mutable/immutable PackedUser
Motiejus Jakštys
parent
f4c4dc535c
commit
b4c7cba627
454
src/user.zig
454
src/user.zig
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@ -20,243 +20,253 @@ pub const User = struct {
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shell: []const u8,
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};
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pub const PackedUser = struct {
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const AlignmentBits = 3;
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const shellIndexFn = fn ([]const u8) ?u6;
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pub const PackedUserMut = packedUser(false);
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pub const PackedUserConst = packedUser(true);
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const InnerSize = @divExact(@bitSizeOf(Inner), 8);
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const Inner = packed struct {
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uid: u32,
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gid: u32,
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additional_gids_offset: u29,
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shell_here: bool,
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shell_len_or_idx: u6,
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home_len: u6,
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name_is_a_suffix: bool,
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name_len: u5,
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gecos_len: u8,
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fn packedUser(immutable: bool) type {
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return struct {
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const Self = @This();
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fn homeLen(self: *const Inner) usize {
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return @as(u32, self.home_len) + 1;
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}
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const AlignmentBits = 3;
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const shellIndexFn = fn ([]const u8) ?u6;
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fn nameStart(self: *const Inner) usize {
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const name_len = self.nameLen();
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if (self.name_is_a_suffix) {
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return self.homeLen() - name_len;
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} else {
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return self.homeLen();
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const InnerSize = @divExact(@bitSizeOf(Inner), 8);
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const Inner = packed struct {
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uid: u32,
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gid: u32,
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additional_gids_offset: u29,
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shell_here: bool,
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shell_len_or_idx: u6,
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home_len: u6,
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name_is_a_suffix: bool,
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name_len: u5,
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gecos_len: u8,
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fn homeLen(self: *const Inner) usize {
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return @as(u32, self.home_len) + 1;
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}
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}
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fn nameLen(self: *const Inner) usize {
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return @as(u32, self.name_len) + 1;
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}
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fn gecosStart(self: *const Inner) usize {
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if (self.name_is_a_suffix) {
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return self.homeLen();
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} else {
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return self.homeLen() + self.nameLen();
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fn nameStart(self: *const Inner) usize {
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const name_len = self.nameLen();
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if (self.name_is_a_suffix) {
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return self.homeLen() - name_len;
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} else {
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return self.homeLen();
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}
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}
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}
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fn gecosLen(self: *const Inner) usize {
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return self.gecos_len;
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}
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fn maybeShellStart(self: *const Inner) usize {
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assert(self.shell_here);
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return self.gecosStart() + self.gecosLen();
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}
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fn shellLen(self: *const Inner) usize {
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return @as(u32, self.shell_len_or_idx) + 1;
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}
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// blobLength returns the length of the blob storing string values.
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fn blobLength(self: *const Inner) usize {
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var result: usize = self.homeLen() + self.gecosLen();
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if (!self.name_is_a_suffix) {
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result += self.nameLen();
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fn nameLen(self: *const Inner) usize {
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return @as(u32, self.name_len) + 1;
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}
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if (self.shell_here) {
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result += self.shellLen();
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fn gecosStart(self: *const Inner) usize {
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if (self.name_is_a_suffix) {
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return self.homeLen();
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} else {
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return self.homeLen() + self.nameLen();
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}
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}
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return result;
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}
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};
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// PackedUser does not allocate; it re-interprets the "bytes" blob field.
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// Both of those fields are pointers to "our representation" of that field.
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inner: *const Inner,
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userdata: []const u8,
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fn gecosLen(self: *const Inner) usize {
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return self.gecos_len;
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}
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pub const Entry = struct {
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user: PackedUser,
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next: ?[]const u8,
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};
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fn maybeShellStart(self: *const Inner) usize {
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assert(self.shell_here);
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return self.gecosStart() + self.gecosLen();
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}
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pub fn fromBytes(bytes: []const u8) Entry {
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const inner = std.mem.bytesAsValue(
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Inner,
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// Should use InnerSize instead of sizeOf, see
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// https://github.com/ziglang/zig/issues/10958
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bytes[0..@sizeOf(Inner)],
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);
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fn shellLen(self: *const Inner) usize {
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return @as(u32, self.shell_len_or_idx) + 1;
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}
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const startBlob = InnerSize;
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const endBlob = startBlob + inner.blobLength();
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const nextStart = pad.roundUp(usize, AlignmentBits, endBlob);
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var next: ?[]const u8 = null;
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if (nextStart < bytes.len) {
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next = bytes[nextStart..];
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}
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return Entry{
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.user = PackedUser{
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.inner = inner,
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.userdata = bytes[startBlob..endBlob],
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},
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.next = next,
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// blobLength returns the length of the blob storing string values.
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fn blobLength(self: *const Inner) usize {
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var result: usize = self.homeLen() + self.gecosLen();
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if (!self.name_is_a_suffix) {
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result += self.nameLen();
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}
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if (self.shell_here) {
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result += self.shellLen();
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}
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return result;
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}
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};
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}
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pub const errInvalid = error{InvalidRecord};
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fn downCast(comptime T: type, n: u64) errInvalid!T {
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return std.math.cast(T, n) catch |err| switch (err) {
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error.Overflow => {
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const Bytes = if (immutable) []const u8 else []u8;
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const InnerPointer = if (immutable) *const Inner else *Inner;
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// PackedUser does not allocate; it re-interprets the "bytes" blob field.
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// Both of those fields are pointers to "our representation" of that field.
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inner: InnerPointer,
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userdata: Bytes,
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pub const Entry = struct {
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user: Self,
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next: ?Bytes,
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};
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pub fn fromBytes(bytes: Bytes) Entry {
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const inner = std.mem.bytesAsValue(
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Inner,
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// Should use InnerSize instead of sizeOf, see
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// https://github.com/ziglang/zig/issues/10958
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bytes[0..@sizeOf(Inner)],
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);
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const startBlob = InnerSize;
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const endBlob = startBlob + inner.blobLength();
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const nextStart = pad.roundUp(usize, AlignmentBits, endBlob);
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var next: ?Bytes = null;
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if (nextStart < bytes.len) {
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next = bytes[nextStart..];
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}
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return Entry{
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.user = Self{
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.inner = inner,
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.userdata = bytes[startBlob..endBlob],
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},
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.next = next,
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};
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}
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pub const errInvalid = error{InvalidRecord};
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fn downCast(comptime T: type, n: u64) errInvalid!T {
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return std.math.cast(T, n) catch |err| switch (err) {
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error.Overflow => {
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return error.InvalidRecord;
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},
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};
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}
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fn validateUtf8(s: []const u8) errInvalid!void {
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if (!std.unicode.utf8ValidateSlice(s)) {
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return error.InvalidRecord;
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},
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}
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}
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// packTo packs the User record and copies it to the given byte slice. The
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// slice must have at least maxRecordSize() bytes available.
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// The slice is passed as a pointer, so it can be mutated.
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const packErr = errInvalid || Allocator.Error;
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pub fn packTo(
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arr: *ArrayList(u8),
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user: User,
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idxFn: shellIndexFn,
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) packErr!void {
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// function arguments are consts. We need to mutate the underlying
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// slice, so passing it via pointer instead.
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const home_len = try downCast(u6, user.home.len - 1);
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const name_len = try downCast(u5, user.name.len - 1);
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const shell_len = try downCast(u6, user.shell.len - 1);
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const gecos_len = try downCast(u8, user.gecos.len);
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try validateUtf8(user.home);
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try validateUtf8(user.name);
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try validateUtf8(user.shell);
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try validateUtf8(user.gecos);
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const inner = Inner{
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.uid = user.uid,
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.gid = user.gid,
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.additional_gids_offset = std.math.maxInt(u29),
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.shell_here = idxFn(user.shell) == null,
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.shell_len_or_idx = idxFn(user.shell) orelse shell_len,
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.home_len = home_len,
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.name_is_a_suffix = mem.endsWith(u8, user.home, user.name),
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.name_len = name_len,
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.gecos_len = gecos_len,
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};
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const innerBytes = mem.asBytes(&inner);
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// innerBytes.len is longer than InnerSize. We want to copy
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// only the InnerSize-number of bytes.
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try arr.*.appendSlice(innerBytes[0..InnerSize]);
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try arr.*.appendSlice(user.home);
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if (!inner.name_is_a_suffix) {
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try arr.*.appendSlice(user.name);
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}
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try arr.*.appendSlice(user.gecos);
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if (inner.shell_here) {
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try arr.*.appendSlice(user.shell);
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}
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try pad.arrayList(arr, AlignmentBits);
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}
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// maxSize is the maximum number of records a PackedUser can take
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// (struct + userdata).
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pub fn maxSize() usize {
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comptime {
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const unpadded = InnerSize +
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std.math.maxInt(u6) + 1 + // home
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std.math.maxInt(u5) + 1 + // name
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std.math.maxInt(u6) + 1 + // shell
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std.math.maxInt(u8); // gecos
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return pad.roundUp(u64, AlignmentBits, unpadded);
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}
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}
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pub fn uid(self: Self) u32 {
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return self.inner.uid;
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}
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pub fn gid(self: Self) u32 {
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return self.inner.gid;
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}
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pub fn home(self: Self) []const u8 {
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return self.userdata[0..self.inner.homeLen()];
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}
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pub fn name(self: Self) []const u8 {
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const name_pos = self.inner.nameStart();
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const name_len = self.inner.nameLen();
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return self.userdata[name_pos .. name_pos + name_len];
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}
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pub fn gecos(self: Self) []const u8 {
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const gecos_pos = self.inner.gecosStart();
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const gecos_len = self.inner.gecosLen();
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return self.userdata[gecos_pos .. gecos_pos + gecos_len];
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}
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pub fn shell(self: Self, idxFn: ShellIndexFn) []const u8 {
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if (self.inner.shell_here) {
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const shell_pos = self.inner.maybeShellStart();
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const shell_len = self.inner.shellLen();
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return self.userdata[shell_pos .. shell_pos + shell_len];
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}
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return idxFn(self.inner.shell_len_or_idx);
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}
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pub const Iterator = struct {
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section: ?Bytes,
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shellIndex: ShellIndexFn,
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pub fn next(it: *Iterator) ?Self {
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if (it.section) |section| {
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const entry = Self.fromBytes(section);
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it.section = entry.next;
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return entry.user;
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}
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return null;
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}
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};
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}
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fn validateUtf8(s: []const u8) errInvalid!void {
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if (!std.unicode.utf8ValidateSlice(s)) {
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return error.InvalidRecord;
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pub fn iterator(section: Bytes, idxFn: ShellIndexFn) Iterator {
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return Iterator{
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.section = section,
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.shellIndex = idxFn,
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};
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}
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}
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// packTo packs the User record and copies it to the given byte slice. The
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// slice must have at least maxRecordSize() bytes available.
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// The slice is passed as a pointer, so it can be mutated.
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const packErr = errInvalid || Allocator.Error;
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pub fn packTo(
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arr: *ArrayList(u8),
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user: User,
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idxFn: shellIndexFn,
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) packErr!void {
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// function arguments are consts. We need to mutate the underlying
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// slice, so passing it via pointer instead.
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const home_len = try downCast(u6, user.home.len - 1);
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const name_len = try downCast(u5, user.name.len - 1);
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const shell_len = try downCast(u6, user.shell.len - 1);
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const gecos_len = try downCast(u8, user.gecos.len);
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try validateUtf8(user.home);
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try validateUtf8(user.name);
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try validateUtf8(user.shell);
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try validateUtf8(user.gecos);
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const inner = Inner{
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.uid = user.uid,
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.gid = user.gid,
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.additional_gids_offset = std.math.maxInt(u29),
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.shell_here = idxFn(user.shell) == null,
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.shell_len_or_idx = idxFn(user.shell) orelse shell_len,
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.home_len = home_len,
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.name_is_a_suffix = mem.endsWith(u8, user.home, user.name),
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.name_len = name_len,
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.gecos_len = gecos_len,
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};
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const innerBytes = mem.asBytes(&inner);
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// innerBytes.len is longer than InnerSize. We want to copy
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// only the InnerSize-number of bytes.
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try arr.*.appendSlice(innerBytes[0..InnerSize]);
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try arr.*.appendSlice(user.home);
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if (!inner.name_is_a_suffix) {
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try arr.*.appendSlice(user.name);
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}
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try arr.*.appendSlice(user.gecos);
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if (inner.shell_here) {
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try arr.*.appendSlice(user.shell);
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}
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try pad.arrayList(arr, AlignmentBits);
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}
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// maxSize is the maximum number of records a PackedUser can take
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// (struct + userdata).
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pub fn maxSize() usize {
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comptime {
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const unpadded = InnerSize +
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std.math.maxInt(u6) + 1 + // home
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std.math.maxInt(u5) + 1 + // name
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std.math.maxInt(u6) + 1 + // shell
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std.math.maxInt(u8); // gecos
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return pad.roundUp(u64, AlignmentBits, unpadded);
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}
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}
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pub fn uid(self: *const PackedUser) u32 {
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return self.inner.uid;
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}
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pub fn gid(self: *const PackedUser) u32 {
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return self.inner.gid;
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}
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pub fn home(self: *const PackedUser) []const u8 {
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return self.userdata[0..self.inner.homeLen()];
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}
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pub fn name(self: *const PackedUser) []const u8 {
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const name_pos = self.inner.nameStart();
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const name_len = self.inner.nameLen();
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return self.userdata[name_pos .. name_pos + name_len];
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}
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pub fn gecos(self: *const PackedUser) []const u8 {
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const gecos_pos = self.inner.gecosStart();
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const gecos_len = self.inner.gecosLen();
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return self.userdata[gecos_pos .. gecos_pos + gecos_len];
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}
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pub fn shell(self: *const PackedUser, idxFn: ShellIndexFn) []const u8 {
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if (self.inner.shell_here) {
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const shell_pos = self.inner.maybeShellStart();
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const shell_len = self.inner.shellLen();
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return self.userdata[shell_pos .. shell_pos + shell_len];
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}
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return idxFn(self.inner.shell_len_or_idx);
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}
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};
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pub fn userIterator(section: []const u8, idxFn: ShellIndexFn) Iterator {
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return Iterator{
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.section = section,
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.shellIndex = idxFn,
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};
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}
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pub const Iterator = struct {
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section: ?[]const u8,
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shellIndex: ShellIndexFn,
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pub fn next(it: *Iterator) ?PackedUser {
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if (it.section) |section| {
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const entry = PackedUser.fromBytes(section);
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it.section = entry.next;
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return entry.user;
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}
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return null;
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}
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};
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const testing = std.testing;
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const ArrayList = std.ArrayList;
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@ -267,7 +277,7 @@ test "PackedUser internal and external alignment" {
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// cannot be converted from/to [@bitSizeOf(PackedUser)/8]u8;
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// asBytes/bytesAsValue use @sizeOf, which is larger. Now we are putting no
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// more than 1, but it probably could be higher.
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try testing.expect(@sizeOf(PackedUser) * 8 - @bitSizeOf(PackedUser) <= 8);
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try testing.expect(@sizeOf(PackedUserMut.Inner) * 8 - @bitSizeOf(PackedUserMut.Inner) <= 8);
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}
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fn testShellIndex(shell: []const u8) ?u6 {
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|
|
@ -321,11 +331,11 @@ test "construct PackedUser section" {
|
|||
.shell = "/",
|
||||
} };
|
||||
for (users) |user| {
|
||||
try buf.ensureUnusedCapacity(PackedUser.maxSize());
|
||||
try PackedUser.packTo(&buf, user, testShellIndex);
|
||||
try buf.ensureUnusedCapacity(PackedUserMut.maxSize());
|
||||
try PackedUserMut.packTo(&buf, user, testShellIndex);
|
||||
}
|
||||
|
||||
var it = userIterator(buf.items, testShell);
|
||||
var it = PackedUserMut.iterator(buf.items, testShell);
|
||||
var i: u32 = 0;
|
||||
while (it.next()) |user| : (i += 1) {
|
||||
try testing.expectEqual(users[i].uid, user.uid());
|
||||
|
|
@ -341,7 +351,7 @@ test "construct PackedUser section" {
|
|||
test "PackedUser.maxSize()" {
|
||||
// TODO(motiejus) try using a slice that points to an array in stack.
|
||||
// As of writing, I am getting a stack smashing error.
|
||||
var buf = try ArrayList(u8).initCapacity(testing.allocator, PackedUser.maxSize());
|
||||
var buf = try ArrayList(u8).initCapacity(testing.allocator, PackedUserConst.maxSize());
|
||||
defer buf.deinit();
|
||||
|
||||
const largeUser = User{
|
||||
|
|
@ -352,6 +362,6 @@ test "PackedUser.maxSize()" {
|
|||
.home = "Home" ** 16, // 64
|
||||
.shell = "She.LllL" ** 8, // 64
|
||||
};
|
||||
try PackedUser.packTo(&buf, largeUser, testShellIndex);
|
||||
try testing.expectEqual(PackedUser.maxSize(), buf.items.len);
|
||||
try PackedUserConst.packTo(&buf, largeUser, testShellIndex);
|
||||
try testing.expectEqual(PackedUserConst.maxSize(), buf.items.len);
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in New Issue