bsnes/snesfilter/nall/filemap.hpp

#ifndef NALL_FILEMAP_HPP
#define NALL_FILEMAP_HPP

#include <nall/stdint.hpp>
#include <nall/utf8.hpp>

#include <stdio.h>
#include <stdlib.h>
#if defined(_WIN32)
  #include <windows.h>
#else
  #include <fcntl.h>
  #include <unistd.h>
  #include <sys/mman.h>
  #include <sys/stat.h>
  #include <sys/types.h>
#endif

namespace nall {
  class filemap {
  public:
    enum filemode { mode_read, mode_write, mode_readwrite, mode_writeread };

    bool open(const char *filename, filemode mode) { return p_open(filename, mode); }
    void close() { return p_close(); }
    unsigned size() const { return p_size; }
    uint8_t* handle() { return p_handle; }
    const uint8_t* handle() const { return p_handle; }
    filemap() : p_size(0), p_handle(0) { p_ctor(); }
    ~filemap() { p_dtor(); }

  private:
    unsigned p_size;
    uint8_t *p_handle;

    #if defined(_WIN32)
    //=============
    //MapViewOfFile
    //=============

    HANDLE p_filehandle, p_maphandle;

    bool p_open(const char *filename, filemode mode) {
      int desired_access, creation_disposition, flprotect, map_access;

      switch(mode) {
        default: return false;
        case mode_read:
          desired_access = GENERIC_READ;
          creation_disposition = OPEN_EXISTING;
          flprotect = PAGE_READONLY;
          map_access = FILE_MAP_READ;
          break;
        case mode_write:
          //write access requires read access
          desired_access = GENERIC_WRITE;
          creation_disposition = CREATE_ALWAYS;
          flprotect = PAGE_READWRITE;
          map_access = FILE_MAP_ALL_ACCESS;
          break;
        case mode_readwrite:
          desired_access = GENERIC_READ | GENERIC_WRITE;
          creation_disposition = OPEN_EXISTING;
          flprotect = PAGE_READWRITE;
          map_access = FILE_MAP_ALL_ACCESS;
          break;
        case mode_writeread:
          desired_access = GENERIC_READ | GENERIC_WRITE;
          creation_disposition = CREATE_NEW;
          flprotect = PAGE_READWRITE;
          map_access = FILE_MAP_ALL_ACCESS;
          break;
      }

      p_filehandle = CreateFileW(utf16_t(filename), desired_access, FILE_SHARE_READ, NULL,
        creation_disposition, FILE_ATTRIBUTE_NORMAL, NULL);
      if(p_filehandle == INVALID_HANDLE_VALUE) return false;

      p_size = GetFileSize(p_filehandle, NULL);

      p_maphandle = CreateFileMapping(p_filehandle, NULL, flprotect, 0, p_size, NULL);
      if(p_maphandle == INVALID_HANDLE_VALUE) {
        CloseHandle(p_filehandle);
        p_filehandle = INVALID_HANDLE_VALUE;
        return false;
      }

      p_handle = (uint8_t*)MapViewOfFile(p_maphandle, map_access, 0, 0, p_size);
      return p_handle;
    }

    void p_close() {
      if(p_handle) {
        UnmapViewOfFile(p_handle);
        p_handle = 0;
      }

      if(p_maphandle != INVALID_HANDLE_VALUE) {
        CloseHandle(p_maphandle);
        p_maphandle = INVALID_HANDLE_VALUE;
      }

      if(p_filehandle != INVALID_HANDLE_VALUE) {
        CloseHandle(p_filehandle);
        p_filehandle = INVALID_HANDLE_VALUE;
      }
    }

    void p_ctor() {
      p_filehandle = INVALID_HANDLE_VALUE;
      p_maphandle  = INVALID_HANDLE_VALUE;
    }

    void p_dtor() {
      close();
    }

    #else
    //====
    //mmap
    //====

    int p_fd;

    bool p_open(const char *filename, filemode mode) {
      int open_flags, mmap_flags;

      switch(mode) {
        default: return false;
        case mode_read:
          open_flags = O_RDONLY;
          mmap_flags = PROT_READ;
          break;
        case mode_write:
          open_flags = O_RDWR | O_CREAT;  //mmap() requires read access
          mmap_flags = PROT_WRITE;
          break;
        case mode_readwrite:
          open_flags = O_RDWR;
          mmap_flags = PROT_READ | PROT_WRITE;
          break;
        case mode_writeread:
          open_flags = O_RDWR | O_CREAT;
          mmap_flags = PROT_READ | PROT_WRITE;
          break;
      }

      p_fd = ::open(filename, open_flags);
      if(p_fd < 0) return false;

      struct stat p_stat;
      fstat(p_fd, &p_stat);
      p_size = p_stat.st_size;

      p_handle = (uint8_t*)mmap(0, p_size, mmap_flags, MAP_SHARED, p_fd, 0);
      if(p_handle == MAP_FAILED) {
        p_handle = 0;
        ::close(p_fd);
        p_fd = -1;
        return false;
      }

      return p_handle;
    }

    void p_close() {
      if(p_handle) {
        munmap(p_handle, p_size);
        p_handle = 0;
      }

      if(p_fd >= 0) {
        ::close(p_fd);
        p_fd = -1;
      }
    }

    void p_ctor() {
      p_fd = -1;
    }

    void p_dtor() {
      p_close();
    }

    #endif
  };
}

#endif