feat(tvix/nar): init writer r/5428

Change-Id: I101f35840cb14c58af708c91e59f997f6d167f75
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7505
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Autosubmit: tazjin <tazjin@tvl.su>

1 files changed, 46 insertions, 0 deletions

diff --git a/tvix/nar/src/wire.rs b/tvix/nar/src/wire.rs
new file mode 100644
index 000000000000..98581ae3aa7c
--- /dev/null
+++ b/tvix/nar/src/wire.rs
@@ -0,0 +1,46 @@
+pub const MAX_NAME_LEN: usize = 255;
+pub const MAX_TARGET_LEN: usize = 4095;
+
+#[cfg(test)]
+fn token(xs: &[&str]) -> Vec<u8> {
+    let mut out = vec![];
+    for x in xs {
+        let len = x.len() as u64;
+        out.extend_from_slice(&len.to_le_bytes());
+        out.extend_from_slice(x.as_bytes());
+
+        let n = x.len() & 7;
+        if n != 0 {
+            const ZERO: [u8; 8] = [0; 8];
+            out.extend_from_slice(&ZERO[n..]);
+        }
+    }
+    out
+}
+
+pub const TOK_NAR: [u8; 56] = *b"\x0d\0\0\0\0\0\0\0nix-archive-1\0\0\0\x01\0\0\0\0\0\0\0(\0\0\0\0\0\0\0\x04\0\0\0\0\0\0\0type\0\0\0\0";
+pub const TOK_REG: [u8; 32] = *b"\x07\0\0\0\0\0\0\0regular\0\x08\0\0\0\0\0\0\0contents";
+pub const TOK_EXE: [u8; 64] = *b"\x07\0\0\0\0\0\0\0regular\0\x0a\0\0\0\0\0\0\0executable\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x08\0\0\0\0\0\0\0contents";
+pub const TOK_SYM: [u8; 32] = *b"\x07\0\0\0\0\0\0\0symlink\0\x06\0\0\0\0\0\0\0target\0\0";
+pub const TOK_DIR: [u8; 24] = *b"\x09\0\0\0\0\0\0\0directory\0\0\0\0\0\0\0";
+pub const TOK_ENT: [u8; 48] = *b"\x05\0\0\0\0\0\0\0entry\0\0\0\x01\0\0\0\0\0\0\0(\0\0\0\0\0\0\0\x04\0\0\0\0\0\0\0name\0\0\0\0";
+pub const TOK_NOD: [u8; 48] = *b"\x04\0\0\0\0\0\0\0node\0\0\0\0\x01\0\0\0\0\0\0\0(\0\0\0\0\0\0\0\x04\0\0\0\0\0\0\0type\0\0\0\0";
+pub const TOK_PAR: [u8; 16] = *b"\x01\0\0\0\0\0\0\0)\0\0\0\0\0\0\0";
+
+#[test]
+fn tokens() {
+    let cases: &[(&[u8], &[&str])] = &[
+        (&TOK_NAR, &["nix-archive-1", "(", "type"]),
+        (&TOK_REG, &["regular", "contents"]),
+        (&TOK_EXE, &["regular", "executable", "", "contents"]),
+        (&TOK_SYM, &["symlink", "target"]),
+        (&TOK_DIR, &["directory"]),
+        (&TOK_ENT, &["entry", "(", "name"]),
+        (&TOK_NOD, &["node", "(", "type"]),
+        (&TOK_PAR, &[")"]),
+    ];
+
+    for &(tok, xs) in cases {
+        assert_eq!(tok, token(xs));
+    }
+}