add tests for leb128 library (#486)

add tests for containers.leb128

also fix a bug in fix zigzag decoding

src/leb128/containers_leb128.ml

@@ -60,7 +60,7 @@ module Decode = struct
     Int64.to_int v, n_consumed
 
   let[@inline] decode_zigzag (v : int64) : int64 =
-    Int64.(logxor (shift_right v 1) (neg (logand v Int64.one)))
+    Int64.(logxor (shift_right_logical v 1) (sub 0L (logand v 1L)))
 
   let[@inline] i64 sl off : int64 * int =
     let v, n_consumed = u64 sl off in

tests/leb128/dune

@@ -0,0 +1,11 @@
+(executable
+ (name t_leb128)
+ (modules t_leb128)
+ (libraries containers containers.leb128 containers_testlib))
+
+(rule
+ (alias runtest)
+ (deps t_leb128.exe)
+ (package containers)
+ (action
+  (run ./t_leb128.exe)))

tests/leb128/t_leb128.ml

@@ -0,0 +1,230 @@
+include (val Containers_testlib.make ~__FILE__ ())
+module Leb128 = Containers_leb128
+module Buf = CCByte_buffer
+module Slice = CCByte_slice
+
+let encode_decode_u64 (i : int64) : bool =
+  let buf = Buf.create () in
+  Leb128.Encode.u64 buf i;
+  let slice = Buf.to_slice buf in
+  let i', n = Leb128.Decode.u64 slice 0 in
+  Int64.equal i i' && n = Slice.len slice
+
+let encode_decode_i64 (i : int64) : bool =
+  let buf = Buf.create () in
+  Leb128.Encode.i64 buf i;
+  let slice = Buf.to_slice buf in
+  let i', n = Leb128.Decode.i64 slice 0 in
+  Int64.equal i i' && n = Slice.len slice
+
+let encode_decode_uint (i : int) : bool =
+  i >= 0
+  &&
+  let buf = Buf.create () in
+  Leb128.Encode.uint buf i;
+  let slice = Buf.to_slice buf in
+  let i', n = Leb128.Decode.uint_truncate slice 0 in
+  Int.equal i i' && n = Slice.len slice
+
+let encode_decode_int (i : int) : bool =
+  let buf = Buf.create () in
+  Leb128.Encode.int buf i;
+  let slice = Buf.to_slice buf in
+  let i', n = Leb128.Decode.int_truncate slice 0 in
+  Int.equal i i' && n = Slice.len slice
+
+let zigzag_roundtrip (i : int64) : bool =
+  let encoded = Leb128.Encode.encode_zigzag i in
+  let decoded = Leb128.Decode.decode_zigzag encoded in
+  Int64.equal i decoded
+;;
+
+q ~count:10_000 ~long_factor:20 Q.int64 @@ fun i ->
+if not (encode_decode_u64 (Int64.abs i)) then
+  Q.Test.fail_reportf "u64 roundtrip failed for %Ld" i;
+true
+;;
+
+q ~count:10_000 ~long_factor:20 Q.int64 @@ fun i ->
+if not (encode_decode_i64 i) then
+  Q.Test.fail_reportf "i64 roundtrip failed for %Ld" i;
+true
+;;
+
+q ~count:10_000 ~long_factor:20 Q.int @@ fun i ->
+(* make sure [i] is non negative *)
+let i = max 0 (abs i) in
+if not (encode_decode_uint i) then
+  Q.Test.fail_reportf "uint roundtrip failed for %d" i;
+true
+;;
+
+q ~count:10_000 ~long_factor:20 Q.int @@ fun i ->
+if not (encode_decode_int i) then
+  Q.Test.fail_reportf "int roundtrip failed for %d" i;
+true
+;;
+
+q ~count:10_000 ~long_factor:20 Q.int64 @@ fun i ->
+if not (zigzag_roundtrip i) then
+  Q.Test.fail_reportf "zigzag roundtrip failed for %Ld" i;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.u64 buf 0L;
+let slice = Buf.to_slice buf in
+let v, n = Leb128.Decode.u64 slice 0 in
+assert_equal ~printer:Int64.to_string 0L v;
+assert_equal ~printer:string_of_int 1 n;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.u64 buf 127L;
+let slice = Buf.to_slice buf in
+let v, n = Leb128.Decode.u64 slice 0 in
+assert_equal ~printer:Int64.to_string 127L v;
+assert_equal ~printer:string_of_int 1 n;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.u64 buf 128L;
+let slice = Buf.to_slice buf in
+let v, n = Leb128.Decode.u64 slice 0 in
+assert_equal ~printer:Int64.to_string 128L v;
+assert_equal ~printer:string_of_int 2 n;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.u64 buf 16383L;
+let slice = Buf.to_slice buf in
+let v, n = Leb128.Decode.u64 slice 0 in
+assert_equal ~printer:Int64.to_string 16383L v;
+assert_equal ~printer:string_of_int 2 n;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.u64 buf 16384L;
+let slice = Buf.to_slice buf in
+let v, n = Leb128.Decode.u64 slice 0 in
+assert_equal ~printer:Int64.to_string 16384L v;
+assert_equal ~printer:string_of_int 3 n;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.i64 buf 0L;
+let slice = Buf.to_slice buf in
+let v, n = Leb128.Decode.i64 slice 0 in
+assert_equal ~printer:Int64.to_string 0L v;
+assert_equal ~printer:string_of_int 1 n;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.u64 buf 127L;
+Leb128.Encode.u64 buf 16384L;
+Leb128.Encode.u64 buf 300L;
+let slice = Buf.to_slice buf in
+let n1 = Leb128.Decode.skip slice 0 in
+let n2 = Leb128.Decode.skip slice n1 in
+let n3 = Leb128.Decode.skip slice (n1 + n2) in
+assert_equal ~printer:string_of_int 1 n1;
+assert_equal ~printer:string_of_int 3 n2;
+assert_equal ~printer:string_of_int 2 n3;
+assert_equal ~printer:string_of_int 6 (n1 + n2 + n3);
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.i64 buf (-1L);
+let slice = Buf.to_slice buf in
+let v, n = Leb128.Decode.i64 slice 0 in
+assert_equal ~printer:Int64.to_string (-1L) v;
+assert_equal ~printer:string_of_int 1 n;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.i64 buf 63L;
+let slice = Buf.to_slice buf in
+let v, n = Leb128.Decode.i64 slice 0 in
+assert_equal ~printer:Int64.to_string 63L v;
+assert_equal ~printer:string_of_int 1 n;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.i64 buf (-64L);
+let slice = Buf.to_slice buf in
+let v, n = Leb128.Decode.i64 slice 0 in
+assert_equal ~printer:Int64.to_string (-64L) v;
+assert_equal ~printer:string_of_int 1 n;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.i64 buf 64L;
+let slice = Buf.to_slice buf in
+let v, n = Leb128.Decode.i64 slice 0 in
+assert_equal ~printer:Int64.to_string 64L v;
+assert_equal ~printer:string_of_int 2 n;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.i64 buf (-65L);
+let slice = Buf.to_slice buf in
+let v, n = Leb128.Decode.i64 slice 0 in
+assert_equal ~printer:Int64.to_string (-65L) v;
+assert_equal ~printer:string_of_int 2 n;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.i64 buf Int64.min_int;
+let slice = Buf.to_slice buf in
+let v, _n = Leb128.Decode.i64 slice 0 in
+assert_equal ~printer:Int64.to_string Int64.min_int v;
+true
+;;
+
+let buf = Buf.create () in
+Leb128.Encode.i64 buf Int64.max_int;
+let slice = Buf.to_slice buf in
+let v, _n = Leb128.Decode.i64 slice 0 in
+assert_equal ~printer:Int64.to_string Int64.max_int v;
+true
+;;
+
+t @@ fun () ->
+let buf = Buf.create () in
+Leb128.Encode.u64 buf 300L;
+Leb128.Encode.u64 buf 500L;
+let slice = Buf.to_slice buf in
+let v1, n1 = Leb128.Decode.u64 slice 0 in
+let v2, n2 = Leb128.Decode.u64 slice n1 in
+assert_equal ~printer:Int64.to_string 300L v1;
+assert_equal ~printer:Int64.to_string 500L v2;
+assert_equal ~printer:string_of_int 2 n1;
+assert_equal ~printer:string_of_int 2 n2;
+true
+
+let () = Containers_testlib.run_all ~descr:"test leb128" [ get () ]