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// SPDX-FileCopyrightText: 2024 Himbeer <himbeer@disroot.org>
//
// SPDX-License-Identifier: AGPL-3.0-or-later
const std = @import("std");
const sysexchange = @import("sysexchange.zig");
const mem = std.mem;
var root: Tree = undefined;
pub const Error = error{
NotFound,
RelativePathNotAllowed,
NotADirectory,
NoAbsoluteContainingDirectory,
TooManyReferences,
};
// A stream is a resource that provides a shared data stream with a driver.
pub const Stream = struct {
readFn: ?ReadFn,
writeFn: ?WriteFn,
pub const ReadFn = *const fn (buffer: []u8) sysexchange.Result(usize);
pub const WriteFn = *const fn (bytes: []const u8) sysexchange.Result(usize);
};
// A file is a resource that creates a unique data stream with a driver.
pub const File = struct {
openFn: OpenFn,
readFn: ?ReadFn,
writeFn: ?WriteFn,
closeFn: ?CloseFn,
pub const OpenFn = *allowzero const fn (pid: u16) sysexchange.Result(*anyopaque);
pub const ReadFn = *const fn (context: *anyopaque, buffer: []u8) sysexchange.Result(usize);
pub const WriteFn = *const fn (context: *anyopaque, bytes: []const u8) sysexchange.Result(usize);
pub const CloseFn = *const fn (context: *anyopaque) void;
};
// A hook is a resource that invokes raw driver callbacks when interacted with.
pub const Hook = struct {
callback: Callback,
pub const Callback = *allowzero const fn (pid: u16, data: usize) sysexchange.Result(usize);
};
pub const MkdirOptions = packed struct(usize) {
full: u1,
reserved: u63,
};
// A directory hook is a resource that provides other resources via driver callbacks.
pub const DirHook = struct {
provideFn: ProvideFn,
findFn: FindFn,
removeFn: RemoveFn,
pub const ProvideFn = *allowzero const fn (inode: Inode) sysexchange.Result(void);
pub const FindFn = *allowzero const fn (name: []const u8) ?Inode;
pub const RemoveFn = *allowzero const fn (name: []const u8) sysexchange.Result(void);
};
pub const Resource = union(enum) {
stream: Stream,
file: File,
hook: Hook,
dir: Tree,
dir_hook: DirHook,
};
pub const Inode = struct {
name: []const u8,
resource: Resource,
refs: usize = 0,
};
pub const Node = std.DoublyLinkedList(Inode).Node;
pub const Tree = struct {
allocator: mem.Allocator,
nodes: std.DoublyLinkedList(Inode),
pub fn init(allocator: mem.Allocator) Tree {
return .{
.allocator = allocator,
.nodes = std.DoublyLinkedList(Inode){},
};
}
pub fn find(self: *const Tree, name: []const u8) ?*Node {
var node = self.nodes.first;
while (node) |current_node| {
if (current_node.next == current_node) break;
if (mem.eql(u8, current_node.data.name, name)) return current_node;
node = current_node.next;
}
return null;
}
pub fn provideResource(self: *Tree, inode: Inode) !void {
var node = try self.allocator.create(Node);
node.data = inode;
self.nodes.append(node);
}
pub fn remove(self: *Tree, name: []const u8) !void {
if (self.find(name)) |node| {
self.nodes.remove(node);
} else return Error.NotFound;
}
};
pub const ResourceDescriptor = struct {
inode: *Inode,
pub fn init(inode: *Inode) !ResourceDescriptor {
inode.refs = std.math.add(usize, inode.refs, 1) catch return Error.TooManyReferences;
return .{
.inode = inode,
};
}
pub fn deinit(self: ResourceDescriptor) void {
self.inode.refs -|= 1;
}
};
pub const UserInfo = union(enum) {
rd: ResourceDescriptor,
value: sysexchange.Result(usize),
};
pub fn init(allocator: mem.Allocator) void {
root = Tree.init(allocator);
}
pub fn find(path: []const u8) ?*Node {
if (!std.fs.path.isAbsolutePosix(path)) return null;
// Error set is empty.
var it = std.fs.path.ComponentIterator(.posix, u8).init(path) catch unreachable;
var tree = root;
while (it.next()) |component| {
const node = tree.find(component.name) orelse return null;
if (mem.eql(u8, component.path, (it.last() orelse return null).path)) {
return node;
}
switch (node.data.resource) {
.dir => |dir| tree = dir,
else => {},
}
}
// Only reached if path has no components.
return null;
}
pub fn provideResource(path: []const u8, resource: Resource) !void {
if (!std.fs.path.isAbsolutePosix(path)) return Error.RelativePathNotAllowed;
const dirname = std.fs.path.dirnamePosix(path) orelse return Error.NoAbsoluteContainingDirectory;
if (find(dirname)) |node| {
return switch (node.data.resource) {
.dir => |dir| @constCast(&dir).provideResource(.{
.name = std.fs.path.basenamePosix(path),
.resource = resource,
}),
else => Error.NotADirectory,
};
} else return Error.NotFound;
}
pub fn provideResourceZ(path_c: [*:0]const u8, resource: Resource) !void {
return provideResource(mem.sliceTo(path_c, 0), resource);
}
pub fn open(path: []const u8, pid: u16, data: usize) !UserInfo {
const node = find(path) orelse return Error.NotFound;
return switch (node.data.resource) {
.hook => |hook| .{ .value = hook.callback(pid, data) },
else => .{ .rd = try ResourceDescriptor.init(&node.data) },
};
}
pub fn openZ(path_c: [*:0]const u8, pid: u16, data: usize) !UserInfo {
return open(mem.sliceTo(path_c, 0), pid, data);
}
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