--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nspr/pr/src/io/prlayer.c	Mon Jul 28 10:47:06 2014 +0200
@@ -0,0 +1,752 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+** File:        prlayer.c
+** Description: Routines for handling pushable protocol modules on sockets.
+*/
+
+#include "primpl.h"
+#include "prerror.h"
+#include "prmem.h"
+#include "prlock.h"
+#include "prlog.h"
+#include "prio.h"
+
+#include <string.h> /* for memset() */
+static PRStatus _PR_DestroyIOLayer(PRFileDesc *stack);
+
+void PR_CALLBACK pl_FDDestructor(PRFileDesc *fd)
+{
+    PR_ASSERT(fd != NULL);
+    if (NULL != fd->lower) fd->lower->higher = fd->higher;
+    if (NULL != fd->higher) fd->higher->lower = fd->lower;
+    PR_DELETE(fd);
+}
+
+/*
+** Default methods that just call down to the next fd.
+*/
+static PRStatus PR_CALLBACK pl_TopClose (PRFileDesc *fd)
+{
+    PRFileDesc *top, *lower;
+	PRStatus rv;
+
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+    PR_ASSERT(fd->secret == NULL);
+    PR_ASSERT(fd->methods->file_type == PR_DESC_LAYERED);
+
+	if (PR_IO_LAYER_HEAD == fd->identity) {
+		/*
+		 * new style stack; close all the layers, before deleting the
+		 * stack head
+		 */
+		rv = fd->lower->methods->close(fd->lower);
+		_PR_DestroyIOLayer(fd);
+		return rv;
+	} else if ((fd->higher) && (PR_IO_LAYER_HEAD == fd->higher->identity)) {
+		/*
+		 * lower layers of new style stack
+		 */
+		lower = fd->lower;
+		/*
+		 * pop and cleanup current layer
+		 */
+    	top = PR_PopIOLayer(fd->higher, PR_TOP_IO_LAYER);
+		top->dtor(top);
+		/*
+		 * then call lower layer
+		 */
+		return (lower->methods->close(lower));
+	} else {
+		/* old style stack */
+    	top = PR_PopIOLayer(fd, PR_TOP_IO_LAYER);
+		top->dtor(top);
+		return (fd->methods->close)(fd);
+	}
+}
+
+static PRInt32 PR_CALLBACK pl_DefRead (PRFileDesc *fd, void *buf, PRInt32 amount)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->read)(fd->lower, buf, amount);
+}
+
+static PRInt32 PR_CALLBACK pl_DefWrite (
+    PRFileDesc *fd, const void *buf, PRInt32 amount)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->write)(fd->lower, buf, amount);
+}
+
+static PRInt32 PR_CALLBACK pl_DefAvailable (PRFileDesc *fd)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->available)(fd->lower);
+}
+
+static PRInt64 PR_CALLBACK pl_DefAvailable64 (PRFileDesc *fd)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->available64)(fd->lower);
+}
+
+static PRStatus PR_CALLBACK pl_DefFsync (PRFileDesc *fd)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->fsync)(fd->lower);
+}
+
+static PRInt32 PR_CALLBACK pl_DefSeek (
+    PRFileDesc *fd, PRInt32 offset, PRSeekWhence how)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->seek)(fd->lower, offset, how);
+}
+
+static PRInt64 PR_CALLBACK pl_DefSeek64 (
+    PRFileDesc *fd, PRInt64 offset, PRSeekWhence how)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->seek64)(fd->lower, offset, how);
+}
+
+static PRStatus PR_CALLBACK pl_DefFileInfo (PRFileDesc *fd, PRFileInfo *info)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->fileInfo)(fd->lower, info);
+}
+
+static PRStatus PR_CALLBACK pl_DefFileInfo64 (PRFileDesc *fd, PRFileInfo64 *info)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->fileInfo64)(fd->lower, info);
+}
+
+static PRInt32 PR_CALLBACK pl_DefWritev (PRFileDesc *fd, const PRIOVec *iov,
+    PRInt32 size, PRIntervalTime timeout)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->writev)(fd->lower, iov, size, timeout);
+}
+
+static PRStatus PR_CALLBACK pl_DefConnect (
+    PRFileDesc *fd, const PRNetAddr *addr, PRIntervalTime timeout)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->connect)(fd->lower, addr, timeout);
+}
+
+static PRStatus PR_CALLBACK pl_DefConnectcontinue (
+    PRFileDesc *fd, PRInt16 out_flags)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->connectcontinue)(fd->lower, out_flags);
+}
+
+static PRFileDesc* PR_CALLBACK pl_TopAccept (
+    PRFileDesc *fd, PRNetAddr *addr, PRIntervalTime timeout)
+{
+    PRStatus rv;
+    PRFileDesc *newfd, *layer = fd;
+    PRFileDesc *newstack;
+	PRBool newstyle_stack = PR_FALSE;
+
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+	/* test for new style stack */
+	while (NULL != layer->higher)
+		layer = layer->higher;
+	newstyle_stack = (PR_IO_LAYER_HEAD == layer->identity) ? PR_TRUE : PR_FALSE;
+    newstack = PR_NEW(PRFileDesc);
+    if (NULL == newstack)
+    {
+        PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
+        return NULL;
+    }
+    *newstack = *fd;  /* make a copy of the accepting layer */
+
+    newfd = (fd->lower->methods->accept)(fd->lower, addr, timeout);
+    if (NULL == newfd)
+    {
+        PR_DELETE(newstack);
+        return NULL;
+    }
+
+    if (newstyle_stack) {
+		newstack->lower = newfd;
+		newfd->higher = newstack;
+		return newstack;
+	} else {
+		/* this PR_PushIOLayer call cannot fail */
+		rv = PR_PushIOLayer(newfd, PR_TOP_IO_LAYER, newstack);
+		PR_ASSERT(PR_SUCCESS == rv);
+    	return newfd;  /* that's it */
+	}
+}
+
+static PRStatus PR_CALLBACK pl_DefBind (PRFileDesc *fd, const PRNetAddr *addr)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->bind)(fd->lower, addr);
+}
+
+static PRStatus PR_CALLBACK pl_DefListen (PRFileDesc *fd, PRIntn backlog)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->listen)(fd->lower, backlog);
+}
+
+static PRStatus PR_CALLBACK pl_DefShutdown (PRFileDesc *fd, PRIntn how)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->shutdown)(fd->lower, how);
+}
+
+static PRInt32 PR_CALLBACK pl_DefRecv (
+    PRFileDesc *fd, void *buf, PRInt32 amount,
+    PRIntn flags, PRIntervalTime timeout)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->recv)(
+        fd->lower, buf, amount, flags, timeout);
+}
+
+static PRInt32 PR_CALLBACK pl_DefSend (
+    PRFileDesc *fd, const void *buf,
+    PRInt32 amount, PRIntn flags, PRIntervalTime timeout)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->send)(fd->lower, buf, amount, flags, timeout);
+}
+
+static PRInt32 PR_CALLBACK pl_DefRecvfrom (
+    PRFileDesc *fd, void *buf, PRInt32 amount,
+    PRIntn flags, PRNetAddr *addr, PRIntervalTime timeout)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->recvfrom)(
+        fd->lower, buf, amount, flags, addr, timeout);
+}
+
+static PRInt32 PR_CALLBACK pl_DefSendto (
+    PRFileDesc *fd, const void *buf, PRInt32 amount, PRIntn flags,
+    const PRNetAddr *addr, PRIntervalTime timeout)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->sendto)(
+        fd->lower, buf, amount, flags, addr, timeout);
+}
+
+static PRInt16 PR_CALLBACK pl_DefPoll (
+    PRFileDesc *fd, PRInt16 in_flags, PRInt16 *out_flags)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->poll)(fd->lower, in_flags, out_flags);
+}
+
+static PRInt32 PR_CALLBACK pl_DefAcceptread (
+    PRFileDesc *sd, PRFileDesc **nd, PRNetAddr **raddr, void *buf,
+    PRInt32 amount, PRIntervalTime t)
+{
+    PRInt32 nbytes;
+    PRStatus rv;
+    PRFileDesc *newstack;
+    PRFileDesc *layer = sd;
+	PRBool newstyle_stack = PR_FALSE;
+
+    PR_ASSERT(sd != NULL);
+    PR_ASSERT(sd->lower != NULL);
+
+	/* test for new style stack */
+	while (NULL != layer->higher)
+		layer = layer->higher;
+	newstyle_stack = (PR_IO_LAYER_HEAD == layer->identity) ? PR_TRUE : PR_FALSE;
+    newstack = PR_NEW(PRFileDesc);
+    if (NULL == newstack)
+    {
+        PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
+        return -1;
+    }
+    *newstack = *sd;  /* make a copy of the accepting layer */
+
+    nbytes = sd->lower->methods->acceptread(
+        sd->lower, nd, raddr, buf, amount, t);
+    if (-1 == nbytes)
+    {
+        PR_DELETE(newstack);
+        return nbytes;
+    }
+    if (newstyle_stack) {
+		newstack->lower = *nd;
+		(*nd)->higher = newstack;
+		*nd = newstack;
+		return nbytes;
+	} else {
+		/* this PR_PushIOLayer call cannot fail */
+		rv = PR_PushIOLayer(*nd, PR_TOP_IO_LAYER, newstack);
+		PR_ASSERT(PR_SUCCESS == rv);
+		return nbytes;
+	}
+}
+
+static PRInt32 PR_CALLBACK pl_DefTransmitfile (
+    PRFileDesc *sd, PRFileDesc *fd, const void *headers, PRInt32 hlen,
+    PRTransmitFileFlags flags, PRIntervalTime t)
+{
+    PR_ASSERT(sd != NULL);
+    PR_ASSERT(sd->lower != NULL);
+
+    return sd->lower->methods->transmitfile(
+        sd->lower, fd, headers, hlen, flags, t);
+}
+
+static PRStatus PR_CALLBACK pl_DefGetsockname (PRFileDesc *fd, PRNetAddr *addr)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->getsockname)(fd->lower, addr);
+}
+
+static PRStatus PR_CALLBACK pl_DefGetpeername (PRFileDesc *fd, PRNetAddr *addr)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->getpeername)(fd->lower, addr);
+}
+
+static PRStatus PR_CALLBACK pl_DefGetsocketoption (
+    PRFileDesc *fd, PRSocketOptionData *data)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->getsocketoption)(fd->lower, data);
+}
+
+static PRStatus PR_CALLBACK pl_DefSetsocketoption (
+    PRFileDesc *fd, const PRSocketOptionData *data)
+{
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(fd->lower != NULL);
+
+    return (fd->lower->methods->setsocketoption)(fd->lower, data);
+}
+
+static PRInt32 PR_CALLBACK pl_DefSendfile (
+	PRFileDesc *sd, PRSendFileData *sfd,
+	PRTransmitFileFlags flags, PRIntervalTime timeout)
+{
+    PR_ASSERT(sd != NULL);
+    PR_ASSERT(sd->lower != NULL);
+
+    return sd->lower->methods->sendfile(
+        sd->lower, sfd, flags, timeout);
+}
+
+/* Methods for the top of the stack.  Just call down to the next fd. */
+static PRIOMethods pl_methods = {
+    PR_DESC_LAYERED,
+    pl_TopClose,
+    pl_DefRead,
+    pl_DefWrite,
+    pl_DefAvailable,
+    pl_DefAvailable64,
+    pl_DefFsync,
+    pl_DefSeek,
+    pl_DefSeek64,
+    pl_DefFileInfo,
+    pl_DefFileInfo64,
+    pl_DefWritev,
+    pl_DefConnect,
+    pl_TopAccept,
+    pl_DefBind,
+    pl_DefListen,
+    pl_DefShutdown,
+    pl_DefRecv,
+    pl_DefSend,
+    pl_DefRecvfrom,
+    pl_DefSendto,
+    pl_DefPoll,
+    pl_DefAcceptread,
+    pl_DefTransmitfile,
+    pl_DefGetsockname,
+    pl_DefGetpeername,
+    (PRReservedFN)_PR_InvalidInt,
+    (PRReservedFN)_PR_InvalidInt,
+    pl_DefGetsocketoption,
+    pl_DefSetsocketoption,
+    pl_DefSendfile,
+    pl_DefConnectcontinue,
+    (PRReservedFN)_PR_InvalidInt,
+    (PRReservedFN)_PR_InvalidInt,
+    (PRReservedFN)_PR_InvalidInt,
+    (PRReservedFN)_PR_InvalidInt
+};
+
+PR_IMPLEMENT(const PRIOMethods*) PR_GetDefaultIOMethods(void)
+{
+    return &pl_methods;
+}  /* PR_GetDefaultIOMethods */
+
+PR_IMPLEMENT(PRFileDesc*) PR_CreateIOLayerStub(
+    PRDescIdentity ident, const PRIOMethods *methods)
+{
+    PRFileDesc *fd = NULL;
+    PR_ASSERT((PR_NSPR_IO_LAYER != ident) && (PR_TOP_IO_LAYER != ident));
+    if ((PR_NSPR_IO_LAYER == ident) || (PR_TOP_IO_LAYER == ident))
+        PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
+    else
+    {
+        fd = PR_NEWZAP(PRFileDesc);
+        if (NULL == fd)
+            PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
+        else
+        {
+            fd->methods = methods;
+            fd->dtor = pl_FDDestructor;
+            fd->identity = ident;
+        }
+    }
+    return fd;
+}  /* PR_CreateIOLayerStub */
+
+/*
+ * PR_CreateIOLayer
+ *		Create a new style stack, where the stack top is a dummy header.
+ *		Unlike the old style stacks, the contents of the stack head
+ *		are not modified when a layer is pushed onto or popped from a new
+ *		style stack.
+ */
+
+PR_IMPLEMENT(PRFileDesc*) PR_CreateIOLayer(PRFileDesc *top)
+{
+    PRFileDesc *fd = NULL;
+
+	fd = PR_NEWZAP(PRFileDesc);
+	if (NULL == fd)
+		PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
+	else
+	{
+		fd->methods = &pl_methods;
+		fd->dtor = pl_FDDestructor;
+		fd->identity = PR_IO_LAYER_HEAD;
+		fd->higher = NULL;
+		fd->lower = top;
+		top->higher = fd;
+		top->lower = NULL;
+	}
+    return fd;
+}  /* PR_CreateIOLayer */
+
+/*
+ * _PR_DestroyIOLayer
+ *		Delete the stack head of a new style stack.
+ */
+
+static PRStatus _PR_DestroyIOLayer(PRFileDesc *stack)
+{
+    if (NULL == stack)
+        return PR_FAILURE;
+    else {
+        PR_DELETE(stack);
+    	return PR_SUCCESS;
+    }
+}  /* _PR_DestroyIOLayer */
+
+PR_IMPLEMENT(PRStatus) PR_PushIOLayer(
+    PRFileDesc *stack, PRDescIdentity id, PRFileDesc *fd)
+{
+    PRFileDesc *insert = PR_GetIdentitiesLayer(stack, id);
+
+    PR_ASSERT(fd != NULL);
+    PR_ASSERT(stack != NULL);
+    PR_ASSERT(insert != NULL);
+    PR_ASSERT(PR_IO_LAYER_HEAD != id);
+    if ((NULL == stack) || (NULL == fd) || (NULL == insert))
+    {
+        PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
+        return PR_FAILURE;
+    }
+
+    if (stack == insert)
+    {
+		/* going on top of the stack */
+		/* old-style stack */	
+		PRFileDesc copy = *stack;
+		*stack = *fd;
+		*fd = copy;
+		fd->higher = stack;
+		if (fd->lower)
+		{
+			PR_ASSERT(fd->lower->higher == stack);
+			fd->lower->higher = fd;
+		}
+		stack->lower = fd;
+		stack->higher = NULL;
+	} else {
+        /*
+		 * going somewhere in the middle of the stack for both old and new
+		 * style stacks, or going on top of stack for new style stack
+		 */
+        fd->lower = insert;
+        fd->higher = insert->higher;
+
+        insert->higher->lower = fd;
+        insert->higher = fd;
+    }
+
+    return PR_SUCCESS;
+}
+
+PR_IMPLEMENT(PRFileDesc*) PR_PopIOLayer(PRFileDesc *stack, PRDescIdentity id)
+{
+    PRFileDesc *extract = PR_GetIdentitiesLayer(stack, id);
+
+    PR_ASSERT(0 != id);
+    PR_ASSERT(NULL != stack);
+    PR_ASSERT(NULL != extract);
+    if ((NULL == stack) || (0 == id) || (NULL == extract))
+    {
+        PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);
+        return NULL;
+    }
+
+    if (extract == stack) {
+        /* popping top layer of the stack */
+		/* old style stack */
+        PRFileDesc copy = *stack;
+        extract = stack->lower;
+        *stack = *extract;
+        *extract = copy;
+        stack->higher = NULL;
+        if (stack->lower) {
+            PR_ASSERT(stack->lower->higher == extract);
+            stack->lower->higher = stack;
+        }
+	} else if ((PR_IO_LAYER_HEAD == stack->identity) &&
+					(extract == stack->lower) && (extract->lower == NULL)) {
+			/*
+			 * new style stack
+			 * popping the only layer in the stack; delete the stack too
+			 */
+			stack->lower = NULL;
+			_PR_DestroyIOLayer(stack);
+	} else {
+		/* for both kinds of stacks */
+        extract->lower->higher = extract->higher;
+        extract->higher->lower = extract->lower;
+    }
+    extract->higher = extract->lower = NULL;
+    return extract;
+}  /* PR_PopIOLayer */
+
+#define ID_CACHE_INCREMENT 16
+typedef struct _PRIdentity_cache
+{
+    PRLock *ml;
+    char **name;
+    PRIntn length;
+    PRDescIdentity ident;
+} _PRIdentity_cache;
+
+static _PRIdentity_cache identity_cache;
+
+PR_IMPLEMENT(PRDescIdentity) PR_GetUniqueIdentity(const char *layer_name)
+{
+    PRDescIdentity identity, length;
+    char **names = NULL, *name = NULL, **old = NULL;
+
+    if (!_pr_initialized) _PR_ImplicitInitialization();
+
+    PR_ASSERT((PRDescIdentity)0x7fff > identity_cache.ident);
+
+    if (NULL != layer_name)
+    {
+        name = (char*)PR_Malloc(strlen(layer_name) + 1);
+        if (NULL == name)
+        {
+            PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
+            return PR_INVALID_IO_LAYER;
+        }
+        strcpy(name, layer_name);
+    }
+
+    /* this initial code runs unsafe */
+retry:
+    PR_ASSERT(NULL == names);
+    /*
+     * In the initial round, both identity_cache.ident and
+     * identity_cache.length are 0, so (identity_cache.ident + 1) is greater
+     * than length.  In later rounds, identity_cache.ident is always less
+     * than length, so (identity_cache.ident + 1) can be equal to but cannot
+     * be greater than length.
+     */
+    length = identity_cache.length;
+    if ((identity_cache.ident + 1) >= length)
+    {
+        length += ID_CACHE_INCREMENT;
+        names = (char**)PR_CALLOC(length * sizeof(char*));
+        if (NULL == names)
+        {
+            if (NULL != name) PR_DELETE(name);
+            PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
+            return PR_INVALID_IO_LAYER;
+        }
+    }
+
+    /* now we get serious about thread safety */
+    PR_Lock(identity_cache.ml);
+    PR_ASSERT(identity_cache.length == 0 ||
+              identity_cache.ident < identity_cache.length);
+    identity = identity_cache.ident + 1;
+    if (identity >= identity_cache.length)  /* there's no room */
+    {
+        /* we have to do something - hopefully it's already done */
+        if ((NULL != names) && (identity < length))
+        {
+            /* what we did is still okay */
+            memcpy(
+                names, identity_cache.name,
+                identity_cache.length * sizeof(char*));
+            old = identity_cache.name;
+            identity_cache.name = names;
+            identity_cache.length = length;
+            names = NULL;
+        }
+        else
+        {
+            PR_Unlock(identity_cache.ml);
+            if (NULL != names) PR_DELETE(names);
+            goto retry;
+        }
+    }
+    if (NULL != name) /* there's a name to be stored */
+    {
+        identity_cache.name[identity] = name;
+    }
+    identity_cache.ident = identity;
+    PR_ASSERT(identity_cache.ident < identity_cache.length);
+    PR_Unlock(identity_cache.ml);
+
+    if (NULL != old) PR_DELETE(old);
+    if (NULL != names) PR_DELETE(names);
+
+    return identity;
+}  /* PR_GetUniqueIdentity */
+
+PR_IMPLEMENT(const char*) PR_GetNameForIdentity(PRDescIdentity ident)
+{
+    if (!_pr_initialized) _PR_ImplicitInitialization();
+
+    if (PR_TOP_IO_LAYER == ident) return NULL;
+
+    PR_ASSERT(ident <= identity_cache.ident);
+    return (ident > identity_cache.ident) ? NULL : identity_cache.name[ident];
+}  /* PR_GetNameForIdentity */
+
+PR_IMPLEMENT(PRDescIdentity) PR_GetLayersIdentity(PRFileDesc* fd)
+{
+    PR_ASSERT(NULL != fd);
+    if (PR_IO_LAYER_HEAD == fd->identity) {
+    	PR_ASSERT(NULL != fd->lower);
+    	return fd->lower->identity;
+	} else
+    	return fd->identity;
+}  /* PR_GetLayersIdentity */
+
+PR_IMPLEMENT(PRFileDesc*) PR_GetIdentitiesLayer(PRFileDesc* fd, PRDescIdentity id)
+{
+    PRFileDesc *layer = fd;
+
+    if (PR_TOP_IO_LAYER == id) {
+    	if (PR_IO_LAYER_HEAD == fd->identity)
+			return fd->lower;
+		else 
+			return fd;
+	}
+
+    for (layer = fd; layer != NULL; layer = layer->lower)
+    {
+        if (id == layer->identity) return layer;
+    }
+    for (layer = fd; layer != NULL; layer = layer->higher)
+    {
+        if (id == layer->identity) return layer;
+    }
+    return NULL;
+}  /* PR_GetIdentitiesLayer */
+
+void _PR_InitLayerCache(void)
+{
+    memset(&identity_cache, 0, sizeof(identity_cache));
+    identity_cache.ml = PR_NewLock();
+    PR_ASSERT(NULL != identity_cache.ml);
+}  /* _PR_InitLayerCache */
+
+void _PR_CleanupLayerCache(void)
+{
+    if (identity_cache.ml)
+    {
+        PR_DestroyLock(identity_cache.ml);
+        identity_cache.ml = NULL;
+    }
+
+    if (identity_cache.name)
+    {
+        PRDescIdentity ident;
+
+        for (ident = 0; ident <= identity_cache.ident; ident++)
+            PR_DELETE(identity_cache.name[ident]);
+
+        PR_DELETE(identity_cache.name);
+    }
+}  /* _PR_CleanupLayerCache */
+
+/* prlayer.c */