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std: mem span functions can take an optional pointer

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daurnimator 2020-03-30 21:56:09 +11:00 committed by Andrew Kelley
parent c1cc1ebc35
commit 3be720a729
1 changed files with 38 additions and 14 deletions
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52
lib/std/mem.zig
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@ -512,36 +512,54 @@ pub fn toSlice(comptime T: type, ptr: [*:0]T) [:0]T {
/// the constness of the input type. `[*c]` pointers are assumed to be 0-terminated,
/// and assumed to not allow null.
pub fn Span(comptime T: type) type {
var ptr_info = @typeInfo(T).Pointer;
switch (ptr_info.size) {
.One => switch (@typeInfo(ptr_info.child)) {
.Array => |info| {
ptr_info.child = info.child;
ptr_info.sentinel = info.sentinel;
},
else => @compileError("invalid type given to std.mem.Span"),
switch(@typeInfo(T)) {
.Optional => |optional_info| {
return ?Span(optional_info.child);
},
.C => {
ptr_info.sentinel = 0;
ptr_info.is_allowzero = false;
.Pointer => |ptr_info| {
var new_ptr_info = ptr_info;
switch (ptr_info.size) {
.One => switch (@typeInfo(ptr_info.child)) {
.Array => |info| {
new_ptr_info.child = info.child;
new_ptr_info.sentinel = info.sentinel;
},
else => @compileError("invalid type given to std.mem.Span"),
},
.C => {
new_ptr_info.sentinel = 0;
new_ptr_info.is_allowzero = false;
},
.Many, .Slice => {},
}
new_ptr_info.size = .Slice;
return @Type(std.builtin.TypeInfo{ .Pointer = new_ptr_info });
},
.Many, .Slice => {},
else => @compileError("invalid type given to std.mem.Span"),
}
ptr_info.size = .Slice;
return @Type(std.builtin.TypeInfo{ .Pointer = ptr_info });
}
test "Span" {
testing.expect(Span(*[5]u16) == []u16);
testing.expect(Span(?*[5]u16) == ?[]u16);
testing.expect(Span(*const [5]u16) == []const u16);
testing.expect(Span(?*const [5]u16) == ?[]const u16);
testing.expect(Span([]u16) == []u16);
testing.expect(Span(?[]u16) == ?[]u16);
testing.expect(Span([]const u8) == []const u8);
testing.expect(Span(?[]const u8) == ?[]const u8);
testing.expect(Span([:1]u16) == [:1]u16);
testing.expect(Span(?[:1]u16) == ?[:1]u16);
testing.expect(Span([:1]const u8) == [:1]const u8);
testing.expect(Span(?[:1]const u8) == ?[:1]const u8);
testing.expect(Span([*:1]u16) == [:1]u16);
testing.expect(Span(?[*:1]u16) == ?[:1]u16);
testing.expect(Span([*:1]const u8) == [:1]const u8);
testing.expect(Span(?[*:1]const u8) == ?[:1]const u8);
testing.expect(Span([*c]u16) == [:0]u16);
testing.expect(Span(?[*c]u16) == ?[:0]u16);
testing.expect(Span([*c]const u8) == [:0]const u8);
testing.expect(Span(?[*c]const u8) == ?[:0]const u8);
}
/// Takes a pointer to an array, a sentinel-terminated pointer, or a slice, and
@ -553,6 +571,9 @@ test "Span" {
/// length value is used instead of the sentinel.
pub fn span(ptr: var) Span(@TypeOf(ptr)) {
const Result = Span(@TypeOf(ptr));
if (@typeInfo(@TypeOf(ptr)) == .Optional and ptr == null) {
return null;
}
const l = len(ptr);
if (@typeInfo(Result).Pointer.sentinel) |s| {
return ptr[0..l :s];
@ -573,6 +594,9 @@ test "span" {
/// rather than using the length.
pub fn spanZ(ptr: var) Span(@TypeOf(ptr)) {
const Result = Span(@TypeOf(ptr));
if (@typeInfo(@TypeOf(ptr)) == .Optional and ptr == null) {
return null;
}
const l = lenZ(ptr);
if (@typeInfo(Result).Pointer.sentinel) |s| {
return ptr[0..l :s];