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 
00181 #if defined(TARGET_LPC4088) || defined(TARGET_LPC4088_DM)
00182 #  if defined (__ICCARM__)
00183 #     define ETHMEM_SECTION
00184 #  elif defined(TOOLCHAIN_GCC_CR)
00185 #     define ETHMEM_SECTION __attribute__((section(".data.$RamPeriph32")))
00186 #  else
00187 #     define ETHMEM_SECTION __attribute__((section("AHBSRAM1"),aligned))
00188 #  endif
00189 #elif defined(TARGET_LPC1768)
00190 #   define ETHMEM_SECTION __attribute((section("AHBSRAM0")))
00191 #else
00192 #       define ETHMEM_SECTION
00193 #endif
00194 
00195 /** the heap. we need one struct mem at the end and some room for alignment */
00196 u8_t ram_heap[MEM_SIZE_ALIGNED + (2*SIZEOF_STRUCT_MEM) + MEM_ALIGNMENT] ETHMEM_SECTION;
00197 #define LWIP_RAM_HEAP_POINTER ram_heap
00198 #endif /* LWIP_RAM_HEAP_POINTER */
00199 
00200 /** pointer to the heap (ram_heap): for alignment, ram is now a pointer instead of an array */
00201 static u8_t *ram;
00202 /** the last entry, always unused! */
00203 static struct mem *ram_end;
00204 /** pointer to the lowest free block, this is used for faster search */
00205 static struct mem *lfree;
00206 
00207 /** concurrent access protection */
00208 static sys_mutex_t mem_mutex;
00209 
00210 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00211 
00212 static volatile u8_t mem_free_count;
00213 
00214 /* Allow mem_free from other (e.g. interrupt) context */
00215 #define LWIP_MEM_FREE_DECL_PROTECT()  SYS_ARCH_DECL_PROTECT(lev_free)
00216 #define LWIP_MEM_FREE_PROTECT()       SYS_ARCH_PROTECT(lev_free)
00217 #define LWIP_MEM_FREE_UNPROTECT()     SYS_ARCH_UNPROTECT(lev_free)
00218 #define LWIP_MEM_ALLOC_DECL_PROTECT() SYS_ARCH_DECL_PROTECT(lev_alloc)
00219 #define LWIP_MEM_ALLOC_PROTECT()      SYS_ARCH_PROTECT(lev_alloc)
00220 #define LWIP_MEM_ALLOC_UNPROTECT()    SYS_ARCH_UNPROTECT(lev_alloc)
00221 
00222 #else /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00223 
00224 /* Protect the heap only by using a semaphore */
00225 #define LWIP_MEM_FREE_DECL_PROTECT()
00226 #define LWIP_MEM_FREE_PROTECT()    sys_mutex_lock(&mem_mutex)
00227 #define LWIP_MEM_FREE_UNPROTECT()  sys_mutex_unlock(&mem_mutex)
00228 /* mem_malloc is protected using semaphore AND LWIP_MEM_ALLOC_PROTECT */
00229 #define LWIP_MEM_ALLOC_DECL_PROTECT()
00230 #define LWIP_MEM_ALLOC_PROTECT()
00231 #define LWIP_MEM_ALLOC_UNPROTECT()
00232 
00233 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00234 
00235 
00236 /**
00237  * "Plug holes" by combining adjacent empty struct mems.
00238  * After this function is through, there should not exist
00239  * one empty struct mem pointing to another empty struct mem.
00240  *
00241  * @param mem this points to a struct mem which just has been freed
00242  * @internal this function is only called by mem_free() and mem_trim()
00243  *
00244  * This assumes access to the heap is protected by the calling function
00245  * already.
00246  */
00247 static void
00248 plug_holes(struct mem *mem)
00249 {
00250   struct mem *nmem;
00251   struct mem *pmem;
00252 
00253   LWIP_ASSERT("plug_holes: mem >= ram", (u8_t *)mem >= ram);
00254   LWIP_ASSERT("plug_holes: mem < ram_end", (u8_t *)mem < (u8_t *)ram_end);
00255   LWIP_ASSERT("plug_holes: mem->used == 0", mem->used == 0);
00256 
00257   /* plug hole forward */
00258   LWIP_ASSERT("plug_holes: mem->next <= MEM_SIZE_ALIGNED", mem->next <= MEM_SIZE_ALIGNED);
00259 
00260   nmem = (struct mem *)(void *)&ram[mem->next];
00261   if (mem != nmem && nmem->used == 0 && (u8_t *)nmem != (u8_t *)ram_end) {
00262     /* if mem->next is unused and not end of ram, combine mem and mem->next */
00263     if (lfree == nmem) {
00264       lfree = mem;
00265     }
00266     mem->next = nmem->next;
00267     ((struct mem *)(void *)&ram[nmem->next])->prev = (mem_size_t)((u8_t *)mem - ram);
00268   }
00269 
00270   /* plug hole backward */
00271   pmem = (struct mem *)(void *)&ram[mem->prev];
00272   if (pmem != mem && pmem->used == 0) {
00273     /* if mem->prev is unused, combine mem and mem->prev */
00274     if (lfree == mem) {
00275       lfree = pmem;
00276     }
00277     pmem->next = mem->next;
00278     ((struct mem *)(void *)&ram[mem->next])->prev = (mem_size_t)((u8_t *)pmem - ram);
00279   }
00280 }
00281 
00282 /**
00283  * Zero the heap and initialize start, end and lowest-free
00284  */
00285 void
00286 mem_init(void)
00287 {
00288   struct mem *mem;
00289 
00290   LWIP_ASSERT("Sanity check alignment",
00291     (SIZEOF_STRUCT_MEM & (MEM_ALIGNMENT-1)) == 0);
00292 
00293   /* align the heap */
00294   ram = (u8_t *)LWIP_MEM_ALIGN(LWIP_RAM_HEAP_POINTER);
00295   /* initialize the start of the heap */
00296   mem = (struct mem *)(void *)ram;
00297   mem->next = MEM_SIZE_ALIGNED;
00298   mem->prev = 0;
00299   mem->used = 0;
00300   /* initialize the end of the heap */
00301   ram_end = (struct mem *)(void *)&ram[MEM_SIZE_ALIGNED];
00302   ram_end->used = 1;
00303   ram_end->next = MEM_SIZE_ALIGNED;
00304   ram_end->prev = MEM_SIZE_ALIGNED;
00305 
00306   /* initialize the lowest-free pointer to the start of the heap */
00307   lfree = (struct mem *)(void *)ram;
00308 
00309   MEM_STATS_AVAIL(avail, MEM_SIZE_ALIGNED);
00310 
00311   if(sys_mutex_new(&mem_mutex) != ERR_OK) {
00312     LWIP_ASSERT("failed to create mem_mutex", 0);
00313   }
00314 }
00315 
00316 /**
00317  * Put a struct mem back on the heap
00318  *
00319  * @param rmem is the data portion of a struct mem as returned by a previous
00320  *             call to mem_malloc()
00321  */
00322 void
00323 mem_free(void *rmem)
00324 {
00325   struct mem *mem;
00326   LWIP_MEM_FREE_DECL_PROTECT();
00327 
00328   if (rmem == NULL) {
00329     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS, ("mem_free(p == NULL) was called.\n"));
00330     return;
00331   }
00332   LWIP_ASSERT("mem_free: sanity check alignment", (((mem_ptr_t)rmem) & (MEM_ALIGNMENT-1)) == 0);
00333 
00334   LWIP_ASSERT("mem_free: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00335     (u8_t *)rmem < (u8_t *)ram_end);
00336 
00337   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00338     SYS_ARCH_DECL_PROTECT(lev);
00339     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SEVERE, ("mem_free: illegal memory\n"));
00340     /* protect mem stats from concurrent access */
00341     SYS_ARCH_PROTECT(lev);
00342     MEM_STATS_INC(illegal);
00343     SYS_ARCH_UNPROTECT(lev);
00344     return;
00345   }
00346   /* protect the heap from concurrent access */
00347   LWIP_MEM_FREE_PROTECT();
00348   /* Get the corresponding struct mem ... */
00349   mem = (struct mem *)(void *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00350   /* ... which has to be in a used state ... */
00351   LWIP_ASSERT("mem_free: mem->used", mem->used);
00352   /* ... and is now unused. */
00353   mem->used = 0;
00354 
00355   if (mem < lfree) {
00356     /* the newly freed struct is now the lowest */
00357     lfree = mem;
00358   }
00359 
00360   MEM_STATS_DEC_USED(used, mem->next - (mem_size_t)(((u8_t *)mem - ram)));
00361 
00362   /* finally, see if prev or next are free also */
00363   plug_holes(mem);
00364 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00365   mem_free_count = 1;
00366 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00367   LWIP_MEM_FREE_UNPROTECT();
00368 }
00369 
00370 /**
00371  * Shrink memory returned by mem_malloc().
00372  *
00373  * @param rmem pointer to memory allocated by mem_malloc the is to be shrinked
00374  * @param newsize required size after shrinking (needs to be smaller than or
00375  *                equal to the previous size)
00376  * @return for compatibility reasons: is always == rmem, at the moment
00377  *         or NULL if newsize is > old size, in which case rmem is NOT touched
00378  *         or freed!
00379  */
00380 void *
00381 mem_trim(void *rmem, mem_size_t newsize)
00382 {
00383   mem_size_t size;
00384   mem_size_t ptr, ptr2;
00385   struct mem *mem, *mem2;
00386   /* use the FREE_PROTECT here: it protects with sem OR SYS_ARCH_PROTECT */
00387   LWIP_MEM_FREE_DECL_PROTECT();
00388 
00389   /* Expand the size of the allocated memory region so that we can
00390      adjust for alignment. */
00391   newsize = LWIP_MEM_ALIGN_SIZE(newsize);
00392 
00393   if(newsize < MIN_SIZE_ALIGNED) {
00394     /* every data block must be at least MIN_SIZE_ALIGNED long */
00395     newsize = MIN_SIZE_ALIGNED;
00396   }
00397 
00398   if (newsize > MEM_SIZE_ALIGNED) {
00399     return NULL;
00400   }
00401 
00402   LWIP_ASSERT("mem_trim: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
00403    (u8_t *)rmem < (u8_t *)ram_end);
00404 
00405   if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
00406     SYS_ARCH_DECL_PROTECT(lev);
00407     LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SEVERE, ("mem_trim: illegal memory\n"));
00408     /* protect mem stats from concurrent access */
00409     SYS_ARCH_PROTECT(lev);
00410     MEM_STATS_INC(illegal);
00411     SYS_ARCH_UNPROTECT(lev);
00412     return rmem;
00413   }
00414   /* Get the corresponding struct mem ... */
00415   mem = (struct mem *)(void *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
00416   /* ... and its offset pointer */
00417   ptr = (mem_size_t)((u8_t *)mem - ram);
00418 
00419   size = mem->next - ptr - SIZEOF_STRUCT_MEM;
00420   LWIP_ASSERT("mem_trim can only shrink memory", newsize <= size);
00421   if (newsize > size) {
00422     /* not supported */
00423     return NULL;
00424   }
00425   if (newsize == size) {
00426     /* No change in size, simply return */
00427     return rmem;
00428   }
00429 
00430   /* protect the heap from concurrent access */
00431   LWIP_MEM_FREE_PROTECT();
00432 
00433   mem2 = (struct mem *)(void *)&ram[mem->next];
00434   if(mem2->used == 0) {
00435     /* The next struct is unused, we can simply move it at little */
00436     mem_size_t next;
00437     /* remember the old next pointer */
00438     next = mem2->next;
00439     /* create new struct mem which is moved directly after the shrinked mem */
00440     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00441     if (lfree == mem2) {
00442       lfree = (struct mem *)(void *)&ram[ptr2];
00443     }
00444     mem2 = (struct mem *)(void *)&ram[ptr2];
00445     mem2->used = 0;
00446     /* restore the next pointer */
00447     mem2->next = next;
00448     /* link it back to mem */
00449     mem2->prev = ptr;
00450     /* link mem to it */
00451     mem->next = ptr2;
00452     /* last thing to restore linked list: as we have moved mem2,
00453      * let 'mem2->next->prev' point to mem2 again. but only if mem2->next is not
00454      * the end of the heap */
00455     if (mem2->next != MEM_SIZE_ALIGNED) {
00456       ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00457     }
00458     MEM_STATS_DEC_USED(used, (size - newsize));
00459     /* no need to plug holes, we've already done that */
00460   } else if (newsize + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED <= size) {
00461     /* Next struct is used but there's room for another struct mem with
00462      * at least MIN_SIZE_ALIGNED of data.
00463      * Old size ('size') must be big enough to contain at least 'newsize' plus a struct mem
00464      * ('SIZEOF_STRUCT_MEM') with some data ('MIN_SIZE_ALIGNED').
00465      * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00466      *       region that couldn't hold data, but when mem->next gets freed,
00467      *       the 2 regions would be combined, resulting in more free memory */
00468     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
00469     mem2 = (struct mem *)(void *)&ram[ptr2];
00470     if (mem2 < lfree) {
00471       lfree = mem2;
00472     }
00473     mem2->used = 0;
00474     mem2->next = mem->next;
00475     mem2->prev = ptr;
00476     mem->next = ptr2;
00477     if (mem2->next != MEM_SIZE_ALIGNED) {
00478       ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00479     }
00480     MEM_STATS_DEC_USED(used, (size - newsize));
00481     /* the original mem->next is used, so no need to plug holes! */
00482   }
00483   /* else {
00484     next struct mem is used but size between mem and mem2 is not big enough
00485     to create another struct mem
00486     -> don't do anyhting. 
00487     -> the remaining space stays unused since it is too small
00488   } */
00489 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00490   mem_free_count = 1;
00491 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00492   LWIP_MEM_FREE_UNPROTECT();
00493   return rmem;
00494 }
00495 
00496 /**
00497  * Adam's mem_malloc() plus solution for bug #17922
00498  * Allocate a block of memory with a minimum of 'size' bytes.
00499  *
00500  * @param size is the minimum size of the requested block in bytes.
00501  * @return pointer to allocated memory or NULL if no free memory was found.
00502  *
00503  * Note that the returned value will always be aligned (as defined by MEM_ALIGNMENT).
00504  */
00505 void *
00506 mem_malloc(mem_size_t size)
00507 {
00508   mem_size_t ptr, ptr2;
00509   struct mem *mem, *mem2;
00510 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00511   u8_t local_mem_free_count = 0;
00512 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00513   LWIP_MEM_ALLOC_DECL_PROTECT();
00514 
00515   if (size == 0) {
00516     return NULL;
00517   }
00518 
00519   /* Expand the size of the allocated memory region so that we can
00520      adjust for alignment. */
00521   size = LWIP_MEM_ALIGN_SIZE(size);
00522 
00523   if(size < MIN_SIZE_ALIGNED) {
00524     /* every data block must be at least MIN_SIZE_ALIGNED long */
00525     size = MIN_SIZE_ALIGNED;
00526   }
00527 
00528   if (size > MEM_SIZE_ALIGNED) {
00529     return NULL;
00530   }
00531 
00532   /* protect the heap from concurrent access */
00533   sys_mutex_lock(&mem_mutex);
00534   LWIP_MEM_ALLOC_PROTECT();
00535 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00536   /* run as long as a mem_free disturbed mem_malloc */
00537   do {
00538     local_mem_free_count = 0;
00539 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00540 
00541     /* Scan through the heap searching for a free block that is big enough,
00542      * beginning with the lowest free block.
00543      */
00544     for (ptr = (mem_size_t)((u8_t *)lfree - ram); ptr < MEM_SIZE_ALIGNED - size;
00545          ptr = ((struct mem *)(void *)&ram[ptr])->next) {
00546       mem = (struct mem *)(void *)&ram[ptr];
00547 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00548       mem_free_count = 0;
00549       LWIP_MEM_ALLOC_UNPROTECT();
00550       /* allow mem_free to run */
00551       LWIP_MEM_ALLOC_PROTECT();
00552       if (mem_free_count != 0) {
00553         local_mem_free_count = mem_free_count;
00554       }
00555       mem_free_count = 0;
00556 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00557 
00558       if ((!mem->used) &&
00559           (mem->next - (ptr + SIZEOF_STRUCT_MEM)) >= size) {
00560         /* mem is not used and at least perfect fit is possible:
00561          * mem->next - (ptr + SIZEOF_STRUCT_MEM) gives us the 'user data size' of mem */
00562 
00563         if (mem->next - (ptr + SIZEOF_STRUCT_MEM) >= (size + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED)) {
00564           /* (in addition to the above, we test if another struct mem (SIZEOF_STRUCT_MEM) containing
00565            * at least MIN_SIZE_ALIGNED of data also fits in the 'user data space' of 'mem')
00566            * -> split large block, create empty remainder,
00567            * remainder must be large enough to contain MIN_SIZE_ALIGNED data: if
00568            * mem->next - (ptr + (2*SIZEOF_STRUCT_MEM)) == size,
00569            * struct mem would fit in but no data between mem2 and mem2->next
00570            * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
00571            *       region that couldn't hold data, but when mem->next gets freed,
00572            *       the 2 regions would be combined, resulting in more free memory
00573            */
00574           ptr2 = ptr + SIZEOF_STRUCT_MEM + size;
00575           /* create mem2 struct */
00576           mem2 = (struct mem *)(void *)&ram[ptr2];
00577           mem2->used = 0;
00578           mem2->next = mem->next;
00579           mem2->prev = ptr;
00580           /* and insert it between mem and mem->next */
00581           mem->next = ptr2;
00582           mem->used = 1;
00583 
00584           if (mem2->next != MEM_SIZE_ALIGNED) {
00585             ((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
00586           }
00587           MEM_STATS_INC_USED(used, (size + SIZEOF_STRUCT_MEM));
00588         } else {
00589           /* (a mem2 struct does no fit into the user data space of mem and mem->next will always
00590            * be used at this point: if not we have 2 unused structs in a row, plug_holes should have
00591            * take care of this).
00592            * -> near fit or excact fit: do not split, no mem2 creation
00593            * also can't move mem->next directly behind mem, since mem->next
00594            * will always be used at this point!
00595            */
00596           mem->used = 1;
00597           MEM_STATS_INC_USED(used, mem->next - (mem_size_t)((u8_t *)mem - ram));
00598         }
00599 
00600         if (mem == lfree) {
00601           /* Find next free block after mem and update lowest free pointer */
00602           while (lfree->used && lfree != ram_end) {
00603             LWIP_MEM_ALLOC_UNPROTECT();
00604             /* prevent high interrupt latency... */
00605             LWIP_MEM_ALLOC_PROTECT();
00606             lfree = (struct mem *)(void *)&ram[lfree->next];
00607           }
00608           LWIP_ASSERT("mem_malloc: !lfree->used", ((lfree == ram_end) || (!lfree->used)));
00609         }
00610         LWIP_MEM_ALLOC_UNPROTECT();
00611         sys_mutex_unlock(&mem_mutex);
00612         LWIP_ASSERT("mem_malloc: allocated memory not above ram_end.",
00613          (mem_ptr_t)mem + SIZEOF_STRUCT_MEM + size <= (mem_ptr_t)ram_end);
00614                 LWIP_ASSERT("mem_malloc: allocated memory properly aligned.",
00615                         ((mem_ptr_t)mem + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT == 0);
00616         LWIP_ASSERT("mem_malloc: sanity check alignment",
00617                         (((mem_ptr_t)mem) & (MEM_ALIGNMENT-1)) == 0);
00618 
00619         return (u8_t *)mem + SIZEOF_STRUCT_MEM;
00620       }
00621     }
00622 #if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
00623     /* if we got interrupted by a mem_free, try again */
00624   } while(local_mem_free_count != 0);
00625 #endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
00626   LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("mem_malloc: could not allocate %"S16_F" bytes\n", (s16_t)size));
00627   MEM_STATS_INC(err);
00628   LWIP_MEM_ALLOC_UNPROTECT();
00629   sys_mutex_unlock(&mem_mutex);
00630   return NULL;
00631 }
00632 
00633 #endif /* MEM_USE_POOLS */
00634 /**
00635  * Contiguously allocates enough space for count objects that are size bytes
00636  * of memory each and returns a pointer to the allocated memory.
00637  *
00638  * The allocated memory is filled with bytes of value zero.
00639  *
00640  * @param count number of objects to allocate
00641  * @param size size of the objects to allocate
00642  * @return pointer to allocated memory / NULL pointer if there is an error
00643  */
00644 void *mem_calloc(mem_size_t count, mem_size_t size)
00645 {
00646   void *p;
00647 
00648   /* allocate 'count' objects of size 'size' */
00649   p = mem_malloc(count * size);
00650   if (p) {
00651     /* zero the memory */
00652     memset(p, 0, count * size);
00653   }
00654   return p;
00655 }
00656 
00657 #endif /* !MEM_LIBC_MALLOC */