mem.c

00001 /**
00002  * @file
00003  * Dynamic memory manager
00004  *
00005  * This is a lightweight replacement for the standard C library malloc().
00006  *
00007  * If you want to use the standard C library malloc() instead, define
00008  * MEM_LIBC_MALLOC to 1 in your lwipopts.h
00009  *
00010  * To let mem_malloc() use pools (prevents fragmentation and is much faster than
00011  * a heap but might waste some memory), define MEM_USE_POOLS to 1, define
00012  * MEM_USE_CUSTOM_POOLS to 1 and create a file "lwippools.h" that includes a list
00013  * of pools like this (more pools can be added between _START and _END):
00014  *
00015  * Define three pools with sizes 256, 512, and 1512 bytes
00016  * LWIP_MALLOC_MEMPOOL_START
00017  * LWIP_MALLOC_MEMPOOL(20, 256)
00018  * LWIP_MALLOC_MEMPOOL(10, 512)
00019  * LWIP_MALLOC_MEMPOOL(5, 1512)
00020  * LWIP_MALLOC_MEMPOOL_END
00021  */
00022 
00023 /*
00024  * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
00025  * All rights reserved.
00026  *
00027  * Redistribution and use in source and binary forms, with or without modification,
00028  * are permitted provided that the following conditions are met:
00029  *
00030  * 1. Redistributions of source code must retain the above copyright notice,
00031  *    this list of conditions and the following disclaimer.
00032  * 2. Redistributions in binary form must reproduce the above copyright notice,
00033  *    this list of conditions and the following disclaimer in the documentation
00034  *    and/or other materials provided with the distribution.
00035  * 3. The name of the author may not be used to endorse or promote products
00036  *    derived from this software without specific prior written permission.
00037  *
00038  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
00039  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
00040  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
00041  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
00042  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
00043  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00044  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
00045  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
00046  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
00047  * OF SUCH DAMAGE.
00048  *
00049  * This file is part of the lwIP TCP/IP stack.
00050  *
00051  * Author: Adam Dunkels <adam@sics.se>
00052  *         Simon Goldschmidt
00053  *
00054  */
00055 
00056 #include "lwip/opt.h"
00057 
00058 #if !MEM_LIBC_MALLOC /* don't build if not configured for use in lwipopts.h */
00059 
00060 #include "lwip/def.h"
00061 #include "lwip/mem.h"
00062 #include "lwip/sys.h"
00063 #include "lwip/stats.h"
00064 
00065 #include <string.h>
00066 
00067 #if MEM_USE_POOLS
00068 /* lwIP head implemented with different sized pools */
00069 
00070 /**
00071  * This structure is used to save the pool one element came from.
00072  */
00073 struct mem_helper
00074 {
00075    memp_t poolnr;
00076 };
00077 
00078 /**
00079  * Allocate memory: determine the smallest pool that is big enough
00080  * to contain an element of 'size' and get an element from that pool.
00081  *
00082  * @param size the size in bytes of the memory needed
00083  * @return a pointer to the allocated memory or NULL if the pool is empty
00084  */
00085 void *
00086 mem_malloc(mem_size_t size)
00087 {
00088   struct mem_helper *element;
00089   memp_t poolnr;
00090 
00091   for (poolnr = MEMP_POOL_FIRST; poolnr <= MEMP_POOL_LAST; poolnr++) {
00092     /* is this pool big enough to hold an element of the required size
00093        plus a struct mem_helper that saves the pool this element came from? */
00094     if ((size + sizeof(struct mem_helper)) <= memp_sizes[poolnr]) {
00095       break;
00096     }
00097   }
00098   if (poolnr > MEMP_POOL_LAST) {
00099     LWIP_ASSERT("mem_malloc(): no pool is that big!", 0);
00100     return NULL;
00101   }
00102   element = (struct mem_helper*)memp_malloc(poolnr);
00103   if (element == NULL) {
00104     /* No need to DEBUGF or ASSERT: This error is already
00105        taken care of in memp.c */
00106     /** @todo: we could try a bigger pool if this one is empty! */
00107     return NULL;
00108   }
00109 
00110   /* save the pool number this element came from */
00111   element->poolnr = poolnr;
00112   /* and return a pointer to the memory directly after the struct mem_helper */
00113   element++;
00114 
00115   return element;
00116 }
00117 
00118 /**
00119  * Free memory previously allocated by mem_malloc. Loads the pool number
00120  * and calls memp_free with that pool number to put the element back into
00121  * its pool
00122  *
00123  * @param rmem the memory element to free
00124  */
00125 void
00126 mem_free(void *rmem)
00127 {
00128   struct mem_helper *hmem = (struct mem_helper*)rmem;
00129 
00130   LWIP_ASSERT("rmem != NULL", (rmem != NULL));
00131   LWIP_ASSERT("rmem == MEM_ALIGN(rmem)", (rmem == LWIP_MEM_ALIGN(rmem)));
00132 
00133   /* get the original struct mem_helper */
00134   hmem--;
00135 
00136   LWIP_ASSERT("hmem != NULL", (hmem != NULL));
00137   LWIP_ASSERT("hmem == MEM_ALIGN(hmem)", (hmem == LWIP_MEM_ALIGN(hmem)));
00138   LWIP_ASSERT("hmem->poolnr < MEMP_MAX", (hmem->poolnr < MEMP_MAX));
00139 
00140   /* and put it in the pool we saved earlier */
00141   memp_free(hmem->poolnr, hmem);
00142 }
00143 
00144 #else /* MEM_USE_POOLS */
00145 /* lwIP replacement for your libc malloc() */
00146 
00147 /**
00148  * The heap is made up as a list of structs of this type.
00149  * This does not have to be aligned since for getting its size,
00150  * we only use the macro SIZEOF_STRUCT_MEM, which automatically alignes.
00151  */
00152 struct mem {
00153   /** index (-> ram[next]) of the next struct */
00154   mem_size_t next;
00155   /** index (-> ram[next]) of the next struct */
00156   mem_size_t prev;
00157   /** 1: this area is used; 0: this area is unused */
00158   u8_t used;
00159 };
00160 
00161 /** All allocated blocks will be MIN_SIZE bytes big, at least!
00162  * MIN_SIZE can be overridden to suit your needs. Smaller values save space,
00163  * larger values could prevent too small blocks to fragment the RAM too much. */
00164 #ifndef MIN_SIZE
00165 #define MIN_SIZE             12
00166 #endif /* MIN_SIZE */
00167 /* some alignment macros: we define them here for better source code layout */
00168 #define MIN_SIZE_ALIGNED     LWIP_MEM_ALIGN_SIZE(MIN_SIZE)
00169 #define SIZEOF_STRUCT_MEM    LWIP_MEM_ALIGN_SIZE(sizeof(struct mem))
00170 #define MEM_SIZE_ALIGNED     LWIP_MEM_ALIGN_SIZE(MEM_SIZE)
00171 
00172 /** the heap. we need one struct mem at the end and some room for alignment */
00173 static u8_t ram_heap[MEM_SIZE_ALIGNED + (2*SIZEOF_STRUCT_MEM) + MEM_ALIGNMENT];
00174 /** pointer to the heap (ram_heap): for alignment, ram is now a pointer instead of an array */
00175 static u8_t *ram;
00176 /** the last entry, always unused! */
00177 static struct mem *ram_end;
00178 /** pointer to the lowest free block, this is used for faster search */
00179 static struct mem *lfree;
00180 /** concurrent access protection */
00181 static sys_sem_t mem_sem;
00182 
00183 /**
00184  * "Plug holes" by combining adjacent empty struct mems.
00185  * After this function is through, there should not exist
00186  * one empty struct mem pointing to another empty struct mem.
00187  *
00188  * @param mem this points to a struct mem which just has been freed
00189  * @internal this function is only called by mem_free() and mem_realloc()
00190  *
00191  * This assumes access to the heap is protected by the calling function
00192  * already.
00193  */
00194 static void
00195 plug_holes(struct mem *mem)
00196 {
00197   struct mem *nmem;
00198   struct mem *pmem;
00199 
00200   LWIP_ASSERT("plug_holes: mem >= ram", (u8_t *)mem >= ram);
00201   LWIP_ASSERT("plug_holes: mem < ram_end", (u8_t *)mem < (u8_t *)ram_end);
00202   LWIP_ASSERT("plug_holes: mem->used == 0", mem->used == 0);
00203 
00204   /* plug hole forward */
00205   LWIP_ASSERT("plug_holes: mem->next <= MEM_SIZE_ALIGNED", mem->next <= MEM_SIZE_ALIGNED);
00206 
00207   nmem = (struct mem *)&ram[mem->next];
00208   if (mem != nmem && nmem->used == 0 && (u8_t *)nmem != (u8_t *)ram_end) {
00209     /* if mem->next is unused and not end of ram, combine mem and mem->next */
00210     if (lfree == nmem) {
00211       lfree = mem;
00212     }
00213     mem->next = nmem->next;
00214     ((struct mem *)&ram[nmem->next])->prev = (u8_t *)mem - ram;
00215   }
00216 
00217   /* plug hole backward */
00218   pmem = (struct mem *)&ram[mem->prev];
00219   if (pmem != mem && pmem->used == 0) {
00220     /* if mem->prev is unused, combine mem and mem->prev */
00221     if (lfree == mem) {
00222       lfree = pmem;
00223     }
00224     pmem->next = mem->next;
00225     ((struct mem *)&ram[mem->next])->prev = (u8_t *)pmem - ram;
00226   }
00227 }
00228 
00229 /**
00230  * Zero the heap and initialize start, end and lowest-free
00231  */
00232 void
00233 mem_init(void)
00234 {
00235   struct mem *mem;
00236 
00237   LWIP_ASSERT("Sanity check alignment",
00238     (SIZEOF_STRUCT_MEM & (MEM_ALIGNMENT-1)) == 0);
00239 
00240   /* align the heap */
00241   ram = LWIP_MEM_ALIGN(ram_heap);
00242   /* initialize the start of the heap */
00243   mem = (struct mem *)ram;
00244   mem->next = MEM_SIZE_ALIGNED;
00245   mem->prev = 0;
00246   mem->used = 0;
00247   /* initialize the end of the heap */
00248   ram_end = (struct mem *)&ram[MEM_SIZE_ALIGNED];
00249   ram_end->used = 1;
00250   ram_end->next = MEM_SIZE_ALIGNED;
00251   ram_end->prev = MEM_SIZE_ALIGNED;
00252 
00253   mem_sem = sys_sem_new(1);
00254 
00255   /* initialize the lowest-free pointer to the start of the heap */
00256   lfree = (struct mem *)ram;
00257 
00258 #if MEM_STATS
00259   lwip_stats.mem.avail = MEM_SIZE_ALIGNED;
00260 #endif /* MEM_STATS */
00261 }
00262 
00263 /**
00264  * Put a struct mem back on the heap
00265  *
00266  * @param rmem is the data portion of a struct mem as returned by a previous
00267  *             call to mem_malloc()
00268  */
00269 void
00270 mem_free(void *rmem)
00271 {
00272   struct mem *mem;
00273 
00274   if (rmem == NULL) {
00275     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_TRACE | 2, ("mem_free(p == NULL) was called.\n"));
00276     return;
00277   }
00278   LWIP_ASSERT("mem_free: sanity check alignment", (((mem_ptr_t)rmem) & (MEM_ALIGNMENT-1)) == 0);
00279 
00280   /* protect the heap from concurrent access */
00281   sys_arch_sem_wait(mem_sem, 0);
00282 
00283   LWIP_ASSERT("mem_free: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00284     (u8_t *)rmem < (u8_t *)ram_end);
00285 
00286   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00287     LWIP_DEBUGF(MEM_DEBUG | 3, ("mem_free: illegal memory\n"));
00288 #if MEM_STATS
00289     ++lwip_stats.mem.err;
00290 #endif /* MEM_STATS */
00291     sys_sem_signal(mem_sem);
00292     return;
00293   }
00294   /* Get the corresponding struct mem ... */
00295   mem = (struct mem *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00296   /* ... which has to be in a used state ... */
00297   LWIP_ASSERT("mem_free: mem->used", mem->used);
00298   /* ... and is now unused. */
00299   mem->used = 0;
00300 
00301   if (mem < lfree) {
00302     /* the newly freed struct is now the lowest */
00303     lfree = mem;
00304   }
00305 
00306 #if MEM_STATS
00307   lwip_stats.mem.used -= mem->next - ((u8_t *)mem - ram);
00308 #endif /* MEM_STATS */
00309 
00310   /* finally, see if prev or next are free also */
00311   plug_holes(mem);
00312   sys_sem_signal(mem_sem);
00313 }
00314 
00315 /**
00316  * In contrast to its name, mem_realloc can only shrink memory, not expand it.
00317  * Since the only use (for now) is in pbuf_realloc (which also can only shrink),
00318  * this shouldn't be a problem!
00319  *
00320  * @param rmem pointer to memory allocated by mem_malloc the is to be shrinked
00321  * @param newsize required size after shrinking (needs to be smaller than or
00322  *                equal to the previous size)
00323  * @return for compatibility reasons: is always == rmem, at the moment
00324  */
00325 void *
00326 mem_realloc(void *rmem, mem_size_t newsize)
00327 {
00328   mem_size_t size;
00329   mem_size_t ptr, ptr2;
00330   struct mem *mem, *mem2;
00331 
00332   /* Expand the size of the allocated memory region so that we can
00333      adjust for alignment. */
00334   newsize = LWIP_MEM_ALIGN_SIZE(newsize);
00335 
00336   if(newsize < MIN_SIZE_ALIGNED) {
00337     /* every data block must be at least MIN_SIZE_ALIGNED long */
00338     newsize = MIN_SIZE_ALIGNED;
00339   }
00340 
00341   if (newsize > MEM_SIZE_ALIGNED) {
00342     return NULL;
00343   }
00344 
00345   LWIP_ASSERT("mem_realloc: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00346    (u8_t *)rmem < (u8_t *)ram_end);
00347 
00348   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00349     LWIP_DEBUGF(MEM_DEBUG | 3, ("mem_realloc: illegal memory\n"));
00350     return rmem;
00351   }
00352   /* Get the corresponding struct mem ... */
00353   mem = (struct mem *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00354   /* ... and its offset pointer */
00355   ptr = (u8_t *)mem - ram;
00356 
00357   size = mem->next - ptr - SIZEOF_STRUCT_MEM;
00358   LWIP_ASSERT("mem_realloc can only shrink memory", newsize <= size);
00359   if (newsize > size) {
00360     /* not supported */
00361     return NULL;
00362   }
00363   if (newsize == size) {
00364     /* No change in size, simply return */
00365     return rmem;
00366   }
00367 
00368   /* protect the heap from concurrent access */
00369   sys_arch_sem_wait(mem_sem, 0);
00370 
00371 #if MEM_STATS
00372   lwip_stats.mem.used -= (size - newsize);
00373 #endif /* MEM_STATS */
00374 
00375   mem2 = (struct mem *)&ram[mem->next];
00376   if(mem2->used == 0) {
00377     /* The next struct is unused, we can simply move it at little */
00378     mem_size_t next;
00379     /* remember the old next pointer */
00380     next = mem2->next;
00381     /* create new struct mem which is moved directly after the shrinked mem */
00382     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00383     if (lfree == mem2) {
00384       lfree = (struct mem *)&ram[ptr2];
00385     }
00386     mem2 = (struct mem *)&ram[ptr2];
00387     mem2->used = 0;
00388     /* restore the next pointer */
00389     mem2->next = next;
00390     /* link it back to mem */
00391     mem2->prev = ptr;
00392     /* link mem to it */
00393     mem->next = ptr2;
00394     /* last thing to restore linked list: as we have moved mem2,
00395      * let 'mem2->next->prev' point to mem2 again. but only if mem2->next is not
00396      * the end of the heap */
00397     if (mem2->next != MEM_SIZE_ALIGNED) {
00398       ((struct mem *)&ram[mem2->next])->prev = ptr2;
00399     }
00400     /* no need to plug holes, we've already done that */
00401   } else if (newsize + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED <= size) {
00402     /* Next struct is used but there's room for another struct mem with
00403      * at least MIN_SIZE_ALIGNED of data.
00404      * Old size ('size') must be big enough to contain at least 'newsize' plus a struct mem
00405      * ('SIZEOF_STRUCT_MEM') with some data ('MIN_SIZE_ALIGNED').
00406      * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00407      *       region that couldn't hold data, but when mem->next gets freed,
00408      *       the 2 regions would be combined, resulting in more free memory */
00409     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00410     mem2 = (struct mem *)&ram[ptr2];
00411     if (mem2 < lfree) {
00412       lfree = mem2;
00413     }
00414     mem2->used = 0;
00415     mem2->next = mem->next;
00416     mem2->prev = ptr;
00417     mem->next = ptr2;
00418     if (mem2->next != MEM_SIZE_ALIGNED) {
00419       ((struct mem *)&ram[mem2->next])->prev = ptr2;
00420     }
00421     /* the original mem->next is used, so no need to plug holes! */
00422   }
00423   /* else {
00424     next struct mem is used but size between mem and mem2 is not big enough
00425     to create another struct mem
00426     -> don't do anyhting. 
00427     -> the remaining space stays unused since it is too small
00428   } */
00429   sys_sem_signal(mem_sem);
00430   return rmem;
00431 }
00432 
00433 /**
00434  * Adam's mem_malloc() plus solution for bug #17922
00435  * Allocate a block of memory with a minimum of 'size' bytes.
00436  *
00437  * @param size is the minimum size of the requested block in bytes.
00438  * @return pointer to allocated memory or NULL if no free memory was found.
00439  *
00440  * Note that the returned value will always be aligned (as defined by MEM_ALIGNMENT).
00441  */
00442 void *
00443 mem_malloc(mem_size_t size)
00444 {
00445   mem_size_t ptr, ptr2;
00446   struct mem *mem, *mem2;
00447 
00448   if (size == 0) {
00449     return NULL;
00450   }
00451 
00452   /* Expand the size of the allocated memory region so that we can
00453      adjust for alignment. */
00454   size = LWIP_MEM_ALIGN_SIZE(size);
00455 
00456   if(size < MIN_SIZE_ALIGNED) {
00457     /* every data block must be at least MIN_SIZE_ALIGNED long */
00458     size = MIN_SIZE_ALIGNED;
00459   }
00460 
00461   if (size > MEM_SIZE_ALIGNED) {
00462     return NULL;
00463   }
00464 
00465   /* protect the heap from concurrent access */
00466   sys_arch_sem_wait(mem_sem, 0);
00467 
00468   /* Scan through the heap searching for a free block that is big enough,
00469    * beginning with the lowest free block.
00470    */
00471   for (ptr = (u8_t *)lfree - ram; ptr < MEM_SIZE_ALIGNED - size;
00472        ptr = ((struct mem *)&ram[ptr])->next) {
00473     mem = (struct mem *)&ram[ptr];
00474 
00475     if ((!mem->used) &&
00476         (mem->next - (ptr + SIZEOF_STRUCT_MEM)) >= size) {
00477       /* mem is not used and at least perfect fit is possible:
00478        * mem->next - (ptr + SIZEOF_STRUCT_MEM) gives us the 'user data size' of mem */
00479 
00480       if (mem->next - (ptr + SIZEOF_STRUCT_MEM) >= (size + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED)) {
00481         /* (in addition to the above, we test if another struct mem (SIZEOF_STRUCT_MEM) containing
00482          * at least MIN_SIZE_ALIGNED of data also fits in the 'user data space' of 'mem')
00483          * -> split large block, create empty remainder,
00484          * remainder must be large enough to contain MIN_SIZE_ALIGNED data: if
00485          * mem->next - (ptr + (2*SIZEOF_STRUCT_MEM)) == size,
00486          * struct mem would fit in but no data between mem2 and mem2->next
00487          * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00488          *       region that couldn't hold data, but when mem->next gets freed,
00489          *       the 2 regions would be combined, resulting in more free memory
00490          */
00491         ptr2 = ptr + SIZEOF_STRUCT_MEM + size;
00492         /* create mem2 struct */
00493         mem2 = (struct mem *)&ram[ptr2];
00494         mem2->used = 0;
00495         mem2->next = mem->next;
00496         mem2->prev = ptr;
00497         /* and insert it between mem and mem->next */
00498         mem->next = ptr2;
00499         mem->used = 1;
00500 
00501         if (mem2->next != MEM_SIZE_ALIGNED) {
00502           ((struct mem *)&ram[mem2->next])->prev = ptr2;
00503         }
00504 #if MEM_STATS
00505         lwip_stats.mem.used += (size + SIZEOF_STRUCT_MEM);
00506         if (lwip_stats.mem.max < lwip_stats.mem.used) {
00507           lwip_stats.mem.max = lwip_stats.mem.used;
00508         }
00509 #endif /* MEM_STATS */
00510       } else {
00511         /* (a mem2 struct does no fit into the user data space of mem and mem->next will always
00512          * be used at this point: if not we have 2 unused structs in a row, plug_holes should have
00513          * take care of this).
00514          * -> near fit or excact fit: do not split, no mem2 creation
00515          * also can't move mem->next directly behind mem, since mem->next
00516          * will always be used at this point!
00517          */
00518         mem->used = 1;
00519 #if MEM_STATS
00520         lwip_stats.mem.used += mem->next - ((u8_t *)mem - ram);
00521         if (lwip_stats.mem.max < lwip_stats.mem.used) {
00522           lwip_stats.mem.max = lwip_stats.mem.used;
00523         }
00524 #endif /* MEM_STATS */
00525       }
00526 
00527       if (mem == lfree) {
00528         /* Find next free block after mem and update lowest free pointer */
00529         while (lfree->used && lfree != ram_end) {
00530           lfree = (struct mem *)&ram[lfree->next];
00531         }
00532         LWIP_ASSERT("mem_malloc: !lfree->used", ((lfree == ram_end) || (!lfree->used)));
00533       }
00534       sys_sem_signal(mem_sem);
00535       LWIP_ASSERT("mem_malloc: allocated memory not above ram_end.",
00536        (mem_ptr_t)mem + SIZEOF_STRUCT_MEM + size <= (mem_ptr_t)ram_end);
00537       LWIP_ASSERT("mem_malloc: allocated memory properly aligned.",
00538        (unsigned long)((u8_t *)mem + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT == 0);
00539       LWIP_ASSERT("mem_malloc: sanity check alignment",
00540         (((mem_ptr_t)mem) & (MEM_ALIGNMENT-1)) == 0);
00541 
00542       return (u8_t *)mem + SIZEOF_STRUCT_MEM;
00543     }
00544   }
00545   LWIP_DEBUGF(MEM_DEBUG | 2, ("mem_malloc: could not allocate %"S16_F" bytes\n", (s16_t)size));
00546 #if MEM_STATS
00547   ++lwip_stats.mem.err;
00548 #endif /* MEM_STATS */
00549   sys_sem_signal(mem_sem);
00550   return NULL;
00551 }
00552 
00553 #endif /* MEM_USE_POOLS */
00554 /**
00555  * Contiguously allocates enough space for count objects that are size bytes
00556  * of memory each and returns a pointer to the allocated memory.
00557  *
00558  * The allocated memory is filled with bytes of value zero.
00559  *
00560  * @param count number of objects to allocate
00561  * @param size size of the objects to allocate
00562  * @return pointer to allocated memory / NULL pointer if there is an error
00563  */
00564 void *mem_calloc(mem_size_t count, mem_size_t size)
00565 {
00566   void *p;
00567 
00568   /* allocate 'count' objects of size 'size' */
00569   p = mem_malloc(count * size);
00570   if (p) {
00571     /* zero the memory */
00572     memset(p, 0, count * size);
00573   }
00574   return p;
00575 }
00576 #endif /* !MEM_LIBC_MALLOC */