xref: /xsrc/external/mit/xorg-server/dist/Xext/xf86bigfont.c

/*
 * BIGFONT extension for sharing font metrics between clients (if possible)
 * and for transmitting font metrics to clients in a compressed form.
 *
 * Copyright (c) 1999-2000  Bruno Haible
 * Copyright (c) 1999-2000  The XFree86 Project, Inc.
 */

/* THIS IS NOT AN X CONSORTIUM STANDARD */

/*
 * Big fonts suffer from the following: All clients that have opened a
 * font can access the complete glyph metrics array (the XFontStruct member
 * `per_char') directly, without going through a macro. Moreover these
 * glyph metrics are ink metrics, i.e. are not redundant even for a
 * fixed-width font. For a Unicode font, the size of this array is 768 KB.
 *
 * Problems: 1. It eats a lot of memory in each client. 2. All this glyph
 * metrics data is piped through the socket when the font is opened.
 *
 * This extension addresses these two problems for local clients, by using
 * shared memory. It also addresses the second problem for non-local clients,
 * by compressing the data before transmit by a factor of nearly 6.
 *
 * If you use this extension, your OS ought to nicely support shared memory.
 * This means: Shared memory should be swappable to the swap, and the limits
 * should be high enough (SHMMNI at least 64, SHMMAX at least 768 KB,
 * SHMALL at least 48 MB). It is a plus if your OS allows shmat() calls
 * on segments that have already been marked "removed", because it permits
 * these segments to be cleaned up by the OS if the X server is killed with
 * signal SIGKILL.
 *
 * This extension is transparently exploited by Xlib (functions XQueryFont,
 * XLoadQueryFont).
 */

#ifdef HAVE_DIX_CONFIG_H
#include <dix-config.h>
#endif

#include <sys/types.h>
#ifdef HAS_SHM
#if defined(linux) && (!defined(__GNU_LIBRARY__) || __GNU_LIBRARY__ < 2)
/* libc4 does not define __GNU_LIBRARY__, libc5 defines __GNU_LIBRARY__ as 1 */
/* Linux libc4 and libc5 only (because glibc doesn't include kernel headers):
   Linux 2.0.x and 2.2.x define SHMLBA as PAGE_SIZE, but forget to define
   PAGE_SIZE. It is defined in <asm/page.h>. */
#include <asm/page.h>
#endif
#ifdef SVR4
#include <sys/sysmacros.h>
#endif
#if defined(__CYGWIN__)
#include <sys/param.h>
#include <sys/sysmacros.h>
#endif
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <errno.h>
#endif

#include <X11/X.h>
#include <X11/Xproto.h>
#include "misc.h"
#include "os.h"
#include "dixstruct.h"
#include "gcstruct.h"
#include "dixfontstr.h"
#include "extnsionst.h"
#include "protocol-versions.h"

#include <X11/extensions/xf86bigfproto.h>
#include "xf86bigfontsrv.h"

static void XF86BigfontResetProc(
    ExtensionEntry *	/* extEntry */
    );


#ifdef HAS_SHM

/* A random signature, transmitted to the clients so they can verify that the
   shared memory segment they are attaching to was really established by the
   X server they are talking to. */
static CARD32 signature;

/* Index for additional information stored in a FontRec's devPrivates array. */
static int FontShmdescIndex;

static unsigned int pagesize;

static Bool badSysCall = FALSE;

#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || defined(__CYGWIN__) || defined(__DragonFly__)

#include <sys/signal.h>

static void
SigSysHandler(
     int signo)
{
    badSysCall = TRUE;
}

static Bool
CheckForShmSyscall(void)
{
    void (*oldHandler)(int);
    int shmid = -1;

    /* If no SHM support in the kernel, the bad syscall will generate SIGSYS */
    oldHandler = signal(SIGSYS, SigSysHandler);

    badSysCall = FALSE;
    shmid = shmget(IPC_PRIVATE, 4096, IPC_CREAT);
    if (shmid != -1)
    {
        /* Successful allocation - clean up */
	shmctl(shmid, IPC_RMID, NULL);
    }
    else
    {
        /* Allocation failed */
        badSysCall = TRUE;
    }
    signal(SIGSYS, oldHandler);
    return !badSysCall;
}

#define MUST_CHECK_FOR_SHM_SYSCALL

#endif

#endif

/* ========== Management of shared memory segments ========== */

#ifdef HAS_SHM

#ifdef __linux__
/* On Linux, shared memory marked as "removed" can still be attached.
   Nice feature, because the kernel will automatically free the associated
   storage when the server and all clients are gone. */
#define EARLY_REMOVE
#endif

typedef struct _ShmDesc {
    struct _ShmDesc *next;
    struct _ShmDesc **prev;
    int shmid;
    char *attach_addr;
} ShmDescRec, *ShmDescPtr;

static ShmDescPtr ShmList = (ShmDescPtr) NULL;

static ShmDescPtr
shmalloc(
    unsigned int size)
{
    ShmDescPtr pDesc;
    int shmid;
    char *addr;

#ifdef MUST_CHECK_FOR_SHM_SYSCALL
    if (pagesize == 0)
	return (ShmDescPtr) NULL;
#endif

    /* On some older Linux systems, the number of shared memory segments
       system-wide is 127. In Linux 2.4, it is 4095.
       Therefore there is a tradeoff to be made between allocating a
       shared memory segment on one hand, and allocating memory and piping
       the glyph metrics on the other hand. If the glyph metrics size is
       small, we prefer the traditional way. */
    if (size < 3500)
	return (ShmDescPtr) NULL;

    pDesc = malloc(sizeof(ShmDescRec));
    if (!pDesc)
	return (ShmDescPtr) NULL;

    size = (size + pagesize-1) & -pagesize;
    shmid = shmget(IPC_PRIVATE, size, S_IWUSR | S_IRUSR | S_IRGRP | S_IROTH);
    if (shmid == -1) {
	ErrorF(XF86BIGFONTNAME " extension: shmget() failed, size = %u, %s\n",
	       size, strerror(errno));
	free(pDesc);
	return (ShmDescPtr) NULL;
    }

    if ((addr = shmat(shmid, 0, 0)) == (char *)-1) {
	ErrorF(XF86BIGFONTNAME " extension: shmat() failed, size = %u, %s\n",
	       size, strerror(errno));
	shmctl(shmid, IPC_RMID, (void *) 0);
	free(pDesc);
	return (ShmDescPtr) NULL;
    }

#ifdef EARLY_REMOVE
    shmctl(shmid, IPC_RMID, (void *) 0);
#endif

    pDesc->shmid = shmid;
    pDesc->attach_addr = addr;
    if (ShmList) ShmList->prev = &pDesc->next;
    pDesc->next = ShmList;
    pDesc->prev = &ShmList;
    ShmList = pDesc;

    return pDesc;
}

static void
shmdealloc(
    ShmDescPtr pDesc)
{
#ifndef EARLY_REMOVE
    shmctl(pDesc->shmid, IPC_RMID, (void *) 0);
#endif
    shmdt(pDesc->attach_addr);

    if (pDesc->next) pDesc->next->prev = pDesc->prev;
    *pDesc->prev = pDesc->next;
    free(pDesc);
}

#endif

/* Called when a font is closed. */
void
XF86BigfontFreeFontShm(
    FontPtr pFont)
{
#ifdef HAS_SHM
    ShmDescPtr pDesc;

    /* If during shutdown of the server, XF86BigfontCleanup() has already
     * called shmdealloc() for all segments, we don't need to do it here.
     */
    if (!ShmList)
	return;

    pDesc = (ShmDescPtr) FontGetPrivate(pFont, FontShmdescIndex);
    if (pDesc)
	shmdealloc(pDesc);
#endif
}

/* Called upon fatal signal. */
void
XF86BigfontCleanup(void)
{
#ifdef HAS_SHM
    while (ShmList)
	shmdealloc(ShmList);
#endif
}

/* Called when a server generation dies. */
static void
XF86BigfontResetProc(
    ExtensionEntry* extEntry)
{
    /* This function is normally called from CloseDownExtensions(), called
     * from main(). It will be followed by a call to FreeAllResources(),
     * which will call XF86BigfontFreeFontShm() for each font. Thus it
     * appears that we do not need to do anything in this function. --
     * But I prefer to write robust code, and not keep shared memory lying
     * around when it's not needed any more. (Someone might close down the
     * extension without calling FreeAllResources()...)
     */
    XF86BigfontCleanup();
}


/* ========== Handling of extension specific requests ========== */

static int
ProcXF86BigfontQueryVersion(
    ClientPtr client)
{
    xXF86BigfontQueryVersionReply reply;

    REQUEST_SIZE_MATCH(xXF86BigfontQueryVersionReq);
    reply.type = X_Reply;
    reply.length = 0;
    reply.sequenceNumber = client->sequence;
    reply.majorVersion = SERVER_XF86BIGFONT_MAJOR_VERSION;
    reply.minorVersion = SERVER_XF86BIGFONT_MINOR_VERSION;
    reply.uid = geteuid();
    reply.gid = getegid();
#ifdef HAS_SHM
    reply.signature = signature;
#else
    reply.signature = 0; /* This is redundant. Avoids uninitialized memory. */
#endif
    reply.capabilities =
#ifdef HAS_SHM
	(LocalClient(client) && !client->swapped ? XF86Bigfont_CAP_LocalShm : 0)
#else
	0
#endif
	; /* may add more bits here in future versions */
    if (client->swapped) {
	char tmp;
	swaps(&reply.sequenceNumber, tmp);
	swapl(&reply.length, tmp);
	swaps(&reply.majorVersion, tmp);
	swaps(&reply.minorVersion, tmp);
	swapl(&reply.uid, tmp);
	swapl(&reply.gid, tmp);
	swapl(&reply.signature, tmp);
    }
    WriteToClient(client,
		  sizeof(xXF86BigfontQueryVersionReply), (char *)&reply);
    return Success;
}

static void
swapCharInfo(
    xCharInfo *pCI)
{
    char tmp;

    swaps(&pCI->leftSideBearing, tmp);
    swaps(&pCI->rightSideBearing, tmp);
    swaps(&pCI->characterWidth, tmp);
    swaps(&pCI->ascent, tmp);
    swaps(&pCI->descent, tmp);
    swaps(&pCI->attributes, tmp);
}

/* static CARD32 hashCI (xCharInfo *p); */
#define hashCI(p) \
	(CARD32)(((p->leftSideBearing << 27) + (p->leftSideBearing >> 5) + \
	          (p->rightSideBearing << 23) + (p->rightSideBearing >> 9) + \
	          (p->characterWidth << 16) + \
	          (p->ascent << 11) + (p->descent << 6)) ^ p->attributes)

static int
ProcXF86BigfontQueryFont(
    ClientPtr client)
{
    FontPtr pFont;
    REQUEST(xXF86BigfontQueryFontReq);
    CARD32 stuff_flags;
    xCharInfo* pmax;
    xCharInfo* pmin;
    int nCharInfos;
    int shmid;
#ifdef HAS_SHM
    ShmDescPtr pDesc = NULL;
#else
#define pDesc 0
#endif
    xCharInfo* pCI;
    CARD16* pIndex2UniqIndex;
    CARD16* pUniqIndex2Index;
    CARD32 nUniqCharInfos;

#if 0
    REQUEST_SIZE_MATCH(xXF86BigfontQueryFontReq);
#else
    switch (client->req_len) {
	case 2: /* client with version 1.0 libX11 */
	    stuff_flags = (LocalClient(client) && !client->swapped ? XF86Bigfont_FLAGS_Shm : 0);
	    break;
	case 3: /* client with version 1.1 libX11 */
	    stuff_flags = stuff->flags;
	    break;
	default:
	    return BadLength;
    }
#endif
    if (dixLookupFontable(&pFont, stuff->id, client, DixGetAttrAccess) != Success)
	return BadFont;    /* procotol spec says only error is BadFont */

    pmax = FONTINKMAX(pFont);
    pmin = FONTINKMIN(pFont);
    nCharInfos =
       (pmax->rightSideBearing == pmin->rightSideBearing
        && pmax->leftSideBearing == pmin->leftSideBearing
        && pmax->descent == pmin->descent
        && pmax->ascent == pmin->ascent
        && pmax->characterWidth == pmin->characterWidth)
       ? 0 : N2dChars(pFont);
    shmid = -1;
    pCI = NULL;
    pIndex2UniqIndex = NULL;
    pUniqIndex2Index = NULL;
    nUniqCharInfos = 0;

    if (nCharInfos > 0) {
#ifdef HAS_SHM
	if (!badSysCall)
	    pDesc = (ShmDescPtr) FontGetPrivate(pFont, FontShmdescIndex);
	if (pDesc) {
	    pCI = (xCharInfo *) pDesc->attach_addr;
	    if (stuff_flags & XF86Bigfont_FLAGS_Shm)
		shmid = pDesc->shmid;
	} else {
	    if (stuff_flags & XF86Bigfont_FLAGS_Shm && !badSysCall)
		pDesc = shmalloc(nCharInfos * sizeof(xCharInfo)
				 + sizeof(CARD32));
	    if (pDesc) {
		pCI = (xCharInfo *) pDesc->attach_addr;
		shmid = pDesc->shmid;
	    } else {
#endif
		pCI = malloc(nCharInfos * sizeof(xCharInfo));
		if (!pCI)
		    return BadAlloc;
#ifdef HAS_SHM
	    }
#endif
	    /* Fill nCharInfos starting at pCI. */
	    {
		xCharInfo* prCI = pCI;
		int ninfos = 0;
		int ncols = pFont->info.lastCol - pFont->info.firstCol + 1;
		int row;
		for (row = pFont->info.firstRow;
		     row <= pFont->info.lastRow && ninfos < nCharInfos;
		     row++) {
		    unsigned char chars[512];
		    xCharInfo* tmpCharInfos[256];
		    unsigned long count;
		    int col;
		    unsigned long i;
		    i = 0;
		    for (col = pFont->info.firstCol;
			 col <= pFont->info.lastCol;
			 col++) {
			chars[i++] = row;
			chars[i++] = col;
		    }
		    (*pFont->get_metrics) (pFont, ncols, chars, TwoD16Bit,
					   &count, tmpCharInfos);
		    for (i = 0; i < count && ninfos < nCharInfos; i++) {
			*prCI++ = *tmpCharInfos[i];
			ninfos++;
		    }
		}
	    }
#ifdef HAS_SHM
	    if (pDesc && !badSysCall) {
		*(CARD32 *)(pCI + nCharInfos) = signature;
		if (!FontSetPrivate(pFont, FontShmdescIndex, pDesc)) {
		    shmdealloc(pDesc);
		    return BadAlloc;
		}
	    }
	}
#endif
	if (shmid == -1) {
	    /* Cannot use shared memory, so remove-duplicates the xCharInfos
	       using a temporary hash table. */
	    /* Note that CARD16 is suitable as index type, because
	       nCharInfos <= 0x10000. */
	    CARD32 hashModulus;
	    CARD16* pHash2UniqIndex;
	    CARD16* pUniqIndex2NextUniqIndex;
	    CARD32 NextIndex;
	    CARD32 NextUniqIndex;
	    CARD16* tmp;
	    CARD32 i, j;

	    hashModulus = 67;
	    if (hashModulus > nCharInfos+1)
		hashModulus = nCharInfos+1;

	    tmp = malloc((4*nCharInfos+1) * sizeof(CARD16));
	    if (!tmp) {
		if (!pDesc) free(pCI);
		return BadAlloc;
	    }
	    pIndex2UniqIndex = tmp;
		/* nCharInfos elements */
	    pUniqIndex2Index = tmp + nCharInfos;
		/* max. nCharInfos elements */
	    pUniqIndex2NextUniqIndex = tmp + 2*nCharInfos;
		/* max. nCharInfos elements */
	    pHash2UniqIndex = tmp + 3*nCharInfos;
		/* hashModulus (<= nCharInfos+1) elements */

	    /* Note that we can use 0xffff as end-of-list indicator, because
	       even if nCharInfos = 0x10000, 0xffff can not occur as valid
	       entry before the last element has been inserted. And once the
	       last element has been inserted, we don't need the hash table
	       any more. */
	    for (j = 0; j < hashModulus; j++)
		pHash2UniqIndex[j] = (CARD16)(-1);

	    NextUniqIndex = 0;
	    for (NextIndex = 0; NextIndex < nCharInfos; NextIndex++) {
		xCharInfo* p = &pCI[NextIndex];
		CARD32 hashCode = hashCI(p) % hashModulus;
		for (i = pHash2UniqIndex[hashCode];
		     i != (CARD16)(-1);
		     i = pUniqIndex2NextUniqIndex[i]) {
		    j = pUniqIndex2Index[i];
		    if (pCI[j].leftSideBearing == p->leftSideBearing
			&& pCI[j].rightSideBearing == p->rightSideBearing
			&& pCI[j].characterWidth == p->characterWidth
			&& pCI[j].ascent == p->ascent
			&& pCI[j].descent == p->descent
			&& pCI[j].attributes == p->attributes)
			break;
		}
		if (i != (CARD16)(-1)) {
		    /* Found *p at Index j, UniqIndex i */
		    pIndex2UniqIndex[NextIndex] = i;
		} else {
		    /* Allocate a new entry in the Uniq table */
		    if (hashModulus <= 2*NextUniqIndex
			&& hashModulus < nCharInfos+1) {
			/* Time to increate hash table size */
			hashModulus = 2*hashModulus+1;
			if (hashModulus > nCharInfos+1)
			    hashModulus = nCharInfos+1;
			for (j = 0; j < hashModulus; j++)
			    pHash2UniqIndex[j] = (CARD16)(-1);
			for (i = 0; i < NextUniqIndex; i++)
			    pUniqIndex2NextUniqIndex[i] = (CARD16)(-1);
			for (i = 0; i < NextUniqIndex; i++) {
			    j = pUniqIndex2Index[i];
			    p = &pCI[j];
			    hashCode = hashCI(p) % hashModulus;
			    pUniqIndex2NextUniqIndex[i] = pHash2UniqIndex[hashCode];
			    pHash2UniqIndex[hashCode] = i;
			}
			p = &pCI[NextIndex];
			hashCode = hashCI(p) % hashModulus;
		    }
		    i = NextUniqIndex++;
		    pUniqIndex2NextUniqIndex[i] = pHash2UniqIndex[hashCode];
		    pHash2UniqIndex[hashCode] = i;
		    pUniqIndex2Index[i] = NextIndex;
		    pIndex2UniqIndex[NextIndex] = i;
		}
	    }
	    nUniqCharInfos = NextUniqIndex;
	    /* fprintf(stderr, "font metrics: nCharInfos = %d, nUniqCharInfos = %d, hashModulus = %d\n", nCharInfos, nUniqCharInfos, hashModulus); */
	}
    }

    {
	int nfontprops = pFont->info.nprops;
	int rlength =
	   sizeof(xXF86BigfontQueryFontReply)
	   + nfontprops * sizeof(xFontProp)
	   + (nCharInfos > 0 && shmid == -1
	      ? nUniqCharInfos * sizeof(xCharInfo)
	        + (nCharInfos+1)/2 * 2 * sizeof(CARD16)
	      : 0);
	xXF86BigfontQueryFontReply* reply = malloc(rlength);
	char* p;
	if (!reply) {
	    if (nCharInfos > 0) {
		if (shmid == -1) free(pIndex2UniqIndex);
		if (!pDesc) free(pCI);
	    }
	    return BadAlloc;
	}
	reply->type = X_Reply;
	reply->length = bytes_to_int32(rlength - sizeof(xGenericReply));
	reply->sequenceNumber = client->sequence;
	reply->minBounds = pFont->info.ink_minbounds;
	reply->maxBounds = pFont->info.ink_maxbounds;
	reply->minCharOrByte2 = pFont->info.firstCol;
	reply->maxCharOrByte2 = pFont->info.lastCol;
	reply->defaultChar = pFont->info.defaultCh;
	reply->nFontProps = pFont->info.nprops;
	reply->drawDirection = pFont->info.drawDirection;
	reply->minByte1 = pFont->info.firstRow;
	reply->maxByte1 = pFont->info.lastRow;
	reply->allCharsExist = pFont->info.allExist;
	reply->fontAscent = pFont->info.fontAscent;
	reply->fontDescent = pFont->info.fontDescent;
	reply->nCharInfos = nCharInfos;
        reply->nUniqCharInfos = nUniqCharInfos;
	reply->shmid = shmid;
	reply->shmsegoffset = 0;
	if (client->swapped) {
	    char tmp;
	    swaps(&reply->sequenceNumber, tmp);
	    swapl(&reply->length, tmp);
	    swapCharInfo(&reply->minBounds);
	    swapCharInfo(&reply->maxBounds);
	    swaps(&reply->minCharOrByte2, tmp);
	    swaps(&reply->maxCharOrByte2, tmp);
	    swaps(&reply->defaultChar, tmp);
	    swaps(&reply->nFontProps, tmp);
	    swaps(&reply->fontAscent, tmp);
	    swaps(&reply->fontDescent, tmp);
	    swapl(&reply->nCharInfos, tmp);
	    swapl(&reply->nUniqCharInfos, tmp);
	    swapl(&reply->shmid, tmp);
	    swapl(&reply->shmsegoffset, tmp);
	}
	p = (char*) &reply[1];
	{
	    FontPropPtr pFP;
	    xFontProp* prFP;
	    int i;
	    for (i = 0, pFP = pFont->info.props, prFP = (xFontProp *) p;
		 i < nfontprops;
		 i++, pFP++, prFP++) {
		prFP->name = pFP->name;
		prFP->value = pFP->value;
		if (client->swapped) {
		    char tmp;
		    swapl(&prFP->name, tmp);
		    swapl(&prFP->value, tmp);
		}
	    }
	    p = (char*) prFP;
	}
	if (nCharInfos > 0 && shmid == -1) {
	    xCharInfo* pci;
	    CARD16* ps;
	    int i, j;
	    pci = (xCharInfo*) p;
	    for (i = 0; i < nUniqCharInfos; i++, pci++) {
		*pci = pCI[pUniqIndex2Index[i]];
		if (client->swapped)
		    swapCharInfo(pci);
	    }
	    ps = (CARD16*) pci;
	    for (j = 0; j < nCharInfos; j++, ps++) {
		*ps = pIndex2UniqIndex[j];
		if (client->swapped) {
		    char tmp;
		    swaps(ps, tmp);
		}
	    }
	}
	WriteToClient(client, rlength, (char *)reply);
	free(reply);
	if (nCharInfos > 0) {
	    if (shmid == -1) free(pIndex2UniqIndex);
	    if (!pDesc) free(pCI);
	}
	return Success;
    }
}

static int
ProcXF86BigfontDispatch(
    ClientPtr client)
{
    REQUEST(xReq);

    switch (stuff->data) {
	case X_XF86BigfontQueryVersion:
	    return ProcXF86BigfontQueryVersion(client);
	case X_XF86BigfontQueryFont:
	    return ProcXF86BigfontQueryFont(client);
	default:
	    return BadRequest;
    }
}

static int
SProcXF86BigfontQueryVersion(
    ClientPtr client)
{
    REQUEST(xXF86BigfontQueryVersionReq);
    char tmp;

    swaps(&stuff->length, tmp);
    return ProcXF86BigfontQueryVersion(client);
}

static int
SProcXF86BigfontQueryFont(
    ClientPtr client)
{
    REQUEST(xXF86BigfontQueryFontReq);
    char tmp;

    swaps(&stuff->length, tmp);
    REQUEST_SIZE_MATCH(xXF86BigfontQueryFontReq);
    swapl(&stuff->id, tmp);
    return ProcXF86BigfontQueryFont(client);
}

static int
SProcXF86BigfontDispatch(
    ClientPtr client)
{
    REQUEST(xReq);

    switch (stuff->data) {
	case X_XF86BigfontQueryVersion:
	    return SProcXF86BigfontQueryVersion(client);
	case X_XF86BigfontQueryFont:
	    return SProcXF86BigfontQueryFont(client);
	default:
	    return BadRequest;
    }
}

void
XFree86BigfontExtensionInit(void)
{
    if (AddExtension(XF86BIGFONTNAME,
		     XF86BigfontNumberEvents,
		     XF86BigfontNumberErrors,
		     ProcXF86BigfontDispatch,
		     SProcXF86BigfontDispatch,
		     XF86BigfontResetProc,
		     StandardMinorOpcode)) {
#ifdef HAS_SHM
#ifdef MUST_CHECK_FOR_SHM_SYSCALL
	/*
	 * Note: Local-clients will not be optimized without shared memory
	 * support. Remote-client optimization does not depend on shared
	 * memory support.  Thus, the extension is still registered even
	 * when shared memory support is not functional.
	 */
	if (!CheckForShmSyscall()) {
	    ErrorF(XF86BIGFONTNAME " extension local-client optimization disabled due to lack of shared memory support in the kernel\n");
	    return;
	}
#endif

	srand((unsigned int) time(NULL));
	signature = ((unsigned int) (65536.0/(RAND_MAX+1.0) * rand()) << 16)
	           + (unsigned int) (65536.0/(RAND_MAX+1.0) * rand());
	/* fprintf(stderr, "signature = 0x%08X\n", signature); */

	FontShmdescIndex = AllocateFontPrivateIndex();

#if !defined(CSRG_BASED) && !defined(__CYGWIN__)
	pagesize = SHMLBA;
#else
# ifdef _SC_PAGESIZE
	pagesize = sysconf(_SC_PAGESIZE);
# else
	pagesize = getpagesize();
# endif
#endif
#endif
    }
}