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[samples/ffi] Add bitfield sample
Issue: https://github.com/dart-lang/sdk/issues/38954 Change-Id: I04b2b81d83a19c5ff88d4364256b23594fe2139b Cq-Include-Trybots: luci.dart.try:vm-ffi-android-debug-arm-try,vm-ffi-android-debug-arm64-try,analyzer-analysis-server-linux-try,analyzer-linux-release-try,front-end-linux-release-x64-try Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/122762 Commit-Queue: Daco Harkes <dacoharkes@google.com> Reviewed-by: Martin Kustermann <kustermann@google.com>
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samples/ffi/sample_ffi_bitfield.dart
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samples/ffi/sample_ffi_bitfield.dart
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// Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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import 'dart:ffi';
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import 'package:ffi/ffi.dart';
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import 'package:expect/expect.dart';
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/// typedef struct {
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/// unsigned int bold : 1;
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/// unsigned int underline : 2;
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/// unsigned int italic : 1;
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/// unsigned int blink : 1;
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/// unsigned int reverse : 1;
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/// unsigned int strike : 1;
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/// unsigned int font : 4;
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/// } ScreenCellAttrs;
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class ScreenCellAttrs extends Struct {
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@Int16()
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int bits;
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int get bold => getBits(kBoldFieldOffset, kBoldFieldLength);
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void set bold(int value) =>
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setBits(kBoldFieldOffset, kBoldFieldLength, value);
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int get underline => getBits(kUnderlineFieldOffset, kUnderlineFieldLength);
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void set underline(int value) =>
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setBits(kUnderlineFieldOffset, kUnderlineFieldLength, value);
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int get italic => getBits(kItalicFieldOffset, kItalicFieldLength);
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void set italic(int value) =>
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setBits(kItalicFieldOffset, kItalicFieldLength, value);
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int get blink => getBits(kBlinkFieldOffset, kBlinkFieldLength);
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void set blink(int value) =>
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setBits(kBlinkFieldOffset, kBlinkFieldLength, value);
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int get reverse => getBits(kReverseFieldOffset, kReverseFieldLength);
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void set reverse(int value) =>
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setBits(kReverseFieldOffset, kReverseFieldLength, value);
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int get strike => getBits(kStrikeFieldOffset, kStrikeFieldLength);
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void set strike(int value) =>
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setBits(kStrikeFieldOffset, kStrikeFieldLength, value);
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int get font => getBits(kFontFieldOffset, kFontFieldLength);
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void set font(int value) =>
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setBits(kFontFieldOffset, kFontFieldLength, value);
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int getBits(int offset, int length) => bits.getBits(offset, length);
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void setBits(int offset, int length, int value) {
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bits = bits.setBits(offset, length, value);
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}
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}
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const int kBoldFieldOffset = 0;
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const int kBoldFieldLength = 1;
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const int kUnderlineFieldOffset = kBoldFieldOffset + kBoldFieldLength;
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const int kUnderlineFieldLength = 2;
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const int kItalicFieldOffset = kUnderlineFieldOffset + kUnderlineFieldLength;
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const int kItalicFieldLength = 1;
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const int kBlinkFieldOffset = kItalicFieldOffset + kItalicFieldLength;
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const int kBlinkFieldLength = 1;
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const int kReverseFieldOffset = kBlinkFieldOffset + kBlinkFieldLength;
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const int kReverseFieldLength = 1;
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const int kStrikeFieldOffset = kReverseFieldOffset + kReverseFieldLength;
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const int kStrikeFieldLength = 1;
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const int kFontFieldOffset = kStrikeFieldOffset + kStrikeFieldLength;
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const int kFontFieldLength = 4;
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/// Extension to use a 64-bit integer as bit field.
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extension IntBitField on int {
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static int _bitMask(int offset, int lenght) => ((1 << lenght) - 1) << offset;
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/// Read `length` bits at `offset`.
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///
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/// Truncates everything.
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int getBits(int offset, int length) {
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final mask = _bitMask(offset, length);
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return (this & mask) >> offset;
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}
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/// Returns a new integer value in which `length` bits are overwritten at
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/// `offset`.
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///
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/// Truncates everything.
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int setBits(int offset, int length, int value) {
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final mask = _bitMask(offset, length);
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return (this & ~mask) | ((value << offset) & mask);
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}
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}
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main() {
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final p = allocate<ScreenCellAttrs>(count: 3);
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// Zeroes out all fields.
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p.ref.bits = 0;
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// Set individual fields.
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p.ref.blink = 0;
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p.ref.bold = 1;
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p.ref.font = 15;
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p.ref.italic = 1;
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p.ref.reverse = 0;
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p.ref.strike = 0;
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p.ref.underline = 2;
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// Read individual fields.
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print(p.ref.blink);
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print(p.ref.bold);
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print(p.ref.font);
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print(p.ref.italic);
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print(p.ref.reverse);
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print(p.ref.strike);
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print(p.ref.underline);
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// A check for automated testing.
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Expect.equals(1933, p.ref.bits);
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free(p);
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}
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@ -6,6 +6,7 @@
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//
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// SharedObjects=ffi_test_dynamic_library ffi_test_functions
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import 'sample_ffi_bitfield.dart' as sample0;
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import 'sample_ffi_data.dart' as sample1;
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import 'sample_ffi_dynamic_library.dart' as sample2;
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import 'sample_ffi_functions_callbacks.dart' as sample3;
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@ -14,6 +15,7 @@ import 'sample_ffi_functions.dart' as sample5;
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import 'sample_ffi_structs.dart' as sample6;
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main() {
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sample0.main();
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sample1.main();
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sample2.main();
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sample3.main();
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