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