mmap file

(inaccessible), the value is often set to Prot_read | Prot_write.Flags are specified by the following constant values: map_shared, Map_private, map_fixed, where map_shared (changes are shared, all processes are visible to the modified shared memory), Map_private (the change is private, Only visible to the process for shared memory modification is required, and map_fixed is not recommended for use.MUNMP () deletes the address mapping relationship, the function prototype is as follows: #inclu

becomes part of the memory. At this point, the CPU can access the peripheral I/O port as if it were accessing a memory unit without having to set up specialized peripheral I/O instructions.However, the difference in hardware implementation is completely transparent to the software, and driver developers can treat the I/O port and peripheral memory as a "I/O Memory" resource in the memory-mapped way.In general, when the system is running, the physical address of the peripheral's I/O memory resou

process is loaded. These system information contains the running space of the current process. When the user program calls Mmap. The function finds the appropriate VMA in the space of the current process to describe the area that it is going to map. The function of this area is to map the contents of the specific file that the file descriptor points to in the

is the process dynamic memory allocation start address (the start address of the heap), and a BRK (the current last address of the heap), which is the current terminating address of the dynamic memory allocation.The basic function of C language dynamic memory allocation is malloc (), and the basic implementation on Linux is called by the kernel's BRK system. BRK () is a very simple system call, simply changing the value of the member variable BRK of the MM_STRUCT structure.The

Title: Question about mmap? -- Linux general technology-Linux programming and kernel information. The following is a detailed description. At the beginning, I learned about linux programming. I don't know much about some basic issues. I have read the original form of the mmap function void * mmap (void * addr, size_t length, int prot, int flags, int fd, off_t of

the function is in the stack frame. function static local variables and the spatial allocation of global variables in the data segment. Process but the scope of the two is different. Stackheap code Snippet data segment heap, stack life cycle either the programmer manually frees the heap space. Otherwise, at the end of the process. Second, use Mmap to map the physical address to the virtual address space of the process.

Mmap function,1. mmap system call The man manual shows that: 1 void * mmap (void * addr, size_t length, int prot, int flags, 2 int fd, off_t offset ); Function: maps the file content to the virtual address space of the process. By reading and modifying the memory, you can read and modify the

1. MmapMmap can map a portion of a disk file directly to memory, so that the location of the file directly has a corresponding memory address, read and write to the file can be directly with the pointer without the need for the Read/write function.Shared memory Exchange data, not switch the power level, fast.Mmap Cons: 1) consumes memory, fragmentation. 2) ordina

belonging to different address spaces actually correspond to the same physical page. One Party modifies the data and the other party can see the changes in real time. General application scenarios are embedded devices, such as refresh the LED display screen and record a large amount of sensor data. This requires developers to implement mmap logic simultaneously in their own drivers and user code. First, provide the following interface functions in t

Initially After reading the memory ing I/O, it means you can understand it, that is, you can directly operate the file and then directly operate through the buffer to reduce the time it takes to call the read and write operations. In addition, the following is an example of copy.However, after I map two files, I can use the memcpy memory replication function to write the files, but this is the operation of the two files, I want to modify a

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 th

Function Description: 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. Munmap performs the opposite operation to delete the object ing of a specific address area.

: size of the memory area to be mapped Prot: The expected memory protection flag Flags: specifies the type of the ing object. FD: file descriptor (returned by the open function) Offset: The offset of the memory area of the user space to be mapped in the memory area allocated in the kernel space. The size is an integer multiple of page_size. II. Implementation First, the driver allocates one page of memory, and then the user process maps a page of mem

Introduction to Linux mmap function, linuxmmap Function I. Introduction Linux provides the memory ing function mmap, which maps the file content to a memory segment (specifically, virtual memory). By reading and modifying this memory segment, to read and modify files, Let's first look at the mmap function declaration:

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

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

Mmap maps a file or other object into memory. Mmap can also implement shared memory. mmap function calls enable shared memory between processes by mapping the same file. After the file is mapped to the process address space, the p

The advanced driver courses over the past few days are really happy. Block devices and MTD devices are really clear and open-minded.When it's still hot and free, record the MMAP implementation in the S3C2410 framebuffer driver. For more information, seePreviously, MMAP was replaced. There is no concept of how to implement an MMAP in the kernel space.There is no

Linux provides the memory ing function MMAP, which maps the file content to a memory segment (specifically, virtual memory). By reading and modifying this memory segment, to read and modify files, Let's first look at the MMAP function declaration: Header file: Prototype: void *

Inter-process Communication-mmap#include The essence of mmap is to synchronize the memory with the files on the hard disk. The contents of a block of memory are synced to the hard disk file, which maps the files to memory. Therefore, the communication between processes is achieved through the reading and writing of the same file.Parameter explanation:Addr: Specif