Implement GPT support

Author: bnuuydev

README.md

@@ -109,7 +109,23 @@ A complete list can be [found on Wikipedia](https://en.wikipedia.org/wiki/Partit
 ### GPT Partition Table (`gpt-part`)
 
 ```plain
+gpt-part
+    [disk-id <guid>] # optional, random guid used
+    [part <…>] # partition 1
+    [part <…>] # partition 2
+    […] # up to 128 partitions total
+endgpt
+```
 
+```plain
+part
+    type <type-id|guid>
+    [part-id <guid>] # optional, random guid used
+    [size <bytes>]
+    [offset <bytes>]
+    [name <string>]
+    contains <content>
+endpart
 ```
 
 ### FAT File System (`vfat`)

src/BuildInterface.zig

@@ -152,6 +152,40 @@ const ContentWriter = struct {
                 }
             },
 
+            .gpt_part_table => |data| {
+                try cw.code.writeAll("gpt-part\n");
+
+                for (data.partitions) |part| {
+                    try cw.code.writeAll("  part\n");
+                    try cw.code.writeAll("    type ");
+                    switch (part.type) {
+                        .name => |name| {
+                            try cw.code.writeAll(@tagName(name));
+                        },
+                        .guid => |guid_text| {
+                            try cw.code.writeAll(&guid_text);
+                        },
+                    }
+                    try cw.code.writeByte('\n');
+
+                    if (part.name) |name| {
+                        try cw.code.print("    name {s}\n", .{name});
+                    }
+                    if (part.offset) |offset| {
+                        try cw.code.print("    offset {d}\n", .{offset});
+                    }
+                    if (part.size) |size| {
+                        try cw.code.print("    size {d}\n", .{size});
+                    }
+                    try cw.code.writeAll("    contains");
+                    try cw.render(part.data);
+                    try cw.code.writeAll("\n");
+                    try cw.code.writeAll("  endpart\n");
+                }
+
+                try cw.code.writeAll("endgpt");
+            },
+
             .vfat => |data| {
                 try cw.code.print("vfat {s}\n", .{
                     @tagName(data.format),
@@ -291,6 +325,7 @@ pub const Content = union(enum) {
     fill: u8,
     paste_file: std.Build.LazyPath,
     mbr_part_table: MbrPartTable,
+    gpt_part_table: GptPartTable,
     vfat: FatFs,
 };
 
@@ -317,6 +352,24 @@ pub const MbrPartTable = struct {
     };
 };
 
+pub const GptPartTable = struct {
+    partitions: []const Partition,
+
+    pub const Partition = struct {
+        type: union(enum) {
+            name: enum {
+                unused,
+                @"efi-system",
+            },
+            guid: [36]u8,
+        },
+        name: ?[]const u8 = null,
+        size: ?u64 = null,
+        offset: ?u64 = null,
+        data: Content,
+    };
+};
+
 pub const FatFs = struct {
     format: enum {
         fat12,