refactoring UserReader

src/user.zig

@@ -35,46 +35,28 @@ pub const PackedUser = struct {
         name_len: u5,
         gecos_len: u8,
 
-        pub fn homeLen(self: *const PackedUser) usize {
+        fn homeLen(self: *const Inner) usize {
             return @as(u32, self.home_len) + 1;
         }
 
-        pub fn nameLen(self: *const PackedUser) usize {
+        fn nameStart(self: *const Inner) usize {
-            return @as(u32, self.name_len) + 1;
-        }
-
-        pub fn gecosLen(self: *const PackedUser) usize {
-            return self.gecos_len;
-        }
-
-        pub fn shellLen(self: *const PackedUser) usize {
-            return @as(u32, self.shell_len_or_idx) + 1;
-        }
-
-        // blobLength returns the length of the blob storing string values.
-        pub fn blobLength(self: *const Inner) usize {
-            var result: usize = self.homeLen();
-            if (!self.name_is_a_suffix) {
-                result += self.nameLen();
-            }
-            result += self.gecosLen();
-            if (self.shell_here) {
-                result += self.shellLen();
-            }
-
-            return result;
-        }
-
-        pub fn namePos(self: *const Inner) usize {
             const name_len = self.nameLen();
             if (self.name_is_a_suffix) {
-                return self.inner.homeLen() - name_len;
+                return self.homeLen() - name_len;
             } else {
                 return self.homeLen();
             }
         }
 
-        pub fn gecosPos(self: *const Inner) usize {
+        fn nameLen(self: *const Inner) usize {
+            return @as(u32, self.name_len) + 1;
+        }
+
+        fn gecosLen(self: *const Inner) usize {
+            return self.gecos_len;
+        }
+
+        fn gecosStart(self: *const Inner) usize {
             if (self.name_is_a_suffix) {
                 return self.homeLen();
             } else {
@@ -82,27 +64,83 @@ pub const PackedUser = struct {
             }
         }
 
-        pub fn maybeShellPos(self: *const Inner) usize {
+        fn maybeShellStart(self: *const Inner) usize {
             assert(self.shell_here);
-            return self.gecosPos() + self.gecosLen();
+            return self.gecosStart() + self.gecosLen();
+        }
+
+        fn shellLen(self: *const Inner) usize {
+            return @as(u32, self.shell_len_or_idx) + 1;
+        }
+
+        // blobLength returns the length of the blob storing string values.
+        fn blobLength(self: *const Inner) usize {
+            var result: usize = self.homeLen() + self.gecosLen();
+            if (!self.name_is_a_suffix) {
+                result += self.nameLen();
+            }
+            if (self.shell_here) {
+                result += self.shellLen();
+            }
+
+            return result;
         }
     };
 
-    inner: Inner,
+    inner: *const Inner,
     userdata: []const u8,
 
-    pub fn fromBytes(bytes: []const u8) PackedUser {
+    pub const Entry = struct {
+        user: PackedUser,
+        next: ?[]const u8,
+    };
+
+    pub fn fromBytes(bytes: []const u8) Entry {
         const inner = std.mem.bytesAsValue(
-            PackedUser,
+            Inner,
             // https://github.com/ziglang/zig/issues/10958
-            bytes[0..@sizeOf(Inner)][0..@sizeOf(Inner)],
+            bytes[0..@sizeOf(Inner)],
         );
 
         const startBlob = InnerSize;
         const endBlob = startBlob + inner.blobLength();
-        return PackedUser{
+
+        const nextStart = pad.roundUp(usize, PackedUserAlignmentBits, endBlob);
+        var next: ?[]const u8 = null;
+        if (nextStart < bytes.len) {
+            next = bytes[nextStart..];
+        }
+
+        std.debug.print("\n", .{});
+        std.debug.print("startBlob:              {d}\n", .{startBlob});
+        std.debug.print("endBlob:                {d}\n", .{endBlob});
+        std.debug.print("nextStart:              {d}\n", .{nextStart});
+        std.debug.print("len(userdata):          {d}\n", .{bytes[startBlob..endBlob].len});
+        std.debug.print("uid:                    {d}\n", .{inner.uid});
+        std.debug.print("gid:                    {d}\n", .{inner.gid});
+        std.debug.print("additional_gids_offset: {d}\n", .{inner.additional_gids_offset});
+        std.debug.print("shell_here:             {d}\n", .{inner.shell_here});
+        std.debug.print("shell_len_or_idx:       {d}\n", .{inner.shell_len_or_idx});
+        std.debug.print("home_len:               {d}\n", .{inner.home_len});
+        std.debug.print("name_is_a_suffix:       {d}\n", .{inner.name_is_a_suffix});
+        std.debug.print("name_len:               {d}\n", .{inner.name_len});
+        std.debug.print("gecos_len:              {d}\n", .{inner.gecos_len});
+        std.debug.print("userdata:               {s}\n", .{bytes[startBlob..endBlob]});
+        std.debug.print("userdata[0]:            {c}\n", .{bytes[startBlob]});
+        std.debug.print("userdata[1]:            {c}\n", .{bytes[startBlob + 1]});
+        std.debug.print("userdata[2]:            {c}\n", .{bytes[startBlob + 2]});
+        std.debug.print("userdata[3]:            {c}\n", .{bytes[startBlob + 3]});
+        std.debug.print("userdata[4]:            {c}\n", .{bytes[startBlob + 4]});
+        std.debug.print("userdata[5]:            {c}\n", .{bytes[startBlob + 5]});
+        std.debug.print("userdata[6]:            {c}\n", .{bytes[startBlob + 6]});
+        std.debug.print("userdata[7]:            {c}\n", .{bytes[startBlob + 7]});
+
+        return Entry{
+            .user = PackedUser{
                 .inner = inner,
                 .userdata = bytes[startBlob..endBlob],
+            },
+            .next = next,
         };
     }
 
@@ -122,12 +160,10 @@ pub const PackedUser = struct {
 
     // packTo packs the User record and copies it to the given byte slice. The
     // slice must have at least maxRecordSize() bytes available.
-    pub fn packTo(bufPtr: *[]u8, user: User, shellIndexFn: shellIndexFnType) error{InvalidRecord}!void {
+    // The slice is passed as a pointer, so it can be mutated.
+    pub fn packTo(buf: *[]u8, user: User, shellIndexFn: shellIndexFnType) error{InvalidRecord}!void {
         // function arguments are consts. We need to mutate the underlying
         // slice, so passing it via pointer instead.
-        var buf = bufPtr.*;
-        const bufStart = @ptrToInt(buf.ptr);
-
         const home_len = try downCast(u6, user.home.len - 1);
         const name_len = try downCast(u5, user.name.len - 1);
         const shell_len = try downCast(u6, user.shell.len - 1);
@@ -150,37 +186,41 @@ pub const PackedUser = struct {
             .gecos_len = gecos_len,
         };
         const innerBytes = mem.asBytes(&inner);
-        buf.len += innerBytes.len +
+        var pos: usize = buf.*.len;
+        buf.*.len += InnerSize +
             user.home.len +
             user.gecos.len;
 
-        mem.copy(u8, buf[0..innerBytes.len], innerBytes);
+        // innerBytes.len is longer than InnerSize. We want to copy
-        buf = buf[innerBytes.len..];
+        // only the InnerSize-number of bytes.
-        mem.copy(u8, buf[0..user.home.len], user.home);
+        mem.copy(u8, buf.*[pos .. pos + InnerSize], innerBytes[0..InnerSize]);
-        buf = buf[user.home.len..];
+        pos += InnerSize;
+        mem.copy(u8, buf.*[pos .. pos + user.home.len], user.home);
+        pos += user.home.len;
 
         if (!inner.name_is_a_suffix) {
-            buf.len += user.name.len;
+            buf.*.len += user.name.len;
-            mem.copy(u8, buf[0..user.name.len], user.name);
+            mem.copy(u8, buf.*[pos .. pos + user.name.len], user.name);
-            buf = buf[user.name.len..];
+            pos += user.name.len;
         }
-        mem.copy(u8, buf, user.gecos);
+        mem.copy(u8, buf.*[pos .. pos + user.gecos.len], user.gecos);
-        buf = buf[user.gecos.len..];
+        pos += user.gecos.len;
+
         if (inner.shell_here) {
-            buf.len += user.shell.len;
+            buf.*.len += user.shell.len;
-            mem.copy(u8, buf[0..user.shell.len], user.shell);
+            mem.copy(u8, buf.*[pos .. pos + user.shell.len], user.shell);
-            buf = buf[user.shell.len..];
+            pos += user.shell.len;
         }
 
-        const bufLen = @ptrToInt(buf.ptr) - bufStart;
+        const padding = pad.roundUpPadding(u64, PackedUserAlignmentBits, pos);
-        const padding = pad.roundUpPadding(u64, PackedUserAlignmentBits, bufLen);
+        buf.*.len += padding;
-        buf.len += padding;
+        mem.set(u8, buf.*[pos .. pos + padding], 0);
-        mem.set(u8, buf[0..padding], 0);
     }
 
     // maxSize is the maximum number of records a PackedUser can take
     // (struct + userdata).
     pub fn maxSize() usize {
+        comptime {
             const unpadded = InnerSize +
                 std.math.maxInt(u6) + // home
                 std.math.maxInt(u5) + // name
@@ -188,26 +228,35 @@ pub const PackedUser = struct {
                 std.math.maxInt(u8); // gecos
             return pad.roundUp(u64, PackedUserAlignmentBits, unpadded);
         }
+    }
+
+    pub fn uid(self: *const PackedUser) u32 {
+        return self.inner.uid;
+    }
+
+    pub fn gid(self: *const PackedUser) u32 {
+        return self.inner.gid;
+    }
 
     pub fn home(self: *const PackedUser) []const u8 {
         return self.userdata[0..self.inner.homeLen()];
     }
 
     pub fn name(self: *const PackedUser) []const u8 {
-        const name_pos = self.inner.namePos();
+        const name_pos = self.inner.nameStart();
         const name_len = self.inner.nameLen();
         return self.userdata[name_pos .. name_pos + name_len];
     }
 
     pub fn gecos(self: *const PackedUser) []const u8 {
-        const gecos_pos = self.inner.gecosPos();
+        const gecos_pos = self.inner.gecosStart();
         const gecos_len = self.inner.gecosLen();
         return self.userdata[gecos_pos .. gecos_pos + gecos_len];
     }
 
     pub fn shell(self: *const PackedUser, shellIndex: shellIndexProto) []const u8 {
         if (self.inner.shell_here) {
-            const shell_pos = self.inner.maybeShellPos();
+            const shell_pos = self.inner.maybeShellStart();
             const shell_len = self.inner.shellLen();
             return self.userdata[shell_pos .. shell_pos + shell_len];
         }
@@ -215,96 +264,25 @@ pub const PackedUser = struct {
     }
 };
 
-pub const UserReader = struct {
+pub fn userIterator(section: []const u8, shellIndex: shellIndexProto) Iterator {
-    section: []const u8,
+    return Iterator{
-    shellIndex: shellIndexProto,
-
-    pub const PackedEntry = struct {
-        packed_user: *PackedUser,
-        section: []const u8,
-    };
-
-    pub fn init(section: []u8, shellIndex: shellIndexProto) UserReader {
-        return UserReader{
         .section = section,
         .shellIndex = shellIndex,
     };
-    }
+}
 
-    pub const Entry = struct {
+pub const Iterator = struct {
-        user: User,
+    section: ?[]const u8,
-        nextOffset: usize,
+    shellIndex: shellIndexProto,
-    };
 
-    // atOffset returns a ?User in a given offset of the User section. Also,
+    pub fn next(it: *Iterator) ?PackedUser {
-    // the offset to the next user.
+        if (it.section) |section| {
-    pub fn atOffset(self: *UserReader, index: usize) ?Entry {
+            const entry = PackedUser.fromBytes(section);
-        if (index == self.section.len) return null;
+            it.section = entry.next;
-        assert(index < self.section.len);
+            return entry.user;
-        const endUser = index + @sizeOf(PackedUser);
-        var u = std.mem.bytesAsValue(
-            PackedUser,
-            self.section[index..endUser][0..@sizeOf(PackedUser)],
-        );
-        const startBlob = endUser;
-        const endBlob = startBlob + u.blobLength();
-        const section = self.section[startBlob..endBlob];
-
-        const home = section[0..u.homeLen()];
-        var name: []const u8 = undefined;
-        var pos: usize = undefined;
-
-        if (u.name_is_a_suffix) {
-            const name_start = u.homeLen() - u.nameLen();
-            name = section[name_start..u.homeLen()];
-            pos = u.homeLen();
-        } else {
-            const name_start = u.homeLen();
-            name = section[name_start .. name_start + u.nameLen()];
-            pos = name_start + u.nameLen();
-        }
-        const gecos = section[pos .. pos + u.gecosLen()];
-        pos += u.gecosLen();
-
-        var shell: []const u8 = undefined;
-        if (u.shell_here) {
-            shell = section[pos .. pos + u.shellLen()];
-        } else {
-            shell = self.shellIndex(u.shell_len_or_idx);
-        }
-
-        return Entry{
-            .user = User{
-                .uid = u.uid,
-                .gid = u.gid,
-                .name = name,
-                .gecos = gecos,
-                .home = home,
-                .shell = shell,
-            },
-            .nextOffset = pad.roundUp(usize, PackedUserAlignmentBits, endBlob),
-        };
-    }
-
-    pub const Iterator = struct {
-        ur: *UserReader,
-        offset: usize = 0,
-
-        pub fn next(it: *Iterator) ?User {
-            if (it.ur.atOffset(it.offset)) |result| {
-                it.offset = result.nextOffset;
-                return result.user;
         }
         return null;
     }
-    };
-
-    pub fn iterator(self: *UserReader) Iterator {
-        return Iterator{
-            .ur = self,
-            .offset = 0,
-        };
-    }
 };
 
 const testing = std.testing;
@@ -340,6 +318,7 @@ test "construct PackedUser section" {
     var buf = ArrayList(u8).init(testing.allocator);
     defer buf.deinit();
 
+    std.debug.print("\n", .{});
     const users = [_]User{ User{
         .uid = 1000,
         .gid = 1000,
@@ -356,27 +335,33 @@ test "construct PackedUser section" {
         .shell = "/usr/bin/nologin",
     }, User{
         .uid = 0,
-        .gid = 4294967295,
+        .gid = math.maxInt(u32),
-        .name = "n" ** 32,
+        .name = "Name" ** 8,
-        .gecos = "g" ** 255,
+        .gecos = "Gecos" ** 51,
-        .home = "h" ** 64,
+        .home = "Home" ** 16,
-        .shell = "s" ** 64,
+        .shell = "She.l..l" ** 8,
+    }, User{
+        .uid = 1002,
+        .gid = 1002,
+        .name = "svc-bar",
+        .gecos = "",
+        .home = "/",
+        .shell = "/",
     } };
     for (users) |user| {
         try buf.ensureUnusedCapacity(PackedUser.maxSize());
         try PackedUser.packTo(&buf.items, user, testShellIndex);
     }
 
-    //var rd = UserReader.init(buf.items, testShell);
+    var it = userIterator(buf.items, testShell);
-
+    var i: u32 = 0;
-    //var it = rd.iterator();
+    while (it.next()) |user| : (i += 1) {
-    //var i: u32 = 0;
+        try testing.expectEqual(users[i].uid, user.uid());
-    //while (it.next()) |user| : (i += 1) {
+        try testing.expectEqual(users[i].gid, user.gid());
-    //    try testing.expectEqual(users[i].uid, user.uid);
+        try testing.expectEqualStrings(users[i].name, user.name());
-    //    try testing.expectEqual(users[i].gid, user.gid);
+        try testing.expectEqualStrings(users[i].gecos, user.gecos());
-    //    try testing.expectEqualStrings(users[i].name, user.name);
+        try testing.expectEqualStrings(users[i].home, user.home());
-    //    try testing.expectEqualStrings(users[i].gecos, user.gecos);
+        try testing.expectEqualStrings(users[i].shell, user.shell(testShell));
-    //    try testing.expectEqualStrings(users[i].home, user.home);
+    }
-    //    try testing.expectEqualStrings(users[i].shell, user.shell);
+    try testing.expectEqual(users.len, i);
-    //}
 }