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  * Allocate memory: determine the smallest pool that is big enough
00072  * to contain an element of 'size' and get an element from that pool.
00073  *
00074  * @param size the size in bytes of the memory needed
00075  * @return a pointer to the allocated memory or NULL if the pool is empty
00076  */
00077 void *
00078 mem_malloc(mem_size_t size)
00079 {
00080   struct memp_malloc_helper *element;
00081   memp_t poolnr;
00082   mem_size_t required_size = size + sizeof(struct memp_malloc_helper);
00083 
00084   for (poolnr = MEMP_POOL_FIRST; poolnr <= MEMP_POOL_LAST; poolnr++) {
00085 #if MEM_USE_POOLS_TRY_BIGGER_POOL
00086 again:
00087 #endif /* MEM_USE_POOLS_TRY_BIGGER_POOL */
00088     /* is this pool big enough to hold an element of the required size
00089        plus a struct memp_malloc_helper that saves the pool this element came from? */
00090     if (required_size <= memp_sizes[poolnr]) {
00091       break;
00092     }
00093   }
00094   if (poolnr > MEMP_POOL_LAST) {
00095     LWIP_ASSERT("mem_malloc(): no pool is that big!", 0);
00096     return NULL;
00097   }
00098   element = (struct memp_malloc_helper*)memp_malloc(poolnr);
00099   if (element == NULL) {
00100     /* No need to DEBUGF or ASSERT: This error is already
00101        taken care of in memp.c */
00102 #if MEM_USE_POOLS_TRY_BIGGER_POOL
00103     /** Try a bigger pool if this one is empty! */
00104     if (poolnr < MEMP_POOL_LAST) {
00105       poolnr++;
00106       goto again;
00107     }
00108 #endif /* MEM_USE_POOLS_TRY_BIGGER_POOL */
00109     return NULL;
00110   }
00111 
00112   /* save the pool number this element came from */
00113   element->poolnr = poolnr;
00114   /* and return a pointer to the memory directly after the struct memp_malloc_helper */
00115   element++;
00116 
00117   return element;
00118 }
00119 
00120 /**
00121  * Free memory previously allocated by mem_malloc. Loads the pool number
00122  * and calls memp_free with that pool number to put the element back into
00123  * its pool
00124  *
00125  * @param rmem the memory element to free
00126  */
00127 void
00128 mem_free(void *rmem)
00129 {
00130   struct memp_malloc_helper *hmem = (struct memp_malloc_helper*)rmem;
00131 
00132   LWIP_ASSERT("rmem != NULL", (rmem != NULL));
00133   LWIP_ASSERT("rmem == MEM_ALIGN(rmem)", (rmem == LWIP_MEM_ALIGN(rmem)));
00134 
00135   /* get the original struct memp_malloc_helper */
00136   hmem--;
00137 
00138   LWIP_ASSERT("hmem != NULL", (hmem != NULL));
00139   LWIP_ASSERT("hmem == MEM_ALIGN(hmem)", (hmem == LWIP_MEM_ALIGN(hmem)));
00140   LWIP_ASSERT("hmem->poolnr < MEMP_MAX", (hmem->poolnr < MEMP_MAX));
00141 
00142   /* and put it in the pool we saved earlier */
00143   memp_free(hmem->poolnr, hmem);
00144 }
00145 
00146 #else /* MEM_USE_POOLS */
00147 /* lwIP replacement for your libc malloc() */
00148 
00149 /**
00150  * The heap is made up as a list of structs of this type.
00151  * This does not have to be aligned since for getting its size,
00152  * we only use the macro SIZEOF_STRUCT_MEM, which automatically alignes.
00153  */
00154 struct mem {
00155   /** index (-> ram[next]) of the next struct */
00156   mem_size_t next;
00157   /** index (-> ram[next]) of the next struct */
00158   mem_size_t prev;
00159   /** 1: this area is used; 0: this area is unused */
00160   u8_t used;
00161 };
00162 
00163 /** All allocated blocks will be MIN_SIZE bytes big, at least!
00164  * MIN_SIZE can be overridden to suit your needs. Smaller values save space,
00165  * larger values could prevent too small blocks to fragment the RAM too much. */
00166 #ifndef MIN_SIZE
00167 #define MIN_SIZE             12
00168 #endif /* MIN_SIZE */
00169 /* some alignment macros: we define them here for better source code layout */
00170 #define MIN_SIZE_ALIGNED     LWIP_MEM_ALIGN_SIZE(MIN_SIZE)
00171 #define SIZEOF_STRUCT_MEM    LWIP_MEM_ALIGN_SIZE(sizeof(struct mem))
00172 #define MEM_SIZE_ALIGNED     LWIP_MEM_ALIGN_SIZE(MEM_SIZE)
00173 
00174 #ifndef MEM_POSITION
00175 #define MEM_POSITION
00176 #endif
00177 
00178 /** the heap. we need one struct mem at the end and some room for alignment */
00179 static u8_t ram_heap[MEM_SIZE_ALIGNED + (2*SIZEOF_STRUCT_MEM) + MEM_ALIGNMENT] MEM_POSITION;
00180 /** pointer to the heap (ram_heap): for alignment, ram is now a pointer instead of an array */
00181 static u8_t *ram;
00182 /** the last entry, always unused! */
00183 static struct mem *ram_end;
00184 /** pointer to the lowest free block, this is used for faster search */
00185 static struct mem *lfree;
00186 
00187 /** concurrent access protection */
00188 //static sys_sem_t mem_sem;
00189 
00190 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00191 
00192 static volatile u8_t mem_free_count;
00193 
00194 /* Allow mem_free from other (e.g. interrupt) context */
00195 #define LWIP_MEM_FREE_DECL_PROTECT()  SYS_ARCH_DECL_PROTECT(lev_free)
00196 #define LWIP_MEM_FREE_PROTECT()       SYS_ARCH_PROTECT(lev_free)
00197 #define LWIP_MEM_FREE_UNPROTECT()     SYS_ARCH_UNPROTECT(lev_free)
00198 #define LWIP_MEM_ALLOC_DECL_PROTECT() SYS_ARCH_DECL_PROTECT(lev_alloc)
00199 #define LWIP_MEM_ALLOC_PROTECT()      SYS_ARCH_PROTECT(lev_alloc)
00200 #define LWIP_MEM_ALLOC_UNPROTECT()    SYS_ARCH_UNPROTECT(lev_alloc)
00201 
00202 #else /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00203 
00204 /* Protect the heap only by using a semaphore */
00205 #define LWIP_MEM_FREE_DECL_PROTECT()
00206 #define LWIP_MEM_FREE_PROTECT()    sys_arch_sem_wait(mem_sem, 0)
00207 #define LWIP_MEM_FREE_UNPROTECT()  sys_sem_signal(mem_sem)
00208 /* mem_malloc is protected using semaphore AND LWIP_MEM_ALLOC_PROTECT */
00209 #define LWIP_MEM_ALLOC_DECL_PROTECT()
00210 #define LWIP_MEM_ALLOC_PROTECT()
00211 #define LWIP_MEM_ALLOC_UNPROTECT()
00212 
00213 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00214 
00215 
00216 /**
00217  * "Plug holes" by combining adjacent empty struct mems.
00218  * After this function is through, there should not exist
00219  * one empty struct mem pointing to another empty struct mem.
00220  *
00221  * @param mem this points to a struct mem which just has been freed
00222  * @internal this function is only called by mem_free() and mem_realloc()
00223  *
00224  * This assumes access to the heap is protected by the calling function
00225  * already.
00226  */
00227 static void
00228 plug_holes(struct mem *mem)
00229 {
00230   struct mem *nmem;
00231   struct mem *pmem;
00232 
00233   LWIP_ASSERT("plug_holes: mem >= ram", (u8_t *)mem >= ram);
00234   LWIP_ASSERT("plug_holes: mem < ram_end", (u8_t *)mem < (u8_t *)ram_end);
00235   LWIP_ASSERT("plug_holes: mem->used == 0", mem->used == 0);
00236 
00237   /* plug hole forward */
00238   LWIP_ASSERT("plug_holes: mem->next <= MEM_SIZE_ALIGNED", mem->next <= MEM_SIZE_ALIGNED);
00239 
00240   nmem = (struct mem *)&ram[mem->next];
00241   if (mem != nmem && nmem->used == 0 && (u8_t *)nmem != (u8_t *)ram_end) {
00242     /* if mem->next is unused and not end of ram, combine mem and mem->next */
00243     if (lfree == nmem) {
00244       lfree = mem;
00245     }
00246     mem->next = nmem->next;
00247     ((struct mem *)&ram[nmem->next])->prev = (u8_t *)mem - ram;
00248   }
00249 
00250   /* plug hole backward */
00251   pmem = (struct mem *)&ram[mem->prev];
00252   if (pmem != mem && pmem->used == 0) {
00253     /* if mem->prev is unused, combine mem and mem->prev */
00254     if (lfree == mem) {
00255       lfree = pmem;
00256     }
00257     pmem->next = mem->next;
00258     ((struct mem *)&ram[mem->next])->prev = (u8_t *)pmem - ram;
00259   }
00260 }
00261 
00262 /**
00263  * Zero the heap and initialize start, end and lowest-free
00264  */
00265 void
00266 mem_init(void)
00267 {
00268   struct mem *mem;
00269 
00270   LWIP_ASSERT("Sanity check alignment",
00271     (SIZEOF_STRUCT_MEM & (MEM_ALIGNMENT-1)) == 0);
00272 
00273   /* align the heap */
00274   ram = LWIP_MEM_ALIGN(ram_heap);
00275   /* initialize the start of the heap */
00276   mem = (struct mem *)ram;
00277   mem->next = MEM_SIZE_ALIGNED;
00278   mem->prev = 0;
00279   mem->used = 0;
00280   /* initialize the end of the heap */
00281   ram_end = (struct mem *)&ram[MEM_SIZE_ALIGNED];
00282   ram_end->used = 1;
00283   ram_end->next = MEM_SIZE_ALIGNED;
00284   ram_end->prev = MEM_SIZE_ALIGNED;
00285 
00286   //mem_sem = sys_sem_new(1);
00287 
00288   /* initialize the lowest-free pointer to the start of the heap */
00289   lfree = (struct mem *)ram;
00290 
00291   MEM_STATS_AVAIL(avail, MEM_SIZE_ALIGNED);
00292 }
00293 
00294 /**
00295  * Put a struct mem back on the heap
00296  *
00297  * @param rmem is the data portion of a struct mem as returned by a previous
00298  *             call to mem_malloc()
00299  */
00300 void
00301 mem_free(void *rmem)
00302 {
00303   struct mem *mem;
00304   LWIP_MEM_FREE_DECL_PROTECT();
00305 
00306   if (rmem == NULL) {
00307     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_TRACE | 2, ("mem_free(p == NULL) was called.\n"));
00308     return;
00309   }
00310   LWIP_ASSERT("mem_free: sanity check alignment", (((mem_ptr_t)rmem) & (MEM_ALIGNMENT-1)) == 0);
00311 
00312   LWIP_ASSERT("mem_free: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00313     (u8_t *)rmem < (u8_t *)ram_end);
00314 
00315   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00316     SYS_ARCH_DECL_PROTECT(lev);
00317     LWIP_DEBUGF(MEM_DEBUG | 3, ("mem_free: illegal memory\n"));
00318     /* protect mem stats from concurrent access */
00319     SYS_ARCH_PROTECT(lev);
00320     MEM_STATS_INC(illegal);
00321     SYS_ARCH_UNPROTECT(lev);
00322     return;
00323   }
00324   /* protect the heap from concurrent access */
00325   LWIP_MEM_FREE_PROTECT();
00326   /* Get the corresponding struct mem ... */
00327   mem = (struct mem *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00328   /* ... which has to be in a used state ... */
00329   LWIP_ASSERT("mem_free: mem->used", mem->used);
00330   /* ... and is now unused. */
00331   mem->used = 0;
00332 
00333   if (mem < lfree) {
00334     /* the newly freed struct is now the lowest */
00335     lfree = mem;
00336   }
00337 
00338   MEM_STATS_DEC_USED(used, mem->next - ((u8_t *)mem - ram));
00339 
00340   /* finally, see if prev or next are free also */
00341   plug_holes(mem);
00342 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00343   mem_free_count = 1;
00344 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00345   LWIP_MEM_FREE_UNPROTECT();
00346 }
00347 
00348 /**
00349  * In contrast to its name, mem_realloc can only shrink memory, not expand it.
00350  * Since the only use (for now) is in pbuf_realloc (which also can only shrink),
00351  * this shouldn't be a problem!
00352  *
00353  * @param rmem pointer to memory allocated by mem_malloc the is to be shrinked
00354  * @param newsize required size after shrinking (needs to be smaller than or
00355  *                equal to the previous size)
00356  * @return for compatibility reasons: is always == rmem, at the moment
00357  *         or NULL if newsize is > old size, in which case rmem is NOT touched
00358  *         or freed!
00359  */
00360 void *
00361 mem_realloc(void *rmem, mem_size_t newsize)
00362 {
00363   mem_size_t size;
00364   mem_size_t ptr, ptr2;
00365   struct mem *mem, *mem2;
00366   /* use the FREE_PROTECT here: it protects with sem OR SYS_ARCH_PROTECT */
00367   LWIP_MEM_FREE_DECL_PROTECT();
00368 
00369   /* Expand the size of the allocated memory region so that we can
00370      adjust for alignment. */
00371   newsize = LWIP_MEM_ALIGN_SIZE(newsize);
00372 
00373   if(newsize < MIN_SIZE_ALIGNED) {
00374     /* every data block must be at least MIN_SIZE_ALIGNED long */
00375     newsize = MIN_SIZE_ALIGNED;
00376   }
00377 
00378   if (newsize > MEM_SIZE_ALIGNED) {
00379     return NULL;
00380   }
00381 
00382   LWIP_ASSERT("mem_realloc: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00383    (u8_t *)rmem < (u8_t *)ram_end);
00384 
00385   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00386     SYS_ARCH_DECL_PROTECT(lev);
00387     LWIP_DEBUGF(MEM_DEBUG | 3, ("mem_realloc: illegal memory\n"));
00388     /* protect mem stats from concurrent access */
00389     SYS_ARCH_PROTECT(lev);
00390     MEM_STATS_INC(illegal);
00391     SYS_ARCH_UNPROTECT(lev);
00392     return rmem;
00393   }
00394   /* Get the corresponding struct mem ... */
00395   mem = (struct mem *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00396   /* ... and its offset pointer */
00397   ptr = (u8_t *)mem - ram;
00398 
00399   size = mem->next - ptr - SIZEOF_STRUCT_MEM;
00400   LWIP_ASSERT("mem_realloc can only shrink memory", newsize <= size);
00401   if (newsize > size) {
00402     /* not supported */
00403     return NULL;
00404   }
00405   if (newsize == size) {
00406     /* No change in size, simply return */
00407     return rmem;
00408   }
00409 
00410   /* protect the heap from concurrent access */
00411   LWIP_MEM_FREE_PROTECT();
00412 
00413   MEM_STATS_DEC_USED(used, (size - newsize));
00414 
00415   mem2 = (struct mem *)&ram[mem->next];
00416   if(mem2->used == 0) {
00417     /* The next struct is unused, we can simply move it at little */
00418     mem_size_t next;
00419     /* remember the old next pointer */
00420     next = mem2->next;
00421     /* create new struct mem which is moved directly after the shrinked mem */
00422     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00423     if (lfree == mem2) {
00424       lfree = (struct mem *)&ram[ptr2];
00425     }
00426     mem2 = (struct mem *)&ram[ptr2];
00427     mem2->used = 0;
00428     /* restore the next pointer */
00429     mem2->next = next;
00430     /* link it back to mem */
00431     mem2->prev = ptr;
00432     /* link mem to it */
00433     mem->next = ptr2;
00434     /* last thing to restore linked list: as we have moved mem2,
00435      * let 'mem2->next->prev' point to mem2 again. but only if mem2->next is not
00436      * the end of the heap */
00437     if (mem2->next != MEM_SIZE_ALIGNED) {
00438       ((struct mem *)&ram[mem2->next])->prev = ptr2;
00439     }
00440     /* no need to plug holes, we've already done that */
00441   } else if (newsize + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED <= size) {
00442     /* Next struct is used but there's room for another struct mem with
00443      * at least MIN_SIZE_ALIGNED of data.
00444      * Old size ('size') must be big enough to contain at least 'newsize' plus a struct mem
00445      * ('SIZEOF_STRUCT_MEM') with some data ('MIN_SIZE_ALIGNED').
00446      * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00447      *       region that couldn't hold data, but when mem->next gets freed,
00448      *       the 2 regions would be combined, resulting in more free memory */
00449     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00450     mem2 = (struct mem *)&ram[ptr2];
00451     if (mem2 < lfree) {
00452       lfree = mem2;
00453     }
00454     mem2->used = 0;
00455     mem2->next = mem->next;
00456     mem2->prev = ptr;
00457     mem->next = ptr2;
00458     if (mem2->next != MEM_SIZE_ALIGNED) {
00459       ((struct mem *)&ram[mem2->next])->prev = ptr2;
00460     }
00461     /* the original mem->next is used, so no need to plug holes! */
00462   }
00463   /* else {
00464     next struct mem is used but size between mem and mem2 is not big enough
00465     to create another struct mem
00466     -> don't do anyhting. 
00467     -> the remaining space stays unused since it is too small
00468   } */
00469 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00470   mem_free_count = 1;
00471 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00472   LWIP_MEM_FREE_UNPROTECT();
00473   return rmem;
00474 }
00475 
00476 /**
00477  * Adam's mem_malloc() plus solution for bug #17922
00478  * Allocate a block of memory with a minimum of 'size' bytes.
00479  *
00480  * @param size is the minimum size of the requested block in bytes.
00481  * @return pointer to allocated memory or NULL if no free memory was found.
00482  *
00483  * Note that the returned value will always be aligned (as defined by MEM_ALIGNMENT).
00484  */
00485 void *
00486 mem_malloc(mem_size_t size)
00487 {
00488   mem_size_t ptr, ptr2;
00489   struct mem *mem, *mem2;
00490 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00491   u8_t local_mem_free_count = 0;
00492 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00493   LWIP_MEM_ALLOC_DECL_PROTECT();
00494 
00495   if (size == 0) {
00496     return NULL;
00497   }
00498 
00499   /* Expand the size of the allocated memory region so that we can
00500      adjust for alignment. */
00501   size = LWIP_MEM_ALIGN_SIZE(size);
00502 
00503   if(size < MIN_SIZE_ALIGNED) {
00504     /* every data block must be at least MIN_SIZE_ALIGNED long */
00505     size = MIN_SIZE_ALIGNED;
00506   }
00507 
00508   if (size > MEM_SIZE_ALIGNED) {
00509     return NULL;
00510   }
00511 
00512   /* protect the heap from concurrent access */
00513   sys_arch_sem_wait(mem_sem, 0);
00514   LWIP_MEM_ALLOC_PROTECT();
00515 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00516   /* run as long as a mem_free disturbed mem_malloc */
00517   do {
00518     local_mem_free_count = 0;
00519 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00520 
00521     /* Scan through the heap searching for a free block that is big enough,
00522      * beginning with the lowest free block.
00523      */
00524     for (ptr = (u8_t *)lfree - ram; ptr < MEM_SIZE_ALIGNED - size;
00525          ptr = ((struct mem *)&ram[ptr])->next) {
00526       mem = (struct mem *)&ram[ptr];
00527 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00528       mem_free_count = 0;
00529       LWIP_MEM_ALLOC_UNPROTECT();
00530       /* allow mem_free to run */
00531       LWIP_MEM_ALLOC_PROTECT();
00532       if (mem_free_count != 0) {
00533         local_mem_free_count = mem_free_count;
00534       }
00535       mem_free_count = 0;
00536 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00537 
00538       if ((!mem->used) &&
00539           (mem->next - (ptr + SIZEOF_STRUCT_MEM)) >= size) {
00540         /* mem is not used and at least perfect fit is possible:
00541          * mem->next - (ptr + SIZEOF_STRUCT_MEM) gives us the 'user data size' of mem */
00542 
00543         if (mem->next - (ptr + SIZEOF_STRUCT_MEM) >= (size + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED)) {
00544           /* (in addition to the above, we test if another struct mem (SIZEOF_STRUCT_MEM) containing
00545            * at least MIN_SIZE_ALIGNED of data also fits in the 'user data space' of 'mem')
00546            * -> split large block, create empty remainder,
00547            * remainder must be large enough to contain MIN_SIZE_ALIGNED data: if
00548            * mem->next - (ptr + (2*SIZEOF_STRUCT_MEM)) == size,
00549            * struct mem would fit in but no data between mem2 and mem2->next
00550            * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00551            *       region that couldn't hold data, but when mem->next gets freed,
00552            *       the 2 regions would be combined, resulting in more free memory
00553            */
00554           ptr2 = ptr + SIZEOF_STRUCT_MEM + size;
00555           /* create mem2 struct */
00556           mem2 = (struct mem *)&ram[ptr2];
00557           mem2->used = 0;
00558           mem2->next = mem->next;
00559           mem2->prev = ptr;
00560           /* and insert it between mem and mem->next */
00561           mem->next = ptr2;
00562           mem->used = 1;
00563 
00564           if (mem2->next != MEM_SIZE_ALIGNED) {
00565             ((struct mem *)&ram[mem2->next])->prev = ptr2;
00566           }
00567           MEM_STATS_INC_USED(used, (size + SIZEOF_STRUCT_MEM));
00568         } else {
00569           /* (a mem2 struct does no fit into the user data space of mem and mem->next will always
00570            * be used at this point: if not we have 2 unused structs in a row, plug_holes should have
00571            * take care of this).
00572            * -> near fit or excact fit: do not split, no mem2 creation
00573            * also can't move mem->next directly behind mem, since mem->next
00574            * will always be used at this point!
00575            */
00576           mem->used = 1;
00577           MEM_STATS_INC_USED(used, mem->next - ((u8_t *)mem - ram));
00578         }
00579 
00580         if (mem == lfree) {
00581           /* Find next free block after mem and update lowest free pointer */
00582           while (lfree->used && lfree != ram_end) {
00583             LWIP_MEM_ALLOC_UNPROTECT();
00584             /* prevent high interrupt latency... */
00585             LWIP_MEM_ALLOC_PROTECT();
00586             lfree = (struct mem *)&ram[lfree->next];
00587           }
00588           LWIP_ASSERT("mem_malloc: !lfree->used", ((lfree == ram_end) || (!lfree->used)));
00589         }
00590         LWIP_MEM_ALLOC_UNPROTECT();
00591         sys_sem_signal(mem_sem);
00592         LWIP_ASSERT("mem_malloc: allocated memory not above ram_end.",
00593          (mem_ptr_t)mem + SIZEOF_STRUCT_MEM + size <= (mem_ptr_t)ram_end);
00594         LWIP_ASSERT("mem_malloc: allocated memory properly aligned.",
00595          ((mem_ptr_t)mem + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT == 0);
00596         LWIP_ASSERT("mem_malloc: sanity check alignment",
00597           (((mem_ptr_t)mem) & (MEM_ALIGNMENT-1)) == 0);
00598 
00599         return (u8_t *)mem + SIZEOF_STRUCT_MEM;
00600       }
00601     }
00602 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00603     /* if we got interrupted by a mem_free, try again */
00604   } while(local_mem_free_count != 0);
00605 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00606   LWIP_DEBUGF(MEM_DEBUG | 2, ("mem_malloc: could not allocate %"S16_F" bytes\n", (s16_t)size));
00607   MEM_STATS_INC(err);
00608   LWIP_MEM_ALLOC_UNPROTECT();
00609   sys_sem_signal(mem_sem);
00610   return NULL;
00611 }
00612 
00613 #endif /* MEM_USE_POOLS */
00614 /**
00615  * Contiguously allocates enough space for count objects that are size bytes
00616  * of memory each and returns a pointer to the allocated memory.
00617  *
00618  * The allocated memory is filled with bytes of value zero.
00619  *
00620  * @param count number of objects to allocate
00621  * @param size size of the objects to allocate
00622  * @return pointer to allocated memory / NULL pointer if there is an error
00623  */
00624 void *mem_calloc(mem_size_t count, mem_size_t size)
00625 {
00626   void *p;
00627 
00628   /* allocate 'count' objects of size 'size' */
00629   p = mem_malloc(count * size);
00630   if (p) {
00631     /* zero the memory */
00632     memset(p, 0, count * size);
00633   }
00634   return p;
00635 }
00636 #endif /* !MEM_LIBC_MALLOC */