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 #include "lwip/err.h"
00065 
00066 #include <string.h>
00067 
00068 #if MEM_USE_POOLS
00069 /* lwIP head implemented with different sized pools */
00070 
00071 /**
00072  * Allocate memory: determine the smallest pool that is big enough
00073  * to contain an element of 'size' and get an element from that pool.
00074  *
00075  * @param size the size in bytes of the memory needed
00076  * @return a pointer to the allocated memory or NULL if the pool is empty
00077  */
00078 void *
00079 mem_malloc(mem_size_t size)
00080 {
00081   struct memp_malloc_helper *element;
00082   memp_t poolnr;
00083   mem_size_t required_size = size + sizeof(struct memp_malloc_helper);
00084 
00085   for (poolnr = MEMP_POOL_FIRST; poolnr <= MEMP_POOL_LAST; poolnr = (memp_t)(poolnr + 1)) {
00086 #if MEM_USE_POOLS_TRY_BIGGER_POOL
00087 again:
00088 #endif /* MEM_USE_POOLS_TRY_BIGGER_POOL */
00089     /* is this pool big enough to hold an element of the required size
00090        plus a struct memp_malloc_helper that saves the pool this element came from? */
00091     if (required_size <= memp_sizes[poolnr]) {
00092       break;
00093     }
00094   }
00095   if (poolnr > MEMP_POOL_LAST) {
00096     LWIP_ASSERT("mem_malloc(): no pool is that big!", 0);
00097     return NULL;
00098   }
00099   element = (struct memp_malloc_helper*)memp_malloc(poolnr);
00100   if (element == NULL) {
00101     /* No need to DEBUGF or ASSERT: This error is already
00102        taken care of in memp.c */
00103 #if MEM_USE_POOLS_TRY_BIGGER_POOL
00104     /** Try a bigger pool if this one is empty! */
00105     if (poolnr < MEMP_POOL_LAST) {
00106       poolnr++;
00107       goto again;
00108     }
00109 #endif /* MEM_USE_POOLS_TRY_BIGGER_POOL */
00110     return NULL;
00111   }
00112 
00113   /* save the pool number this element came from */
00114   element->poolnr = poolnr;
00115   /* and return a pointer to the memory directly after the struct memp_malloc_helper */
00116   element++;
00117 
00118   return element;
00119 }
00120 
00121 /**
00122  * Free memory previously allocated by mem_malloc. Loads the pool number
00123  * and calls memp_free with that pool number to put the element back into
00124  * its pool
00125  *
00126  * @param rmem the memory element to free
00127  */
00128 void
00129 mem_free(void *rmem)
00130 {
00131   struct memp_malloc_helper *hmem = (struct memp_malloc_helper*)rmem;
00132 
00133   LWIP_ASSERT("rmem != NULL", (rmem != NULL));
00134   LWIP_ASSERT("rmem == MEM_ALIGN(rmem)", (rmem == LWIP_MEM_ALIGN(rmem)));
00135 
00136   /* get the original struct memp_malloc_helper */
00137   hmem--;
00138 
00139   LWIP_ASSERT("hmem != NULL", (hmem != NULL));
00140   LWIP_ASSERT("hmem == MEM_ALIGN(hmem)", (hmem == LWIP_MEM_ALIGN(hmem)));
00141   LWIP_ASSERT("hmem->poolnr < MEMP_MAX", (hmem->poolnr < MEMP_MAX));
00142 
00143   /* and put it in the pool we saved earlier */
00144   memp_free(hmem->poolnr, hmem);
00145 }
00146 
00147 #else /* MEM_USE_POOLS */
00148 /* lwIP replacement for your libc malloc() */
00149 
00150 /**
00151  * The heap is made up as a list of structs of this type.
00152  * This does not have to be aligned since for getting its size,
00153  * we only use the macro SIZEOF_STRUCT_MEM, which automatically alignes.
00154  */
00155 struct mem {
00156   /** index (-> ram[next]) of the next struct */
00157   mem_size_t next;
00158   /** index (-> ram[prev]) of the previous struct */
00159   mem_size_t prev;
00160   /** 1: this area is used; 0: this area is unused */
00161   u8_t used;
00162 };
00163 
00164 /** All allocated blocks will be MIN_SIZE bytes big, at least!
00165  * MIN_SIZE can be overridden to suit your needs. Smaller values save space,
00166  * larger values could prevent too small blocks to fragment the RAM too much. */
00167 #ifndef MIN_SIZE
00168 #define MIN_SIZE             12
00169 #endif /* MIN_SIZE */
00170 /* some alignment macros: we define them here for better source code layout */
00171 #define MIN_SIZE_ALIGNED     LWIP_MEM_ALIGN_SIZE(MIN_SIZE)
00172 #define SIZEOF_STRUCT_MEM    LWIP_MEM_ALIGN_SIZE(sizeof(struct mem))
00173 #define MEM_SIZE_ALIGNED     LWIP_MEM_ALIGN_SIZE(MEM_SIZE)
00174 
00175 /** If you want to relocate the heap to external memory, simply define
00176  * LWIP_RAM_HEAP_POINTER as a void-pointer to that location.
00177  * If so, make sure the memory at that location is big enough (see below on
00178  * how that space is calculated). */
00179 #ifndef LWIP_RAM_HEAP_POINTER
00180 /** the heap. we need one struct mem at the end and some room for alignment */
00181 u8_t ram_heap[MEM_SIZE_ALIGNED + (2*SIZEOF_STRUCT_MEM) + MEM_ALIGNMENT];
00182 #define LWIP_RAM_HEAP_POINTER ram_heap
00183 #endif /* LWIP_RAM_HEAP_POINTER */
00184 
00185 /** pointer to the heap (ram_heap): for alignment, ram is now a pointer instead of an array */
00186 static u8_t *ram;
00187 /** the last entry, always unused! */
00188 static struct mem *ram_end;
00189 /** pointer to the lowest free block, this is used for faster search */
00190 static struct mem *lfree;
00191 
00192 /** concurrent access protection */
00193 static sys_mutex_t mem_mutex;
00194 
00195 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00196 
00197 static volatile u8_t mem_free_count;
00198 
00199 /* Allow mem_free from other (e.g. interrupt) context */
00200 #define LWIP_MEM_FREE_DECL_PROTECT()  SYS_ARCH_DECL_PROTECT(lev_free)
00201 #define LWIP_MEM_FREE_PROTECT()       SYS_ARCH_PROTECT(lev_free)
00202 #define LWIP_MEM_FREE_UNPROTECT()     SYS_ARCH_UNPROTECT(lev_free)
00203 #define LWIP_MEM_ALLOC_DECL_PROTECT() SYS_ARCH_DECL_PROTECT(lev_alloc)
00204 #define LWIP_MEM_ALLOC_PROTECT()      SYS_ARCH_PROTECT(lev_alloc)
00205 #define LWIP_MEM_ALLOC_UNPROTECT()    SYS_ARCH_UNPROTECT(lev_alloc)
00206 
00207 #else /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00208 
00209 /* Protect the heap only by using a semaphore */
00210 #define LWIP_MEM_FREE_DECL_PROTECT()
00211 #define LWIP_MEM_FREE_PROTECT()    sys_mutex_lock(&mem_mutex)
00212 #define LWIP_MEM_FREE_UNPROTECT()  sys_mutex_unlock(&mem_mutex)
00213 /* mem_malloc is protected using semaphore AND LWIP_MEM_ALLOC_PROTECT */
00214 #define LWIP_MEM_ALLOC_DECL_PROTECT()
00215 #define LWIP_MEM_ALLOC_PROTECT()
00216 #define LWIP_MEM_ALLOC_UNPROTECT()
00217 
00218 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00219 
00220 
00221 /**
00222  * "Plug holes" by combining adjacent empty struct mems.
00223  * After this function is through, there should not exist
00224  * one empty struct mem pointing to another empty struct mem.
00225  *
00226  * @param mem this points to a struct mem which just has been freed
00227  * @internal this function is only called by mem_free() and mem_trim()
00228  *
00229  * This assumes access to the heap is protected by the calling function
00230  * already.
00231  */
00232 static void
00233 plug_holes(struct mem *mem)
00234 {
00235   struct mem *nmem;
00236   struct mem *pmem;
00237 
00238   LWIP_ASSERT("plug_holes: mem >= ram", (u8_t *)mem >= ram);
00239   LWIP_ASSERT("plug_holes: mem < ram_end", (u8_t *)mem < (u8_t *)ram_end);
00240   LWIP_ASSERT("plug_holes: mem->used == 0", mem->used == 0);
00241 
00242   /* plug hole forward */
00243   LWIP_ASSERT("plug_holes: mem->next <= MEM_SIZE_ALIGNED", mem->next <= MEM_SIZE_ALIGNED);
00244 
00245   nmem = (struct mem *)(void *)&ram[mem->next];
00246   if (mem != nmem && nmem->used == 0 && (u8_t *)nmem != (u8_t *)ram_end) {
00247     /* if mem->next is unused and not end of ram, combine mem and mem->next */
00248     if (lfree == nmem) {
00249       lfree = mem;
00250     }
00251     mem->next = nmem->next;
00252     ((struct mem *)(void *)&ram[nmem->next])->prev = (mem_size_t)((u8_t *)mem - ram);
00253   }
00254 
00255   /* plug hole backward */
00256   pmem = (struct mem *)(void *)&ram[mem->prev];
00257   if (pmem != mem && pmem->used == 0) {
00258     /* if mem->prev is unused, combine mem and mem->prev */
00259     if (lfree == mem) {
00260       lfree = pmem;
00261     }
00262     pmem->next = mem->next;
00263     ((struct mem *)(void *)&ram[mem->next])->prev = (mem_size_t)((u8_t *)pmem - ram);
00264   }
00265 }
00266 
00267 /**
00268  * Zero the heap and initialize start, end and lowest-free
00269  */
00270 void
00271 mem_init(void)
00272 {
00273   struct mem *mem;
00274 
00275   LWIP_ASSERT("Sanity check alignment",
00276     (SIZEOF_STRUCT_MEM & (MEM_ALIGNMENT-1)) == 0);
00277 
00278   /* align the heap */
00279   ram = (u8_t *)LWIP_MEM_ALIGN(LWIP_RAM_HEAP_POINTER);
00280   /* initialize the start of the heap */
00281   mem = (struct mem *)(void *)ram;
00282   mem->next = MEM_SIZE_ALIGNED;
00283   mem->prev = 0;
00284   mem->used = 0;
00285   /* initialize the end of the heap */
00286   ram_end = (struct mem *)(void *)&ram[MEM_SIZE_ALIGNED];
00287   ram_end->used = 1;
00288   ram_end->next = MEM_SIZE_ALIGNED;
00289   ram_end->prev = MEM_SIZE_ALIGNED;
00290 
00291   /* initialize the lowest-free pointer to the start of the heap */
00292   lfree = (struct mem *)(void *)ram;
00293 
00294   MEM_STATS_AVAIL(avail, MEM_SIZE_ALIGNED);
00295 
00296   if(sys_mutex_new(&mem_mutex) != ERR_OK) {
00297     LWIP_ASSERT("failed to create mem_mutex", 0);
00298   }
00299 }
00300 
00301 /**
00302  * Put a struct mem back on the heap
00303  *
00304  * @param rmem is the data portion of a struct mem as returned by a previous
00305  *             call to mem_malloc()
00306  */
00307 void
00308 mem_free(void *rmem)
00309 {
00310   struct mem *mem;
00311   LWIP_MEM_FREE_DECL_PROTECT();
00312 
00313   if (rmem == NULL) {
00314     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS, ("mem_free(p == NULL) was called.\n"));
00315     return;
00316   }
00317   LWIP_ASSERT("mem_free: sanity check alignment", (((mem_ptr_t)rmem) & (MEM_ALIGNMENT-1)) == 0);
00318 
00319   LWIP_ASSERT("mem_free: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00320     (u8_t *)rmem < (u8_t *)ram_end);
00321 
00322   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00323     SYS_ARCH_DECL_PROTECT(lev);
00324     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SEVERE, ("mem_free: illegal memory\n"));
00325     /* protect mem stats from concurrent access */
00326     SYS_ARCH_PROTECT(lev);
00327     MEM_STATS_INC(illegal);
00328     SYS_ARCH_UNPROTECT(lev);
00329     return;
00330   }
00331   /* protect the heap from concurrent access */
00332   LWIP_MEM_FREE_PROTECT();
00333   /* Get the corresponding struct mem ... */
00334   mem = (struct mem *)(void *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00335   /* ... which has to be in a used state ... */
00336   LWIP_ASSERT("mem_free: mem->used", mem->used);
00337   /* ... and is now unused. */
00338   mem->used = 0;
00339 
00340   if (mem < lfree) {
00341     /* the newly freed struct is now the lowest */
00342     lfree = mem;
00343   }
00344 
00345   MEM_STATS_DEC_USED(used, mem->next - (mem_size_t)(((u8_t *)mem - ram)));
00346 
00347   /* finally, see if prev or next are free also */
00348   plug_holes(mem);
00349 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00350   mem_free_count = 1;
00351 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00352   LWIP_MEM_FREE_UNPROTECT();
00353 }
00354 
00355 /**
00356  * Shrink memory returned by mem_malloc().
00357  *
00358  * @param rmem pointer to memory allocated by mem_malloc the is to be shrinked
00359  * @param newsize required size after shrinking (needs to be smaller than or
00360  *                equal to the previous size)
00361  * @return for compatibility reasons: is always == rmem, at the moment
00362  *         or NULL if newsize is > old size, in which case rmem is NOT touched
00363  *         or freed!
00364  */
00365 void *
00366 mem_trim(void *rmem, mem_size_t newsize)
00367 {
00368   mem_size_t size;
00369   mem_size_t ptr, ptr2;
00370   struct mem *mem, *mem2;
00371   /* use the FREE_PROTECT here: it protects with sem OR SYS_ARCH_PROTECT */
00372   LWIP_MEM_FREE_DECL_PROTECT();
00373 
00374   /* Expand the size of the allocated memory region so that we can
00375      adjust for alignment. */
00376   newsize = LWIP_MEM_ALIGN_SIZE(newsize);
00377 
00378   if(newsize < MIN_SIZE_ALIGNED) {
00379     /* every data block must be at least MIN_SIZE_ALIGNED long */
00380     newsize = MIN_SIZE_ALIGNED;
00381   }
00382 
00383   if (newsize > MEM_SIZE_ALIGNED) {
00384     return NULL;
00385   }
00386 
00387   LWIP_ASSERT("mem_trim: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00388    (u8_t *)rmem < (u8_t *)ram_end);
00389 
00390   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00391     SYS_ARCH_DECL_PROTECT(lev);
00392     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SEVERE, ("mem_trim: illegal memory\n"));
00393     /* protect mem stats from concurrent access */
00394     SYS_ARCH_PROTECT(lev);
00395     MEM_STATS_INC(illegal);
00396     SYS_ARCH_UNPROTECT(lev);
00397     return rmem;
00398   }
00399   /* Get the corresponding struct mem ... */
00400   mem = (struct mem *)(void *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00401   /* ... and its offset pointer */
00402   ptr = (mem_size_t)((u8_t *)mem - ram);
00403 
00404   size = mem->next - ptr - SIZEOF_STRUCT_MEM;
00405   LWIP_ASSERT("mem_trim can only shrink memory", newsize <= size);
00406   if (newsize > size) {
00407     /* not supported */
00408     return NULL;
00409   }
00410   if (newsize == size) {
00411     /* No change in size, simply return */
00412     return rmem;
00413   }
00414 
00415   /* protect the heap from concurrent access */
00416   LWIP_MEM_FREE_PROTECT();
00417 
00418   mem2 = (struct mem *)(void *)&ram[mem->next];
00419   if(mem2->used == 0) {
00420     /* The next struct is unused, we can simply move it at little */
00421     mem_size_t next;
00422     /* remember the old next pointer */
00423     next = mem2->next;
00424     /* create new struct mem which is moved directly after the shrinked mem */
00425     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00426     if (lfree == mem2) {
00427       lfree = (struct mem *)(void *)&ram[ptr2];
00428     }
00429     mem2 = (struct mem *)(void *)&ram[ptr2];
00430     mem2->used = 0;
00431     /* restore the next pointer */
00432     mem2->next = next;
00433     /* link it back to mem */
00434     mem2->prev = ptr;
00435     /* link mem to it */
00436     mem->next = ptr2;
00437     /* last thing to restore linked list: as we have moved mem2,
00438      * let 'mem2->next->prev' point to mem2 again. but only if mem2->next is not
00439      * the end of the heap */
00440     if (mem2->next != MEM_SIZE_ALIGNED) {
00441       ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00442     }
00443     MEM_STATS_DEC_USED(used, (size - newsize));
00444     /* no need to plug holes, we've already done that */
00445   } else if (newsize + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED <= size) {
00446     /* Next struct is used but there's room for another struct mem with
00447      * at least MIN_SIZE_ALIGNED of data.
00448      * Old size ('size') must be big enough to contain at least 'newsize' plus a struct mem
00449      * ('SIZEOF_STRUCT_MEM') with some data ('MIN_SIZE_ALIGNED').
00450      * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00451      *       region that couldn't hold data, but when mem->next gets freed,
00452      *       the 2 regions would be combined, resulting in more free memory */
00453     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00454     mem2 = (struct mem *)(void *)&ram[ptr2];
00455     if (mem2 < lfree) {
00456       lfree = mem2;
00457     }
00458     mem2->used = 0;
00459     mem2->next = mem->next;
00460     mem2->prev = ptr;
00461     mem->next = ptr2;
00462     if (mem2->next != MEM_SIZE_ALIGNED) {
00463       ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00464     }
00465     MEM_STATS_DEC_USED(used, (size - newsize));
00466     /* the original mem->next is used, so no need to plug holes! */
00467   }
00468   /* else {
00469     next struct mem is used but size between mem and mem2 is not big enough
00470     to create another struct mem
00471     -> don't do anyhting. 
00472     -> the remaining space stays unused since it is too small
00473   } */
00474 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00475   mem_free_count = 1;
00476 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00477   LWIP_MEM_FREE_UNPROTECT();
00478   return rmem;
00479 }
00480 
00481 /**
00482  * Adam's mem_malloc() plus solution for bug #17922
00483  * Allocate a block of memory with a minimum of 'size' bytes.
00484  *
00485  * @param size is the minimum size of the requested block in bytes.
00486  * @return pointer to allocated memory or NULL if no free memory was found.
00487  *
00488  * Note that the returned value will always be aligned (as defined by MEM_ALIGNMENT).
00489  */
00490 void *
00491 mem_malloc(mem_size_t size)
00492 {
00493   mem_size_t ptr, ptr2;
00494   struct mem *mem, *mem2;
00495 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00496   u8_t local_mem_free_count = 0;
00497 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00498   LWIP_MEM_ALLOC_DECL_PROTECT();
00499 
00500   if (size == 0) {
00501     return NULL;
00502   }
00503 
00504   /* Expand the size of the allocated memory region so that we can
00505      adjust for alignment. */
00506   size = LWIP_MEM_ALIGN_SIZE(size);
00507 
00508   if(size < MIN_SIZE_ALIGNED) {
00509     /* every data block must be at least MIN_SIZE_ALIGNED long */
00510     size = MIN_SIZE_ALIGNED;
00511   }
00512 
00513   if (size > MEM_SIZE_ALIGNED) {
00514     return NULL;
00515   }
00516 
00517   /* protect the heap from concurrent access */
00518   sys_mutex_lock(&mem_mutex);
00519   LWIP_MEM_ALLOC_PROTECT();
00520 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00521   /* run as long as a mem_free disturbed mem_malloc */
00522   do {
00523     local_mem_free_count = 0;
00524 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00525 
00526     /* Scan through the heap searching for a free block that is big enough,
00527      * beginning with the lowest free block.
00528      */
00529     for (ptr = (mem_size_t)((u8_t *)lfree - ram); ptr < MEM_SIZE_ALIGNED - size;
00530          ptr = ((struct mem *)(void *)&ram[ptr])->next) {
00531       mem = (struct mem *)(void *)&ram[ptr];
00532 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00533       mem_free_count = 0;
00534       LWIP_MEM_ALLOC_UNPROTECT();
00535       /* allow mem_free to run */
00536       LWIP_MEM_ALLOC_PROTECT();
00537       if (mem_free_count != 0) {
00538         local_mem_free_count = mem_free_count;
00539       }
00540       mem_free_count = 0;
00541 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00542 
00543       if ((!mem->used) &&
00544           (mem->next - (ptr + SIZEOF_STRUCT_MEM)) >= size) {
00545         /* mem is not used and at least perfect fit is possible:
00546          * mem->next - (ptr + SIZEOF_STRUCT_MEM) gives us the 'user data size' of mem */
00547 
00548         if (mem->next - (ptr + SIZEOF_STRUCT_MEM) >= (size + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED)) {
00549           /* (in addition to the above, we test if another struct mem (SIZEOF_STRUCT_MEM) containing
00550            * at least MIN_SIZE_ALIGNED of data also fits in the 'user data space' of 'mem')
00551            * -> split large block, create empty remainder,
00552            * remainder must be large enough to contain MIN_SIZE_ALIGNED data: if
00553            * mem->next - (ptr + (2*SIZEOF_STRUCT_MEM)) == size,
00554            * struct mem would fit in but no data between mem2 and mem2->next
00555            * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00556            *       region that couldn't hold data, but when mem->next gets freed,
00557            *       the 2 regions would be combined, resulting in more free memory
00558            */
00559           ptr2 = ptr + SIZEOF_STRUCT_MEM + size;
00560           /* create mem2 struct */
00561           mem2 = (struct mem *)(void *)&ram[ptr2];
00562           mem2->used = 0;
00563           mem2->next = mem->next;
00564           mem2->prev = ptr;
00565           /* and insert it between mem and mem->next */
00566           mem->next = ptr2;
00567           mem->used = 1;
00568 
00569           if (mem2->next != MEM_SIZE_ALIGNED) {
00570             ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00571           }
00572           MEM_STATS_INC_USED(used, (size + SIZEOF_STRUCT_MEM));
00573         } else {
00574           /* (a mem2 struct does no fit into the user data space of mem and mem->next will always
00575            * be used at this point: if not we have 2 unused structs in a row, plug_holes should have
00576            * take care of this).
00577            * -> near fit or excact fit: do not split, no mem2 creation
00578            * also can't move mem->next directly behind mem, since mem->next
00579            * will always be used at this point!
00580            */
00581           mem->used = 1;
00582           MEM_STATS_INC_USED(used, mem->next - (mem_size_t)((u8_t *)mem - ram));
00583         }
00584 
00585         if (mem == lfree) {
00586           /* Find next free block after mem and update lowest free pointer */
00587           while (lfree->used && lfree != ram_end) {
00588             LWIP_MEM_ALLOC_UNPROTECT();
00589             /* prevent high interrupt latency... */
00590             LWIP_MEM_ALLOC_PROTECT();
00591             lfree = (struct mem *)(void *)&ram[lfree->next];
00592           }
00593           LWIP_ASSERT("mem_malloc: !lfree->used", ((lfree == ram_end) || (!lfree->used)));
00594         }
00595         LWIP_MEM_ALLOC_UNPROTECT();
00596         sys_mutex_unlock(&mem_mutex);
00597         LWIP_ASSERT("mem_malloc: allocated memory not above ram_end.",
00598          (mem_ptr_t)mem + SIZEOF_STRUCT_MEM + size <= (mem_ptr_t)ram_end);
00599         LWIP_ASSERT("mem_malloc: allocated memory properly aligned.",
00600          ((mem_ptr_t)mem + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT == 0);
00601         LWIP_ASSERT("mem_malloc: sanity check alignment",
00602           (((mem_ptr_t)mem) & (MEM_ALIGNMENT-1)) == 0);
00603 
00604         return (u8_t *)mem + SIZEOF_STRUCT_MEM;
00605       }
00606     }
00607 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00608     /* if we got interrupted by a mem_free, try again */
00609   } while(local_mem_free_count != 0);
00610 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00611   LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("mem_malloc: could not allocate %"S16_F" bytes\n", (s16_t)size));
00612   MEM_STATS_INC(err);
00613   LWIP_MEM_ALLOC_UNPROTECT();
00614   sys_mutex_unlock(&mem_mutex);
00615   return NULL;
00616 }
00617 
00618 #endif /* MEM_USE_POOLS */
00619 /**
00620  * Contiguously allocates enough space for count objects that are size bytes
00621  * of memory each and returns a pointer to the allocated memory.
00622  *
00623  * The allocated memory is filled with bytes of value zero.
00624  *
00625  * @param count number of objects to allocate
00626  * @param size size of the objects to allocate
00627  * @return pointer to allocated memory / NULL pointer if there is an error
00628  */
00629 void *mem_calloc(mem_size_t count, mem_size_t size)
00630 {
00631   void *p;
00632 
00633   /* allocate 'count' objects of size 'size' */
00634   p = mem_malloc(count * size);
00635   if (p) {
00636     /* zero the memory */
00637     memset(p, 0, count * size);
00638   }
00639   return p;
00640 }
00641 
00642 #endif /* !MEM_LIBC_MALLOC */