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   void *ret;
00082   struct memp_malloc_helper *element;
00083   memp_t poolnr;
00084   mem_size_t required_size = size + LWIP_MEM_ALIGN_SIZE(sizeof(struct memp_malloc_helper));
00085 
00086   for (poolnr = MEMP_POOL_FIRST; poolnr <= MEMP_POOL_LAST; poolnr = (memp_t)(poolnr + 1)) {
00087 #if MEM_USE_POOLS_TRY_BIGGER_POOL
00088 again:
00089 #endif /* MEM_USE_POOLS_TRY_BIGGER_POOL */
00090     /* is this pool big enough to hold an element of the required size
00091        plus a struct memp_malloc_helper that saves the pool this element came from? */
00092     if (required_size <= memp_sizes[poolnr]) {
00093       break;
00094     }
00095   }
00096   if (poolnr > MEMP_POOL_LAST) {
00097     LWIP_ASSERT("mem_malloc(): no pool is that big!", 0);
00098     return NULL;
00099   }
00100   element = (struct memp_malloc_helper*)memp_malloc(poolnr);
00101   if (element == NULL) {
00102     /* No need to DEBUGF or ASSERT: This error is already
00103        taken care of in memp.c */
00104 #if MEM_USE_POOLS_TRY_BIGGER_POOL
00105     /** Try a bigger pool if this one is empty! */
00106     if (poolnr < MEMP_POOL_LAST) {
00107       poolnr++;
00108       goto again;
00109     }
00110 #endif /* MEM_USE_POOLS_TRY_BIGGER_POOL */
00111     return NULL;
00112   }
00113 
00114   /* save the pool number this element came from */
00115   element->poolnr = poolnr;
00116   /* and return a pointer to the memory directly after the struct memp_malloc_helper */
00117   ret = (u8_t*)element + LWIP_MEM_ALIGN_SIZE(sizeof(struct memp_malloc_helper));
00118 
00119   return ret;
00120 }
00121 
00122 /**
00123  * Free memory previously allocated by mem_malloc. Loads the pool number
00124  * and calls memp_free with that pool number to put the element back into
00125  * its pool
00126  *
00127  * @param rmem the memory element to free
00128  */
00129 void
00130 mem_free(void *rmem)
00131 {
00132   struct memp_malloc_helper *hmem;
00133 
00134   LWIP_ASSERT("rmem != NULL", (rmem != NULL));
00135   LWIP_ASSERT("rmem == MEM_ALIGN(rmem)", (rmem == LWIP_MEM_ALIGN(rmem)));
00136 
00137   /* get the original struct memp_malloc_helper */
00138   hmem = (struct memp_malloc_helper*)(void*)((u8_t*)rmem - LWIP_MEM_ALIGN_SIZE(sizeof(struct memp_malloc_helper)));
00139 
00140   LWIP_ASSERT("hmem != NULL", (hmem != NULL));
00141   LWIP_ASSERT("hmem == MEM_ALIGN(hmem)", (hmem == LWIP_MEM_ALIGN(hmem)));
00142   LWIP_ASSERT("hmem->poolnr < MEMP_MAX", (hmem->poolnr < MEMP_MAX));
00143 
00144   /* and put it in the pool we saved earlier */
00145   memp_free(hmem->poolnr, hmem);
00146 }
00147 
00148 #else /* MEM_USE_POOLS */
00149 /* lwIP replacement for your libc malloc() */
00150 
00151 /**
00152  * The heap is made up as a list of structs of this type.
00153  * This does not have to be aligned since for getting its size,
00154  * we only use the macro SIZEOF_STRUCT_MEM, which automatically alignes.
00155  */
00156 struct mem {
00157   /** index (-> ram[next]) of the next struct */
00158   mem_size_t next;
00159   /** index (-> ram[prev]) of the previous struct */
00160   mem_size_t prev;
00161   /** 1: this area is used; 0: this area is unused */
00162   u8_t used;
00163 };
00164 
00165 /** All allocated blocks will be MIN_SIZE bytes big, at least!
00166  * MIN_SIZE can be overridden to suit your needs. Smaller values save space,
00167  * larger values could prevent too small blocks to fragment the RAM too much. */
00168 #ifndef MIN_SIZE
00169 #define MIN_SIZE             12
00170 #endif /* MIN_SIZE */
00171 /* some alignment macros: we define them here for better source code layout */
00172 #define MIN_SIZE_ALIGNED     LWIP_MEM_ALIGN_SIZE(MIN_SIZE)
00173 #define SIZEOF_STRUCT_MEM    LWIP_MEM_ALIGN_SIZE(sizeof(struct mem))
00174 #define MEM_SIZE_ALIGNED     LWIP_MEM_ALIGN_SIZE(MEM_SIZE)
00175 
00176 /** If you want to relocate the heap to external memory, simply define
00177  * LWIP_RAM_HEAP_POINTER as a void-pointer to that location.
00178  * If so, make sure the memory at that location is big enough (see below on
00179  * how that space is calculated). */
00180 #ifndef LWIP_RAM_HEAP_POINTER
00181 /** the heap. we need one struct mem at the end and some room for alignment */
00182 u8_t ram_heap[MEM_SIZE_ALIGNED + (2*SIZEOF_STRUCT_MEM) + MEM_ALIGNMENT];
00183 #define LWIP_RAM_HEAP_POINTER ram_heap
00184 #endif /* LWIP_RAM_HEAP_POINTER */
00185 
00186 /** pointer to the heap (ram_heap): for alignment, ram is now a pointer instead of an array */
00187 static u8_t *ram;
00188 /** the last entry, always unused! */
00189 static struct mem *ram_end;
00190 /** pointer to the lowest free block, this is used for faster search */
00191 static struct mem *lfree;
00192 
00193 /** concurrent access protection */
00194 #if !NO_SYS
00195 static sys_mutex_t mem_mutex;
00196 #endif
00197 
00198 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00199 
00200 static volatile u8_t mem_free_count;
00201 
00202 /* Allow mem_free from other (e.g. interrupt) context */
00203 #define LWIP_MEM_FREE_DECL_PROTECT()  SYS_ARCH_DECL_PROTECT(lev_free)
00204 #define LWIP_MEM_FREE_PROTECT()       SYS_ARCH_PROTECT(lev_free)
00205 #define LWIP_MEM_FREE_UNPROTECT()     SYS_ARCH_UNPROTECT(lev_free)
00206 #define LWIP_MEM_ALLOC_DECL_PROTECT() SYS_ARCH_DECL_PROTECT(lev_alloc)
00207 #define LWIP_MEM_ALLOC_PROTECT()      SYS_ARCH_PROTECT(lev_alloc)
00208 #define LWIP_MEM_ALLOC_UNPROTECT()    SYS_ARCH_UNPROTECT(lev_alloc)
00209 
00210 #else /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00211 
00212 /* Protect the heap only by using a semaphore */
00213 #define LWIP_MEM_FREE_DECL_PROTECT()
00214 #define LWIP_MEM_FREE_PROTECT()    sys_mutex_lock(&mem_mutex)
00215 #define LWIP_MEM_FREE_UNPROTECT()  sys_mutex_unlock(&mem_mutex)
00216 /* mem_malloc is protected using semaphore AND LWIP_MEM_ALLOC_PROTECT */
00217 #define LWIP_MEM_ALLOC_DECL_PROTECT()
00218 #define LWIP_MEM_ALLOC_PROTECT()
00219 #define LWIP_MEM_ALLOC_UNPROTECT()
00220 
00221 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00222 
00223 
00224 /**
00225  * "Plug holes" by combining adjacent empty struct mems.
00226  * After this function is through, there should not exist
00227  * one empty struct mem pointing to another empty struct mem.
00228  *
00229  * @param mem this points to a struct mem which just has been freed
00230  * @internal this function is only called by mem_free() and mem_trim()
00231  *
00232  * This assumes access to the heap is protected by the calling function
00233  * already.
00234  */
00235 static void
00236 plug_holes(struct mem *mem)
00237 {
00238   struct mem *nmem;
00239   struct mem *pmem;
00240 
00241   LWIP_ASSERT("plug_holes: mem >= ram", (u8_t *)mem >= ram);
00242   LWIP_ASSERT("plug_holes: mem < ram_end", (u8_t *)mem < (u8_t *)ram_end);
00243   LWIP_ASSERT("plug_holes: mem->used == 0", mem->used == 0);
00244 
00245   /* plug hole forward */
00246   LWIP_ASSERT("plug_holes: mem->next <= MEM_SIZE_ALIGNED", mem->next <= MEM_SIZE_ALIGNED);
00247 
00248   nmem = (struct mem *)(void *)&ram[mem->next];
00249   if (mem != nmem && nmem->used == 0 && (u8_t *)nmem != (u8_t *)ram_end) {
00250     /* if mem->next is unused and not end of ram, combine mem and mem->next */
00251     if (lfree == nmem) {
00252       lfree = mem;
00253     }
00254     mem->next = nmem->next;
00255     ((struct mem *)(void *)&ram[nmem->next])->prev = (mem_size_t)((u8_t *)mem - ram);
00256   }
00257 
00258   /* plug hole backward */
00259   pmem = (struct mem *)(void *)&ram[mem->prev];
00260   if (pmem != mem && pmem->used == 0) {
00261     /* if mem->prev is unused, combine mem and mem->prev */
00262     if (lfree == mem) {
00263       lfree = pmem;
00264     }
00265     pmem->next = mem->next;
00266     ((struct mem *)(void *)&ram[mem->next])->prev = (mem_size_t)((u8_t *)pmem - ram);
00267   }
00268 }
00269 
00270 /**
00271  * Zero the heap and initialize start, end and lowest-free
00272  */
00273 void
00274 mem_init(void)
00275 {
00276   struct mem *mem;
00277 
00278   LWIP_ASSERT("Sanity check alignment",
00279     (SIZEOF_STRUCT_MEM & (MEM_ALIGNMENT-1)) == 0);
00280 
00281   /* align the heap */
00282   ram = (u8_t *)LWIP_MEM_ALIGN(LWIP_RAM_HEAP_POINTER);
00283   /* initialize the start of the heap */
00284   mem = (struct mem *)(void *)ram;
00285   mem->next = MEM_SIZE_ALIGNED;
00286   mem->prev = 0;
00287   mem->used = 0;
00288   /* initialize the end of the heap */
00289   ram_end = (struct mem *)(void *)&ram[MEM_SIZE_ALIGNED];
00290   ram_end->used = 1;
00291   ram_end->next = MEM_SIZE_ALIGNED;
00292   ram_end->prev = MEM_SIZE_ALIGNED;
00293 
00294   /* initialize the lowest-free pointer to the start of the heap */
00295   lfree = (struct mem *)(void *)ram;
00296 
00297   MEM_STATS_AVAIL(avail, MEM_SIZE_ALIGNED);
00298 
00299   if(sys_mutex_new(&mem_mutex) != ERR_OK) {
00300     LWIP_ASSERT("failed to create mem_mutex", 0);
00301   }
00302 }
00303 
00304 /**
00305  * Put a struct mem back on the heap
00306  *
00307  * @param rmem is the data portion of a struct mem as returned by a previous
00308  *             call to mem_malloc()
00309  */
00310 void
00311 mem_free(void *rmem)
00312 {
00313   struct mem *mem;
00314   LWIP_MEM_FREE_DECL_PROTECT();
00315 
00316   if (rmem == NULL) {
00317     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS, ("mem_free(p == NULL) was called.\n"));
00318     return;
00319   }
00320   LWIP_ASSERT("mem_free: sanity check alignment", (((mem_ptr_t)rmem) & (MEM_ALIGNMENT-1)) == 0);
00321 
00322   LWIP_ASSERT("mem_free: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00323     (u8_t *)rmem < (u8_t *)ram_end);
00324 
00325   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00326     SYS_ARCH_DECL_PROTECT(lev);
00327     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SEVERE, ("mem_free: illegal memory\n"));
00328     /* protect mem stats from concurrent access */
00329     SYS_ARCH_PROTECT(lev);
00330     MEM_STATS_INC(illegal);
00331     SYS_ARCH_UNPROTECT(lev);
00332     return;
00333   }
00334   /* protect the heap from concurrent access */
00335   LWIP_MEM_FREE_PROTECT();
00336   /* Get the corresponding struct mem ... */
00337   mem = (struct mem *)(void *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00338   /* ... which has to be in a used state ... */
00339   LWIP_ASSERT("mem_free: mem->used", mem->used);
00340   /* ... and is now unused. */
00341   mem->used = 0;
00342 
00343   if (mem < lfree) {
00344     /* the newly freed struct is now the lowest */
00345     lfree = mem;
00346   }
00347 
00348   MEM_STATS_DEC_USED(used, mem->next - (mem_size_t)(((u8_t *)mem - ram)));
00349 
00350   /* finally, see if prev or next are free also */
00351   plug_holes(mem);
00352 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00353   mem_free_count = 1;
00354 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00355   LWIP_MEM_FREE_UNPROTECT();
00356 }
00357 
00358 /**
00359  * Shrink memory returned by mem_malloc().
00360  *
00361  * @param rmem pointer to memory allocated by mem_malloc the is to be shrinked
00362  * @param newsize required size after shrinking (needs to be smaller than or
00363  *                equal to the previous size)
00364  * @return for compatibility reasons: is always == rmem, at the moment
00365  *         or NULL if newsize is > old size, in which case rmem is NOT touched
00366  *         or freed!
00367  */
00368 void *
00369 mem_trim(void *rmem, mem_size_t newsize)
00370 {
00371   mem_size_t size;
00372   mem_size_t ptr, ptr2;
00373   struct mem *mem, *mem2;
00374   /* use the FREE_PROTECT here: it protects with sem OR SYS_ARCH_PROTECT */
00375   LWIP_MEM_FREE_DECL_PROTECT();
00376 
00377   /* Expand the size of the allocated memory region so that we can
00378      adjust for alignment. */
00379   newsize = LWIP_MEM_ALIGN_SIZE(newsize);
00380 
00381   if(newsize < MIN_SIZE_ALIGNED) {
00382     /* every data block must be at least MIN_SIZE_ALIGNED long */
00383     newsize = MIN_SIZE_ALIGNED;
00384   }
00385 
00386   if (newsize > MEM_SIZE_ALIGNED) {
00387     return NULL;
00388   }
00389 
00390   LWIP_ASSERT("mem_trim: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00391    (u8_t *)rmem < (u8_t *)ram_end);
00392 
00393   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00394     SYS_ARCH_DECL_PROTECT(lev);
00395     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SEVERE, ("mem_trim: illegal memory\n"));
00396     /* protect mem stats from concurrent access */
00397     SYS_ARCH_PROTECT(lev);
00398     MEM_STATS_INC(illegal);
00399     SYS_ARCH_UNPROTECT(lev);
00400     return rmem;
00401   }
00402   /* Get the corresponding struct mem ... */
00403   mem = (struct mem *)(void *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00404   /* ... and its offset pointer */
00405   ptr = (mem_size_t)((u8_t *)mem - ram);
00406 
00407   size = mem->next - ptr - SIZEOF_STRUCT_MEM;
00408   LWIP_ASSERT("mem_trim can only shrink memory", newsize <= size);
00409   if (newsize > size) {
00410     /* not supported */
00411     return NULL;
00412   }
00413   if (newsize == size) {
00414     /* No change in size, simply return */
00415     return rmem;
00416   }
00417 
00418   /* protect the heap from concurrent access */
00419   LWIP_MEM_FREE_PROTECT();
00420 
00421   mem2 = (struct mem *)(void *)&ram[mem->next];
00422   if(mem2->used == 0) {
00423     /* The next struct is unused, we can simply move it at little */
00424     mem_size_t next;
00425     /* remember the old next pointer */
00426     next = mem2->next;
00427     /* create new struct mem which is moved directly after the shrinked mem */
00428     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00429     if (lfree == mem2) {
00430       lfree = (struct mem *)(void *)&ram[ptr2];
00431     }
00432     mem2 = (struct mem *)(void *)&ram[ptr2];
00433     mem2->used = 0;
00434     /* restore the next pointer */
00435     mem2->next = next;
00436     /* link it back to mem */
00437     mem2->prev = ptr;
00438     /* link mem to it */
00439     mem->next = ptr2;
00440     /* last thing to restore linked list: as we have moved mem2,
00441      * let 'mem2->next->prev' point to mem2 again. but only if mem2->next is not
00442      * the end of the heap */
00443     if (mem2->next != MEM_SIZE_ALIGNED) {
00444       ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00445     }
00446     MEM_STATS_DEC_USED(used, (size - newsize));
00447     /* no need to plug holes, we've already done that */
00448   } else if (newsize + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED <= size) {
00449     /* Next struct is used but there's room for another struct mem with
00450      * at least MIN_SIZE_ALIGNED of data.
00451      * Old size ('size') must be big enough to contain at least 'newsize' plus a struct mem
00452      * ('SIZEOF_STRUCT_MEM') with some data ('MIN_SIZE_ALIGNED').
00453      * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00454      *       region that couldn't hold data, but when mem->next gets freed,
00455      *       the 2 regions would be combined, resulting in more free memory */
00456     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00457     mem2 = (struct mem *)(void *)&ram[ptr2];
00458     if (mem2 < lfree) {
00459       lfree = mem2;
00460     }
00461     mem2->used = 0;
00462     mem2->next = mem->next;
00463     mem2->prev = ptr;
00464     mem->next = ptr2;
00465     if (mem2->next != MEM_SIZE_ALIGNED) {
00466       ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00467     }
00468     MEM_STATS_DEC_USED(used, (size - newsize));
00469     /* the original mem->next is used, so no need to plug holes! */
00470   }
00471   /* else {
00472     next struct mem is used but size between mem and mem2 is not big enough
00473     to create another struct mem
00474     -> don't do anyhting. 
00475     -> the remaining space stays unused since it is too small
00476   } */
00477 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00478   mem_free_count = 1;
00479 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00480   LWIP_MEM_FREE_UNPROTECT();
00481   return rmem;
00482 }
00483 
00484 /**
00485  * Adam's mem_malloc() plus solution for bug #17922
00486  * Allocate a block of memory with a minimum of 'size' bytes.
00487  *
00488  * @param size is the minimum size of the requested block in bytes.
00489  * @return pointer to allocated memory or NULL if no free memory was found.
00490  *
00491  * Note that the returned value will always be aligned (as defined by MEM_ALIGNMENT).
00492  */
00493 void *
00494 mem_malloc(mem_size_t size)
00495 {
00496   mem_size_t ptr, ptr2;
00497   struct mem *mem, *mem2;
00498 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00499   u8_t local_mem_free_count = 0;
00500 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00501   LWIP_MEM_ALLOC_DECL_PROTECT();
00502 
00503   if (size == 0) {
00504     return NULL;
00505   }
00506 
00507   /* Expand the size of the allocated memory region so that we can
00508      adjust for alignment. */
00509   size = LWIP_MEM_ALIGN_SIZE(size);
00510 
00511   if(size < MIN_SIZE_ALIGNED) {
00512     /* every data block must be at least MIN_SIZE_ALIGNED long */
00513     size = MIN_SIZE_ALIGNED;
00514   }
00515 
00516   if (size > MEM_SIZE_ALIGNED) {
00517     return NULL;
00518   }
00519 
00520   /* protect the heap from concurrent access */
00521   sys_mutex_lock(&mem_mutex);
00522   LWIP_MEM_ALLOC_PROTECT();
00523 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00524   /* run as long as a mem_free disturbed mem_malloc or mem_trim */
00525   do {
00526     local_mem_free_count = 0;
00527 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00528 
00529     /* Scan through the heap searching for a free block that is big enough,
00530      * beginning with the lowest free block.
00531      */
00532     for (ptr = (mem_size_t)((u8_t *)lfree - ram); ptr < MEM_SIZE_ALIGNED - size;
00533          ptr = ((struct mem *)(void *)&ram[ptr])->next) {
00534       mem = (struct mem *)(void *)&ram[ptr];
00535 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00536       mem_free_count = 0;
00537       LWIP_MEM_ALLOC_UNPROTECT();
00538       /* allow mem_free or mem_trim to run */
00539       LWIP_MEM_ALLOC_PROTECT();
00540       if (mem_free_count != 0) {
00541         /* If mem_free or mem_trim have run, we have to restart since they
00542            could have altered our current struct mem. */
00543         local_mem_free_count = 1;
00544         break;
00545       }
00546 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00547 
00548       if ((!mem->used) &&
00549           (mem->next - (ptr + SIZEOF_STRUCT_MEM)) >= size) {
00550         /* mem is not used and at least perfect fit is possible:
00551          * mem->next - (ptr + SIZEOF_STRUCT_MEM) gives us the 'user data size' of mem */
00552 
00553         if (mem->next - (ptr + SIZEOF_STRUCT_MEM) >= (size + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED)) {
00554           /* (in addition to the above, we test if another struct mem (SIZEOF_STRUCT_MEM) containing
00555            * at least MIN_SIZE_ALIGNED of data also fits in the 'user data space' of 'mem')
00556            * -> split large block, create empty remainder,
00557            * remainder must be large enough to contain MIN_SIZE_ALIGNED data: if
00558            * mem->next - (ptr + (2*SIZEOF_STRUCT_MEM)) == size,
00559            * struct mem would fit in but no data between mem2 and mem2->next
00560            * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00561            *       region that couldn't hold data, but when mem->next gets freed,
00562            *       the 2 regions would be combined, resulting in more free memory
00563            */
00564           ptr2 = ptr + SIZEOF_STRUCT_MEM + size;
00565           /* create mem2 struct */
00566           mem2 = (struct mem *)(void *)&ram[ptr2];
00567           mem2->used = 0;
00568           mem2->next = mem->next;
00569           mem2->prev = ptr;
00570           /* and insert it between mem and mem->next */
00571           mem->next = ptr2;
00572           mem->used = 1;
00573 
00574           if (mem2->next != MEM_SIZE_ALIGNED) {
00575             ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00576           }
00577           MEM_STATS_INC_USED(used, (size + SIZEOF_STRUCT_MEM));
00578         } else {
00579           /* (a mem2 struct does no fit into the user data space of mem and mem->next will always
00580            * be used at this point: if not we have 2 unused structs in a row, plug_holes should have
00581            * take care of this).
00582            * -> near fit or excact fit: do not split, no mem2 creation
00583            * also can't move mem->next directly behind mem, since mem->next
00584            * will always be used at this point!
00585            */
00586           mem->used = 1;
00587           MEM_STATS_INC_USED(used, mem->next - (mem_size_t)((u8_t *)mem - ram));
00588         }
00589 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00590 mem_malloc_adjust_lfree:
00591 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00592         if (mem == lfree) {
00593           struct mem *cur = lfree;
00594           /* Find next free block after mem and update lowest free pointer */
00595           while (cur->used && cur != ram_end) {
00596 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00597             mem_free_count = 0;
00598             LWIP_MEM_ALLOC_UNPROTECT();
00599             /* prevent high interrupt latency... */
00600             LWIP_MEM_ALLOC_PROTECT();
00601             if (mem_free_count != 0) {
00602               /* If mem_free or mem_trim have run, we have to restart since they
00603                  could have altered our current struct mem or lfree. */
00604               goto mem_malloc_adjust_lfree;
00605             }
00606 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00607             cur = (struct mem *)(void *)&ram[cur->next];
00608           }
00609           lfree = cur;
00610           LWIP_ASSERT("mem_malloc: !lfree->used", ((lfree == ram_end) || (!lfree->used)));
00611         }
00612         LWIP_MEM_ALLOC_UNPROTECT();
00613         sys_mutex_unlock(&mem_mutex);
00614         LWIP_ASSERT("mem_malloc: allocated memory not above ram_end.",
00615          (mem_ptr_t)mem + SIZEOF_STRUCT_MEM + size <= (mem_ptr_t)ram_end);
00616         LWIP_ASSERT("mem_malloc: allocated memory properly aligned.",
00617          ((mem_ptr_t)mem + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT == 0);
00618         LWIP_ASSERT("mem_malloc: sanity check alignment",
00619           (((mem_ptr_t)mem) & (MEM_ALIGNMENT-1)) == 0);
00620 
00621         return (u8_t *)mem + SIZEOF_STRUCT_MEM;
00622       }
00623     }
00624 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00625     /* if we got interrupted by a mem_free, try again */
00626   } while(local_mem_free_count != 0);
00627 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00628   LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("mem_malloc: could not allocate %"S16_F" bytes\n", (s16_t)size));
00629   MEM_STATS_INC(err);
00630   LWIP_MEM_ALLOC_UNPROTECT();
00631   sys_mutex_unlock(&mem_mutex);
00632   return NULL;
00633 }
00634 
00635 #endif /* MEM_USE_POOLS */
00636 /**
00637  * Contiguously allocates enough space for count objects that are size bytes
00638  * of memory each and returns a pointer to the allocated memory.
00639  *
00640  * The allocated memory is filled with bytes of value zero.
00641  *
00642  * @param count number of objects to allocate
00643  * @param size size of the objects to allocate
00644  * @return pointer to allocated memory / NULL pointer if there is an error
00645  */
00646 void *mem_calloc(mem_size_t count, mem_size_t size)
00647 {
00648   void *p;
00649 
00650   /* allocate 'count' objects of size 'size' */
00651   p = mem_malloc(count * size);
00652   if (p) {
00653     /* zero the memory */
00654     memset(p, 0, count * size);
00655   }
00656   return p;
00657 }
00658 
00659 #endif /* !MEM_LIBC_MALLOC */