* enabling interrupts often, which can be slow! Also, on low memory, mem_malloc * can need longer. * * If you don't want that, at least for NO_SYS=0, you can still use the following * functions to enqueue a deallocation call which then runs in the tcpip_thread * context: * - pbuf_free_callback(p); * - mem_free_callback(m); */ #ifndef LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT #define LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT 0 #endif
Mem.h中的几个宏、
/** Calculate memory size for an aligned buffer - returns the next highest * multiple of MEM_ALIGNMENT (e.g. LWIP_MEM_ALIGN_SIZE(3) and * LWIP_MEM_ALIGN_SIZE(4) will both yield 4 for MEM_ALIGNMENT == 4). */ 计算内存对齐状态下size的实际大小。例如4字节对齐时，MEM_ALIGNMENT = 4，这时LWIP_MEM_ALIGN_SIZE(3或4)的结果都是4 #ifndef LWIP_MEM_ALIGN_SIZE #define LWIP_MEM_ALIGN_SIZE(size) (((size) + MEM_ALIGNMENT - 1) & ~(MEM_ALIGNMENT-1)) #endif /** Calculate safe memory size for an aligned buffer when using an unaligned * type as storage. This includes a safety-margin on (MEM_ALIGNMENT - 1) at the * start (e.g. if buffer is u8_t[] and actual data will be u32_t*) */ 当申请一个内存大小时，假如当前是4字节对齐，要申请3个字节的空间，但使用过程中地址要对齐，为使用对齐的地址仍然在安全地址空间，申请的内存大小要在一个安全范围内。 #ifndef LWIP_MEM_ALIGN_BUFFER #define LWIP_MEM_ALIGN_BUFFER(size) (((size) + MEM_ALIGNMENT - 1)) #endif /** Align a memory pointer to the alignment defined by MEM_ALIGNMENT * so that ADDR % MEM_ALIGNMENT == 0 */ 当一个内存不对齐时，返回一个对齐的内存地址（不对齐时，去掉不对齐的空间，取得的对齐地址大于参数ADDR） #ifndef LWIP_MEM_ALIGN #define LWIP_MEM_ALIGN(addr) ((void *)(((mem_ptr_t)(addr) + MEM_ALIGNMENT - 1) & ~(mem_ptr_t)(MEM_ALIGNMENT-1))) #endif