make ndigits more generic (#30384)

(cherry picked from commit 2c71488)

Author: JeffBezanson

base/intfuncs.jl

@@ -445,15 +445,18 @@ ndigits0znb(x::Unsigned, b::Integer) = ndigits0znb(-signed(fld(x, -b)), b) + (x
 ndigits0znb(x::Bool, b::Integer) = x % Int
 
 # The suffix "pb" stands for "positive base"
-# TODO: allow b::Integer
-function ndigits0zpb(x::Base.BitUnsigned, b::Int)
+function ndigits0zpb(x::Integer, b::Integer)
     # precondition: b > 1
     x == 0 && return 0
-    b < 0   && return ndigits0znb(signed(x), b)
-    b == 2  && return sizeof(x)<<3 - leading_zeros(x)
-    b == 8  && return (sizeof(x)<<3 - leading_zeros(x) + 2) ÷ 3
-    b == 16 && return sizeof(x)<<1 - leading_zeros(x)>>2
-    b == 10 && return ndigits0z(x)
+    b = Int(b)
+    x = abs(x)
+    if x isa Base.BitInteger
+        x = unsigned(x)
+        b == 2  && return sizeof(x)<<3 - leading_zeros(x)
+        b == 8  && return (sizeof(x)<<3 - leading_zeros(x) + 2) ÷ 3
+        b == 16 && return sizeof(x)<<1 - leading_zeros(x)>>2
+        b == 10 && return ndigits0z(x)
+    end
 
     d = 0
     while x > typemax(Int)
@@ -471,8 +474,6 @@ function ndigits0zpb(x::Base.BitUnsigned, b::Int)
     return d
 end
 
-ndigits0zpb(x::Base.BitSigned, b::Integer) = ndigits0zpb(unsigned(abs(x)), Int(b))
-ndigits0zpb(x::Base.BitUnsigned, b::Integer) = ndigits0zpb(x, Int(b))
 ndigits0zpb(x::Bool, b::Integer) = x % Int
 
 # The suffix "0z" means that the output is 0 on input zero (cf. #16841)