Correct int truncating/saturating + avoid one toPosixPath()

src/main.zig

@@ -132,6 +132,8 @@ fn writeTree(out: anytype, e: *model.Entry, indent: u32) @TypeOf(out).Error!void
     } else if (e.link()) |l| {
         try out.print("  ino={x}  nlinks={d}", .{ l.ino, l.nlink });
     }
+    if (e.ext()) |ext|
+        try out.print("  mtime={d}  uid={d}  gid={d}  mode={o}", .{ ext.mtime, ext.uid, ext.gid, ext.mode });
 
     try out.writeByte('\n');
     if (e.dir()) |d| {
@@ -185,7 +187,7 @@ pub fn main() anyerror!void {
     std.log.info("align={}, Entry={}, Dir={}, Link={}, File={}.",
         .{@alignOf(model.Dir), @sizeOf(model.Entry), @sizeOf(model.Dir), @sizeOf(model.Link), @sizeOf(model.File)});
     try scan.scanRoot(scan_dir orelse ".");
-    
+
     //var out = std.io.bufferedWriter(std.io.getStdOut().writer());
     //try writeTree(out.writer(), &model.root.entry, 0);
     //try out.flush();

src/model.zig

@@ -9,6 +9,16 @@ const main = @import("main.zig");
 // memory overhead turns out to be insignificant.)
 var allocator = std.heap.ArenaAllocator.init(std.heap.page_allocator);
 
+fn saturateAdd(a: anytype, b: @TypeOf(a)) @TypeOf(a) {
+    std.debug.assert(@typeInfo(@TypeOf(a)).Int.signedness == .unsigned);
+    return std.math.add(@TypeOf(a), a, b) catch std.math.maxInt(@TypeOf(a));
+}
+
+fn saturateSub(a: anytype, b: @TypeOf(a)) @TypeOf(a) {
+    std.debug.assert(@typeInfo(@TypeOf(a)).Int.signedness == .unsigned);
+    return std.math.sub(@TypeOf(a), a, b) catch std.math.minInt(@TypeOf(a));
+}
+
 pub const EType = packed enum(u2) { dir, link, file };
 
 // Memory layout:
@@ -122,22 +132,22 @@ pub const Entry = packed struct {
                 // First time we encounter this file in this dir, count it.
                 if (d.entry.key.num_files == 1) {
                     add_total = true;
-                    p.shared_size += self.size;
-                    p.shared_blocks += self.blocks;
-                    p.shared_items += 1;
+                    p.shared_size = saturateAdd(p.shared_size, self.size);
+                    p.shared_blocks = saturateAdd(p.shared_blocks, self.blocks);
+                    p.shared_items = saturateAdd(p.shared_items, 1);
                 // Encountered this file in this dir the same number of times as its link count, meaning it's not shared with other dirs.
                 } else if(d.entry.key.num_files == l.nlink) {
-                    p.shared_size -= self.size;
-                    p.shared_blocks -= self.blocks;
-                    p.shared_items -= 1;
+                    p.shared_size = saturateSub(p.shared_size, self.size);
+                    p.shared_blocks = saturateSub(p.shared_blocks, self.blocks);
+                    p.shared_items = saturateSub(p.shared_items, 1);
                 }
             } else {
                 add_total = true;
             }
             if(add_total) {
-                p.total_size += self.size;
-                p.total_blocks += self.blocks;
-                p.total_items += 1;
+                p.total_size = saturateAdd(p.total_size, self.size);
+                p.total_blocks = saturateAdd(p.total_blocks, self.blocks);
+                p.total_items = saturateAdd(p.total_items, 1);
             }
         }
     }
@@ -200,8 +210,8 @@ pub const File = packed struct {
 
 pub const Ext = packed struct {
     mtime: u64,
-    uid: i32,
-    gid: i32,
+    uid: u32,
+    gid: u32,
     mode: u16,
 };
 

src/scan.zig

@@ -16,8 +16,7 @@ const Stat = struct {
     ext: model.Ext,
 };
 
-// Cast any integer type to the target type, clamping the
-// value to the supported maximum if necessary.
+// Cast any integer type to the target type, clamping the value to the supported maximum if necessary.
 fn castClamp(comptime T: type, x: anytype) T {
     // (adapted from std.math.cast)
     if (std.math.maxInt(@TypeOf(x)) > std.math.maxInt(T) and x > std.math.maxInt(T)) {
@@ -29,17 +28,20 @@ fn castClamp(comptime T: type, x: anytype) T {
     }
 }
 
-// Cast any integer type to the unsigned target type, wrapping/truncating as necessary.
-fn castWrap(comptime T: type, x: anytype) T {
-    return @intCast(T, x); // TODO
+// Cast any integer type to the target type, truncating if necessary.
+fn castTruncate(comptime T: type, x: anytype) T {
+    const Ti = @typeInfo(T).Int;
+    const Xi = @typeInfo(@TypeOf(x)).Int;
+    const nx = if (Xi.signedness != Ti.signedness) @bitCast(std.meta.Int(Ti.signedness, Xi.bits), x) else x;
+    return if (Xi.bits > Ti.bits) @truncate(T, nx) else nx;
 }
 
 fn clamp(comptime T: type, comptime field: anytype, x: anytype) std.meta.fieldInfo(T, field).field_type {
     return castClamp(std.meta.fieldInfo(T, field).field_type, x);
 }
 
-fn wrap(comptime T: type, comptime field: anytype, x: anytype) std.meta.fieldInfo(T, field).field_type {
-    return castWrap(std.meta.fieldInfo(T, field).field_type, x);
+fn truncate(comptime T: type, comptime field: anytype, x: anytype) std.meta.fieldInfo(T, field).field_type {
+    return castTruncate(std.meta.fieldInfo(T, field).field_type, x);
 }
 
 fn readStat(parent: std.fs.Dir, name: [:0]const u8, follow: bool) !Stat {
@@ -47,17 +49,17 @@ fn readStat(parent: std.fs.Dir, name: [:0]const u8, follow: bool) !Stat {
     return Stat{
         .blocks = clamp(Stat, .blocks, stat.blocks),
         .size = clamp(Stat, .size, stat.size),
-        .dev = wrap(Stat, .dev, stat.dev),
-        .ino = wrap(Stat, .ino, stat.ino),
+        .dev = truncate(Stat, .dev, stat.dev),
+        .ino = truncate(Stat, .ino, stat.ino),
         .nlink = clamp(Stat, .nlink, stat.nlink),
         .dir = std.os.system.S_ISDIR(stat.mode),
         .reg = std.os.system.S_ISREG(stat.mode),
         .symlink = std.os.system.S_ISLNK(stat.mode),
         .ext = .{
             .mtime = clamp(model.Ext, .mtime, stat.mtime().tv_sec),
-            .uid = wrap(model.Ext, .uid, stat.uid),
-            .gid = wrap(model.Ext, .gid, stat.gid),
-            .mode = clamp(model.Ext, .mode, stat.mode & 0xffff),
+            .uid = truncate(model.Ext, .uid, stat.uid),
+            .gid = truncate(model.Ext, .gid, stat.gid),
+            .mode = truncate(model.Ext, .mode, stat.mode),
         },
     };
 }
@@ -157,19 +159,17 @@ fn scanDir(parents: *model.Parents, dir: std.fs.Dir) std.mem.Allocator.Error!voi
 }
 
 pub fn scanRoot(path: []const u8) !void {
-    // XXX: Both realpathAlloc() and toPosixPath are limited to PATH_MAX.
-    // Oh well, I suppose we can accept that as limitation for the top-level dir we're scanning.
-    const full_path = try std.os.toPosixPath(try std.fs.realpathAlloc(main.allocator, path));
+    const full_path = std.fs.realpathAlloc(main.allocator, path) catch path;
+    model.root = (try model.Entry.create(.dir, false, full_path)).dir().?;
 
-    const stat = try readStat(std.fs.cwd(), &full_path, true);
+    const stat = try readStat(std.fs.cwd(), model.root.entry.name(), true);
     if (!stat.dir) return error.NotADirectory;
-    model.root = (try model.Entry.create(.dir, false, &full_path)).dir().?;
     model.root.entry.blocks = stat.blocks;
     model.root.entry.size = stat.size;
     model.root.dev = try model.getDevId(stat.dev);
     if (model.root.entry.ext()) |ext| ext.* = stat.ext;
 
     var parents = model.Parents{};
-    const dir = try std.fs.cwd().openDirZ(&full_path, .{ .access_sub_paths = true, .iterate = true });
+    const dir = try std.fs.cwd().openDirZ(model.root.entry.name(), .{ .access_sub_paths = true, .iterate = true });
     try scanDir(&parents, dir);
 }