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[/] [openrisc/] [trunk/] [rtos/] [freertos-6.1.1/] [Demo/] [uIP_Demo_IAR_ARM7/] [uip/] [memb.c] - Rev 605
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/** * \addtogroup exampleapps * @{ */ /** * \file * Memory block allocation routines. * \author Adam Dunkels <adam@sics.se> * * The memory block allocation routines provide a simple yet powerful * set of functions for managing a set of memory blocks of fixed * size. A set of memory blocks is statically declared with the * MEMB() macro. Memory blocks are allocated from the declared * memory by the memb_alloc() function, and are deallocated with the * memb_free() function. * * \note Because of namespace clashes only one MEMB() can be * declared per C module, and the name scope of a MEMB() memory * block is local to each C module. * * The following example shows how to declare and use a memory block * called "cmem" which has 8 chunks of memory with each memory chunk * being 20 bytes large. * \code MEMB(cmem, 20, 8); int main(int argc, char *argv[]) { char *ptr; memb_init(&cmem); ptr = memb_alloc(&cmem); if(ptr != NULL) { do_something(ptr); } else { printf("Could not allocate memory.\n"); } if(memb_free(ptr) == 0) { printf("Deallocation succeeded.\n"); } } \endcode * */ #include <string.h> #include "memb.h" /*------------------------------------------------------------------------------*/ /** * Initialize a memory block that was declared with MEMB(). * * \param m A memory block previosly declared with MEMB(). */ /*------------------------------------------------------------------------------*/ void memb_init(struct memb_blocks *m) { memset(m->mem, (m->size + 1) * m->num, 0); } /*------------------------------------------------------------------------------*/ /** * Allocate a memory block from a block of memory declared with MEMB(). * * \param m A memory block previosly declared with MEMB(). */ /*------------------------------------------------------------------------------*/ char * memb_alloc(struct memb_blocks *m) { int i; char *ptr; ptr = m->mem; for(i = 0; i < m->num; ++i) { if(*ptr == 0) { /* If this block was unused, we increase the reference count to indicate that it now is used and return a pointer to the first byte following the reference counter. */ ++*ptr; return ptr + 1; } ptr += m->size + 1; } /* No free block was found, so we return NULL to indicate failure to allocate block. */ return NULL; } /*------------------------------------------------------------------------------*/ /** * Deallocate a memory block from a memory block previously declared * with MEMB(). * * \param m m A memory block previosly declared with MEMB(). * * \param ptr A pointer to the memory block that is to be deallocated. * * \return The new reference count for the memory block (should be 0 * if successfully deallocated) or -1 if the pointer "ptr" did not * point to a legal memory block. */ /*------------------------------------------------------------------------------*/ char memb_free(struct memb_blocks *m, char *ptr) { int i; char *ptr2; /* Walk through the list of blocks and try to find the block to which the pointer "ptr" points to. */ ptr2 = m->mem; for(i = 0; i < m->num; ++i) { if(ptr2 == ptr - 1) { /* We've found to block to which "ptr" points so we decrease the reference count and return the new value of it. */ return --*ptr2; } ptr2 += m->size + 1; } return -1; } /*------------------------------------------------------------------------------*/ /** * Increase the reference count for a memory chunk. * * \note No sanity checks are currently made. * * \param m m A memory block previosly declared with MEMB(). * * \param ptr A pointer to the memory chunk for which the reference * count should be increased. * * \return The new reference count. */ /*------------------------------------------------------------------------------*/ char memb_ref(struct memb_blocks *m, char *ptr) { return ++*(ptr - 1); } /*------------------------------------------------------------------------------*/
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