refactor(mmap): change from posix.mmap to Io.File.MemoryMap

Author: Gaweringo

assets/src/01-02.zig

@@ -3,11 +3,6 @@ const std = @import("std");
 const filename = "/tmp/zig-cookbook-01-02.txt";
 
 pub fn main(init: std.process.Init) !void {
-    if (.windows == @import("builtin").os.tag) {
-        std.debug.print("MMap is not supported in Windows\n", .{});
-        return;
-    }
-
     const io = init.io;
     const file = try std.Io.Dir.cwd().createFile(io, filename, .{
         .read = true,
@@ -17,25 +12,22 @@ pub fn main(init: std.process.Init) !void {
     defer file.close(io);
     const content_to_write = "hello zig cookbook";
 
-    // Before mmap, we need to ensure file isn't empty
+    // Before mapping the memory, we need to ensure file isn't empty
     try file.setLength(io, content_to_write.len);
 
-    const md = try file.stat(io);
-    try std.testing.expectEqual(md.size, content_to_write.len);
+    const length = try file.length(io);
+    try std.testing.expectEqual(length, content_to_write.len);
 
-    const ptr = try std.posix.mmap(
-        null,
-        content_to_write.len,
-        .{ .READ = true, .WRITE = true },
-        .{ .TYPE = .SHARED },
-        file.handle,
-        0,
-    );
-    defer std.posix.munmap(ptr);
+    var mm = try file.createMemoryMap(io, .{ .len = content_to_write.len });
+    defer mm.destroy(io);
 
-    // Write file via mmap
-    std.mem.copyForwards(u8, ptr, content_to_write);
+    // Write file via mapped memory
+    std.mem.copyForwards(u8, mm.memory, content_to_write);
+    // Synchronize the mapped memory with the file (store it to the file)
+    try mm.write(io);
 
-    // Read file via mmap
-    try std.testing.expectEqualStrings(content_to_write, ptr);
+    // Synchronize memory with contents of file
+    try mm.read(io);
+    // Read via mapped memory
+    try std.testing.expectEqualStrings(content_to_write, mm.memory);
 }

src/en-US/01-02-mmap-file.smd

@@ -5,6 +5,12 @@
 .layout = "section.shtml",
 ---
 
-Creates a memory map of a file using [mmap](https://man7.org/linux/man-pages/man2/mmap.2.html) and simulates some non-sequential reads from the file. Using a memory map means you just index into a slice rather than having to deal with seek to navigate a file.
+Creates a memory map of a file and simulates some non-sequential reads from the file. Using a memory
+map means you just index into a slice rather than having to deal with seek to navigate a file.
+
+This uses [NtCreateSection](https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntifs/nf-ntifs-ntcreatesection)
+and [NtMapViewOfSection](https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/nf-wdm-zwmapviewofsection)
+on Windows, and [mmap](https://man7.org/linux/man-pages/man2/mmap.2.html) on other operating
+systems that support it (When using [`std.Io.Threaded`](https://codeberg.org/ziglang/zig/src/commit/9908b10d928a12731a288bd59068151d386efdac/lib/std/Io/Threaded.zig#L18222-L18355)).
 
 []($code.siteAsset('src/01-02.zig').language('zig'))