From 2fc925923ff4184b417dc7c218b62723671411ce Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Motiejus=20Jak=C5=A1tys?= <motiejus@jakstys.lt>
Date: Sat, 19 Feb 2022 18:18:14 +0200
Subject: [PATCH] wip between-user padding

---
 src/padding.zig   | 29 +++++++++++++++++++++++++++++
 src/shell.zig     | 31 +++----------------------------
 src/test_main.zig |  1 +
 src/user.zig      |  4 ++++
 4 files changed, 37 insertions(+), 28 deletions(-)
 create mode 100644 src/padding.zig

diff --git a/src/padding.zig b/src/padding.zig
new file mode 100644
index 0000000..cfd9a13
--- /dev/null
+++ b/src/padding.zig
@@ -0,0 +1,29 @@
+const std = @import("std");
+
+// rounds up a u12 to the nearest factor of 4 and returns the difference
+// (padding)
+pub fn roundUp4Padding(comptime T: type, n: T) T {
+    return roundUp4(T, n) - n;
+}
+
+// rounds up a u12 to the nearest factor of 4.
+pub fn roundUp4(comptime T: type, n: T) T {
+    return ((n + 3) & ~@as(T, 3));
+}
+
+const testing = std.testing;
+
+test "padding" {
+    try testing.expectEqual(roundUp4Padding(u12, 0), 0);
+    try testing.expectEqual(roundUp4Padding(u12, 1), 3);
+    try testing.expectEqual(roundUp4Padding(u12, 2), 2);
+    try testing.expectEqual(roundUp4Padding(u12, 3), 1);
+    try testing.expectEqual(roundUp4Padding(u12, 4), 0);
+    try testing.expectEqual(roundUp4Padding(u12, 40), 0);
+    try testing.expectEqual(roundUp4Padding(u12, 41), 3);
+    try testing.expectEqual(roundUp4Padding(u12, 42), 2);
+    try testing.expectEqual(roundUp4Padding(u12, 43), 1);
+    try testing.expectEqual(roundUp4Padding(u12, 44), 0);
+    try testing.expectEqual(roundUp4Padding(u12, 4091), 1);
+    try testing.expectEqual(roundUp4Padding(u12, 4092), 0);
+}
diff --git a/src/shell.zig b/src/shell.zig
index 40d8a0c..9dcacfb 100644
--- a/src/shell.zig
+++ b/src/shell.zig
@@ -1,4 +1,5 @@
 const std = @import("std");
+const pad = @import("padding.zig");
 const Allocator = std.mem.Allocator;
 const PriorityDequeue = std.PriorityDequeue;
 const StringArrayHashMap = std.StringArrayHashMap;
@@ -70,7 +71,7 @@ pub const ShellWriter = struct {
                 });
 
                 fullOffset += len;
-                const padding = roundUp4Padding(fullOffset);
+                const padding = pad.roundUp4Padding(u12, fullOffset);
                 fullOffset += padding;
                 //const stderr = std.io.getStdErr().writer();
                 //stderr.print("\n", .{}) catch unreachable;
@@ -167,17 +168,6 @@ pub const ShellWriter = struct {
     }
 };
 
-// rounds up a u12 to the nearest factor of 4 and returns the difference
-// (padding)
-inline fn roundUp4Padding(n: u12) u12 {
-    return roundUp4(n) - n;
-}
-
-// rounds up a u12 to the nearest factor of 4.
-inline fn roundUp4(n: u12) u12 {
-    return ((n + 3) & ~@intCast(u12, 3));
-}
-
 // ShellIndex is an index to the shell strings. As shell can be up to 64 bytes
 // (1<<6), maximum number of shells is 63 (1<<6-1), the maximum location offset
 // is 1<<12. To make location resolvable in 10 bits, all shells will be padded
@@ -219,7 +209,7 @@ test "basic shellpopcon" {
     try testing.expectEqual(sections.getIndex(nobody), null);
     try testing.expectEqual(
         sections.sectionBlob().len,
-        roundUp4(bash.len) + roundUp4(zsh.len) + roundUp4(long.len),
+        pad.roundUp4(u12, bash.len) + pad.roundUp4(u12, zsh.len) + pad.roundUp4(u12, long.len),
     );
 
     const shellReader = ShellReader.init(
@@ -232,18 +222,3 @@ test "basic shellpopcon" {
 
     try testing.expectEqual(shellReader.sectionIndex.len, 3);
 }
-
-test "padding" {
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 0)), 0);
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 1)), 3);
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 2)), 2);
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 3)), 1);
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 4)), 0);
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 40)), 0);
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 41)), 3);
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 42)), 2);
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 43)), 1);
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 44)), 0);
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 4091)), 1);
-    try testing.expectEqual(roundUp4Padding(@intCast(u12, 4092)), 0);
-}
diff --git a/src/test_main.zig b/src/test_main.zig
index 0eb0a4c..6dc2f8f 100644
--- a/src/test_main.zig
+++ b/src/test_main.zig
@@ -3,4 +3,5 @@ test "turbonss test suite" {
     _ = @import("shell.zig");
     _ = @import("header.zig");
     _ = @import("user.zig");
+    _ = @import("padding.zig");
 }
diff --git a/src/user.zig b/src/user.zig
index 44b24fc..fd46454 100644
--- a/src/user.zig
+++ b/src/user.zig
@@ -1,4 +1,5 @@
 const std = @import("std");
+const pad = @import("padding.zig");
 
 const Allocator = std.mem.Allocator;
 const ArrayList = std.ArrayList;
@@ -72,6 +73,9 @@ pub const UserWriter = struct {
         if (puser.shell_here) {
             try self.appendTo.appendSlice(user.shell);
         }
+
+        const padding = pad.roundUp4Padding(u64, self.appendTo.items.len);
+        try self.appendTo.appendNTimes(0, padding);
     }
 };