mmap mindmap

/ * Use Mmap to operate the file * /#include #include #include #include #include #include #define FILELENGTHintMainvoid){intFD =-1;/ * The string that will be written to the file * / Charbuf[]="Quick brown fox jumps over the lazy dog";Char*ptr = NULL;/* Open the file mmap.txt and reduce the file length to 0, create it if the file does not exist, and read/write the permission to execute */FD = open ("Mmap.txt", O_RDWR/* Readable/writable */| O_creat/

void *mmap (void *addr, size_t length, int prot, int flags, int fd, off_t offset);function function: Map the contents of the file to a piece of memory (virtual memory), through the memory read and modify, to achieve the file read and modify.Parameter descriptionAddr: Specifies the starting address of the map, usually set to null (indicated by the system).Length: Represents how much part of the file is mapped to memory.PORT: How the Map area is protect

mmap where Linux is. what is mmap. On the illustrated, Mmap is a way to operate these devices, the so-called operating equipment, such as IO port (light an LED), LCD controller, disk controller, is actually to the physical address of the device read and write data. However, because the application cannot directly manipulate the device hardware address, the ope

How the kernel guarantees that each process addresses the memory page of the same shared memory area1. Page cache and swap cache pages: a physical page of an accessed file resides in the page cache or swap cache, and all the information for a page is described by a struct page. There is a field in the struct page that is pointer mapping, which points to a struct ADDRESS_SPACE type structure. All pages in the page cache or swap cache are differentiated according to the address_space structure and

Note: The sys/Mman. h header file does not have to be passed in Linux in windows. Method Introduction: MMAP maps a file or other objects to the memory. The file is mapped to multiple pages. If the file size is not the sum of the sizes of all pages, the unused space of the last page will be cleared. Void * MMAP (void * Start, size_t length, int Prot, int flags, int FD, off_t offset); the parameters are

1. Write filesWith open ('?? ' ' r+b ' As F: With contextlib.closing (Mmap.mmap (F.fileno (), size, flags=mmap. map_shared, access=mmap. Access_write)) as mm: = ?? Mm.flush ()2. Key Reminders>>> mmap.ACCESS_READ1>>> mmap.ACCESS_WRITE2>>> mmap.ACCESS_COPY3>>> mmap.ACCESS_READ | mmap.ACCESS_WRITE3In and words, is the access=mmap.ACCESS_READ|mmap.ACCESS_WRITE same as access=mmap.ACCESS_COPY . What do

650) this.width=650; "src="/img/fz.gif "alt=" Copy Code "style=" border:0px; "/>importmmapmmap_file=none# #从内存中读取信息, Defread_mmap_info (): globalmmap_filemmap_file.seek (0) ## Convert the binary to String info_str=mmap_file.read (). Translate (none,b ' \x00 '). Decode () print (INFO_STR) # #如果内存中没有对应信息, writes the information to memory for the next call to use Defget_mmap_info (): globalmmap_file# #第二个参数1024是设定的内存大小, units: bytes. If you have more content, you can turn it up a little bit mmap_f

); Mapfd (FD, size); // obtain a piece of memory by using the MMAP method of the FD. // Do not understand. Check man MMAP. After mapfd is complete, the mbase variable points to the starting position of the memory. msize indicates the size of the allocated memory, and MFD indicates File descriptor returned by ashmem_create_region } Memoryheapbase provides several functions to obtain the size and location o

MMAP can map a part of the disk file directly to the memory, so that the location in the file has a corresponding memory address, you can directly use pointers to read and write files without the need for the read/write function. Prototype: # include Void * MMAP (void * ADDR, size_t Len, int Prot, int flag, int filedes, off_t off ); Int munmap (void * ADDR, size_t Len ); The parameters are expla

SELF: http://hi.baidu.com/flying5/blog good blog, you can go to have a look Linux MMAP File Memory ing mechanism MMAP: Memory Map When talking about the concept of file ing, it is inevitable that virtual memory (SVR 4 VM) is involved. In fact,File ing is the central concept of virtual storage.,On the one hand, file ing provides users with a set of measures, as if users map files to a part of their own addre

#作用: Create a memory-mapped file instead of reading the content directlyText message content: as follows (name is Text.txt)Lorem ipsum dolor sit amet, consectetuer adipiscing elit. DonecEgestas, enim et consectetuer ullamcorper, lectus ligula rutrum Leo,A elementum elit tortor EU quam.Duis tincidunt nisi ut ante. NullaFacilisi.Sed tristique eros eu libero. Pellentesque velArcu. Vivamus purus Orci, iaculis ac, suscipit sit amet, pulvinar EU,Lacus.Praesent placerat tortor sed nisl. Nunc blandit di

Mmap Basic ConceptsMmap is a memory-mapped file method that maps a file or other object to the address space of a process, implementing a one by one-mapping relationship between the file disk address and a virtual address in the process virtual address space. After such a mapping relationship is implemented, the process can read and write the memory in a pointer way, and the system will automatically write back the dirty page to the corresponding file

->gpi;PRINTK (kern_alert "GPIO =%08x", (int) ugpio);Copy_to_user (void *) arg, (const void *) ugpio,sizeof (Ugpio));Break}Case get_io_dir:{PRINTK (Kern_alert "get_io_dir\r\n");Break}}return 0;}2. At the application layer use the MMAP function at the application layer to obtain the virtual address pointer of the GPIO physical base site, and then use this pointer to read and write the Gpio register, here is a bit of program snippet for everyone to refer

IPC Three communication mechanism refers to: semaphore, shared memory, message queue,signal Volume: Through the operating system of the PV operation to achieve;Shared Memory: Request a piece of memory, process A to write in shared memory, other processes can read out the contents of the shared memory to obtain the information transmitted by process A;Message Queuing: Create a message queue, process a writes to the queue, and process B gets the information that process a transmits by reading the

Preface Work encountered some of the demand for KV storage, such as the recommendation system needs to store a commodity ID corresponding to the similar Product ID list, or a user's browsing the Product ID list, which requires a key value to store. This article describes the storage based on the requirements of a simple implementation of a version, the actual work is much more complex, in order to make the reader easy to understand, based on this analysis of a primary key to String key,value is

Mmap,mmap64,munmap---Map or unmap files or devices into memoryvoid *mmap (void* addr,size_t length, int prot, int flags, int fd, off_t offset);void *mmap64 (void* addr,size_t length, int prot, int flags, int fd, off_t offset);int Munmap (void *addr, size_t lenght);Mmap function creates a new mapping in the virtual address space of the the calling process. The sha

One. Mmap system call1. Mmap system callMmap maps a file or other object into memory. Files are mapped to multiple pages, and if the size of the file is not the sum of the size of all pages, the space that is not used by the last page will be zeroed out. Munmap performs the opposite operation by deleting the object mappings for a specific address area.When using the mma