[wpiutil] Add MappedFileRegion

2026-06-20 00:51:42 +00:00 · 2021-12-10 20:01:47 -08:00
parent ac5d46cfa7
commit b8c4d7527b
2 changed files with 219 additions and 0 deletions
--- a/wpiutil/src/main/native/cpp/MappedFileRegion.cpp
+++ b/wpiutil/src/main/native/cpp/MappedFileRegion.cpp
@@ -0,0 +1,133 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "wpi/MappedFileRegion.h"
+
+#include <sys/types.h>
+
+#ifdef _WIN32
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+
+#include <windows.h>  // NOLINT(build/include_order)
+
+#include <memoryapi.h>
+#include <sysinfoapi.h>
+
+#else  // _WIN32
+
+#include <sys/mman.h>
+#include <unistd.h>
+
+#endif  // _WIN32
+
+#ifdef _MSC_VER
+#include <io.h>
+#endif
+
+#ifdef _WIN32
+#include "wpi/WindowsError.h"
+#endif
+
+using namespace wpi;
+
+MappedFileRegion::MappedFileRegion(fs::file_t f, uint64_t length,
+                                   uint64_t offset, MapMode mapMode,
+                                   std::error_code& ec)
+    : m_size(length) {
+#ifdef _WIN32
+  if (f == INVALID_HANDLE_VALUE) {
+    ec = std::make_error_code(std::errc::bad_file_descriptor);
+    return;
+  }
+
+  HANDLE fileMappingHandle = ::CreateFileMappingW(
+      f, 0, mapMode == kReadOnly ? PAGE_READONLY : PAGE_READWRITE, length >> 32,
+      length & 0xffffffff, 0);
+  if (fileMappingHandle == nullptr) {
+    ec = wpi::mapWindowsError(GetLastError());
+    return;
+  }
+
+  DWORD dwDesiredAccess = 0;
+  switch (mapMode) {
+    case kReadOnly:
+      dwDesiredAccess = FILE_MAP_READ;
+      break;
+    case kReadWrite:
+      dwDesiredAccess = FILE_MAP_WRITE;
+      break;
+    case kPriv:
+      dwDesiredAccess = FILE_MAP_WRITE | FILE_MAP_COPY;
+      break;
+  }
+  m_mapping = ::MapViewOfFile(fileMappingHandle, dwDesiredAccess, offset >> 32,
+                              offset & 0xffffffff, length);
+  if (m_mapping == nullptr) {
+    ec = wpi::mapWindowsError(GetLastError());
+    ::CloseHandle(fileMappingHandle);
+    return;
+  }
+
+  // Close the file mapping handle, as it's kept alive by the file mapping. But
+  // neither the file mapping nor the file mapping handle keep the file handle
+  // alive, so we need to keep a reference to the file in case all other handles
+  // are closed and the file is deleted, which may cause invalid data to be read
+  // from the file.
+  ::CloseHandle(fileMappingHandle);
+  if (!::DuplicateHandle(::GetCurrentProcess(), f, ::GetCurrentProcess(),
+                         &m_fileHandle, 0, 0, DUPLICATE_SAME_ACCESS)) {
+    ec = wpi::mapWindowsError(GetLastError());
+    ::UnmapViewOfFile(m_mapping);
+    m_mapping = nullptr;
+    return;
+  }
+#else
+  m_mapping =
+      ::mmap(nullptr, length,
+             mapMode == kReadOnly ? PROT_READ : (PROT_READ | PROT_WRITE),
+             mapMode == kPriv ? MAP_PRIVATE : MAP_SHARED, f, offset);
+  if (m_mapping == MAP_FAILED) {
+    ec = std::error_code(errno, std::generic_category());
+    m_mapping = nullptr;
+  }
+#endif
+}
+
+void MappedFileRegion::Flush() {
+#ifdef _WIN32
+  ::FlushViewOfFile(m_mapping, 0);
+  ::FlushFileBuffers(m_fileHandle);
+#else
+  ::msync(m_mapping, m_size, MS_ASYNC);
+#endif
+}
+
+void MappedFileRegion::Unmap() {
+  if (!m_mapping) {
+    return;
+  }
+#ifdef _WIN32
+  ::UnmapViewOfFile(m_mapping);
+  ::CloseHandle(m_fileHandle);
+#else
+  ::munmap(m_mapping, m_size);
+#endif
+  m_mapping = nullptr;
+}
+
+size_t MappedFileRegion::GetAlignment() {
+#ifdef _WIN32
+  SYSTEM_INFO SysInfo;
+  ::GetSystemInfo(&SysInfo);
+  return SysInfo.dwAllocationGranularity;
+#else
+  static long pageSize = ::getpagesize();  // NOLINT
+  if (pageSize < 0) {
+    pageSize = 4096;
+  }
+  return pageSize;
+#endif
+}