memory-mapped-files

问题 Why doesn't boost interprocess support write only memory mapping? Maybe I'm missing something but wouldn't a write only mapping be significantly faster than a read/write mapping as the OS doesn't have to read in the pages from the disk, just flush out pages from memory to the disk? Also it would have the benefit of being entirely non blocking (except for flushing and destruction). Would I benefit by switching from boost to native OS memory mapping? 回答1: In fact if you allocate a new memory

问题 I've a small and simple storage system which is accessible through memory mapped files. As I need to address more than 2GB space I need a list of MappedByteBuffer with a fixed size like 2GB (I'm using less for different reasons). Then all is relativly simple: a buffer maps to a certain space say to 1GB and when I need more I map a new MappedByteBuffer (the file automatically increases), then when I need more a third buffer is mapped etc. This just worked. But then I've read in the Java NIO

问题 I am trying to use memory-mapped files as: hFile = ::CreateFile(State.Path, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, 0, OPEN_EXISTING,FILE_FLAG_SEQUENTIAL_SCAN, 0);//open the file if(hFile !=INVALID_HANDLE_VALUE){ hMap= ::CreateFileMapping(hFile, 0, PAGE_READONLY | SEC_COMMIT, 0, 0, 0);//create Mem mapping for the file in virtual memory if( hMap!=NULL){ base = ::MapViewOfFile(hMap, FILE_MAP_READ, 0, 0, 0);//load the mapped file into the RAM //start to compare some bytes (values) from

问题 I've a very large bitmap that I'm trying to view using a C# application . The main issue here I can't load it directly into memory , thus I tried to use memory mapped view library to load it using guidance from Reference One, Reference Two , Reference Three , Reference Four and Reference Five . What I reached till now is the following:- Reading the bitmap in parts as I need ( For example I read the first 200 row). Create another bitmap from the rows I read and display it. Porblem:- The

问题 I am in need of a way to store a file in memory very briefly in PHP, the file is being built and then sent right off to another web service. I see that as of PHP 5.1 the php://temp and php://memory streams are available, but there doesn't seem to be a whole lot of difference between the two: php://temp supports the stream_select() function and php://memory does not. Which one should I be using in this case, or is there a better way to do memory mapped files in PHP? 回答1: Straight out of the

问题 I am in need of a way to store a file in memory very briefly in PHP, the file is being built and then sent right off to another web service. I see that as of PHP 5.1 the php://temp and php://memory streams are available, but there doesn't seem to be a whole lot of difference between the two: php://temp supports the stream_select() function and php://memory does not. Which one should I be using in this case, or is there a better way to do memory mapped files in PHP? 回答1: Straight out of the

问题 In Python on Windows I can create a large file by from mmap import mmap f = open('big.file', 'w') f.close() f = open('big.file', 'r+') m = mmap(f.fileno(), 10**9) And now big.file is (about) 1 gigabyte. On Linux, though, this will return ValueError: mmap length is greater than file size . Is there a way to get the same behavior on Linux as with Windows? That is, to be able to increase a file's size using mmap ? 回答1: On POSIX systems at least, mmap() cannot be used to increase (or decrease)

问题 I realize .NET 4.0 is in Beta, but I'm hoping someone has a resolution for this. I'm trying to create a memory mapped file from a DLL: FileStream file = File.OpenRead("C:\mydll.dll"); using (MemoryMappedFile mappedFile = MemoryMappedFile.CreateFromFile(file, "PEIMAGE", 1024 * 1024, MemoryMappedFileAccess.ReadExecute)) { using (MemoryMappedViewStream viewStream = mappedFile.CreateViewStream()) { // read from the view stream } } Unfortunately, no matter what I do, I always get an

问题 Memory mapped file is an efficient way for using regex or doing manipulation on large binary files. In case I have a large text file (~1GB), is it possible to work with an encoding-aware mapped file? Regex like [\u1234-\u5678] won't work on bytes objects and converting the pattern to unicode will not work either (as "[\u1234-\u5678]".encode("utf-32") for example will not understand the range correctly). Searching might work if I convert the search pattern from str to bytes using .encode() but

问题 I am working on memory mapped files. Is there any way to know the length of memory mapped file content? What I want is to append the existing memory mapped file. Its easy to append the bytes in the file but I am looking to append string. We can check the CAPACITY property, but it returns the bytes size I think. To be more clear, I am explaining the scenario. I am creating Memory mapped file A. I write "Hello" when I create it. It works fine. Now I want to write the "World" into existing file