From 33fdc43714e34f5c4bc02c416ef4c6534acc56ca Mon Sep 17 00:00:00 2001
From: Ryan Liptak <squeek502@hotmail.com>
Date: Thu, 13 Oct 2022 22:18:35 -0700
Subject: [PATCH] std.fs: Add MAX_NAME_BYTES

Also add some NAME_MAX or equivalent definitions where necessary
---
 lib/std/c/darwin.zig    |  1 +
 lib/std/c/dragonfly.zig |  1 +
 lib/std/c/haiku.zig     |  2 ++
 lib/std/fs.zig          | 17 +++++++++++++++++
 lib/std/os/windows.zig  |  6 ++++++
 5 files changed, 27 insertions(+)

diff --git a/lib/std/c/darwin.zig b/lib/std/c/darwin.zig
index 0dfe7a2500..17a4957e94 100644
--- a/lib/std/c/darwin.zig
+++ b/lib/std/c/darwin.zig
@@ -1014,6 +1014,7 @@ pub const vm_machine_attribute_val_t = isize;
 pub const CALENDAR_CLOCK = 1;
 
 pub const PATH_MAX = 1024;
+pub const NAME_MAX = 255;
 pub const IOV_MAX = 16;
 
 pub const STDIN_FILENO = 0;
diff --git a/lib/std/c/dragonfly.zig b/lib/std/c/dragonfly.zig
index 35436d7017..ddc0db2709 100644
--- a/lib/std/c/dragonfly.zig
+++ b/lib/std/c/dragonfly.zig
@@ -234,6 +234,7 @@ pub const SA = struct {
 };
 
 pub const PATH_MAX = 1024;
+pub const NAME_MAX = 255;
 pub const IOV_MAX = KERN.IOV_MAX;
 
 pub const ino_t = c_ulong;
diff --git a/lib/std/c/haiku.zig b/lib/std/c/haiku.zig
index ba7e55ccb1..300dc9076c 100644
--- a/lib/std/c/haiku.zig
+++ b/lib/std/c/haiku.zig
@@ -266,6 +266,7 @@ pub const area_info = extern struct {
 };
 
 pub const MAXPATHLEN = PATH_MAX;
+pub const MAXNAMLEN = NAME_MAX;
 
 pub const image_info = extern struct {
     id: u32,
@@ -371,6 +372,7 @@ pub const KERN = struct {};
 pub const IOV_MAX = 1024;
 
 pub const PATH_MAX = 1024;
+pub const NAME_MAX = 256;
 
 pub const STDIN_FILENO = 0;
 pub const STDOUT_FILENO = 1;
diff --git a/lib/std/fs.zig b/lib/std/fs.zig
index dfadb144eb..208f456184 100644
--- a/lib/std/fs.zig
+++ b/lib/std/fs.zig
@@ -48,6 +48,23 @@ pub const MAX_PATH_BYTES = switch (builtin.os.tag) {
         @compileError("PATH_MAX not implemented for " ++ @tagName(builtin.os.tag)),
 };
 
+/// This represents the maximum size of a UTF-8 encoded file name component that the
+/// operating system will accept. All file name components returned by file system
+/// operations are assumed to fit into a UTF-8 encoded array of this length.
+/// The byte count does not include a null sentinel byte.
+pub const MAX_NAME_BYTES = switch (builtin.os.tag) {
+    .linux, .macos, .ios, .freebsd, .dragonfly, .haiku => os.NAME_MAX,
+    .netbsd, .openbsd, .solaris => os.MAXNAMLEN,
+    // Each UTF-16LE character may be expanded to 3 UTF-8 bytes.
+    // If it would require 4 UTF-8 bytes, then there would be a surrogate
+    // pair in the UTF-16LE, and we (over)account 3 bytes for it that way.
+    .windows => os.NAME_MAX * 3,
+    else => if (@hasDecl(root, "os") and @hasDecl(root.os, "NAME_MAX"))
+        root.os.NAME_MAX
+    else
+        @compileError("NAME_MAX not implemented for " ++ @tagName(builtin.os.tag)),
+};
+
 pub const base64_alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_".*;
 
 /// Base64 encoder, replacing the standard `+/` with `-_` so that it can be used in a file name on any filesystem.
diff --git a/lib/std/os/windows.zig b/lib/std/os/windows.zig
index d68a66ed87..7bed48a2bf 100644
--- a/lib/std/os/windows.zig
+++ b/lib/std/os/windows.zig
@@ -2977,6 +2977,12 @@ pub const PMEMORY_BASIC_INFORMATION = *MEMORY_BASIC_INFORMATION;
 /// from https://docs.microsoft.com/en-us/windows/desktop/FileIO/naming-a-file#maximum-path-length-limitation
 pub const PATH_MAX_WIDE = 32767;
 
+/// > [Each file name component can be] up to the value returned in the
+/// > lpMaximumComponentLength parameter of the GetVolumeInformation function
+/// > (this value is commonly 255 characters)
+/// from https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation
+pub const NAME_MAX = 255;
+
 pub const FORMAT_MESSAGE_ALLOCATE_BUFFER = 0x00000100;
 pub const FORMAT_MESSAGE_ARGUMENT_ARRAY = 0x00002000;
 pub const FORMAT_MESSAGE_FROM_HMODULE = 0x00000800;