Revert "Revert part of "Extract mmap support from dart2js into package:mmap""

This re-applies the changes that makes package:compiler use
package:mmap.

The flutter engine PR in [0] will land before this CL, making the
autoroller have no problems rolling this into engine.

We'll also try to land [1] to prepare this rolling into g3.

[0] https://github.com/flutter/engine/pull/39090
[1] https://critique.corp.google.com/cl/503931029

Change-Id: Ie9cefd716968de62a953b5634ad52e29d645e04f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/279507
Commit-Queue: Martin Kustermann <kustermann@google.com>
Reviewed-by: William Hesse <whesse@google.com>

pkg/compiler/lib/src/io/mapped_file.dart

@@ -6,172 +6,24 @@
 // SDK is rolled.
 // ignore_for_file: deprecated_member_use
 
-import 'dart:ffi';
-import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:compiler/src/source_file_provider.dart';
-import 'package:ffi/ffi.dart';
-
-// int open(const char *path, int oflag, ...);
-@FfiNative<Int32 Function(Pointer<Utf8>, Int32)>("open")
-external int open(Pointer<Utf8> filename, int flags);
-
-// int close(int fd);
-@FfiNative<Int32 Function(Int32)>("close")
-external int close(int fd);
-
-// void* mmap(void* addr, size_t length,
-//            int prot, int flags,
-//            int fd, off_t offset)
-@FfiNative<
-    Pointer<Uint8> Function(
-        Pointer<Uint8>, IntPtr, Int32, Int32, Int32, IntPtr)>("mmap")
-external Pointer<Uint8> mmap(
-    Pointer<Uint8> address, int len, int prot, int flags, int fd, int offset);
-
-// int munmap(void *addr, size_t length)
-@FfiNative<IntPtr Function(Pointer<Uint8> address, IntPtr len)>("munmap")
-external int munmap(Pointer<Uint8> address, int len);
-
-final processSymbols = DynamicLibrary.process();
-final munmapNative = processSymbols.lookup<Void>('munmap');
-final closeNative = processSymbols.lookup<Void>('close');
-final freeNative = processSymbols.lookup<Void>('free');
-
-// int mprotect(void *addr, size_t len, int prot)
-@FfiNative<Int32 Function(Pointer<Uint8>, IntPtr, Int32)>("mprotect")
-external int mprotect(Pointer<Uint8> addr, int len, int prot);
-
-// DART_EXPORT Dart_Handle
-// Dart_NewExternalTypedDataWithFinalizer(Dart_TypedData_Type type,
-//                                       void* data,
-//                                       intptr_t length,
-//                                       void* peer,
-//                                       intptr_t external_allocation_size,
-//                                       Dart_HandleFinalizer callback)
-typedef Dart_NewExternalTypedDataWithFinalizerNative = Handle Function(
-    Int32, Pointer<Void>, IntPtr, Pointer<Void>, IntPtr, Pointer<Void>);
-typedef Dart_NewExternalTypedDataWithFinalizerDart = Object Function(
-    int, Pointer<Void>, int, Pointer<Void>, int, Pointer<Void>);
-final Dart_NewExternalTypedDataWithFinalizer = processSymbols.lookupFunction<
-        Dart_NewExternalTypedDataWithFinalizerNative,
-        Dart_NewExternalTypedDataWithFinalizerDart>(
-    'Dart_NewExternalTypedDataWithFinalizer');
-
-const int kPageSize = 4096;
-const int kProtRead = 1;
-const int kProtWrite = 2;
-const int kProtExec = 4;
-const int kMapPrivate = 2;
-const int kMapAnon = 0x20;
-const int kMapFailed = -1;
-
-// We need to attach the finalizer which calls close() and
-
-final finalizerAddress = () {
-  final finalizerStub = mmap(nullptr, kPageSize, kProtRead | kProtWrite,
-      kMapPrivate | kMapAnon, -1, 0);
-  finalizerStub.cast<Uint8>().asTypedList(kPageSize).setAll(0, <int>[
-// Regenerate by running dart mmap.dart gen
-// ASM_START
-//    #include <cstddef>
-//    #include <cstdint>
-//
-//    struct PeerData {
-//        int (*close)(int);
-//        int (*munmap)(void*, size_t);
-//        int (*free)(void*);
-//        void* mapping;
-//        intptr_t size;
-//        intptr_t fd;
-//    };
-//
-//    extern "C" void finalizer(void* callback_data, void* peer) {
-//        auto data = static_cast<PeerData*>(peer);
-//        data->munmap(data->mapping, data->size);
-//        data->close(data->fd);
-//        data->free(peer);
-//    }
-//
-    0x55, 0x48, 0x89, 0xf5, 0x48, 0x8b, 0x76, 0x20, 0x48, 0x8b, 0x7d, 0x18, //
-    0xff, 0x55, 0x08, 0x8b, 0x7d, 0x28, 0xff, 0x55, 0x00, 0x48, 0x8b, 0x45, //
-    0x10, 0x48, 0x89, 0xef, 0x5d, 0xff, 0xe0, //
-// ASM_END
-  ]);
-  if (mprotect(finalizerStub, kPageSize, kProtRead | kProtExec) != 0) {
-    throw 'Failed to write executable code to the memory.';
-  }
-
-  return finalizerStub.cast<Void>();
-}();
-
-class PeerData extends Struct {
-  external Pointer<Void> close;
-  external Pointer<Void> munmap;
-  external Pointer<Void> free;
-  external Pointer<Uint8> mapping;
-  @IntPtr()
-  external int size;
-  @IntPtr()
-  external int fd;
-}
-
-Uint8List toExternalDataWithFinalizer(
-    Pointer<Uint8> memory, int size, int length, int fd) {
-  final peer = malloc.allocate<PeerData>(sizeOf<PeerData>());
-  peer.ref.close = closeNative;
-  peer.ref.munmap = munmapNative;
-  peer.ref.free = freeNative;
-  peer.ref.mapping = memory;
-  peer.ref.size = size;
-  peer.ref.fd = fd;
-  return Dart_NewExternalTypedDataWithFinalizer(
-    /*Dart_TypedData_kUint8*/ 2,
-    memory.cast(),
-    length,
-    peer.cast(),
-    size,
-    finalizerAddress,
-  ) as Uint8List;
-}
+import 'package:mmap/mmap.dart';
 
 Uint8List viewOfFile(String filename, bool zeroTerminated) {
-  final cfilename = filename.toNativeUtf8();
-  final int fd = open(cfilename, 0);
-  malloc.free(cfilename);
-  if (fd == 0) throw 'failed to open';
-  try {
-    final length = File(filename).lengthSync();
-    int lengthRoundedUp = (length + kPageSize - 1) & ~(kPageSize - 1);
-    final result =
-        mmap(nullptr, lengthRoundedUp, kProtRead, kMapPrivate, fd, 0);
-    if (result.address == kMapFailed) throw 'failed to map';
-    try {
-      if (zeroTerminated) {
-        if (length == lengthRoundedUp) {
-          // In the rare case we need a zero-terminated list and the file size
-          // is exactly page-aligned we need to allocate a new list with extra
-          // room for the terminating 0.
-          return Uint8List(length + 1)
-            ..setRange(
-                0,
-                length,
-                toExternalDataWithFinalizer(
-                    result, lengthRoundedUp, length, fd));
-        }
-        return toExternalDataWithFinalizer(
-            result, lengthRoundedUp, length + 1, fd);
-      }
-      return toExternalDataWithFinalizer(result, lengthRoundedUp, length, fd);
-    } catch (_) {
-      munmap(result, lengthRoundedUp);
-      rethrow;
-    }
-  } catch (e) {
-    close(fd);
-    rethrow;
+  final mappedFile = mmapFile(filename);
+  if (!zeroTerminated) {
+    return mappedFile.fileBytes;
   }
+  if (mappedFile.hasZeroPadding) {
+    return mappedFile.fileBytesZeroTerminated;
+  }
+  // In the rare case we need a zero-terminated list and the file size
+  // is exactly page-aligned we need to allocate a new list with extra
+  // room for the terminating 0.
+  return Uint8List(mappedFile.fileLength + 1)
+    ..setRange(0, mappedFile.fileLength, mappedFile.fileBytes);
 }
 
 class MemoryMapSourceFileByteReader implements SourceFileByteReader {
@@ -179,7 +31,7 @@ class MemoryMapSourceFileByteReader implements SourceFileByteReader {
 
   @override
   Uint8List getBytes(String filename, {bool zeroTerminated = true}) {
-    if (Platform.isLinux) {
+    if (supportsMMap) {
       try {
         return viewOfFile(filename, zeroTerminated);
       } catch (e) {

pkg/compiler/pubspec.yaml

@@ -13,12 +13,12 @@ dependencies:
   collection: any
   crypto: any
   dart2js_info: any
-  ffi: any
   front_end: any
   js_ast: any
   js_runtime: any
   js_shared: any
   kernel: any
+  mmap: any
   vm_service: any
 
 # Use 'any' constraints here; we get our versions from the DEPS file.