vfs: Get rid of File OpenFn callback

Context initialization is now left to the provider, allowing the kernel itself to interact with resources of this kind.

3 files changed, 38 insertions, 29 deletions

diff --git a/src/lib/resources.zig b/src/lib/resources.zig
index 25835d5..93e9f04 100644
--- a/src/lib/resources.zig
+++ b/src/lib/resources.zig
@@ -278,7 +278,6 @@ fn addFile(path: []const u8, file: File) !void {
         .tag = .file,
         .data = .{
             .file = .{
-                .openFn = open,
                 .readFn = read,
                 .writeFn = null,
                 .closeFn = close,
@@ -303,30 +302,36 @@ fn addDir(path: []const u8) !void {
     });
 }
 
-fn open(initializer: ?*anyopaque, _: u16) callconv(.C) Result(*anyopaque) {
-    const file_template: *File = @alignCast(@ptrCast(initializer orelse {
-        return Result(*anyopaque).fromAnyTypeOrError(Error.NoTarFileInitializer);
-    }));
-
+fn open(context: *vfs.FileContext) !void {
     const allocator = vfs.treeRoot().allocator;
-    const context = allocator.create(File) catch |err| {
-        return Result(*anyopaque).fromAnyTypeOrError(err);
-    };
-    context.* = file_template.*;
 
-    return Result(*anyopaque).fromAnyTypeOrError(context);
+    const inner = context.inner orelse return Error.NoTarFileInitializer;
+    const old_context: *File = @alignCast(@ptrCast(inner));
+
+    const new_context = try allocator.create(File);
+    new_context.* = old_context.*;
+
+    context.inner = new_context;
 }
 
-fn read(context: *anyopaque, ptr: [*]u8, len: usize) callconv(.C) Result(usize) {
-    const ctx: *File = @alignCast(@ptrCast(context));
+fn read(context: *vfs.FileContext, ptr: [*]u8, len: usize) callconv(.C) Result(usize) {
+    if (context.inner == null) {
+        open(context) catch |err| {
+            return Result(usize).fromAnyTypeOrError(err);
+        };
+    }
+
+    const inner: *File = @alignCast(@ptrCast(context.inner.?));
 
     const buffer = ptr[0..len];
-    return Result(usize).fromAnyTypeOrError(ctx.read(buffer));
+    return Result(usize).fromAnyTypeOrError(inner.read(buffer));
 }
 
-fn close(context: *anyopaque) callconv(.C) void {
-    const ctx: *File = @alignCast(@ptrCast(context));
+fn close(context: *vfs.FileContext) callconv(.C) void {
+    if (context.inner) |inner_opaque| {
+        const allocator = vfs.treeRoot().allocator;
 
-    const allocator = vfs.treeRoot().allocator;
-    allocator.destroy(ctx);
+        const inner: *File = @alignCast(@ptrCast(inner_opaque));
+        allocator.destroy(inner);
+    }
 }
diff --git a/src/lib/syscall.zig b/src/lib/syscall.zig
index c124373..37be59d 100644
--- a/src/lib/syscall.zig
+++ b/src/lib/syscall.zig
@@ -106,7 +106,6 @@ fn provideStream(proc: *const process.Info, trap_frame: *trap.Frame) void {
 // provideFile(
 //     path_c: [*:0]const u8, // fixme: Kernel panic if null pointer
 //     options: *const vfs.Options, // fixme: Kernel panic if null pointer
-//     openFn: vfs.File.OpenFn,
 //     readFn: ?vfs.File.ReadFn,
 //     writeFn: ?vfs.File.WriteFn,
 //     closeFn: ?vfs.File.CloseFn,
@@ -117,7 +116,6 @@ fn provideFile(proc: *const process.Info, trap_frame: *trap.Frame) void {
 
     const path_c: [*:0]const u8 = @ptrFromInt(trap_frame.general_purpose_registers[10]);
     const options: *const vfs.Options = @ptrFromInt(trap_frame.general_purpose_registers[11]);
-    const openFn: vfs.File.OpenFn = @ptrFromInt(trap_frame.general_purpose_registers[12]);
     const readFn: ?vfs.File.ReadFn = @ptrFromInt(trap_frame.general_purpose_registers[13]);
     const writeFn: ?vfs.File.WriteFn = @ptrFromInt(trap_frame.general_purpose_registers[14]);
     const closeFn: ?vfs.File.CloseFn = @ptrFromInt(trap_frame.general_purpose_registers[15]);
@@ -125,7 +123,6 @@ fn provideFile(proc: *const process.Info, trap_frame: *trap.Frame) void {
     sysexchange.frameReturn(null, trap_frame, vfs.provideResourceZ(path_c, .{
         .tag = .file,
         .data = .{ .file = .{
-            .openFn = openFn,
             .readFn = readFn,
             .writeFn = writeFn,
             .closeFn = closeFn,
diff --git a/src/lib/vfs.zig b/src/lib/vfs.zig
index 7083c7c..951c666 100644
--- a/src/lib/vfs.zig
+++ b/src/lib/vfs.zig
@@ -61,16 +61,14 @@ pub const Stream = extern struct {
 
 // A file is a resource that creates a unique data stream with a driver.
 pub const File = extern struct {
-    openFn: OpenFn,
     readFn: ?ReadFn,
     writeFn: ?WriteFn,
     closeFn: ?CloseFn,
     initializer: ?*anyopaque,
 
-    pub const OpenFn = *allowzero const fn (initializer: ?*anyopaque, pid: u16) callconv(.C) sysexchange.Result(*anyopaque);
-    pub const ReadFn = *const fn (context: *anyopaque, ptr: [*]u8, len: usize) callconv(.C) sysexchange.Result(usize);
-    pub const WriteFn = *const fn (context: *anyopaque, ptr: [*]const u8, len: usize) callconv(.C) sysexchange.Result(usize);
-    pub const CloseFn = *const fn (context: *anyopaque) callconv(.C) void;
+    pub const ReadFn = *const fn (context: *FileContext, ptr: [*]u8, len: usize) callconv(.C) sysexchange.Result(usize);
+    pub const WriteFn = *const fn (context: *FileContext, ptr: [*]const u8, len: usize) callconv(.C) sysexchange.Result(usize);
+    pub const CloseFn = *const fn (context: *FileContext) callconv(.C) void;
 };
 
 // A hook is a resource that invokes raw driver callbacks when interacted with.
@@ -92,7 +90,7 @@ pub const DirHook = extern struct {
 };
 
 pub const FileContext = extern struct {
-    inner: *allowzero anyopaque,
+    inner: ?*anyopaque,
 };
 
 pub const ResourceKind = enum(u32) {
@@ -185,10 +183,19 @@ pub const ResourceDescriptor = struct {
     pub fn init(allocator: Allocator, inode: *Inode) !ResourceDescriptor {
         inode.refs = std.math.add(usize, inode.refs, 1) catch return Error.TooManyReferences;
 
-        const context = if (inode.resource.tag == .file) try allocator.create(FileContext) else null;
+        if (inode.resource.tag == .file) {
+            const context = try allocator.create(FileContext);
+            context.inner = inode.resource.data.file.initializer;
+
+            return .{
+                .inode = inode,
+                .context = context,
+            };
+        }
+
         return .{
             .inode = inode,
-            .context = context,
+            .context = null,
         };
     }