diff --git a/base/intfuncs.jl b/base/intfuncs.jl index db1a1ae121251..e430603defb35 100644 --- a/base/intfuncs.jl +++ b/base/intfuncs.jl @@ -460,6 +460,10 @@ function ndigits0zpb(x::Integer, b::Integer) b == 8 && return (sizeof(x)<<3 - leading_zeros(x) + 2) รท 3 b == 16 && return sizeof(x)<<1 - leading_zeros(x)>>2 b == 10 && return bit_ndigits0z(x) + if ispow2(b) + dv, rm = divrem(sizeof(x)<<3 - leading_zeros(x), trailing_zeros(b)) + return iszero(rm) ? dv : dv + 1 + end end d = 0 @@ -755,9 +759,18 @@ function digits!(a::AbstractVector{T}, n::Integer; base::Integer = 10) where T<: isempty(a) && return a if base > 0 - for i in eachindex(a) - n, d = divrem(n, base) - a[i] = d + if ispow2(base) && n >= 0 && n isa Base.BitInteger && base <= typemax(Int) + base = Int(base) + k = trailing_zeros(base) + c = base - 1 + for i in eachindex(a) + a[i] = (n >> (k * (i - firstindex(a)))) & c + end + else + for i in eachindex(a) + n, d = divrem(n, base) + a[i] = d + end end else # manually peel one loop iteration for type stability diff --git a/test/intfuncs.jl b/test/intfuncs.jl index 4bf9d3b71b4bf..9065e85206511 100644 --- a/test/intfuncs.jl +++ b/test/intfuncs.jl @@ -117,6 +117,14 @@ end @test ndigits(146, base=-3) == 5 end + @testset "ndigits with base power of 2" begin + @test ndigits(17, base = 2) == 5 + @test ndigits(123, base = 4) == 4 + @test ndigits(64, base = 8) == 3 + @test ndigits(8436, base = 16) == 4 + @test ndigits(159753, base = 32) == 4 + @test ndigits(3578951, base = 64) == 4 + end let (n, b) = rand(Int, 2) -1 <= b <= 1 && (b = 2) # invalid bases @test ndigits(n) == ndigits(big(n)) == ndigits(n, base=10) @@ -181,11 +189,22 @@ end @test bitstring(Int128(3)) == "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000011" end @testset "digits/base" begin - @test digits(4, base = 2) == [0, 0, 1] @test digits(5, base = 3) == [2, 1] - @test digits(5, base = Int32(2), pad=Int32(3)) == [1, 0, 1] @test digits(5, pad = 3) == [5, 0, 0] @test digits(5, pad = Int32(3)) == [5, 0, 0] + # The following have bases powers of 2, but don't enter the fast path + @test digits(-3, base = 2) == -[1, 1] + @test digits(-42, base = 4) == -[2, 2, 2] + + @testset "digits/base with bases powers of 2" begin + @test digits(4, base = 2) == [0, 0, 1] + @test digits(5, base = Int32(2), pad=Int32(3)) == [1, 0, 1] + @test digits(42, base = 4) == [2, 2, 2] + @test digits(321, base = 8) == [1, 0, 5] + @test digits(0x123456789abcdef, base = 16) == 15:-1:1 + @test digits(0x2b1a210a750, base = 64) == [16, 29, 10, 4, 34, 6, 43] + @test digits(0x02a01407, base = Int128(1024)) == [7, 5, 42] + end @testset "digits/base with negative bases" begin @testset "digits(n::$T, base = b)" for T in (Int, UInt, BigInt, Int32, UInt32)