sv_mortalcopy(this->curkey);
	else
		XSRETURN_UNDEF; /* empty database */

SV *
cdb_NEXTKEY(this, k)
	cdb *		this
	SV *		k

        PREINIT:
	char buf[8], *kp;
	int found;
	off_t pos;
	U32 dlen, klen0;
	STRLEN klen1;

	CODE:
	if (!SvOK(k)) {
		XSRETURN_UNDEF;
    }
	/* Sometimes NEXTKEY gets called before FIRSTKEY if the hash
	 * gets re-tied so we call iter_start() anyway here */
	if (this->end == 0 || !sv_eq(this->curkey, k))
	    iter_start(this);
	iter_advance(this);
	if (iter_key(this))
		ST(0) = sv_mortalcopy(this->curkey);
	else {
		iter_start(this);
		(void)iter_key(this); /* prepare curkey for FETCH */
		this->fetch_advance = 1;
		XSRETURN_UNDEF;
	}

cdb_make *
cdb_new(CLASS, fn, fntemp)
	char *		CLASS
	char *		fn
	char *		fntemp

        PREINIT:
	cdb_make *cdbmake;
	int i;

	CODE:
        New(0, cdbmake, 1, cdb_make);
	cdbmake->f = PerlIO_open(fntemp, "wb");
	if (!cdbmake->f) XSRETURN_UNDEF;

	if (cdb_make_start(cdbmake) < 0) XSRETURN_UNDEF;

	/* Oh, for referential transparency. */
	New(0, cdbmake->fn, strlen(fn) + 1, char);
	New(0, cdbmake->fntemp, strlen(fntemp) + 1, char);
	strncpy(cdbmake->fn, fn, strlen(fn) + 1);
	strncpy(cdbmake->fntemp, fntemp, strlen(fntemp) + 1);

        CLASS = "CDB_File::Maker"; /* OK, so this is a hack */

        RETVAL = cdbmake;
        
	OUTPUT:
		RETVAL

MODULE = CDB_File	PACKAGE = CDB_File::Maker	PREFIX = cdbmaker_

void
cdbmaker_DESTROY(sv)
        SV *   sv
        
        PREINIT:
        cdb_make *  this;
        
        CODE:
        if (sv_isobject(sv) && (SvTYPE(SvRV(sv)) == SVt_PVMG) ) {
          this = (cdb_make*)SvIV(SvRV(sv));
          
          Safefree(this);
        }

void
cdbmaker_insert(this, ...)
	cdb_make *		this

        PREINIT:
	char *kp, *vp, packbuf[8];
	int c, i, x;
	STRLEN klen, vlen;
	U32 h;
	SV *k;
	SV *v;

	PPCODE:
	for (x = 1; x < items; x += 2) {
		k = ST(x);
		v = ST(x+1);
		kp = SvPV(k, klen); vp = SvPV(v, vlen);
		uint32_pack(packbuf, klen);
		uint32_pack(packbuf + 4, vlen);
	
		if (PerlIO_write(this->f, packbuf, 8) < 8) writeerror();
	
		h = cdb_hash(kp, klen);
		if (PerlIO_write(this->f, kp, klen) < klen) writeerror();
		if (PerlIO_write(this->f, vp, vlen) < vlen) writeerror();
	
		if (cdb_make_addend(this, klen, vlen, h) == -1) nomem();
	}

int
cdbmaker_finish(this)
	cdb_make *		this

        PREINIT:
	char buf[8];
	int i;
	U32 len, u;
	U32 count, memsize, where;
	struct cdb_hplist *x, *prev;
	struct cdb_hp *hp;

	CODE:
	for (i = 0; i < 256; ++i)
		this->count[i] = 0;

	for (x = this->head; x; x = x->next) {
		i = x->num;
		while (i--)
			++this->count[255 & x->hp[i].h];
	}

	memsize = 1;
	for (i = 0; i < 256; ++i) {
		u = this->count[i] * 2;
		if (u > memsize)
			memsize = u;
	}

	memsize += this->numentries; /* no overflow possible up to now */
	u = (U32) 0 - (U32) 1;
	u /= sizeof(struct cdb_hp);
	if (memsize > u) { errno = ENOMEM; XSRETURN_UNDEF; }

	New(0xCDB, this->split, memsize, struct cdb_hp);

	this->hash = this->split + this->numentries;

	u = 0;
	for (i = 0; i < 256; ++i) {
		u += this->count[i]; /* bounded by numentries, so no overflow */
		this->start[i] = u;
	}

	prev = 0;
	for (x = this->head; x; x = x->next) {
		i = x->num;
		while (i--)
			this->split[--this->start[255 & x->hp[i].h]] = x->hp[i];
		if (prev) Safefree(prev);
		prev = x;
	}
	if (prev) Safefree(prev);

	for (i = 0; i < 256; ++i) {
		count = this->count[i];

		len = count + count; /* no overflow possible */
		uint32_pack(this->final + 8 * i, this->pos);
		uint32_pack(this->final + 8 * i + 4, len);

		for (u = 0; u < len; ++u)
			this->hash[u].h = this->hash[u].p = 0;

		hp = this->split + this->start[i];
		for (u = 0; u < count; ++u) {
			where = (hp->h >> 8) % len;
			while (this->hash[where].p)
				if (++where == len)
					where = 0;
			this->hash[where] = *hp++;
		}

		for (u = 0; u < len; ++u) {
			uint32_pack(buf, this->hash[u].h);
			uint32_pack(buf + 4, this->hash[u].p);
			if (PerlIO_write(this->f, buf, 8) == -1) XSRETURN_UNDEF;
			if (posplus(this, 8) == -1) XSRETURN_UNDEF;
		}
	}

	Safefree(this->split);

	if (PerlIO_flush(this->f) == EOF) writeerror();
	PerlIO_rewind(this->f);

	if (PerlIO_write(this->f, this->final, sizeof this->final) < sizeof this->final) writeerror();
	if (PerlIO_flush(this->f) == EOF) writeerror();

	if (fsync(PerlIO_fileno(this->f)) == -1) XSRETURN_NO;
	if (PerlIO_close(this->f) == EOF) XSRETURN_NO;

	if (rename(this->fntemp, this->fn)) XSRETURN_NO;
	
	Safefree(this->fn);
	Safefree(this->fntemp);

	RETVAL = 1;

	OUTPUT:
		RETVAL