From 31b5bb2d727214df89a60ac4bec4baedcb9caf21 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Motiejus=20Jak=C5=A1tys?= <motiejus@jakstys.lt>
Date: Tue, 7 Jun 2022 05:32:21 +0300
Subject: [PATCH] Group.fromReader

---
 src/Group.zig        | 44 +++++++++++++++++++++++++++++++++++++++++++-
 src/User.zig         |  9 +++++----
 src/unix2db/main.zig |  3 +++
 3 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/src/Group.zig b/src/Group.zig
index 57961f7..674818d 100644
--- a/src/Group.zig
+++ b/src/Group.zig
@@ -1,8 +1,11 @@
 const std = @import("std");
-
+const os = std.os;
 const mem = std.mem;
+const fmt = std.fmt;
 const meta = std.meta;
+const maxInt = std.math.maxInt;
 const Allocator = mem.Allocator;
+const ArrayList = std.ArrayList;
 const Group = @This();
 
 gid: u32,
@@ -55,6 +58,45 @@ pub fn deinit(self: *Group, allocator: Allocator) void {
     self.* = undefined;
 }
 
+pub const FromReaderError = error{ InvalidRecord, OutOfMemory } || os.ReadError;
+
+pub fn fromReader(allocator: Allocator, reader: anytype) FromReaderError![]Group {
+    var groups = ArrayList(Group).init(allocator);
+    var member_ptrs = ArrayList([]const u8).init(allocator);
+    defer member_ptrs.deinit();
+    var line = ArrayList(u8).init(allocator);
+    defer line.deinit();
+
+    while (true) {
+        // TODO: catch and interpret different errors
+        const max = std.math.maxInt(u32);
+        reader.readUntilDelimiterArrayList(&line, '\n', max) catch |err| switch (err) {
+            error.EndOfStream => break,
+            error.StreamTooLong => unreachable,
+            else => |e| return e,
+        };
+
+        var it = mem.split(u8, line.items, ":");
+        const name = it.next() orelse return error.InvalidRecord;
+        _ = it.next() orelse return error.InvalidRecord; // password
+        const gids = it.next() orelse return error.InvalidRecord;
+        const members_commas = it.next() orelse return error.InvalidRecord;
+        // the line must be exhaustive.
+        if (it.next() != null) return error.InvalidRecord;
+
+        const gid = fmt.parseInt(u32, gids, 10) catch return error.InvalidRecord;
+
+        var members_it = mem.split(u8, members_commas, ",");
+        while (members_it.next()) |member|
+            try member_ptrs.append(member);
+
+        try groups.append(try init(allocator, gid, name, member_ptrs.items));
+        member_ptrs.shrinkRetainingCapacity(0);
+    }
+
+    return groups.toOwnedSlice();
+}
+
 // suggested buffer size in bytes if all strings were zero-terminated
 // (for CGroup).
 pub fn strlenZ(self: *const Group) usize {
diff --git a/src/User.zig b/src/User.zig
index a5a0bbd..c6bf370 100644
--- a/src/User.zig
+++ b/src/User.zig
@@ -43,15 +43,14 @@ pub fn clone(
     };
 }
 
-const line_fmt = "{s}:x:{d}:{d}:{s}:{s}:{s}\n";
-
 // fromLine accepts a line of /etc/passwd (with or without the EOL) and makes a
 // User.
 fn fromLine(allocator: Allocator, line: []const u8) error{ InvalidRecord, OutOfMemory }!User {
     var it = mem.split(u8, line, ":");
+    const name = it.next() orelse return error.InvalidRecord;
+    _ = it.next() orelse return error.InvalidRecord; // password
     const uids = it.next() orelse return error.InvalidRecord;
     const gids = it.next() orelse return error.InvalidRecord;
-    const name = it.next() orelse return error.InvalidRecord;
     const gecos = it.next() orelse return error.InvalidRecord;
     const home = it.next() orelse return error.InvalidRecord;
     const shell = it.next() orelse return error.InvalidRecord;
@@ -84,6 +83,8 @@ fn strlen(self: *const User) usize {
         self.shell.len;
 }
 
+const line_fmt = "{s}:x:{d}:{d}:{s}:{s}:{s}\n";
+
 const max_line_len = fmt.count(line_fmt, .{
     max_user.name,
     max_user.uid,
@@ -120,7 +121,7 @@ pub fn deinit(self: *User, allocator: Allocator) void {
 
 pub fn fromReader(allocator: Allocator, reader: anytype) ![]User {
     var users = ArrayList(User).init(allocator);
-    var buf: [max_line_len]u8 = undefined;
+    var buf: [max_line_len + 1]u8 = undefined;
     // TODO: catch and interpret error
     while (try reader.readUntilDelimiterOrEof(buf[0..], '\n')) |line| {
         const user = try fromLine(allocator, line);
diff --git a/src/unix2db/main.zig b/src/unix2db/main.zig
index e33895d..0970446 100644
--- a/src/unix2db/main.zig
+++ b/src/unix2db/main.zig
@@ -9,6 +9,7 @@ const GeneralPurposeAllocator = std.heap.GeneralPurposeAllocator;
 
 const flags = @import("../flags.zig");
 const User = @import("../User.zig");
+const Group = @import("../Group.zig");
 
 const usage =
     \\usage: turbonss-unix2db [options]
@@ -66,8 +67,10 @@ fn execute(
     defer groupFile.close();
 
     var users = try User.fromReader(allocator, passwdFile.reader());
+    var groups = try Group.fromReader(allocator, groupFile.reader());
 
     try stderr.print("read {d} users\n", .{users.len});
+    try stderr.print("read {d} groups\n", .{groups.len});
     return 0;
 }