rtl: add read_struct

src/rtl/mem.zig

@@ -0,0 +1,32 @@
+const std = @import("std");
+
+/// Read an extern or packed struct's fields with a given endianness from a byte
+/// slice.
+pub fn read_struct(
+    comptime T: type,
+    bytes: []const u8,
+    comptime endian: std.lang.Endian,
+) T {
+    comptime {
+        const info = @typeInfo(T);
+        if (info != .@"struct" or
+            (info.@"struct".layout != .@"extern" and
+                info.@"struct".layout != .@"packed"))
+        {
+            @compileError("Type must be an 'extern' or 'packed' struct.");
+        }
+    }
+
+    var result: T = undefined;
+    const str = @typeInfo(T).@"struct";
+
+    inline for (str.field_names, str.field_types) |name, ftype| {
+        const offset = @offsetOf(T, name);
+        const size = @sizeOf(ftype);
+        const field_bytes = bytes[offset .. offset + size];
+
+        @field(result, name) = std.mem.readInt(ftype, field_bytes, endian);
+    }
+
+    return result;
+}

src/rtl/root.zig

@@ -18,6 +18,7 @@ pub const AtomicBitmapType = @import("bitmap.zig").AtomicBitmapType;
 pub const HandoffList = @import("handoff.zig").HandoffList;
 pub const LinkerSetType = @import("linker_set.zig").LinkerSetType;
 pub const CachePaddedType = @import("cache_padded.zig").CachePaddedType;
+pub const mem = @import("mem.zig");
 
 pub fn comptime_error(comptime msg: []const u8, args: anytype) void {
     @compileError(std.fmt.comptimePrint(msg, args));