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fix std.mem.span handling of sentinel-terminated arrays

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previously this function would use the array length, but now it scans
the array looking for the first sentinel that occurs.
This commit is contained in:
Andrew Kelley 2020-03-15 15:46:56 -04:00
parent 701aaf0ddf
commit 6c2b23593b
1 changed files with 16 additions and 2 deletions
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18
lib/std/mem.zig
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@ -567,12 +567,20 @@ test "span" {
/// Takes a pointer to an array, an array, a sentinel-terminated pointer,
/// or a slice, and returns the length.
/// In the case of a sentinel-terminated array, it scans the array
/// for a sentinel and uses that for the length, rather than using the array length.
pub fn len(ptr: var) usize {
return switch (@typeInfo(@TypeOf(ptr))) {
.Array => |info| info.len,
.Array => |info| if (info.sentinel) |sentinel|
indexOfSentinel(info.child, sentinel, &ptr)
else
info.len,
.Pointer => |info| switch (info.size) {
.One => switch (@typeInfo(info.child)) {
.Array => |x| x.len,
.Array => |x| if (x.sentinel) |sentinel|
indexOfSentinel(x.child, sentinel, ptr)
else
ptr.len,
else => @compileError("invalid type given to std.mem.length"),
},
.Many => if (info.sentinel) |sentinel|
@ -597,6 +605,12 @@ test "len" {
const ptr = array[0..2 :0].ptr;
testing.expect(len(ptr) == 2);
}
{
var array: [5:0]u16 = [_]u16{ 1, 2, 3, 4, 5 };
testing.expect(len(&array) == 5);
array[2] = 0;
testing.expect(len(&array) == 2);
}
}
pub fn indexOfSentinel(comptime Elem: type, comptime sentinel: Elem, ptr: [*:sentinel]const Elem) usize {