Generalize join.

std/mem.zig

@@ -1,4 +1,5 @@
-const assert = @import("debug.zig").assert;
+const debug = @import("debug.zig");
+const assert = debug.assert;
 const math = @import("math.zig");
 const os = @import("os/index.zig");
 const io = @import("io.zig");
@@ -285,6 +286,44 @@ const SplitIterator = struct {
     }
 };
 
+/// Naively combines a series of strings with a separator.
+/// Allocates memory for the result, which must be freed by the caller.
+pub fn join(allocator: &Allocator, sep: u8, strings: ...) -> %[]u8 {
+    comptime assert(strings.len >= 1);
+    var total_strings_len: usize = strings.len; // 1 slash per string
+    {
+        comptime var string_i = 0;
+        inline while (string_i < strings.len) : (string_i += 1) {
+            const arg = ([]const u8)(strings[string_i]);
+            total_strings_len += arg.len;
+        }
+    }
+
+    const buf = %return allocator.alloc(u8, total_strings_len);
+    %defer allocator.free(buf);
+
+    var buf_index: usize = 0;
+    comptime var string_i = 0;
+    inline while (true) {
+        const arg = ([]const u8)(strings[string_i]);
+        string_i += 1;
+        copy(u8, buf[buf_index..], arg);
+        buf_index += arg.len;
+        if (string_i >= strings.len) break;
+        if (buf[buf_index - 1] != sep) {
+            buf[buf_index] = sep;
+            buf_index += 1;
+        }
+    }
+
+    return buf[0..buf_index];
+}
+
+test "mem.join" {
+    assert(eql(u8, %%join(&debug.global_allocator, ',', "a", "b", "c"), "a,b,c"));
+    assert(eql(u8, %%join(&debug.global_allocator, ',', "a"), "a"));
+}
+
 test "testStringEquality" {
     assert(eql(u8, "abcd", "abcd"));
     assert(!eql(u8, "abcdef", "abZdef"));

std/os/path.zig

@@ -21,34 +21,7 @@ pub const delimiter = switch (builtin.os) {
 /// Naively combines a series of paths with the native path seperator.
 /// Allocates memory for the result, which must be freed by the caller.
 pub fn join(allocator: &Allocator, paths: ...) -> %[]u8 {
-    comptime assert(paths.len >= 2);
+    mem.join(allocator, sep, paths)
-    var total_paths_len: usize = paths.len; // 1 slash per path
-    {
-        comptime var path_i = 0;
-        inline while (path_i < paths.len) : (path_i += 1) {
-            const arg = ([]const u8)(paths[path_i]);
-            total_paths_len += arg.len;
-        }
-    }
-
-    const buf = %return allocator.alloc(u8, total_paths_len);
-    %defer allocator.free(buf);
-
-    var buf_index: usize = 0;
-    comptime var path_i = 0;
-    inline while (true) {
-        const arg = ([]const u8)(paths[path_i]);
-        path_i += 1;
-        mem.copy(u8, buf[buf_index..], arg);
-        buf_index += arg.len;
-        if (path_i >= paths.len) break;
-        if (buf[buf_index - 1] != sep) {
-            buf[buf_index] = sep;
-            buf_index += 1;
-        }
-    }
-
-    return buf[0..buf_index];
 }
 
 test "os.path.join" {