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implement startsWithCodePoint

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This commit is contained in:
Folkert 2021-05-02 19:26:08 +02:00
parent 8df810fe0c
commit c071cfba13
12 changed files with 105 additions and 17 deletions
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35
compiler/builtins/bitcode/src/str.zig
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@ -806,6 +806,41 @@ pub fn startsWith(string: RocStr, prefix: RocStr) callconv(.C) bool {
return true;
}
// Str.startsWithCodePoint
pub fn startsWithCodePoint(string: RocStr, prefix: u32) callconv(.C) bool {
const bytes_len = string.len();
const bytes_ptr = string.asU8ptr();
var buffer: [4]u8 = undefined;
var width = std.unicode.utf8Encode(@truncate(u21, prefix), &buffer) catch unreachable;
var i: usize = 0;
while (i < width) : (i += 1) {
const a = buffer[i];
const b = bytes_ptr[i];
if (a != b) {
return false;
}
}
return true;
}
test "startsWithCodePoint: ascii char" {
const whole = RocStr.init(testing.allocator, "foobar", 6);
const prefix = 'f';
expect(startsWithCodePoint(whole, prefix));
}
test "startsWithCodePoint: emoji" {
const yes = RocStr.init(testing.allocator, "💖foobar", 10);
const no = RocStr.init(testing.allocator, "foobar", 6);
const prefix = '💖';
expect(startsWithCodePoint(yes, prefix));
expect(!startsWithCodePoint(no, prefix));
}
test "startsWith: foo starts with fo" {
const foo = RocStr.init(testing.allocator, "foo", 3);
const fo = RocStr.init(testing.allocator, "fo", 2);