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Merge pull request #7084 from xackus/mem-volatile 

std.mem: make sliceAsBytes, etc. respect volatile
master
Veikka Tuominen 2020-11-18 13:06:35 +02:00 committed by GitHub
parent 27b73cc395 109a3ebcca
commit 1e1a490600
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1 changed files with 88 additions and 35 deletions
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123
lib/std/mem.zig
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@ -7,13 +7,14 @@ const std = @import("std.zig");
const debug = std.debug;
const assert = debug.assert;
const math = std.math;
const builtin = @import("builtin");
const builtin = std.builtin;
const mem = @This();
const meta = std.meta;
const trait = meta.trait;
const testing = std.testing;
/// https://github.com/ziglang/zig/issues/2564
/// Compile time known minimum page size.
/// https://github.com/ziglang/zig/issues/4082
pub const page_size = switch (builtin.arch) {
.wasm32, .wasm64 => 64 * 1024,
.aarch64 => switch (builtin.os.tag) {
@ -139,7 +140,7 @@ test "mem.Allocator basics" {
/// Copy all of source into dest at position 0.
/// dest.len must be >= source.len.
/// dest.ptr must be <= src.ptr.
/// If the slices overlap, dest.ptr must be <= src.ptr.
pub fn copy(comptime T: type, dest: []T, source: []const T) void {
// TODO instead of manually doing this check for the whole array
// and turning off runtime safety, the compiler should detect loops like
@ -152,7 +153,7 @@ pub fn copy(comptime T: type, dest: []T, source: []const T) void {
/// Copy all of source into dest at position 0.
/// dest.len must be >= source.len.
/// dest.ptr must be >= src.ptr.
/// If the slices overlap, dest.ptr must be >= src.ptr.
pub fn copyBackwards(comptime T: type, dest: []T, source: []const T) void {
// TODO instead of manually doing this check for the whole array
// and turning off runtime safety, the compiler should detect loops like
@ -1916,25 +1917,31 @@ pub fn nativeToBig(comptime T: type, x: T) T {
};
}
fn CopyPtrAttrs(comptime source: type, comptime size: builtin.TypeInfo.Pointer.Size, comptime child: type) type {
const info = @typeInfo(source).Pointer;
return @Type(.{
.Pointer = .{
.size = size,
.is_const = info.is_const,
.is_volatile = info.is_volatile,
.is_allowzero = info.is_allowzero,
.alignment = info.alignment,
.child = child,
.sentinel = null,
},
});
}
fn AsBytesReturnType(comptime P: type) type {
if (!trait.isSingleItemPtr(P))
@compileError("expected single item pointer, passed " ++ @typeName(P));
const size = @sizeOf(meta.Child(P));
const alignment = meta.alignment(P);
if (alignment == 0) {
if (trait.isConstPtr(P))
return *const [size]u8;
return *[size]u8;
}
if (trait.isConstPtr(P))
return *align(alignment) const [size]u8;
return *align(alignment) [size]u8;
return CopyPtrAttrs(P, .One, [size]u8);
}
/// Given a pointer to a single item, returns a slice of the underlying bytes, preserving constness.
/// Given a pointer to a single item, returns a slice of the underlying bytes, preserving pointer attributes.
pub fn asBytes(ptr: anytype) AsBytesReturnType(@TypeOf(ptr)) {
const P = @TypeOf(ptr);
return @ptrCast(AsBytesReturnType(P), ptr);
@ -1974,6 +1981,20 @@ test "asBytes" {
testing.expect(eql(u8, asBytes(&zero), ""));
}
test "asBytes preserves pointer attributes" {
const inArr: u32 align(16) = 0xDEADBEEF;
const inPtr = @ptrCast(*align(16) const volatile u32, &inArr);
const outSlice = asBytes(inPtr);
const in = @typeInfo(@TypeOf(inPtr)).Pointer;
const out = @typeInfo(@TypeOf(outSlice)).Pointer;
testing.expectEqual(in.is_const, out.is_const);
testing.expectEqual(in.is_volatile, out.is_volatile);
testing.expectEqual(in.is_allowzero, out.is_allowzero);
testing.expectEqual(in.alignment, out.alignment);
}
/// Given any value, returns a copy of its bytes in an array.
pub fn toBytes(value: anytype) [@sizeOf(@TypeOf(value))]u8 {
return asBytes(&value).*;
@ -2003,13 +2024,11 @@ fn BytesAsValueReturnType(comptime T: type, comptime B: type) type {
@compileError(std.fmt.bufPrint(&buf, "expected *[{}]u8, passed " ++ @typeName(B), .{size}) catch unreachable);
}
const alignment = comptime meta.alignment(B);
return if (comptime trait.isConstPtr(B)) *align(alignment) const T else *align(alignment) T;
return CopyPtrAttrs(B, .One, T);
}
/// Given a pointer to an array of bytes, returns a pointer to a value of the specified type
/// backed by those bytes, preserving constness.
/// backed by those bytes, preserving pointer attributes.
pub fn bytesAsValue(comptime T: type, bytes: anytype) BytesAsValueReturnType(T, @TypeOf(bytes)) {
return @ptrCast(BytesAsValueReturnType(T, @TypeOf(bytes)), bytes);
}
@ -2051,6 +2070,20 @@ test "bytesAsValue" {
testing.expect(meta.eql(inst, inst2.*));
}
test "bytesAsValue preserves pointer attributes" {
const inArr align(16) = [4]u8{ 0xDE, 0xAD, 0xBE, 0xEF };
const inSlice = @ptrCast(*align(16) const volatile [4]u8, &inArr)[0..];
const outPtr = bytesAsValue(u32, inSlice);
const in = @typeInfo(@TypeOf(inSlice)).Pointer;
const out = @typeInfo(@TypeOf(outPtr)).Pointer;
testing.expectEqual(in.is_const, out.is_const);
testing.expectEqual(in.is_volatile, out.is_volatile);
testing.expectEqual(in.is_allowzero, out.is_allowzero);
testing.expectEqual(in.alignment, out.alignment);
}
/// Given a pointer to an array of bytes, returns a value of the specified type backed by a
/// copy of those bytes.
pub fn bytesToValue(comptime T: type, bytes: anytype) T {
@ -2066,9 +2099,8 @@ test "bytesToValue" {
testing.expect(deadbeef == @as(u32, 0xDEADBEEF));
}
//TODO copy also is_volatile, etc. I tried to use @typeInfo, modify child type, use @Type, but ran into issues.
fn BytesAsSliceReturnType(comptime T: type, comptime bytesType: type) type {
if (!(trait.isSlice(bytesType) and meta.Child(bytesType) == u8) and !(trait.isPtrTo(.Array)(bytesType) and meta.Child(meta.Child(bytesType)) == u8)) {
if (!(trait.isSlice(bytesType) or trait.isPtrTo(.Array)(bytesType)) or meta.Elem(bytesType) != u8) {
@compileError("expected []u8 or *[_]u8, passed " ++ @typeName(bytesType));
}
@ -2076,11 +2108,11 @@ fn BytesAsSliceReturnType(comptime T: type, comptime bytesType: type) type {
@compileError("number of bytes in " ++ @typeName(bytesType) ++ " is not divisible by size of " ++ @typeName(T));
}
const alignment = meta.alignment(bytesType);
return if (trait.isConstPtr(bytesType)) []align(alignment) const T else []align(alignment) T;
return CopyPtrAttrs(bytesType, .Slice, T);
}
/// Given a slice of bytes, returns a slice of the specified type
/// backed by those bytes, preserving pointer attributes.
pub fn bytesAsSlice(comptime T: type, bytes: anytype) BytesAsSliceReturnType(T, @TypeOf(bytes)) {
// let's not give an undefined pointer to @ptrCast
// it may be equal to zero and fail a null check
@ -2088,10 +2120,7 @@ pub fn bytesAsSlice(comptime T: type, bytes: anytype) BytesAsSliceReturnType(T,
return &[0]T{};
}
const Bytes = @TypeOf(bytes);
const alignment = comptime meta.alignment(Bytes);
const cast_target = if (comptime trait.isConstPtr(Bytes)) [*]align(alignment) const T else [*]align(alignment) T;
const cast_target = CopyPtrAttrs(@TypeOf(bytes), .Many, T);
return @ptrCast(cast_target, bytes)[0..@divExact(bytes.len, @sizeOf(T))];
}
@ -2149,17 +2178,29 @@ test "bytesAsSlice with specified alignment" {
testing.expect(slice[0] == 0x33333333);
}
//TODO copy also is_volatile, etc. I tried to use @typeInfo, modify child type, use @Type, but ran into issues.
test "bytesAsSlice preserves pointer attributes" {
const inArr align(16) = [4]u8{ 0xDE, 0xAD, 0xBE, 0xEF };
const inSlice = @ptrCast(*align(16) const volatile [4]u8, &inArr)[0..];
const outSlice = bytesAsSlice(u16, inSlice);
const in = @typeInfo(@TypeOf(inSlice)).Pointer;
const out = @typeInfo(@TypeOf(outSlice)).Pointer;
testing.expectEqual(in.is_const, out.is_const);
testing.expectEqual(in.is_volatile, out.is_volatile);
testing.expectEqual(in.is_allowzero, out.is_allowzero);
testing.expectEqual(in.alignment, out.alignment);
}
fn SliceAsBytesReturnType(comptime sliceType: type) type {
if (!trait.isSlice(sliceType) and !trait.isPtrTo(.Array)(sliceType)) {
@compileError("expected []T or *[_]T, passed " ++ @typeName(sliceType));
}
const alignment = meta.alignment(sliceType);
return if (trait.isConstPtr(sliceType)) []align(alignment) const u8 else []align(alignment) u8;
return CopyPtrAttrs(sliceType, .Slice, u8);
}
/// Given a slice, returns a slice of the underlying bytes, preserving pointer attributes.
pub fn sliceAsBytes(slice: anytype) SliceAsBytesReturnType(@TypeOf(slice)) {
const Slice = @TypeOf(slice);
@ -2169,9 +2210,7 @@ pub fn sliceAsBytes(slice: anytype) SliceAsBytesReturnType(@TypeOf(slice)) {
return &[0]u8{};
}
const alignment = comptime meta.alignment(Slice);
const cast_target = if (comptime trait.isConstPtr(Slice)) [*]align(alignment) const u8 else [*]align(alignment) u8;
const cast_target = CopyPtrAttrs(Slice, .Many, u8);
return @ptrCast(cast_target, slice)[0 .. slice.len * @sizeOf(meta.Elem(Slice))];
}
@ -2243,6 +2282,20 @@ test "sliceAsBytes and bytesAsSlice back" {
testing.expect(bytes[11] == math.maxInt(u8));
}
test "sliceAsBytes preserves pointer attributes" {
const inArr align(16) = [2]u16{ 0xDEAD, 0xBEEF };
const inSlice = @ptrCast(*align(16) const volatile [2]u16, &inArr)[0..];
const outSlice = sliceAsBytes(inSlice);
const in = @typeInfo(@TypeOf(inSlice)).Pointer;
const out = @typeInfo(@TypeOf(outSlice)).Pointer;
testing.expectEqual(in.is_const, out.is_const);
testing.expectEqual(in.is_volatile, out.is_volatile);
testing.expectEqual(in.is_allowzero, out.is_allowzero);
testing.expectEqual(in.alignment, out.alignment);
}
/// Round an address up to the nearest aligned address
/// The alignment must be a power of 2 and greater than 0.
pub fn alignForward(addr: usize, alignment: usize) usize {