memory-mapped-files

问题 I need something similar to ReadToEnd or ReadAllBytes to read all of the contents of the MemoryMappedFile using the MappedViewAccessor if I don't know the size of it, how can I do it? I have searched for it, I have seen this question, but it is not the thing I am looking for: How can I quickly read bytes from a memory mapped file in .NET? Edit: There is a problem, the (int)stream.Length is not giving me the correct length, it rather gives the size of the internal buffer used! I need to

问题 I have a rather large amount of data to analyse - each file is about 5gigs. Each file is of the following format: xxxxx yyyyy Both key and value can repeat, but the keys are sorted in increasing order. I'm trying to use a memory mapped file for this purpose and then find the required keys and work with them. This is what I've written: if (data_file != "") { clock_start = clock(); data_file_mapped.open(data_file); data_multimap = (std::multimap<double, unsigned int> *)data_file_mapped.data();

问题 I am very new to the memory mapping and trying to understand memory mapped files to use them in my project(linux based). My requirement is to write & then read from memory mapped files. I wrote a sample program which only writes and it works fine but i have a few very basic doubts as i do not understand this funda of memory mapping properly. #include <unordered_map> #include <boost/iostreams/device/mapped_file.hpp> using namespace boost::interprocess; using namespace std; typedef unordered

问题 I'm trying to implement custom allocator for storing memory mapped files in the std::vector . Files mapping performed by boost::iostreams::mapped_file Allocator type for file memory mapping: template<typename T> class mmap_allocator { public: typedef T value_type; mmap_allocator(const std::string& filename) : _mmfile(filename) { } T* allocate (size_t n) { return reinterpret_cast<T*>(_mmfile.data()); } void deallocate (T* p, size_t n) { p = nullptr; _mmfile.close(); } private: boost::iostreams

问题 While attempting to use boost::interprocess for storing a std::vector in a memory mapped file, I am getting the exception Exception thrown: read access violation. when I try to push back on a loaded vector, but only in debug mode . This minimal example code (written by @sehe) is retrieved from https://stackoverflow.com/a/29602884/2741329, and it crashes on MSVC14 in debug mode and executed more than once: #include <boost/interprocess/managed_mapped_file.hpp> namespace bi = boost::interprocess

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 5 years ago . Wants to create an application storing data in memory. But i dont want the data to be lost even if my app crashes. What concept should i use? Should I use a shared memory, or is there some other concept that suits my requirement better. 回答1: You are asking for persistence (or even

问题 I am trying to implement the caesar cipher with mmap. I think the cipher works so fine but the problem is, the mmap. The idea of it is to update the file, if there was a change. So far it isn't working. I can just read the memory mapped file and print it. But if I make any modificaiton, I get a segmentation fault. Unfortunately, I couldn't solve the problem myself. So, I would appreciate it, if you could help me with it. Here is the code. int main (int argc, char *argv[]) { if(argc != 5)

问题 I have created the following demo to see the MMF begaviour (I want to use it as a very large array of long values). import java.nio._, java.io._, java.nio.channels.FileChannel object Index extends App { val formatter = java.text.NumberFormat.getIntegerInstance def format(l: Number) = formatter.format(l) val raf = new RandomAccessFile("""C:\Users\...\Temp\96837624\mmf""", "rw") raf.setLength(20) def newBuf(capacity: Int) = { var bytes= 8.toLong*capacity println("new buf " + format(capacity) +

问题 I want to implement memory mapped file concept as a shared memory to share data between two processes running in my windows system. One in Java and another in native (C# layer). Both are running processes and hence i want to use non persisted mechanism for memory mapped files instead of persisted file option (because a file poses a security threat ). Java File Channels http://docs.oracle.com/javase/6/docs/api/java/nio/channels/FileChannel.html#map(java.nio.channels.FileChannel.MapMode, long,

问题 i have a txt file that has millions of lines, each line has 3 floats, i read it using the following code : ifstream file(path) float x,y,z; while(!file.eof()) file >> x >> y >> z; and i works perfectly. Now i want to try doing the same thing using Boost mapped files, so i do the following string filename = "C:\\myfile.txt"; file_mapping mapping(filename.c_str(), read_only); mapped_region mapped_rgn(mapping, read_only); char* const mmaped_data = static_cast<char*>(mapped_rgn.get_address());