turbonss/lib/sections.zig

const std = @import("std");
const os = std.os;
const fmt = std.fmt;
const mem = std.mem;
const math = std.math;
const meta = std.meta;
const sort = std.sort;
const assert = std.debug.assert;
const unicode = std.unicode;
const Allocator = std.mem.Allocator;
const ArenaAllocator = std.heap.ArenaAllocator;
const ArrayListUnmanaged = std.ArrayListUnmanaged;
const ArrayList = std.ArrayList;
const MultiArrayList = std.MultiArrayList;
const StringHashMap = std.StringHashMap;
const AutoHashMap = std.AutoHashMap;
const BufSet = std.BufSet;
const BoundedArray = std.BoundedArray;

const pad = @import("padding.zig");
const compress = @import("compress.zig");
const PackedUser = @import("user.zig").PackedUser;
const User = @import("user.zig").User;
const Group = @import("group.zig").Group;
const GroupStored = @import("group.zig").GroupStored;
const PackedGroup = @import("group.zig").PackedGroup;
const ShellSections = @import("shell.zig").ShellWriter.ShellSections;
const ShellReader = @import("shell.zig").ShellReader;
const ShellWriter = @import("shell.zig").ShellWriter;
const Header = @import("header.zig").Header;
const max_shells = @import("shell.zig").max_shells;
const section_length_bits = @import("header.zig").section_length_bits;
const section_length = @import("header.zig").section_length;
const cmph = @import("cmph.zig");
const bdz = @import("bdz.zig");

const zeroes = &[_]u8{0} ** section_length;

const Corpus = struct {
    arena: ArenaAllocator,

    // sorted by name, by unicode codepoint
    users: MultiArrayList(User),
    // sorted by gid
    groups: MultiArrayList(Group),

    name2user: StringHashMap(u32),
    name2group: StringHashMap(u32),
    group2users: []const []const u32,
    user2groups: []const []const u32,

    pub fn init(
        baseAllocator: Allocator,
        usersConst: []const User,
        groupsConst: []const Group,
    ) error{ OutOfMemory, InvalidUtf8, Duplicate, NotFound, TooMany }!Corpus {
        if (usersConst.len >= math.maxInt(u32)) return error.TooMany;
        if (groupsConst.len >= math.maxInt(u32)) return error.TooMany;

        var arena = ArenaAllocator.init(baseAllocator);
        var allocator = arena.allocator();
        errdefer arena.deinit();

        var users_arr = try allocator.alloc(User, usersConst.len);
        var groups_arr = try allocator.alloc(Group, groupsConst.len);
        for (usersConst) |*user, i|
            users_arr[i] = try user.clone(allocator);
        for (groupsConst) |*group, i|
            groups_arr[i] = try group.clone(allocator);

        sort.sort(User, users_arr, {}, cmpUser);
        sort.sort(Group, groups_arr, {}, cmpGroup);

        var users = MultiArrayList(User){};
        try users.ensureTotalCapacity(allocator, users_arr.len);
        for (users_arr) |user|
            users.appendAssumeCapacity(user);
        var groups = MultiArrayList(Group){};
        try groups.ensureTotalCapacity(allocator, groups_arr.len);
        for (groups_arr) |group|
            groups.appendAssumeCapacity(group);

        var name2user = StringHashMap(u32).init(allocator);
        var name2group = StringHashMap(u32).init(allocator);
        for (users.items(.name)) |name, i| {
            var res1 = try name2user.getOrPut(name);
            if (res1.found_existing)
                return error.Duplicate;
            res1.value_ptr.* = @intCast(u32, i);
        }

        for (groups.items(.name)) |name, i| {
            var res1 = try name2group.getOrPut(name);
            if (res1.found_existing)
                return error.Duplicate;
            res1.value_ptr.* = @intCast(u32, i);
        }

        var group2users = try allocator.alloc([]u32, groups.len);

        // uses baseAllocator, because it will be freed before
        // returning from this function. This keeps the arena clean.
        var user2groups = try baseAllocator.alloc(ArrayListUnmanaged(u32), users.len);
        defer baseAllocator.free(user2groups);
        mem.set(ArrayListUnmanaged(u32), user2groups, ArrayListUnmanaged(u32){});

        for (groups.items(.members)) |groupmembers, i| {
            var members = try allocator.alloc(u32, groupmembers.count());
            members.len = 0;

            var it = groupmembers.iterator();
            while (it.next()) |member_name| {
                if (name2user.get(member_name.*)) |user_idx| {
                    members.len += 1;
                    members[members.len - 1] = user_idx;
                    try user2groups[user_idx].append(allocator, @intCast(u32, i));
                } else return error.NotFound;
            }

            group2users[i] = members;
        }

        for (group2users) |*groupusers|
            sort.sort(u32, groupusers.*, {}, comptime sort.asc(u32));

        var user2groups_final = try allocator.alloc([]const u32, users.len);
        user2groups_final.len = users.len;
        for (user2groups) |*usergroups, i| {
            sort.sort(u32, usergroups.items, {}, comptime sort.asc(u32));
            user2groups_final[i] = usergroups.toOwnedSlice(allocator);
        }

        return Corpus{
            .arena = arena,
            .users = users,
            .groups = groups,
            .name2user = name2user,
            .name2group = name2group,
            .group2users = group2users,
            .user2groups = user2groups_final,
        };
    }

    pub fn deinit(self: *Corpus) void {
        self.arena.deinit();
        self.* = undefined;
    }
};

pub fn shellSections(
    allocator: Allocator,
    corpus: *const Corpus,
) error{OutOfMemory}!ShellSections {
    var popcon = ShellWriter.init(allocator);
    for (corpus.users.items(.shell)) |shell|
        try popcon.put(shell);
    return popcon.toOwnedSections(max_shells);
}

pub const AdditionalGids = struct {
    // user index -> offset in blob
    idx2offset: []const u64,
    // compressed user gids blob. A blob contains N <= users.len items,
    // an item is:
    //   len: varint
    //   gid: [varint]varint,
    // ... and the gid list is delta-compressed.
    blob: []const u8,

    pub fn deinit(self: *AdditionalGids, allocator: Allocator) void {
        allocator.free(self.idx2offset);
        allocator.free(self.blob);
        self.* = undefined;
    }
};

pub fn additionalGids(
    allocator: Allocator,
    corpus: *const Corpus,
) error{OutOfMemory}!AdditionalGids {
    var blob = ArrayList(u8).init(allocator);
    errdefer blob.deinit();
    var idx2offset = try allocator.alloc(u64, corpus.users.len);
    errdefer allocator.free(idx2offset);

    // zero'th entry is empty, so groupless users can refer to it.
    try compress.appendUvarint(&blob, 0);

    var scratch = try allocator.alloc(u32, 256);
    defer allocator.free(scratch);
    for (corpus.user2groups) |usergroups, user_idx| {
        if (usergroups.len == 0) {
            idx2offset[user_idx] = 0;
            continue;
        }
        idx2offset[user_idx] = blob.items.len;
        scratch = try allocator.realloc(scratch, usergroups.len);
        scratch.len = usergroups.len;
        const corpusGids = corpus.groups.items(.gid);
        for (usergroups) |group_idx, i|
            scratch[i] = corpusGids[group_idx];
        compress.deltaCompress(u32, scratch) catch |err| switch (err) {
            error.NotSorted => unreachable,
        };
        try compress.appendUvarint(&blob, usergroups.len);
        for (scratch) |gid|
            try compress.appendUvarint(&blob, gid);
    }

    return AdditionalGids{
        .idx2offset = idx2offset,
        .blob = blob.toOwnedSlice(),
    };
}

pub const UsersSection = struct {
    // number of users in this section
    len: u32,
    // user index -> offset in blob
    idx2offset: []const u32,
    blob: []const u8,

    pub fn deinit(self: *UsersSection, allocator: Allocator) void {
        allocator.free(self.idx2offset);
        allocator.free(self.blob);
        self.* = undefined;
    }
};

pub fn usersSection(
    allocator: Allocator,
    corpus: *const Corpus,
    gids: *const AdditionalGids,
    shells: *const ShellSections,
) error{ OutOfMemory, InvalidRecord, TooMany }!UsersSection {
    var idx2offset = try allocator.alloc(u32, corpus.users.len);
    errdefer allocator.free(idx2offset);
    // as of writing each user takes 12 bytes + blobs + padding, padded to
    // 8 bytes. 24 is an optimistic lower bound for an average record size.
    var blob = try ArrayList(u8).initCapacity(allocator, 24 * corpus.users.len);
    errdefer blob.deinit();
    var i: usize = 0;
    while (i < corpus.users.len) : (i += 1) {
        // TODO: this is inefficient by calling `.slice()` on every iteration
        const user = corpus.users.get(i);
        const user_offset = math.cast(u35, blob.items.len) catch |err| switch (err) {
            error.Overflow => return error.TooMany,
        };
        assert(user_offset & 7 == 0);
        idx2offset[i] = @truncate(u32, user_offset >> 3);
        try PackedUser.packTo(
            &blob,
            user,
            gids.idx2offset[i],
            shells.shell2idx,
        );
        try pad.arrayList(&blob, PackedUser.alignment_bits);
    }
    return UsersSection{
        .len = @intCast(u32, corpus.users.len),
        .idx2offset = idx2offset,
        .blob = blob.toOwnedSlice(),
    };
}

pub const GroupMembers = struct {
    // group index to it's offset in blob
    idx2offset: []const u64,
    // members are delta-varint encoded byte-offsets to the user struct
    blob: []const u8,

    pub fn deinit(self: *GroupMembers, allocator: Allocator) void {
        allocator.free(self.idx2offset);
        allocator.free(self.blob);
        self.* = undefined;
    }
};

pub fn groupMembers(
    allocator: Allocator,
    corpus: *const Corpus,
    user2offset: []const u32,
) error{OutOfMemory}!GroupMembers {
    var idx2offset = try allocator.alloc(u64, corpus.groups.len);
    errdefer allocator.free(idx2offset);
    var blob = ArrayList(u8).init(allocator);
    errdefer blob.deinit();
    // zero'th entry is empty, so empty groups can refer to it
    try compress.appendUvarint(&blob, 0);

    var scratch = try ArrayList(u32).initCapacity(allocator, 1024);
    defer scratch.deinit();

    for (corpus.group2users) |members, group_idx| {
        if (members.len == 0) {
            idx2offset[group_idx] = 0;
            continue;
        }

        idx2offset[group_idx] = blob.items.len;
        try scratch.ensureTotalCapacity(members.len);
        scratch.items.len = members.len;
        for (members) |user_idx, i|
            scratch.items[i] = user2offset[user_idx];

        compress.deltaCompress(u32, scratch.items) catch |err| switch (err) {
            error.NotSorted => unreachable,
        };
        try compress.appendUvarint(&blob, members.len);
        for (scratch.items) |elem|
            try compress.appendUvarint(&blob, elem);
    }
    return GroupMembers{
        .idx2offset = idx2offset,
        .blob = blob.toOwnedSlice(),
    };
}

pub const GroupsSection = struct {
    // number of groups in this section
    len: u32,
    // group index -> offset in blob
    idx2offset: []const u32,
    blob: []const u8,

    pub fn deinit(self: *GroupsSection, allocator: Allocator) void {
        allocator.free(self.idx2offset);
        allocator.free(self.blob);
        self.* = undefined;
    }
};

pub fn groupsSection(
    allocator: Allocator,
    corpus: *const Corpus,
    members_offset: []const u64,
) error{ OutOfMemory, InvalidRecord }!GroupsSection {
    var idx2offset = try allocator.alloc(u32, corpus.groups.len);
    errdefer allocator.free(idx2offset);

    var blob = try ArrayList(u8).initCapacity(allocator, 8 * corpus.groups.len);
    errdefer blob.deinit();

    var i: usize = 0;
    while (i < corpus.groups.len) : (i += 1) {
        // TODO: this is inefficient; it's calling `.slice()` on every iteration
        const group = corpus.groups.get(i);
        const group_offset = @intCast(u32, blob.items.len);
        assert(group_offset & 7 == 0);
        idx2offset[i] = @truncate(u32, group_offset >> 3);
        const group_stored = GroupStored{
            .gid = group.gid,
            .name = group.name,
            .members_offset = members_offset[i],
        };
        try PackedGroup.packTo(&blob, group_stored);
        try pad.arrayList(&blob, PackedGroup.alignment_bits);
    }

    return GroupsSection{
        .len = @intCast(u32, corpus.groups.len),
        .idx2offset = idx2offset,
        .blob = blob.toOwnedSlice(),
    };
}

// creates a bdz index using packed_mphf.
//   hash = bdz_search(packed_mphf, keys[i]);
//   result[hash] = idx2offset[i];
pub fn bdzIdx(
    comptime T: type,
    allocator: Allocator,
    packed_mphf: []const u8,
    keys: []const T,
    idx2offset: []const u32,
) error{OutOfMemory}![]const u32 {
    const search_fn = comptime blk: {
        switch (T) {
            u32 => break :blk bdz.search_u32,
            []const u8 => break :blk bdz.search,
            else => unreachable,
        }
    };
    assert(keys.len <= math.maxInt(u32));
    var result = try allocator.alloc(u32, keys.len);
    for (keys) |key, i|
        result[search_fn(packed_mphf, key)] = idx2offset[i];
    return result;
}

// cmpUser compares two users for sorting. By username's utf8 codepoints, ascending.
fn cmpUser(_: void, a: User, b: User) bool {
    var utf8_a = (unicode.Utf8View.init(a.name) catch unreachable).iterator();
    var utf8_b = (unicode.Utf8View.init(b.name) catch unreachable).iterator();
    while (utf8_a.nextCodepoint()) |codepoint_a| {
        if (utf8_b.nextCodepoint()) |codepoint_b| {
            if (codepoint_a == codepoint_b) {
                continue;
            } else return codepoint_a < codepoint_b;
        }

        // a is a prefix of b. It is thus shorter.
        return false;
    }
    // b is a prefix of a
    return true;
}

fn cmpGroup(_: void, a: Group, b: Group) bool {
    return a.gid < b.gid;
}

// nblocks returns how many blocks a particular slice will take.
fn nblocks(comptime T: type, arr: []const u8) T {
    const B = switch (T) {
        u8 => u14,
        u32 => u38,
        u64 => u70,
        else => @compileError("only u8, u32 and u64 are supported"),
    };
    const upper = pad.roundUp(B, section_length_bits, @intCast(B, arr.len));
    assert(upper & (section_length - 1) == 0);
    return @truncate(T, upper >> 6);
}

pub const DB = struct {
    // All sections, as they end up in the DB. Order is important.
    header: []const u8,
    bdz_gid: []const u8,
    bdz_groupname: []const u8,
    bdz_uid: []const u8,
    bdz_username: []const u8,
    idx_gid2group: []const u32,
    idx_groupname2group: []const u32,
    idx_uid2user: []const u32,
    idx_name2user: []const u32,
    shell_index: []const u16,
    shell_blob: []const u8,
    groups: []const u8,
    users: []const u8,
    groupmembers: []const u8,
    additional_gids: []const u8,

    pub fn fromCorpus(
        allocator: Allocator,
        corpus: *const Corpus,
    ) error{ OutOfMemory, InvalidRecord, TooMany }!DB {
        const gids = corpus.groups.items(.gid);
        const gnames = corpus.groups.items(.name);
        const uids = corpus.users.items(.uid);
        const unames = corpus.users.items(.name);

        var bdz_gid = try cmph.packU32(allocator, gids);
        errdefer allocator.free(bdz_gid);

        var bdz_groupname = try cmph.packStr(allocator, gnames);
        errdefer allocator.free(bdz_groupname);

        var bdz_uid = try cmph.packU32(allocator, uids);
        errdefer allocator.free(bdz_uid);

        const bdz_username = try cmph.packStr(allocator, unames);
        errdefer allocator.free(bdz_username);

        var shell = try shellSections(allocator, corpus);
        defer shell.deinit();

        var additional_gids = try additionalGids(allocator, corpus);
        errdefer allocator.free(additional_gids.blob);

        var users = try usersSection(allocator, corpus, &additional_gids, &shell);
        allocator.free(additional_gids.idx2offset);
        errdefer allocator.free(users.blob);

        var groupmembers = try groupMembers(allocator, corpus, users.idx2offset);
        errdefer allocator.free(groupmembers.blob);

        var groups = try groupsSection(allocator, corpus, groupmembers.idx2offset);
        allocator.free(groupmembers.idx2offset);
        errdefer allocator.free(groups.blob);

        var idx_gid2group = try bdzIdx(u32, allocator, bdz_gid, gids, groups.idx2offset);
        errdefer allocator.free(idx_gid2group);

        var idx_groupname2group = try bdzIdx([]const u8, allocator, bdz_groupname, gnames, groups.idx2offset);
        allocator.free(groups.idx2offset);
        errdefer allocator.free(idx_groupname2group);

        var idx_uid2user = try bdzIdx(u32, allocator, bdz_uid, uids, users.idx2offset);
        errdefer allocator.free(idx_uid2user);

        var idx_name2user = try bdzIdx([]const u8, allocator, bdz_username, unames, users.idx2offset);
        allocator.free(users.idx2offset);
        errdefer allocator.free(idx_name2user);

        const header = Header{
            .nblocks_shell_blob = nblocks(u8, shell.blob.constSlice()),
            .num_shells = shell.len,
            .num_groups = groups.len,
            .num_users = users.len,
            .nblocks_bdz_gid = nblocks(u32, bdz_gid),
            .nblocks_bdz_groupname = nblocks(u32, bdz_groupname),
            .nblocks_bdz_uid = nblocks(u32, bdz_uid),
            .nblocks_bdz_username = nblocks(u32, bdz_username),
            .nblocks_groups = nblocks(u64, groups.blob),
            .nblocks_users = nblocks(u64, users.blob),
            .nblocks_groupmembers = nblocks(u64, groupmembers.blob),
            .nblocks_additional_gids = nblocks(u64, additional_gids.blob),
        };

        return DB{
            .header = header.asBytes(),
            .bdz_gid = bdz_gid,
            .bdz_groupname = bdz_groupname,
            .bdz_uid = bdz_uid,
            .bdz_username = bdz_username,
            .idx_gid2group = idx_gid2group,
            .idx_groupname2group = idx_groupname2group,
            .idx_uid2user = idx_uid2user,
            .idx_name2user = idx_name2user,
            .shell_index = shell.index.constSlice(),
            .shell_blob = shell.blob.constSlice(),
            .groups = groups.blob,
            .users = users.blob,
            .groupmembers = groupmembers.blob,
            .additional_gids = additional_gids.blob,
        };
    }

    pub fn iov(self: *const DB) error{OutOfMemory}![]const os.iovec_const {
        const fields = comptime meta.fieldNames(DB);
        var result = BoundedArray(os.iovec_const, fields.len * 2).init(0) catch |err| switch (err) {
            error.Overflow => unreachable,
        };

        inline for (fields) |fname| {
            const bytes = mem.sliceAsBytes(@field(self, fname));
            result.appendAssumeCapacity(os.iovec_const{
                .iov_base = bytes.ptr,
                .iov_len = bytes.len,
            });
            const padding = pad.until(usize, section_length_bits, bytes.len);
            if (padding != 0)
                result.appendAssumeCapacity(.{
                    .iov_base = zeroes,
                    .iov_len = padding,
                });
        }

        return result.constSlice();
    }

    pub fn deinit(self: *DB, allocator: Allocator) void {
        allocator.free(self.bdz_gid);
        allocator.free(self.bdz_groupname);
        allocator.free(self.bdz_uid);
        allocator.free(self.bdz_username);
        allocator.free(self.idx_gid2group);
        allocator.free(self.idx_groupname2group);
        allocator.free(self.idx_uid2user);
        allocator.free(self.idx_name2user);
        allocator.free(self.groups);
        allocator.free(self.users);
        allocator.free(self.groupmembers);
        allocator.free(self.additional_gids);
        self.* = undefined;
    }
};

const testing = std.testing;
const someMembers = @import("group.zig").someMembers;

fn testCorpus(allocator: Allocator) !Corpus {
    const users = [_]User{ User{
        .uid = 0,
        .gid = 0,
        .name = "root",
        .gecos = "",
        .home = "/root",
        .shell = "/bin/bash",
    }, User{
        .uid = 128,
        .gid = 128,
        .name = "vidmantas",
        .gecos = "Vidmantas Kaminskas",
        .home = "/home/vidmantas",
        .shell = "/bin/bash",
    }, User{
        .uid = 1000,
        .gid = math.maxInt(u32),
        .name = "Name" ** 8,
        .gecos = "Gecos" ** 51,
        .home = "Home" ** 16,
        .shell = "She.LllL" ** 8,
    }, User{
        .uid = 100000,
        .gid = 1002,
        .name = "svc-bar",
        .gecos = "",
        .home = "/",
        .shell = "/",
    }, User{
        .uid = 65534,
        .gid = 65534,
        .name = "nobody",
        .gecos = "nobody",
        .home = "/nonexistent",
        .shell = "/usr/sbin/nologin",
    } };

    var members0 = try someMembers(
        allocator,
        &[_][]const u8{"root"},
    );
    defer members0.deinit();

    var members1 = try someMembers(
        allocator,
        &[_][]const u8{"vidmantas"},
    );
    defer members1.deinit();

    var members2 = try someMembers(
        allocator,
        &[_][]const u8{ "svc-bar", "vidmantas" },
    );
    defer members2.deinit();

    var members3 = try someMembers(
        allocator,
        &[_][]const u8{ "svc-bar", "Name" ** 8, "vidmantas", "root" },
    );
    defer members3.deinit();

    const groups = [_]Group{
        Group{ .gid = 0, .name = "root", .members = members0 },
        Group{ .gid = 128, .name = "vidmantas", .members = members1 },
        Group{ .gid = 9999, .name = "all", .members = members3 },
        Group{ .gid = 100000, .name = "service-account", .members = members2 },
    };

    return try Corpus.init(allocator, users[0..], groups[0..]);
}

test "test corpus" {
    var corpus = try testCorpus(testing.allocator);
    defer corpus.deinit();

    const name_name = 0;
    const nobody = 1;
    const root = 2;
    const svc_bar = 3;
    const vidmantas = 4;

    const usernames = corpus.users.items(.name);
    try testing.expectEqualStrings(usernames[name_name], "Name" ** 8);
    try testing.expectEqualStrings(usernames[nobody], "nobody");
    try testing.expectEqualStrings(usernames[root], "root");
    try testing.expectEqualStrings(usernames[svc_bar], "svc-bar");
    try testing.expectEqualStrings(usernames[vidmantas], "vidmantas");

    const g_root = 0;
    const g_vidmantas = 1;
    const g_all = 2;
    const g_service_account = 3;

    const groupnames = corpus.groups.items(.name);
    try testing.expectEqualStrings(groupnames[g_root], "root");
    try testing.expectEqualStrings(groupnames[g_service_account], "service-account");
    try testing.expectEqualStrings(groupnames[g_vidmantas], "vidmantas");
    try testing.expectEqualStrings(groupnames[g_all], "all");

    try testing.expectEqual(corpus.name2user.get("404"), null);
    try testing.expectEqual(corpus.name2user.get("vidmantas").?, vidmantas);
    try testing.expectEqual(corpus.name2group.get("404"), null);
    try testing.expectEqual(corpus.name2group.get("vidmantas").?, g_vidmantas);

    const membersOfAll = corpus.group2users[g_all];
    try testing.expectEqual(membersOfAll[0], name_name);
    try testing.expectEqual(membersOfAll[1], root);
    try testing.expectEqual(membersOfAll[2], svc_bar);
    try testing.expectEqual(membersOfAll[3], vidmantas);

    const groupsOfVidmantas = corpus.user2groups[vidmantas];
    try testing.expectEqual(groupsOfVidmantas[0], g_vidmantas);
    try testing.expectEqual(groupsOfVidmantas[1], g_all);
    try testing.expectEqual(groupsOfVidmantas[2], g_service_account);
}

test "test groups, group members and users" {
    const allocator = testing.allocator;
    var corpus = try testCorpus(allocator);
    defer corpus.deinit();

    var db = try DB.fromCorpus(allocator, &corpus);
    defer db.deinit(allocator);

    // TODO: replace with an integration test when high-level
    // reader API is present
    //const blob = sections.groupmembers.blob;
    //var i: usize = 0;
    //while (i < corpus.groups.len) : (i += 1) {
    //const offset = sections.groupmembers.idx2offset[i];
    //var vit = try compress.VarintSliceIterator(blob[offset..]);
    //var it = compress.DeltaDecompressionIterator(&vit);
    //for (corpus.group2users[i]) |user_idx| {
    //    const got_user_offset = (try it.next()).?;
    //    const want_user_offset = sections.users.idx2offset[user_idx];
    //    try testing.expectEqual(got_user_offset, want_user_offset);
    //}
    //try testing.expectEqual(it.next(), null);
    //}

    //var it = PackedUser.iterator(sections.users.blob, sections.shell_reader);
    //i = 0;
    //while (i < corpus.users.len) : (i += 1) {
    //    const got = (try it.next()).?;
    //    const user = corpus.users.get(i);
    //    try testing.expectEqual(user.uid, got.uid());
    //    try testing.expectEqual(user.gid, got.gid());
    //    try testing.expectEqualStrings(user.name, got.name());
    //    try testing.expectEqualStrings(user.gecos, got.gecos());
    //    try testing.expectEqualStrings(user.home, got.home());
    //    try testing.expectEqualStrings(user.shell, got.shell(sections.shell_reader));
    //}

    var iovec = try db.iov();
    _ = iovec;
}

test "additionalGids" {
    const allocator = testing.allocator;
    var corpus = try testCorpus(allocator);
    defer corpus.deinit();

    var additional_gids = try additionalGids(allocator, &corpus);
    defer additional_gids.deinit(allocator);

    var user_idx: usize = 0;
    while (user_idx < corpus.users.len) : (user_idx += 1) {
        const groups = corpus.user2groups[user_idx];
        const offset = additional_gids.idx2offset[user_idx];
        if (groups.len == 0) {
            try testing.expect(offset == 0);
            continue;
        }
        var vit = try compress.VarintSliceIterator(additional_gids.blob[offset..]);
        var it = compress.DeltaDecompressionIterator(&vit);
        try testing.expectEqual(it.remaining(), groups.len);
        var i: u64 = 0;
        const corpusGids = corpus.groups.items(.gid);
        while (try it.next()) |gid| : (i += 1) {
            try testing.expectEqual(gid, corpusGids[groups[i]]);
        }
        try testing.expectEqual(i, groups.len);
    }
}

test "pack gids" {
    const allocator = testing.allocator;
    var corpus = try testCorpus(allocator);
    defer corpus.deinit();

    const cmph_gid = try cmph.packU32(allocator, corpus.groups.items(.gid));
    defer allocator.free(cmph_gid);

    const k1 = bdz.search_u32(cmph_gid, 0);
    const k2 = bdz.search_u32(cmph_gid, 128);
    const k3 = bdz.search_u32(cmph_gid, 9999);
    const k4 = bdz.search_u32(cmph_gid, 100000);
    var hashes = &[_]u32{ k1, k2, k3, k4 };
    sort.sort(u32, hashes, {}, comptime sort.asc(u32));
    for (hashes) |hash, i|
        try testing.expectEqual(i, hash);
}

fn testUser(name: []const u8) User {
    var result = mem.zeroes(User);
    result.name = name;
    return result;
}

test "users compare function" {
    const a = testUser("a");
    const b = testUser("b");
    const bb = testUser("bb");
    try testing.expect(cmpUser({}, a, b));
    try testing.expect(!cmpUser({}, b, a));
    try testing.expect(cmpUser({}, a, bb));
    try testing.expect(!cmpUser({}, bb, a));
    try testing.expect(cmpUser({}, b, bb));
    try testing.expect(!cmpUser({}, bb, b));
}

const hash_offsets = &[_]u32{ 0, 10, 20, 30 };

fn expectUsedHashes(allocator: Allocator, arr: []const u32) !void {
    var used = AutoHashMap(u32, void).init(allocator);
    defer used.deinit();

    for (arr) |elem|
        try used.putNoClobber(elem, {});
    for (hash_offsets) |item|
        try testing.expect(used.get(item) != null);
}

test "bdzIdx on u32" {
    const keys = [_]u32{ 42, 1, 2, 3 };
    const mphf = try cmph.packU32(testing.allocator, keys[0..]);
    defer testing.allocator.free(mphf);
    var result = try bdzIdx(u32, testing.allocator, mphf, keys[0..], hash_offsets);
    defer testing.allocator.free(result);
    try expectUsedHashes(testing.allocator, result);
}

test "bdzIdx on str" {
    const keys = [_][]const u8{ "42", "1", "2", "3" };
    const mphf = try cmph.packStr(testing.allocator, keys[0..]);
    defer testing.allocator.free(mphf);
    var result = try bdzIdx([]const u8, testing.allocator, mphf, keys[0..], hash_offsets);
    defer testing.allocator.free(result);
    try expectUsedHashes(testing.allocator, result);
}

test "nblocks" {
    const tests = .{
        .{ 0, &[_]u8{} },
        .{ 1, &[_]u8{ 1, 2, 42 } },
        .{ 1, &[_]u8{1} ** 63 },
        .{ 1, &[_]u8{1} ** 64 },
        .{ 2, &[_]u8{1} ** 65 },
        .{ 255, &[_]u8{1} ** (255 * 64) },
    };

    inline for (tests) |tt| {
        try testing.expectEqual(nblocks(u8, tt[1]), tt[0]);
        try testing.expectEqual(nblocks(u32, tt[1]), tt[0]);
        try testing.expectEqual(nblocks(u64, tt[1]), tt[0]);
    }
}