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