嵌入式操作系统内核原理和开发（最快、最优、最差内存分配算法）-2

上一篇 / 下一篇 2012-06-29 13:54:30 / 个人分类：杂谈

#if MAX_SIZE_MALLOC
)S8t7m6s4b0/*************************************************
d!w-b5a!O2[^5Ta0* function: find best fit node in max size
**************************************************/

(Y&i(j2f%sL9N0MNG_NODE* find_best_fit_node(unsigned int size)
qo{ {$@g0{51Testing软件测试网 a,v x-yyA;P
MNG_NODE* pCur = pFreeList;51Testing软件测试网_u o)Pr
MNG_NODE* pPre = pCur;
%H/qLy+A5sa`0 MNG_NODE* pFind = NULL;51Testing软件测试网`K4p%?v

    while(pCur)51Testing软件测试网RO#q` L:wa&K
    {51Testing软件测试网)lx,OS S
  if(pCur->size > (size + sizeof(MNG_NODE)))
,u7V#_%Z8iP^!R0  {51Testing软件测试网q7`,wz-J)wg
      if(NULL == pFind || pFind->size < pCur->size)
   {51Testing软件测试网cp*p:yF;R#u
       pFind = pCur;
*R-c$T2G%i%aU;l0   }
\^2G$E-B,e0  }

9b ~_(c7Ef9c/z?$c0        pPre = pCur;
        pCur = pCur->next;51Testing软件测试网-Yq6Psj]8XG
    }  51Testing软件测试网3{@SsC

6Dp5_(Pa0 if(NULL == pFind)
return NULL;51Testing软件测试网~eW RV:Em

6[Le4B y%G0 pPre = find_previous_node_in_list(pFind, pFreeList);
%g#F G.i)];G0    if(NULL == pPre)
        pFreeList = pFreeList->next;
    else
"QH.`F?#q5W3|0        pPre->next = pFind->next;

return pFind;
}
d&`1bK}Vb"M0#endif51Testing软件测试网"y@C,A|4i4p t

"p4r-d:`$A8J&uf051Testing软件测试网$PNS;BC7j!U
/*************************************************
* function: implement memory allocation
**************************************************/

static void* _mem_malloc(unsigned int size)
^oRK)p;z&n@;Y0{
2d2s(V Y]0 MNG_NODE* pOld;
c&Nlk:FV^C)e0 MNG_NODE* pNew;

?"Lu;mn#e0    pOld = find_best_fit_node(size);
;V|*x@F8S2\w0    if(NULL == pOld)
.ay4w eV1yi0        return NULL;51Testing软件测试网2S)DY$bsdH

    pNew = (MNG_NODE*)((char*)pOld + sizeof(MNG_NODE) + pOld->size - (sizeof(MNG_NODE) + size));
L Y!pBX"P8h3{9K)hM9`0    pNew->size = size;
$[} VKo$G0    pOld->size -= sizeof(MNG_NODE) + size;51Testing软件测试网p,GQN*`|,X

add_node_into_list_head(pOld, &pFreeList);51Testing软件测试网/n,}Ag_A
add_node_into_list_head(pNew, &pAllocList);

return (void*)((char*)pNew + sizeof(MNG_NODE));
}qe*k"Q tW|-ii0}51Testing软件测试网$J$Y{ HPb

i$A|(G$f'[-u|0/*************************************************51Testing软件测试网ys:nP4WrC
* function: memory allocation51Testing软件测试网/wq1l'|Z
**************************************************/

void* mem_malloc(unsigned int size)51Testing软件测试网K)o/z$}t;\
{
if(0 == size)
5_)]"x?j j0\0 return NULL;

if(size > (MEM_BUFFER_LENGTH - sizeof(MNG_NODE)))
{$N S m9ro[6uE l]0 return NULL;51Testing软件测试网s.dI'F_a

7Jv hK2L0 return _mem_malloc(size);
`*K7T j([ t7c0}

!}7aa*Rg Gn`0
D+I$n`F{#d0/*************************************************
* function: find previous node
Gei1W%Y/A J0**************************************************/

MNG_NODE* find_previous_node_in_list(MNG_NODE* pNode, MNG_NODE* pList)
P!f8GD [Du5Nk0{51Testing软件测试网5prj,CE |
    MNG_NODE* pFind = pList;
+rTmbt*U?3d0    MNG_NODE* pPre = NULL;51Testing软件测试网XFfoh(x {:V

    while(pFind && pFind != pNode)
]1_ KmB g q0    {
wE1g"Kz6pq&|6@ C5K0        pPre = pFind;
Lkh_2p#{0        pFind = pFind->next;
%H CZf@+a*n g3I0    }

if(NULL == pFind)
W0cYXV[6e0 return NULL;

MBP-aJ8_ mA[)M0 return pPre;
{|6g3QGW0}51Testing软件测试网+\PwR*m%dQ(E

NM,E lI?+Dd\`0/*************************************************
#BM8a,Xqyuq0* function: implement memory free51Testing软件测试网B~J w;~
**************************************************/

static void _mem_free(MNG_NODE* pNode)
{51Testing软件测试网e'p ^R]t
MNG_NODE* pPreNode;51Testing软件测试网(X ~7^U]3T{

@~:zh%M#J:O0    if(pNode == pAllocList)
:}u]\[0    {
D'XJ"ly7ez0        pAllocList = pAllocList->next;
        add_node_into_list_head(pNode, &pFreeList);
~D5|qF^)NS0        return;51Testing软件测试网K!y ]~ w
    }

    pPreNode = find_previous_node_in_list(pNode, pAllocList);
SZ4IY#d#LlZP0    if(NULL == pPreNode)
-z tj&L/F.EV7WD0        return;

']%c(Z`.VdL0    pPreNode->next = pNode->next;
@&Pq{*w XP#rg0    add_node_into_list_head(pNode, &pFreeList);
    return;
&~0dQ*Ar0}

]*J&c+F`yo0
WRz!d8iR^ik~@4{|T0/*************************************************51Testing软件测试网3~GW q5PP
* function: free memory function
|b%F/hl0**************************************************/

void mem_free(void* pData)51Testing软件测试网Y0|N??4Y*[
{
o7t:Dxz jF6E+a0PU0 if(NULL == pData)
return;

N~,OQ&uJo0 if(pData < pGlbData || pData >= (void*)((char*)pGlbData + MEM_BUFFER_LENGTH))
v5`I$r$ns2?1Pb0 return;51Testing软件测试网VQcfClV

p1s,? XgS]E Q$Q0 _mem_free((MNG_NODE*)((char*)pData - sizeof(MNG_NODE)));51Testing软件测试网;P}h)t%K8d:M
}

/*************************************************
* function: get memory buffer
1D_#o/{|#v0**************************************************/

+my"~5__0HZ0void mem_init()
2Y d3f5P\7w0{
C#^8c$z#x0    pGlbData = (void*)malloc(MEM_BUFFER_LENGTH);
    if(NULL == pGlbData)
        return;

    memset(pGlbData, 0, MEM_BUFFER_LENGTH);51Testing软件测试网L.{$fjO y
    pFreeList = (MNG_NODE*)pGlbData;
.{D!f+t)m?@\Zr0    pFreeList->size = MEM_BUFFER_LENGTH - sizeof(MNG_NODE);
    pAllocList = NULL;
}51Testing软件测试网&a3G7m}ba2{

51Testing软件测试网Y uOU1q
/*************************************************51Testing软件测试网Qn2L^Tf
* function: free memory buffer
**************************************************/

5Z$Bn2j{mr:HK(q0void mem_exit()
{
}._OtB0 if(NULL != pGlbData)
MI B$@~ `*h5v6d!N0 free(pGlbData);

pFreeList = NULL;
j^'PDmx[%ay8]&Q0 pAllocList = NULL;
Au1v3g zcp'aH0}51Testing软件测试网4N+}!@-x"_u WL

*} u4D;H F+o&c0/*************************************************51Testing软件测试网(S"V/h`9NbO
* function: file starts here
Qs,m L*SzW ]3a0**************************************************/

6}Ap9LfW,o0int main(int argc, char* argv[])
P`J Q;dU#L0{
#] xDg G0    mem_init();
'X1V*qy+}}y9c0    mem_exit();
    return 1;
:_2Ou.Lv-s4\5@ K0}

嵌入式操作系统内核原理和开发（最快、最优、最差内存分配算法）-2

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