wip refactoring PackedUser
Motiejus Jakštys
parent
b924e3a935
commit
0f43f8b2d0
290
src/user.zig
290
src/user.zig
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@ -4,50 +4,11 @@ const pad = @import("padding.zig");
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const assert = std.debug.assert;
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const Allocator = std.mem.Allocator;
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const ArrayList = std.ArrayList;
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const cast = std.math.cast;
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const math = std.math;
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const mem = std.mem;
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const PackedUserSize = @divExact(@bitSizeOf(PackedUser), 8);
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pub const PackedUser = 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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// blobLength returns the length of the blob storing string values.
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pub fn blobLength(self: *const PackedUser) usize {
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var result: usize = self.realHomeLen();
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if (!self.name_is_a_suffix) {
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result += self.realNameLen();
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}
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result += self.realGecosLen();
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if (self.shell_here) {
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result += self.realShellLen();
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}
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return result;
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}
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pub fn realHomeLen(self: *const PackedUser) usize {
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return @as(u32, self.home_len) + 1;
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}
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pub fn realNameLen(self: *const PackedUser) usize {
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return @as(u32, self.name_len) + 1;
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}
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pub fn realShellLen(self: *const PackedUser) usize {
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return @as(u32, self.shell_len_or_idx) + 1;
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}
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pub fn realGecosLen(self: *const PackedUser) usize {
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return self.gecos_len;
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}
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};
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// TODO(motiejus) move to the struct where it's used.
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const shellIndexProto = fn (u6) []const u8;
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const PackedUserAlignmentBits = 3;
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pub const User = struct {
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@ -59,28 +20,94 @@ pub const User = struct {
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shell: []const u8,
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};
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// UserWriter accepts a naive User struct and returns a PackedUser
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pub const UserWriter = struct {
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// shellIndexFnType is a signature for a function that accepts a shell
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// string and returns it's index in the global shell section. Passing a
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// function makes tests easier, and removes the Shell dependency of this
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// module.
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pub const PackedUser = struct {
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// TODO: use @bitSizeOf(Inner)/8:
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//const InnerSize = @divExact(@bitSizeOf(Inner), 8);
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const shellIndexFnType = fn ([]const u8) ?u6;
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appendTo: *ArrayList(u8),
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shellIndexFn: shellIndexFnType,
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const InnerSize = @sizeOf(Inner);
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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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pub fn init(
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appendTo: *ArrayList(u8),
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shellIndexFn: shellIndexFnType,
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) UserWriter {
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return UserWriter{
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.appendTo = appendTo,
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.shellIndexFn = shellIndexFn,
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pub fn homeLen(self: *const PackedUser) usize {
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return @as(u32, self.home_len) + 1;
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}
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pub fn nameLen(self: *const PackedUser) usize {
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return @as(u32, self.name_len) + 1;
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}
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pub fn gecosLen(self: *const PackedUser) usize {
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return self.gecos_len;
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}
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pub fn shellLen(self: *const PackedUser) 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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pub fn blobLength(self: *const Inner) usize {
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var result: usize = self.homeLen();
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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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result += self.gecosLen();
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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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pub fn namePos(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.inner.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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pub fn gecosPos(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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pub fn maybeShellPos(self: *const Inner) usize {
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assert(self.shell_here);
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return self.gecosPos() + self.gecosLen();
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}
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};
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inner: Inner,
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userdata: []const u8,
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pub fn fromBytes(bytes: []const u8) PackedUser {
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const inner = std.mem.bytesAsValue(
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PackedUser,
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bytes[0..@sizeOf(Inner)][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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return PackedUser{
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.inner = inner,
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.userdata = bytes[startBlob..endBlob],
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};
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}
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pub fn downCast(comptime T: type, n: u64) error{InvalidRecord}!T {
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fn downCast(comptime T: type, n: u64) error{InvalidRecord}!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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@ -88,23 +115,19 @@ pub const UserWriter = struct {
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};
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}
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pub fn validateUtf8(s: []const u8) error{InvalidRecord}!void {
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fn validateUtf8(s: []const u8) error{InvalidRecord}!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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// FIXME(motiejus) record valiation should return a separate type. For User
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// case, it should be length-bound slices and utf8-codepoints instead of
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// strings.
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//
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// zig does not have error contexts
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// (https://github.com/ziglang/zig/issues/2647) and length-limited slices.
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// (It does have bounded_array, but that preallocates the maximum length,
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// which is not great for User records). So I am using those excuses to
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// do the validation here. I may move it once I learn the language better.
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const appendUserErr = error{InvalidRecord} || Allocator.Error;
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pub fn appendUser(self: *UserWriter, user: User) appendUserErr!void {
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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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pub fn packTo(buf1: *[]u8, user: User, shellIndexFn: shellIndexFnType) error{InvalidRecord}!void {
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std.debug.print("\nbuf1.len: {d}\n", .{buf1.*.len});
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var buf = buf1.*;
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const bufStart = @ptrToInt(&buf[0]);
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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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@ -115,39 +138,79 @@ pub const UserWriter = struct {
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try validateUtf8(user.shell);
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try validateUtf8(user.gecos);
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var puser = PackedUser{
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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 = 1 << 29 - 1,
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.shell_here = self.shellIndexFn(user.shell) == null,
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.shell_len_or_idx = self.shellIndexFn(user.shell) orelse shell_len,
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.additional_gids_offset = std.math.maxInt(u29),
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.shell_here = shellIndexFn(user.shell) == null,
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.shell_len_or_idx = shellIndexFn(user.shell) orelse shell_len,
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.home_len = home_len,
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.name_is_a_suffix = std.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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try self.appendTo.appendSlice(std.mem.asBytes(&puser));
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try self.appendTo.appendSlice(user.home);
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if (!puser.name_is_a_suffix) {
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try self.appendTo.appendSlice(user.name);
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mem.copy(u8, buf, innerBytes);
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buf = buf[innerBytes.len..];
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mem.copy(u8, buf, user.home);
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buf = buf[user.home.len..];
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if (!inner.name_is_a_suffix) {
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mem.copy(u8, buf, user.name);
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buf = buf[user.name.len..];
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}
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try self.appendTo.appendSlice(user.gecos);
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if (puser.shell_here) {
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try self.appendTo.appendSlice(user.shell);
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mem.copy(u8, buf, user.gecos);
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buf = buf[user.gecos.len..];
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if (inner.shell_here) {
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mem.copy(u8, buf, user.shell);
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buf = buf[user.shell.len..];
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}
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try self.appendTo.appendNTimes(0, pad.roundUpPadding(
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u64,
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PackedUserAlignmentBits,
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self.appendTo.items.len,
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));
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_ = bufStart;
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//const bufLen = @ptrToInt(&buf[0]) - bufStart;
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//const padding = pad.roundUpPadding(u64, PackedUserAlignmentBits, bufLen);
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//mem.set(u8, buf[0..padding], 0);
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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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const unpadded = InnerSize +
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std.math.maxInt(u6) + // home
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std.math.maxInt(u5) + // name
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std.math.maxInt(u6) + // shell
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std.math.maxInt(u8); // gecos
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return pad.roundUp(u64, PackedUserAlignmentBits, unpadded);
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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.namePos();
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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.gecosPos();
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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, shellIndex: shellIndexProto) []const u8 {
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if (self.inner.shell_here) {
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const shell_pos = self.inner.maybeShellPos();
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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 shellIndex(self.inner.shell_len_or_idx);
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}
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};
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pub const UserReader = struct {
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const shellIndexProto = fn (u6) []const u8;
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section: []const u8,
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shellIndex: shellIndexProto,
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@ -182,25 +245,25 @@ pub const UserReader = struct {
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const endBlob = startBlob + u.blobLength();
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const section = self.section[startBlob..endBlob];
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const home = section[0..u.realHomeLen()];
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const home = section[0..u.homeLen()];
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var name: []const u8 = undefined;
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var pos: usize = undefined;
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if (u.name_is_a_suffix) {
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const name_start = u.realHomeLen() - u.realNameLen();
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name = section[name_start..u.realHomeLen()];
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pos = u.realHomeLen();
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const name_start = u.homeLen() - u.nameLen();
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name = section[name_start..u.homeLen()];
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pos = u.homeLen();
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} else {
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const name_start = u.realHomeLen();
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name = section[name_start .. name_start + u.realNameLen()];
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pos = name_start + u.realNameLen();
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const name_start = u.homeLen();
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name = section[name_start .. name_start + u.nameLen()];
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pos = name_start + u.nameLen();
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}
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const gecos = section[pos .. pos + u.realGecosLen()];
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pos += u.realGecosLen();
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const gecos = section[pos .. pos + u.gecosLen()];
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pos += u.gecosLen();
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var shell: []const u8 = undefined;
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if (u.shell_here) {
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shell = section[pos .. pos + u.realShellLen()];
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shell = section[pos .. pos + u.shellLen()];
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} else {
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shell = self.shellIndex(u.shell_len_or_idx);
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}
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@ -272,7 +335,6 @@ test "construct PackedUser section" {
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var buf = ArrayList(u8).init(testing.allocator);
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defer buf.deinit();
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var writer = UserWriter.init(&buf, testShellIndex);
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const users = [_]User{ User{
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.uid = 1000,
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.gid = 1000,
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@ -296,19 +358,23 @@ test "construct PackedUser section" {
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.shell = "s" ** 64,
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} };
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for (users) |user| {
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try writer.appendUser(user);
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std.debug.print("\nmaxSize: {d}\n", .{PackedUser.maxSize()});
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try buf.ensureUnusedCapacity(PackedUser.maxSize());
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buf.items[0] = 1;
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std.debug.print("\nbuf.items.len: {d}\n", .{buf.items.len});
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try PackedUser.packTo(&buf.items, user, testShellIndex);
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}
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var rd = UserReader.init(buf.items, testShell);
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//var rd = UserReader.init(buf.items, testShell);
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var it = rd.iterator();
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var i: u32 = 0;
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while (it.next()) |user| : (i += 1) {
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try testing.expectEqual(users[i].uid, user.uid);
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try testing.expectEqual(users[i].gid, user.gid);
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try testing.expectEqualStrings(users[i].name, user.name);
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try testing.expectEqualStrings(users[i].gecos, user.gecos);
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try testing.expectEqualStrings(users[i].home, user.home);
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try testing.expectEqualStrings(users[i].shell, user.shell);
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}
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//var it = rd.iterator();
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//var i: u32 = 0;
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//while (it.next()) |user| : (i += 1) {
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// try testing.expectEqual(users[i].uid, user.uid);
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// try testing.expectEqual(users[i].gid, user.gid);
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// try testing.expectEqualStrings(users[i].name, user.name);
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// try testing.expectEqualStrings(users[i].gecos, user.gecos);
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// try testing.expectEqualStrings(users[i].home, user.home);
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// try testing.expectEqualStrings(users[i].shell, user.shell);
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//}
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}
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