Added TLV encoding example in Zig

Author Mitja Felicijan <mitja.felicijan@gmail.com> 2024-09-19 06:25:42 +0200
Committer Mitja Felicijan <mitja.felicijan@gmail.com> 2024-09-19 06:25:42 +0200
Commit 7ceb2589d901a13b8a65df134b5325ef4c6fd6a9 (patch)
-rw-r--r-- README.md 33
-rw-r--r-- zig-tlv-encoding/Makefile 2
-rw-r--r-- zig-tlv-encoding/main.zig 97
3 files changed, 116 insertions, 16 deletions
diff --git a/README.md b/README.md
...
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> also written in the most explicit way and lacks massively when it
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> also written in the most explicit way and lacks massively when it
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> comes to checking of errors etc.
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> comes to checking of errors etc.
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| Example                          | Compiler   | What does it do?                                               |
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| Example                                | Compiler   | What does it do?                                               |
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|----------------------------------|------------|----------------------------------------------------------------|
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|----------------------------------------|------------|----------------------------------------------------------------|
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| [c-asm](./c-asm)                 | clang-17   | Calls a function written in ASM from C code.                   |
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| [c-asm](./c-asm)                       | clang-17   | Calls a function written in ASM from C code.                   |
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| [c-embed](./c-embed)             | clang-17   | Embedding external resources in compiled binary.               |
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| [c-embed](./c-embed)                   | clang-17   | Embedding external resources in compiled binary.               |
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| [c-signals](./c-signals)         | clang-17   | Uses SIGUSR1 and SIGUSR2 as IPC mechanism.                     |
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| [c-signals](./c-signals)               | clang-17   | Uses SIGUSR1 and SIGUSR2 as IPC mechanism.                     |
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| [c-structs](./c-structs)         | clang-17   | Saves and reads structs in/from binary files.                  |
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| [c-structs](./c-structs)               | clang-17   | Saves and reads structs in/from binary files.                  |
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| [zig-c-interop](./zig-c-interop) | zig-0.11.0 | Uses functions written in C from Zig code.                     |
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| [zig-c-interop](./zig-c-interop)       | zig-0.11.0 | Uses functions written in C from Zig code.                     |
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| [zig-ppm](./zig-ppm)             | zig-0.11.0 | Creates an image with random pixels in PPM image format.       |
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| [zig-ppm](./zig-ppm)                   | zig-0.11.0 | Creates an image with random pixels in PPM image format.       |
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| [zig-structs](./zig-structs)     | zig-0.11.0 | Serialization of a struct into JSON and then reading it back.  |
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| [zig-structs](./zig-structs)           | zig-0.11.0 | Serialization of a struct into JSON and then reading it back.  |
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| [zig-telnet](./zig-telnet)       | zig-0.11.0 | Connects to Redis server like it is a basic telnet server.     |
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| [zig-telnet](./zig-telnet)             | zig-0.11.0 | Connects to Redis server like it is a basic telnet server.     |
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| [zig-x11](./zig-x11)             | zig-0.11.0 | Uses X11 to create a basic window without any bindings needed. |
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| [zig-x11](./zig-x11)                   | zig-0.11.0 | Uses X11 to create a basic window without any bindings needed. |
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| [zig-http](./zig-http)           | zig-0.11.0 | Basic example of a HTTP 1.1 server without any routing etc.    |
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| [zig-http](./zig-http)                 | zig-0.11.0 | Basic example of a HTTP 1.1 server without any routing etc.    |
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| [zig-x11-box](./zig-x11-box)     | zig-0.11.0 | Move a box around with arrow keys with Xlib and Zig.           |
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| [zig-x11-box](./zig-x11-box)           | zig-0.11.0 | Move a box around with arrow keys with Xlib and Zig.           |
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| [zig-kv-store](./zig-kv-store)   | zig-0.11.0 | Simple Key-value store that mimics memcached written in Zig.   |
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| [zig-kv-store](./zig-kv-store)         | zig-0.11.0 | Simple Key-value store that mimics memcached written in Zig.   |
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| [zig-wad](./zig-wad)             | zig-0.11.0 | Reads doom.wad and extracts the identification header.         |
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| [zig-wad](./zig-wad)                   | zig-0.11.0 | Reads doom.wad and extracts the identification header.         |
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| [zig-os-props](./zig-os-props)   | zig-0.11.0 | Detects properties of the target operating system.             |
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| [zig-os-props](./zig-os-props)         | zig-0.11.0 | Detects properties of the target operating system.             |
 
  
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| [zig-tlv-encoding](./zig-tlv-encoding) | zig-0.13.0 | Naive implementation of TLV encoding in Zig.                   |
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## License
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## License
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...
diff --git a/zig-tlv-encoding/Makefile b/zig-tlv-encoding/Makefile 
  
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default:
 
  
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	zig test main.zig
diff --git a/zig-tlv-encoding/main.zig b/zig-tlv-encoding/main.zig 
  
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// TLV format: https://devopedia.org/tlv-format
 
  
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// Real world example: https://www.rfc-editor.org/rfc/rfc8609
 
  
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// Cool article: https://www.huy.rocks/everyday/12-11-2022-zig-using-zig-for-advent-of-code
 
  
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// Dummy TLV spec for encoding Linux devicei information
 
  
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//
 
  
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// Packet specification
 
  
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//   1byte    ... Tag
 
  
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//   2bytes   ... Length
 
  
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//   unknown  ... Value
 
  
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//
 
  
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// Available tags: { 0x00 = vendor_name, 0x01 = model_name }
 
  
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// Packet presented as a struct: Packet{ .vendor_name, .model_name }
 
  
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// This assumes that the max value length can be 255.
 
  
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//
 
  
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// Test data from `lsusb` (`lscpu`):
 
  
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// Bus 002 Device 003: ID 046d:086b Logitech, Inc. BRIO 4K Stream Edition
 
  
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// Bus 001 Device 009: ID 3434:0350 Keychron Keychron V5
 
  
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// Bus 001 Device 006: ID 2433:b200 ASETEK [NZXT Kraken X60]
 
  
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// Bus 001 Device 005: ID 046d:c548 Logitech, Inc. Logi Bolt Receiver
 
  
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const std = @import("std");
 
  
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const TLVTag = enum(u8) {
 
  
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    VENDOR_NAME = 0x00,
 
  
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    MODEL_NAME = 0x01,
 
  
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};
 
  
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const TLVPacket = struct {
 
  
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    tag: TLVTag,
 
  
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    length: u8,
 
  
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    value: std.ArrayList(u8),
 
  
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    pub fn printEncoded(self: *TLVPacket) void {
 
  
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        std.debug.print("\t", .{});
 
  
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        std.debug.print("{X:0>2}-", .{@intFromEnum(self.tag)});
 
  
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        std.debug.print("{X:0>2}-", .{self.length});
 
  
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        for (self.value.items) |val| {
 
  
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            std.debug.print("{X:0>2}", .{val});
 
  
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        }
 
  
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        std.debug.print("\n", .{});
 
  
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    }
 
  
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};
 
  
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const TLVPayload = struct {
 
  
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    packets: std.ArrayList(TLVPacket),
 
  
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    allocator: std.mem.Allocator,
 
  
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    pub fn init(allocator: std.mem.Allocator) TLVPayload {
 
  
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        return TLVPayload{
 
  
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            .packets = std.ArrayList(TLVPacket).init(allocator),
 
  
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            .allocator = allocator,
 
  
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        };
 
  
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    }
 
  
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    pub fn deinit(self: *TLVPayload) void {
 
  
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        for (self.packets.items) |*packet| {
 
  
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            packet.value.deinit();
 
  
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        }
 
  
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        self.packets.deinit();
 
  
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    }
 
  
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    pub fn append(self: *TLVPayload, tag: TLVTag, message: []const u8) !void {
 
  
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        var value = try std.ArrayList(u8).initCapacity(self.allocator, message.len);
 
  
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        try value.appendSlice(message);
 
  
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        try self.packets.append(.{
 
  
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            .tag = tag,
 
  
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            .length = @intCast(message.len),
 
  
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            .value = value,
 
  
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        });
 
  
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    }
 
  
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};
 
  
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test "Create TLV payload manually" {
 
  
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    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
 
  
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    defer _ = gpa.deinit();
 
  
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    var payload = TLVPayload.init(gpa.allocator());
 
  
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    defer payload.deinit();
 
  
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    try payload.append(.VENDOR_NAME, "Logitech, Inc.");
 
  
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    try payload.append(.MODEL_NAME, "BRIO 4K Stream Edition");
 
  
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    std.debug.print("Capacity: {d}\n", .{payload.packets.capacity});
 
  
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    for (payload.packets.items) |*packet| {
 
  
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        std.debug.print("Tag: {}, Length: {d}\n", .{ packet.tag, packet.length });
 
  
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        packet.printEncoded();
 
  
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    }
 
  
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}
 
  
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pub fn main() void {
 
  
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    std.debug.print("Use `make test` or `zig test main.zig` instead.\n", .{});
 
  
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}