Made it easier to change bits_kind

Introduced the parameters max_digits and overflow_bits to be used in checking
for overflows on reads and writes. The parameters need to be changed if
bits_kind is changed, and preferred parameters for bits_kind==int64 are
defined, but commented out.

[ticket: X]

Author: wclodius2

src/stdlib_bitsets.fypp

@@ -6,8 +6,8 @@ module stdlib_bitsets
 !! having the sign bit set.
 
     use :: stdlib_kinds, only:  &
-           bits_kind  => int32, &
-           block_kind => int64, &
+           bits_kind  => int32, & ! If changed change also max_digits, and
+           block_kind => int64, & ! overflow_bits
            int8,                &
            int16,               &
            int32,               &
@@ -24,12 +24,21 @@ module stdlib_bitsets
     integer(bits_kind), parameter ::        &
         block_size  = bit_size(0_block_kind)
 
+    public :: max_digits, overflow_bits
+    integer, parameter ::                   &
+        max_digits = 10 ! bits_kind == int32
+!        max_digits = 20 ! bits_kind == int64
+
+    integer(bits_kind), parameter ::     &
+        overflow_bits = 2_bits_kind**30/5 ! bits_kind == int32
+!        overflow_bits = 2_bits_kind**62/5 ! bits_kind == int64
+
     integer(block_kind), parameter :: all_zeros  = 0_block_kind
     integer(block_kind), parameter :: all_ones   = not(all_zeros)
 
     character(*), parameter :: module_name = "STDLIB_BITSETS"
-    integer, parameter :: &
-        ia0   = iachar('0'),       &
+    integer, parameter ::    &
+        ia0   = iachar('0'), &
         ia9   = iachar('9')
 
     integer, parameter, public :: success = 0

src/stdlib_bitsets_64.fypp

@@ -644,9 +644,10 @@ contains
             select case( iachar( string(pos:pos) ) )
             case(ia0:ia9)
                 digits = digits + 1
-                if ( digits == 10 .AND. bits > 2_bits_kind**30/5 ) go to 996
+                if (  digits == max_digits .AND. bits > overflow_bits ) &
+                    go to 996
 !! May not be quite right
-                if ( digits > 10 ) go to 996
+                if ( digits > max_digits ) go to 996
                 bits = bits*10 + iachar( string(pos:pos) ) - ia0
                 if ( bits < 0 ) go to 996
             case(iachar('b'), iachar('B'))
@@ -776,17 +777,18 @@ contains
             select case( char )
             case( '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' )
                 digits = digits + 1
-                if ( digits == 10 .AND. bits > 2_bits_kind**30/5 ) go to 996
+                if (  digits == max_digits .AND. bits > overflow_bits ) &
+                    go to 996
 !! May not be quite right
-                if ( digits > 10 ) go to 996
+                if ( digits > max_digits ) go to 996
                 bits = 10*bits + iachar(char) - iachar('0')
                 if ( bits < 0 ) go to 996
             case default
                 go to 999
             end select
         end do
 
-        if ( bits < 0 .OR. digits == 0 .OR. digits > 10 ) go to 999
+        if ( bits < 0 .OR. digits == 0 .OR. digits > max_digits ) go to 999
 
         if ( bits > 64 ) then
             call error_handler( 'BITS in UNIT was greater than 64.', &
@@ -870,9 +872,11 @@ contains
 !
         class(bitset_64), intent(inout) :: self
         integer(bits_kind), intent(in)  :: pos
+        integer(block_kind) :: dummy
 
         if ( pos < 0 .OR. pos > self % num_bits-1 ) return
-        self % block = ibset( self % block, pos )
+        dummy = ibset( self % block, pos )
+        self % block = dummy
 
     end subroutine set_bit_64
 

src/stdlib_bitsets_large.fypp

@@ -834,9 +834,9 @@ contains
             select case( iachar( string(pos:pos) ) )
             case(ia0:ia9)
                 digits = digits + 1
-                if ( digits == 10 .AND. bits > 2_bits_kind**30/5 ) go to 996
+                if ( digits == max_digits .AND. bits > overflow_bits ) go to 996
 !! May not be quite right
-                if ( digits > 10 ) go to 996
+                if ( digits > max_digits ) go to 996
                 bits = bits*10 + iachar( string(pos:pos) ) - ia0
                 if ( bits < 0 ) go to 996
             case(iachar('b'), iachar('B'))
@@ -963,16 +963,17 @@ contains
             select case( char )
             case( '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' )
                 digits = digits + 1
-                if ( digits == 10 .AND. bits > 2_bits_kind**30/5 ) go to 996
-                if ( digits > 10 ) go to 996
+                if (  digits == max_digits .AND. bits > overflow_bits ) &
+                    go to 996
+                if ( digits > max_digits ) go to 996
                 bits = 10*bits + iachar(char) - iachar('0')
                 if ( bits < 0 ) go to 996
             case default
                 go to 999
             end select
         end do
 
-        if ( bits < 0 .OR. digits == 0 .OR. digits > 10 ) go to 999
+        if ( bits < 0 .OR. digits == 0 .OR. digits > max_digits ) go to 999
 
         call self % init( bits, status )
         if ( present(status) ) then