std: add containsAtLeastScalar to mem (#22826)

lib/std/mem.zig

@@ -1611,6 +1611,8 @@ test count {
 /// Returns true if the haystack contains expected_count or more needles
 /// needle.len must be > 0
 /// does not count overlapping needles
+//
+/// See also: `containsAtLeastScalar`
 pub fn containsAtLeast(comptime T: type, haystack: []const T, expected_count: usize, needle: []const T) bool {
     assert(needle.len > 0);
     if (expected_count == 0) return true;
@@ -1642,6 +1644,34 @@ test containsAtLeast {
     try testing.expect(!containsAtLeast(u8, "   radar      radar   ", 3, "radar"));
 }
 
+/// Returns true if the haystack contains expected_count or more needles
+//
+/// See also: `containsAtLeast`
+pub fn containsAtLeastScalar(comptime T: type, haystack: []const T, expected_count: usize, needle: T) bool {
+    if (expected_count == 0) return true;
+
+    var found: usize = 0;
+
+    for (haystack) |item| {
+        if (item == needle) {
+            found += 1;
+            if (found == expected_count) return true;
+        }
+    }
+
+    return false;
+}
+
+test containsAtLeastScalar {
+    try testing.expect(containsAtLeastScalar(u8, "aa", 0, 'a'));
+    try testing.expect(containsAtLeastScalar(u8, "aa", 1, 'a'));
+    try testing.expect(containsAtLeastScalar(u8, "aa", 2, 'a'));
+    try testing.expect(!containsAtLeastScalar(u8, "aa", 3, 'a'));
+
+    try testing.expect(containsAtLeastScalar(u8, "adadda", 3, 'd'));
+    try testing.expect(!containsAtLeastScalar(u8, "adadda", 4, 'd'));
+}
+
 /// Reads an integer from memory with size equal to bytes.len.
 /// T specifies the return type, which must be large enough to store
 /// the result.