feat(users/sterni/nix): add sternis nix lib r/2257

What you see here is mostly the fallout of me implementing a correct
urlencode implementation in nix for Profpatsch's blog implementation
(although they'll probably keep it at arm's length).

Where I want to go from here:

* Extend this library towards general purpose nix™, mainly by
  implementing missing interfaces which you'd still have to use
  <nixpkgs/lib> for right now. Reexposing parts of <nixpkgs/lib>
  with better naming is fine for now, at some point I'd contemplate
  making this depend on nothing outside of depot, maybe even itself
  (should be easy we only use yants for an easily replaceable check).

* Improve error messages possibly by carefully reintroducing yants. I
  originally typed essentially everything using yants, but turns out
  this can a) be dangerous when stuff you are handling throws because
  type checking means evaluating and b) has a incredible performance
  cost in some cases.

* Reexpose builtins with better naming and slightly wrapped so they
  don't unrecoverably throw in cases where a null or something would
  suffice.

Change-Id: I33ab08ca4e62dbc16b86c66c653935686e6b0e79
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2541
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: Profpatsch <mail@profpatsch.de>
Tested-by: BuildkiteCI

1 files changed, 204 insertions, 0 deletions

diff --git a/users/sterni/nix/int/tests/default.nix b/users/sterni/nix/int/tests/default.nix
new file mode 100644
index 000000000000..966ac5a1289e
--- /dev/null
+++ b/users/sterni/nix/int/tests/default.nix
@@ -0,0 +1,204 @@
+{ depot, lib, ... }:
+
+let
+
+  inherit (depot.nix.runTestsuite)
+    runTestsuite
+    it
+    assertEq
+    ;
+
+  inherit (depot.users.sterni.nix)
+    int
+    string
+    fun
+    flow
+    ;
+
+  testBounds = it "checks minBound and maxBound" [
+    # this is gonna blow up in my face because
+    # integer overflow is undefined behavior in
+    # C++, so most likely anything could happen?
+    (assertEq "maxBound is the maxBound" true
+      (int.maxBound + 1 < int.maxBound))
+    (assertEq "minBound is the minBound" true
+      (int.minBound - 1 > int.minBound))
+    (assertEq "maxBound overflows to minBound"
+      (int.maxBound + 1)
+      int.minBound)
+    (assertEq "minBound overflows to maxBound"
+      (int.minBound - 1)
+      int.maxBound)
+  ];
+
+  expectedBytes = [
+    "00" "01" "02" "03" "04" "05" "06" "07" "08" "09" "0A" "0B" "0C" "0D" "0E" "0F"
+    "10" "11" "12" "13" "14" "15" "16" "17" "18" "19" "1A" "1B" "1C" "1D" "1E" "1F"
+    "20" "21" "22" "23" "24" "25" "26" "27" "28" "29" "2A" "2B" "2C" "2D" "2E" "2F"
+    "30" "31" "32" "33" "34" "35" "36" "37" "38" "39" "3A" "3B" "3C" "3D" "3E" "3F"
+    "40" "41" "42" "43" "44" "45" "46" "47" "48" "49" "4A" "4B" "4C" "4D" "4E" "4F"
+    "50" "51" "52" "53" "54" "55" "56" "57" "58" "59" "5A" "5B" "5C" "5D" "5E" "5F"
+    "60" "61" "62" "63" "64" "65" "66" "67" "68" "69" "6A" "6B" "6C" "6D" "6E" "6F"
+    "70" "71" "72" "73" "74" "75" "76" "77" "78" "79" "7A" "7B" "7C" "7D" "7E" "7F"
+    "80" "81" "82" "83" "84" "85" "86" "87" "88" "89" "8A" "8B" "8C" "8D" "8E" "8F"
+    "90" "91" "92" "93" "94" "95" "96" "97" "98" "99" "9A" "9B" "9C" "9D" "9E" "9F"
+    "A0" "A1" "A2" "A3" "A4" "A5" "A6" "A7" "A8" "A9" "AA" "AB" "AC" "AD" "AE" "AF"
+    "B0" "B1" "B2" "B3" "B4" "B5" "B6" "B7" "B8" "B9" "BA" "BB" "BC" "BD" "BE" "BF"
+    "C0" "C1" "C2" "C3" "C4" "C5" "C6" "C7" "C8" "C9" "CA" "CB" "CC" "CD" "CE" "CF"
+    "D0" "D1" "D2" "D3" "D4" "D5" "D6" "D7" "D8" "D9" "DA" "DB" "DC" "DD" "DE" "DF"
+    "E0" "E1" "E2" "E3" "E4" "E5" "E6" "E7" "E8" "E9" "EA" "EB" "EC" "ED" "EE" "EF"
+    "F0" "F1" "F2" "F3" "F4" "F5" "F6" "F7" "F8" "F9" "FA" "FB" "FC" "FD" "FE" "FF"
+  ];
+
+  hexByte = i: string.fit { width = 2; char = "0"; } (int.toHex i);
+
+  hexInts = [
+    { left = 0; right = "0"; }
+    { left = 1; right = "1"; }
+    { left = 11; right = "B"; }
+    { left = 123; right = "7B"; }
+    { left = 9000; right = "2328"; }
+    { left = 2323; right = "913"; }
+    { left = 4096; right = "1000"; }
+    { left = int.maxBound; right = "7FFFFFFFFFFFFFFF"; }
+    { left = int.minBound; right = "-8000000000000000"; }
+  ];
+
+  testHex = it "checks conversion to hex" (lib.flatten [
+    (lib.imap0 (i: hex: [
+      (assertEq "hexByte ${toString i} == ${hex}" (hexByte i) hex)
+      (assertEq "${toString i} == fromHex ${hex}" i (int.fromHex hex))
+    ]) expectedBytes)
+    (builtins.map ({ left, right }: [
+      (assertEq "toHex ${toString left} == ${right}" (int.toHex left) right)
+      (assertEq "${toString left} == fromHex ${right}" left (int.fromHex right))
+    ]) hexInts)
+  ]);
+
+  testBasic = it "checks basic int operations" [
+    (assertEq "122 is even" (int.even 122 && !(int.odd 122)) true)
+    (assertEq "123 is odd" (int.odd 123 && !(int.even 123)) true)
+    (assertEq "abs -4959" (int.abs (-4959)) 4959)
+  ];
+
+  expNumbers = [
+    { left = -3; right = 0.125; }
+    { left = -2; right = 0.25; }
+    { left = -1; right = 0.5; }
+    { left = 0; right = 1; }
+    { left = 1; right = 2; }
+    { left = 2; right = 4; }
+    { left = 3; right = 8; }
+    { left = 4; right = 16; }
+    { left = 5; right = 32; }
+    { left = 16; right = 65536; }
+  ];
+
+  testExp = it "checks exponentiation"
+    (builtins.map ({ left, right }:
+      assertEq
+        "2 ^ ${toString left} == ${toString right}"
+        (int.exp 2 left) right) expNumbers);
+
+  shifts = [
+    { a =   2; b = 5; c =   64; op = "<<"; }
+    { a =  -2; b = 5; c =  -64; op = "<<"; }
+    { a = 123; b = 4; c = 1968; op = "<<"; }
+    { a =   1; b = 8; c =  256; op = "<<"; }
+    { a = 256; b = 8; c =    1; op = ">>"; }
+    { a = 374; b = 2; c =   93; op = ">>"; }
+    { a =   2; b = 2; c =    0; op = ">>"; }
+    { a =  99; b = 9; c =    0; op = ">>"; }
+  ];
+
+  checkShift = { a, b, c, op }@args:
+    let
+      f = flow.match op {
+        "<<" = int.bitShiftL;
+        ">>" = int.bitShiftR;
+      };
+    in assertEq "${toString a} ${op} ${toString b} == ${toString c}" (f a b) c;
+
+  checkShiftRDivExp = n:
+    assertEq "${toString n} >> 5 == ${toString n} / 2 ^ 5"
+      (int.bitShiftR n 5) (int.div n (int.exp 2 5));
+
+  checkShiftLMulExp = n:
+    assertEq "${toString n} >> 6 == ${toString n} * 2 ^ 6"
+      (int.bitShiftL n 5) (int.mul n (int.exp 2 5));
+
+  testBit = it "checks bitwise operations" (lib.flatten [
+    (builtins.map checkShift shifts)
+    (builtins.map checkShiftRDivExp [
+      1
+      2
+      3
+      5
+      7
+      23
+      1623
+      238
+      34
+      348
+      2834
+      834
+      348
+    ])
+    (builtins.map checkShiftLMulExp [
+      1
+      2
+      3
+      5
+      7
+      23
+      384
+      3
+      2
+      5991
+      85109
+      38
+    ])
+  ]);
+
+  divisions = [
+    { a =  2; b =  1; c = 2; mod = 0;}
+    { a =  2; b =  2; c = 1; mod = 0;}
+    { a = 20; b = 10; c = 2; mod = 0;}
+    { a = 12; b =  5; c = 2; mod = 2;}
+    { a = 23; b =  4; c = 5; mod = 3;}
+  ];
+
+  checkDiv = n: { a, b, c, mod }: [
+    (assertEq "${n}: div result" (int.div a b) c)
+    (assertEq "${n}: mod result" (int.mod a b) mod)
+    (assertEq "${n}: divMod law" ((int.div a b) * b + (int.mod a b)) a)
+  ];
+
+  testDivMod = it "checks integer division and modulo"
+    (lib.flatten [
+      (builtins.map (checkDiv "+a / +b") divisions)
+      (builtins.map (fun.rl (checkDiv "-a / +b") (x: x // {
+        a = -x.a;
+        c = -x.c;
+        mod = -x.mod;
+      })) divisions)
+      (builtins.map (fun.rl (checkDiv "+a / -b") (x: x // {
+        b = -x.b;
+        c = -x.c;
+      })) divisions)
+      (builtins.map (fun.rl (checkDiv "-a / -b") (x: x // {
+        a = -x.a;
+        b = -x.b;
+        mod = -x.mod;
+      })) divisions)
+    ]);
+
+in
+  runTestsuite "nix.int" [
+    testBounds
+    testHex
+    testBasic
+    testExp
+    testBit
+    testDivMod
+  ]