| 164 | } |
| 165 | |
| 166 | int MemoryManager::allocatePages(enum AddressPoolType type, const int count) |
| 167 | { |
| 168 | // 第一步：从虚拟地址池中分配若干虚拟页 |
| 169 | int virtualAddress = allocateVirtualPages(type, count); |
| 170 | if (!virtualAddress) |
| 171 | { |
| 172 | return 0; |
| 173 | } |
| 174 | |
| 175 | bool flag; |
| 176 | int physicalPageAddress; |
| 177 | int vaddress = virtualAddress; |
| 178 | |
| 179 | // 依次为每一个虚拟页指定物理页 |
| 180 | for (int i = 0; i < count; ++i, vaddress += PAGE_SIZE) |
| 181 | { |
| 182 | flag = false; |
| 183 | // 第二步：从物理地址池中分配一个物理页 |
| 184 | physicalPageAddress = allocatePhysicalPages(type, 1); |
| 185 | if (physicalPageAddress) |
| 186 | { |
| 187 | //printf("allocate physical page 0x%x\n", physicalPageAddress); |
| 188 | |
| 189 | // 第三步：为虚拟页建立页目录项和页表项，使虚拟页内的地址经过分页机制变换到物理页内。 |
| 190 | flag = connectPhysicalVirtualPage(vaddress, physicalPageAddress); |
| 191 | } |
| 192 | else |
| 193 | { |
| 194 | flag = false; |
| 195 | } |
| 196 | |
| 197 | // 分配失败，释放前面已经分配的虚拟页和物理页表 |
| 198 | if (!flag) |
| 199 | { |
| 200 | // 前i个页表已经指定了物理页 |
| 201 | releasePages(type, virtualAddress, i); |
| 202 | // 剩余的页表未指定物理页 |
| 203 | releaseVirtualPages(type, virtualAddress + i * PAGE_SIZE, count - i); |
| 204 | return 0; |
| 205 | } |
| 206 | } |
| 207 | |
| 208 | return virtualAddress; |
| 209 | } |
| 210 | |
| 211 | int MemoryManager::allocateVirtualPages(enum AddressPoolType type, const int count) |
| 212 | { |