remove refactor Base.GMP.MPZ.import! from base

rename Base.GMP.MPZ.export! "dynamic" variable from `a`	to `x`,	since it is more in line with comment on L141 in base/gmp.jl

add tests, that	numbers and vectors can be exported and imported correctly and composed import and export is identity

base/gmp.jl

@@ -251,21 +251,21 @@ get_str!(x, a, b::BigInt) = (ccall((:__gmpz_get_str,libgmp), Ptr{Cchar}, (Ptr{Cc
 set_str!(x::BigInt, a, b) = Int(ccall((:__gmpz_set_str, libgmp), Cint, (mpz_t, Ptr{UInt8}, Cint), x, a, b))
 get_d(a::BigInt) = ccall((:__gmpz_get_d, libgmp), Cdouble, (mpz_t,), a)
 
-function export!(a::AbstractVector{T}, n::BigInt; order::Integer=-1, nails::Integer=0, endian::Integer=0) where {T<:Base.BitInteger}
-    stride(a, 1) == 1 || throw(ArgumentError("a must have stride 1"))
+function export!(x::AbstractVector{T}, n::BigInt; order::Integer=-1, nails::Integer=0, endian::Integer=0) where {T<:Base.BitInteger}
+    stride(x, 1) == 1 || throw(ArgumentError("x must have stride 1"))
     ndigits = cld(sizeinbase(n, 2), 8*sizeof(T) - nails)
-    length(a) < ndigits && resize!(a, ndigits)
+    length(x) < ndigits && resize!(x, ndigits)
     count = Ref{Csize_t}()
-    ccall((:__gmpz_export, libgmp), Ptr{T}, (Ptr{T}, Ref{Csize_t}, Cint, Csize_t, Cint, Csize_t, mpz_t),
-        a, count, order, sizeof(T), endian, nails, n)
-    @assert count[] ≤ length(a)
-    return a, Int(count[])
+    ccall((:__gmpz_export, libgmp),
+           Ptr{T},
+           (Ptr{T}, Ref{Csize_t}, Cint, Csize_t, Cint, Csize_t, mpz_t),
+           x, count, order, sizeof(T), endian, nails, n)
+    @assert count[] ≤ length(x)
+    return x, Int(count[])
 end
 
 limbs_write!(x::BigInt, a) = ccall((:__gmpz_limbs_write, libgmp), Ptr{Limb}, (mpz_t, Clong), x, a)
 limbs_finish!(x::BigInt, a) = ccall((:__gmpz_limbs_finish, libgmp), Cvoid, (mpz_t, Clong), x, a)
-import!(x::BigInt, a, b, c, d, e, f) = ccall((:__gmpz_import, libgmp), Cvoid,
-    (mpz_t, Csize_t, Cint, Csize_t, Cint, Csize_t, Ptr{Cvoid}), x, a, b, c, d, e, f)
 
 setbit!(x, a) = (ccall((:__gmpz_setbit, libgmp), Cvoid, (mpz_t, bitcnt_t), x, a); x)
 tstbit(a::BigInt, b) = ccall((:__gmpz_tstbit, libgmp), Cint, (mpz_t, bitcnt_t), a, b) % Bool

test/gmp.jl

@@ -445,6 +445,44 @@ end
     @test string(big(0), base = rand(2:62), pad = 0) == ""
 end
 
+@testset "Base.GMP.MPZ.import!/export!" begin
+
+    function Base_GMP_MPZ_import!(x::BigInt, n::AbstractVector{T}; order::Integer=-1, nails::Integer=0, endian::Integer=0) where {T<:Base.BitInteger}
+        ccall((:__gmpz_import, Base.GMP.MPZ.libgmp),
+               Cvoid,
+               (Base.GMP.MPZ.mpz_t, Csize_t, Cint, Csize_t, Cint, Csize_t, Ptr{Cvoid}),
+               x, length(n), order, sizeof(T), endian, nails, n)
+        return x
+    end
+    # test import
+    bytes_to_import_from = Vector{UInt8}([1, 0])
+    int_to_import_to = BigInt()
+    Base_GMP_MPZ_import!(int_to_import_to, bytes_to_import_from, order=0)
+    @test int_to_import_to == BigInt(256)
+
+    # test export
+    int_to_export_from = BigInt(256)
+    bytes_to_export_to = Vector{UInt8}(undef, 2)
+    Base.GMP.MPZ.export!(bytes_to_export_to, int_to_export_from, order=0)
+    @test all(bytes_to_export_to .== bytes_to_import_from)
+
+    # test both composed import(export) is identity
+    int_to_export_from = BigInt(256)
+    bytes_to_export_to = Vector{UInt8}(undef, 2)
+    Base.GMP.MPZ.export!(bytes_to_export_to, int_to_export_from, order=0)
+    int_to_import_to = BigInt()
+    Base_GMP_MPZ_import!(int_to_import_to, bytes_to_export_to, order=0)
+    @test int_to_export_from == int_to_import_to
+
+    # test both composed export(import) is identity
+    bytes_to_import_from = Vector{UInt8}([1, 0])
+    int_to_import_to = BigInt()
+    Base_GMP_MPZ_import!(int_to_import_to, bytes_to_import_from, order=0)
+    bytes_to_export_to = Vector{UInt8}(undef, 2)
+    Base.GMP.MPZ.export!(bytes_to_export_to, int_to_export_from, order=0)
+    @test all(bytes_to_export_to .== bytes_to_import_from)
+end
+
 @test isqrt(big(4)) == 2
 @test isqrt(big(5)) == 2