3 heap.c - Heap Manager
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5 #include <acess/sys.h>
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10 // === Constants ===
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11 #define MAGIC 0xACE55051 //AcessOS1
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12 #define MAGIC_FREE (~MAGIC)
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13 #define BLOCK_SIZE 16 //Minimum
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14 #define HEAP_INIT_SIZE 0x10000
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16 typedef unsigned int Uint;
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28 // === LOCAL VARIABLES ===
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29 static void *_heap_start = NULL;
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30 static void *_heap_end = NULL;
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32 // === PROTOTYPES ===
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33 EXPORT void *malloc(size_t bytes);
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34 EXPORT void *calloc(size_t bytes, size_t count);
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35 EXPORT void free(void *mem);
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36 EXPORT void *realloc(void *mem, Uint bytes);
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37 EXPORT void *sbrk(int increment);
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38 LOCAL void *extendHeap(int bytes);
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39 LOCAL uint brk(Uint newpos);
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44 \fn EXPORT void *malloc(size_t bytes)
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45 \brief Allocates memory from the heap space
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46 \param bytes Integer - Size of buffer to return
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47 \return Pointer to buffer
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49 EXPORT void *malloc(size_t bytes)
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52 Uint closestMatch = 0;
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53 Uint bestMatchAddr = 0;
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54 heap_head *curBlock;
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57 if(_heap_start == NULL)
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59 _heap_start = sbrk(0);
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60 _heap_end = _heap_start;
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61 extendHeap(HEAP_INIT_SIZE);
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64 curBlock = _heap_start;
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66 bestSize = bytes + sizeof(heap_head) + sizeof(heap_foot) + BLOCK_SIZE - 1;
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67 bestSize = (bestSize/BLOCK_SIZE)*BLOCK_SIZE; //Round up to block size
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69 while((Uint)curBlock < (Uint)_heap_end)
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71 //SysDebug(" malloc: curBlock = 0x%x, curBlock->magic = 0x%x\n", curBlock, curBlock->magic);
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72 if(curBlock->magic == MAGIC_FREE)
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74 if(curBlock->size == bestSize)
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76 if(bestSize < curBlock->size && (curBlock->size < closestMatch || closestMatch == 0)) {
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77 closestMatch = curBlock->size;
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78 bestMatchAddr = (Uint)curBlock;
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81 else if(curBlock->magic != MAGIC)
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84 //SysDebug("malloc: Corrupt Heap\n");
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87 curBlock = (heap_head*)((Uint)curBlock + curBlock->size);
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90 if((Uint)curBlock < (Uint)_heap_start) {
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91 //SysDebug("malloc: Heap underrun for some reason\n");
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95 //Found a perfect match
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96 if((Uint)curBlock < (Uint)_heap_end) {
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97 curBlock->magic = MAGIC;
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98 return (void*)((Uint)curBlock + sizeof(heap_head));
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101 //Out of Heap Space
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102 if(!closestMatch) {
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103 curBlock = extendHeap(bestSize); //Allocate more
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104 if(curBlock == NULL) {
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105 //SysDebug("malloc: Out of Heap Space\n");
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108 curBlock->magic = MAGIC;
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109 return (void*)((Uint)curBlock + sizeof(heap_head));
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113 if(closestMatch - bestSize > BLOCK_SIZE) {
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115 curBlock = (heap_head*)bestMatchAddr;
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116 curBlock->magic = MAGIC;
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117 curBlock->size = bestSize;
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118 foot = (heap_foot*)(bestMatchAddr + bestSize - sizeof(heap_foot));
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119 foot->header = curBlock;
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120 foot->magic = MAGIC;
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122 curBlock = (heap_head*)(bestMatchAddr + bestSize);
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123 curBlock->magic = MAGIC_FREE;
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124 curBlock->size = closestMatch - bestSize;
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126 foot = (heap_foot*)(bestMatchAddr + closestMatch - sizeof(heap_foot));
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127 foot->header = curBlock;
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129 ((heap_head*)bestMatchAddr)->magic = MAGIC; //mark as used
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130 return (void*)(bestMatchAddr + sizeof(heap_head));
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133 //Don't Split the block
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134 ((heap_head*)bestMatchAddr)->magic = MAGIC;
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135 return (void*)(bestMatchAddr+sizeof(heap_head));
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139 * \fn EXPORT void *calloc(size_t bytes, size_t count)
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140 * \brief Allocate and zero a block of memory
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141 * \param __nmemb Number of memeber elements
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142 * \param __size Size of one element
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144 EXPORT void *calloc(size_t __nmemb, size_t __size)
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146 void *ret = malloc(__size*__nmemb);
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147 if(!ret) return NULL;
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148 memset(ret, 0, __size*__nmemb);
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153 \fn EXPORT void free(void *mem)
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154 \brief Free previously allocated memory
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155 \param mem Pointer - Memory to free
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157 EXPORT void free(void *mem)
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159 heap_head *head = (void*)((intptr_t)mem-sizeof(heap_head));
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164 if(head->magic != MAGIC) //Valid Heap Address
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167 head->magic = MAGIC_FREE;
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170 if((intptr_t)head + head->size < (intptr_t)_heap_end)
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172 heap_head *nextHead = (heap_head*)((intptr_t)head + head->size);
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173 if(nextHead->magic == MAGIC_FREE) { //Is the next block free
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174 head->size += nextHead->size; //Amalgamate
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175 nextHead->magic = 0; //For Security
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179 if((intptr_t)head - sizeof(heap_foot) > (intptr_t)_heap_start)
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181 heap_head *prevHead;
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182 heap_foot *prevFoot = (heap_foot *)((intptr_t)head - sizeof(heap_foot));
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183 if(prevFoot->magic == MAGIC) {
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184 prevHead = prevFoot->header;
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185 if(prevHead->magic == MAGIC_FREE) {
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186 prevHead->size += head->size; //Amalgamate
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187 head->magic = 0; //For Security
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194 \fn EXPORT void *realloc(void *oldPos, size_t bytes)
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195 \brief Reallocate a block of memory
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196 \param bytes Integer - Size of new buffer
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197 \param oldPos Pointer - Old Buffer
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198 \return Pointer to new buffer
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200 EXPORT void *realloc(void *oldPos, size_t bytes)
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205 if(oldPos == NULL) {
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206 return malloc(bytes);
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209 //Check for free space after block
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210 head = (heap_head*)((Uint)oldPos-sizeof(heap_head));
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212 //Hack to used free's amagamating algorithym and malloc's splitting
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215 //Allocate new memory
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216 ret = malloc(bytes);
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221 if((Uint)ret != (Uint)oldPos) {
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222 memcpy(ret, oldPos, head->size-sizeof(heap_head)-sizeof(heap_foot));
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230 * \fn LOCAL void *extendHeap(int bytes)
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231 * \brief Create a new block at the end of the heap area
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232 * \param bytes Integer - Size reqired
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233 * \return Pointer to last free block
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236 LOCAL void *extendHeap(int bytes)
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238 heap_head *head = _heap_end;
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241 //Expand Memory Space (Use foot as a temp pointer)
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242 foot = sbrk(bytes);
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243 if(foot == (void*)-1)
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249 head->magic = MAGIC_FREE; //Unallocated
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250 head->size = bytes;
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252 foot = _heap_end + bytes - sizeof(heap_foot);
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253 foot->header = head;
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254 foot->magic = MAGIC;
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256 //Combine with previous block if nessasary
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257 if(_heap_end != _heap_start && ((heap_foot*)((Uint)_heap_end-sizeof(heap_foot)))->magic == MAGIC) {
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258 heap_head *tmpHead = ((heap_foot*)((Uint)_heap_end-sizeof(heap_foot)))->header;
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259 if(tmpHead->magic == MAGIC_FREE) {
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260 tmpHead->size += bytes;
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261 foot->header = tmpHead;
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266 _heap_end = (void*) ((Uint)foot+sizeof(heap_foot));
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271 \fn EXPORT void *sbrk(int increment)
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272 \brief Increases the program's memory space
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273 \param count Integer - Size of heap increase
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274 \return Pointer to start of new region
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276 EXPORT void *sbrk(int increment)
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279 static size_t oldEnd = 0;
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280 static size_t curEnd = 0;
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282 //_SysDebug("sbrk: (increment=%i)\n", increment);
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284 if (oldEnd == 0) curEnd = oldEnd = brk(0);
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286 //SysDebug(" sbrk: oldEnd = 0x%x\n", oldEnd);
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287 if (increment == 0) return (void *) curEnd;
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289 newEnd = curEnd + increment;
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291 if (brk(newEnd) == curEnd) return (void *) -1;
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294 //SysDebug(" sbrk: newEnd = 0x%x\n", newEnd);
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296 return (void *) oldEnd;
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300 * \fn EXPORT int IsHeap(void *ptr)
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302 EXPORT int IsHeap(void *ptr)
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308 if( (Uint)ptr < (Uint)_heap_start ) return 0;
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309 if( (Uint)ptr > (Uint)_heap_end ) return 0;
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312 head = (void*)((Uint)ptr - 4);
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313 if( head->magic != MAGIC ) return 0;
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314 foot = (void*)( (Uint)ptr + head->size - sizeof(heap_foot) );
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315 if( foot->magic != MAGIC ) return 0;
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320 // === STATIC FUNCTIONS ===
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322 * Does the job of brk(0)
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324 static void *FindHeapBase()
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327 #define MAX 0xC0000000 // Address
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328 #define THRESHOLD 512 // Pages
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333 // Scan address space
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339 tmp = _SysGetPhys(addr);
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344 if(stretch > THRESHOLD)
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346 return (void*)( addr - stretch*0x1000 );
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349 //__asm__ __volatile__ (
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350 // "push %%ebx;mov %%edx,%%ebx;int $0xAC;pop %%ebx"
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351 // ::"a"(256),"d"("%x"),"c"(addr));
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356 return (void*)0x00900000;
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360 LOCAL uint brk(Uint newpos)
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362 static uint curpos;
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367 //_SysDebug("brk: (newpos=0x%x)", newpos);
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369 // Find initial position
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370 if(curpos == 0) curpos = (uint)FindHeapBase();
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372 // Get Current Position
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373 if(newpos == 0) return curpos;
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375 if(newpos < curpos) return newpos;
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377 delta = newpos - curpos;
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378 //_SysDebug(" brk: delta = 0x%x", delta);
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380 // Do we need to add pages
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381 if(curpos & 0xFFF && (curpos & 0xFFF) + delta < 0x1000)
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382 return curpos += delta;
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384 // Page align current position
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385 if(curpos & 0xFFF) delta -= 0x1000 - (curpos & 0xFFF);
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386 curpos = (curpos + 0xFFF) & ~0xFFF;
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389 pages = (delta + 0xFFF) >> 12;
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392 _SysAllocate(curpos);
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397 // Bring the current position to exactly what we want
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398 curpos -= ((delta + 0xFFF) & ~0xFFF) - delta;
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400 return ret; // Return old curpos
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