introduce std.event.fs for async file system functions

only works on linux so far

3 files changed, 59 insertions, 22 deletions

diff --git a/std/os/file.zig b/std/os/file.zig
index 6998ba00d1..c402aa0522 100644
--- a/std/os/file.zig
+++ b/std/os/file.zig
@@ -15,10 +15,21 @@ pub const File = struct {
     /// The OS-specific file descriptor or file handle.
     handle: os.FileHandle,
 
+    pub const Mode = switch (builtin.os) {
+        Os.windows => void,
+        else => u32,
+    };
+
+    pub const default_mode = switch (builtin.os) {
+        Os.windows => {},
+        else => 0o666,
+    };
+
     pub const OpenError = os.WindowsOpenError || os.PosixOpenError;
 
     /// `path` needs to be copied in memory to add a null terminating byte, hence the allocator.
     /// Call close to clean up.
+    /// TODO deprecated, just use open
     pub fn openRead(allocator: *mem.Allocator, path: []const u8) OpenError!File {
         if (is_posix) {
             const flags = posix.O_LARGEFILE | posix.O_RDONLY;
@@ -39,16 +50,18 @@ pub const File = struct {
         }
     }
 
-    /// Calls `openWriteMode` with os.default_file_mode for the mode.
+    /// Calls `openWriteMode` with os.File.default_mode for the mode.
+    /// TODO deprecated, just use open
     pub fn openWrite(allocator: *mem.Allocator, path: []const u8) OpenError!File {
-        return openWriteMode(allocator, path, os.default_file_mode);
+        return openWriteMode(allocator, path, os.File.default_mode);
     }
 
     /// If the path does not exist it will be created.
     /// If a file already exists in the destination it will be truncated.
     /// `path` needs to be copied in memory to add a null terminating byte, hence the allocator.
     /// Call close to clean up.
-    pub fn openWriteMode(allocator: *mem.Allocator, path: []const u8, file_mode: os.FileMode) OpenError!File {
+    /// TODO deprecated, just use open
+    pub fn openWriteMode(allocator: *mem.Allocator, path: []const u8, file_mode: Mode) OpenError!File {
         if (is_posix) {
             const flags = posix.O_LARGEFILE | posix.O_WRONLY | posix.O_CREAT | posix.O_CLOEXEC | posix.O_TRUNC;
             const fd = try os.posixOpen(allocator, path, flags, file_mode);
@@ -72,7 +85,8 @@ pub const File = struct {
     /// If a file already exists in the destination this returns OpenError.PathAlreadyExists
     /// `path` needs to be copied in memory to add a null terminating byte, hence the allocator.
     /// Call close to clean up.
-    pub fn openWriteNoClobber(allocator: *mem.Allocator, path: []const u8, file_mode: os.FileMode) OpenError!File {
+    /// TODO deprecated, just use open
+    pub fn openWriteNoClobber(allocator: *mem.Allocator, path: []const u8, file_mode: Mode) OpenError!File {
         if (is_posix) {
             const flags = posix.O_LARGEFILE | posix.O_WRONLY | posix.O_CREAT | posix.O_CLOEXEC | posix.O_EXCL;
             const fd = try os.posixOpen(allocator, path, flags, file_mode);
@@ -282,7 +296,7 @@ pub const File = struct {
         Unexpected,
     };
 
-    pub fn mode(self: *File) ModeError!os.FileMode {
+    pub fn mode(self: *File) ModeError!Mode {
         if (is_posix) {
             var stat: posix.Stat = undefined;
             const err = posix.getErrno(posix.fstat(self.handle, &stat));
@@ -296,7 +310,7 @@ pub const File = struct {
 
             // TODO: we should be able to cast u16 to ModeError!u32, making this
             // explicit cast not necessary
-            return os.FileMode(stat.mode);
+            return Mode(stat.mode);
         } else if (is_windows) {
             return {};
         } else {
@@ -305,9 +319,11 @@ pub const File = struct {
     }
 
     pub const ReadError = error{
-        BadFd,
-        Io,
+        FileClosed,
+        InputOutput,
         IsDir,
+        WouldBlock,
+        SystemResources,
 
         Unexpected,
     };
@@ -323,9 +339,12 @@ pub const File = struct {
                         posix.EINTR => continue,
                         posix.EINVAL => unreachable,
                         posix.EFAULT => unreachable,
-                        posix.EBADF => return error.BadFd,
-                        posix.EIO => return error.Io,
+                        posix.EAGAIN => return error.WouldBlock,
+                        posix.EBADF => return error.FileClosed,
+                        posix.EIO => return error.InputOutput,
                         posix.EISDIR => return error.IsDir,
+                        posix.ENOBUFS => return error.SystemResources,
+                        posix.ENOMEM => return error.SystemResources,
                         else => return os.unexpectedErrorPosix(read_err),
                     }
                 }
diff --git a/std/os/index.zig b/std/os/index.zig
index 77fd2a78ad..727c71c435 100644
--- a/std/os/index.zig
+++ b/std/os/index.zig
@@ -38,16 +38,6 @@ pub const path = @import("path.zig");
 pub const File = @import("file.zig").File;
 pub const time = @import("time.zig");
 
-pub const FileMode = switch (builtin.os) {
-    Os.windows => void,
-    else => u32,
-};
-
-pub const default_file_mode = switch (builtin.os) {
-    Os.windows => {},
-    else => 0o666,
-};
-
 pub const page_size = 4 * 1024;
 
 pub const UserInfo = @import("get_user_id.zig").UserInfo;
@@ -256,6 +246,26 @@ pub fn posixRead(fd: i32, buf: []u8) !void {
     }
 }
 
+pub fn posix_preadv(fd: i32, iov: [*]const posix.iovec, count: usize, offset: u64) !usize {
+    while (true) {
+        const rc = posix.preadv(fd, iov, count, offset);
+        const err = posix.getErrno(rc);
+        switch (err) {
+            0 => return rc,
+            posix.EINTR => continue,
+            posix.EINVAL => unreachable,
+            posix.EFAULT => unreachable,
+            posix.EAGAIN => return error.WouldBlock,
+            posix.EBADF => return error.FileClosed,
+            posix.EIO => return error.InputOutput,
+            posix.EISDIR => return error.IsDir,
+            posix.ENOBUFS => return error.SystemResources,
+            posix.ENOMEM => return error.SystemResources,
+            else => return unexpectedErrorPosix(err),
+        }
+    }
+}
+
 pub const PosixWriteError = error{
     WouldBlock,
     FileClosed,
@@ -853,7 +863,7 @@ pub fn copyFile(allocator: *Allocator, source_path: []const u8, dest_path: []con
 /// Guaranteed to be atomic. However until https://patchwork.kernel.org/patch/9636735/ is
 /// merged and readily available,
 /// there is a possibility of power loss or application termination leaving temporary files present
-pub fn copyFileMode(allocator: *Allocator, source_path: []const u8, dest_path: []const u8, mode: FileMode) !void {
+pub fn copyFileMode(allocator: *Allocator, source_path: []const u8, dest_path: []const u8, mode: File.Mode) !void {
     var in_file = try os.File.openRead(allocator, source_path);
     defer in_file.close();
 
@@ -879,7 +889,7 @@ pub const AtomicFile = struct {
 
     /// dest_path must remain valid for the lifetime of AtomicFile
     /// call finish to atomically replace dest_path with contents
-    pub fn init(allocator: *Allocator, dest_path: []const u8, mode: FileMode) !AtomicFile {
+    pub fn init(allocator: *Allocator, dest_path: []const u8, mode: File.Mode) !AtomicFile {
         const dirname = os.path.dirname(dest_path);
 
         var rand_buf: [12]u8 = undefined;
diff --git a/std/os/linux/index.zig b/std/os/linux/index.zig
index 69bc30bad0..cf68e03ff0 100644
--- a/std/os/linux/index.zig
+++ b/std/os/linux/index.zig
@@ -692,6 +692,10 @@ pub fn futex_wait(uaddr: usize, futex_op: u32, val: i32, timeout: ?*timespec) us
     return syscall4(SYS_futex, uaddr, futex_op, @bitCast(u32, val), @ptrToInt(timeout));
 }
 
+pub fn futex_wake(uaddr: usize, futex_op: u32, val: i32) usize {
+    return syscall3(SYS_futex, uaddr, futex_op, @bitCast(u32, val));
+}
+
 pub fn getcwd(buf: [*]u8, size: usize) usize {
     return syscall2(SYS_getcwd, @ptrToInt(buf), size);
 }
@@ -742,6 +746,10 @@ pub fn read(fd: i32, buf: [*]u8, count: usize) usize {
     return syscall3(SYS_read, @intCast(usize, fd), @ptrToInt(buf), count);
 }
 
+pub fn preadv(fd: i32, iov: [*]const iovec, count: usize, offset: u64) usize {
+    return syscall4(SYS_preadv, @intCast(usize, fd), @ptrToInt(iov), count, offset);
+}
+
 // TODO https://github.com/ziglang/zig/issues/265
 pub fn rmdir(path: [*]const u8) usize {
     return syscall1(SYS_rmdir, @ptrToInt(path));