decode_bits Subroutine

  1. befor64.F90
  2. befor64
  3. decode_bits

private pure subroutine decode_bits(code, bits)

Arguments

TypeIntentOptionalAttributesName
character, intent(in) :: code
integer(kind=I1P), intent(out) :: bits(1:)

Called by

proc~~decode_bits~3~~CalledByGraph proc~decode_bits~3 decode_bits proc~b64_decode_r4~3 b64_decode_R4 proc~b64_decode_r4~3->proc~decode_bits~3 proc~b64_decode_i1~3 b64_decode_I1 proc~b64_decode_i1~3->proc~decode_bits~3 proc~b64_decode_i4_a~3 b64_decode_I4_a proc~b64_decode_i4_a~3->proc~decode_bits~3 proc~b64_decode_i4~3 b64_decode_I4 proc~b64_decode_i4~3->proc~decode_bits~3 proc~b64_decode_r4_a~3 b64_decode_R4_a proc~b64_decode_r4_a~3->proc~decode_bits~3 proc~b64_decode_i1_a~3 b64_decode_I1_a proc~b64_decode_i1_a~3->proc~decode_bits~3 proc~b64_decode_r16_a~3 b64_decode_R16_a proc~b64_decode_r16_a~3->proc~decode_bits~3 proc~b64_decode_r8~3 b64_decode_R8 proc~b64_decode_r8~3->proc~decode_bits~3 proc~b64_decode_i8~3 b64_decode_I8 proc~b64_decode_i8~3->proc~decode_bits~3 proc~b64_decode_i2~3 b64_decode_I2 proc~b64_decode_i2~3->proc~decode_bits~3 proc~b64_decode_string~3 b64_decode_string proc~b64_decode_string~3->proc~decode_bits~3 proc~b64_decode_r8_a~3 b64_decode_R8_a proc~b64_decode_r8_a~3->proc~decode_bits~3 proc~b64_decode_i8_a~3 b64_decode_I8_a proc~b64_decode_i8_a~3->proc~decode_bits~3 proc~b64_decode_i2_a~3 b64_decode_I2_a proc~b64_decode_i2_a~3->proc~decode_bits~3 proc~b64_decode_string_a~3 b64_decode_string_a proc~b64_decode_string_a~3->proc~decode_bits~3 proc~b64_decode_r16~3 b64_decode_R16 proc~b64_decode_r16~3->proc~decode_bits~3 proc~b64_decode_up~3 b64_decode_up proc~b64_decode_up~3->proc~b64_decode_r4~3 proc~b64_decode_up~3->proc~b64_decode_i1~3 proc~b64_decode_up~3->proc~b64_decode_i4~3 proc~b64_decode_up~3->proc~b64_decode_r8~3 proc~b64_decode_up~3->proc~b64_decode_i8~3 proc~b64_decode_up~3->proc~b64_decode_i2~3 proc~b64_decode_up~3->proc~b64_decode_string~3 proc~b64_decode_up_a~3 b64_decode_up_a proc~b64_decode_up_a~3->proc~b64_decode_i4_a~3 proc~b64_decode_up_a~3->proc~b64_decode_r4_a~3 proc~b64_decode_up_a~3->proc~b64_decode_i1_a~3 proc~b64_decode_up_a~3->proc~b64_decode_r8_a~3 proc~b64_decode_up_a~3->proc~b64_decode_i8_a~3 proc~b64_decode_up_a~3->proc~b64_decode_i2_a~3 proc~b64_decode_up_a~3->proc~b64_decode_string_a~3 interface~b64_decode~3 b64_decode interface~b64_decode~3->proc~b64_decode_r4~3 interface~b64_decode~3->proc~b64_decode_i1~3 interface~b64_decode~3->proc~b64_decode_i4_a~3 interface~b64_decode~3->proc~b64_decode_i4~3 interface~b64_decode~3->proc~b64_decode_r4_a~3 interface~b64_decode~3->proc~b64_decode_i1_a~3 interface~b64_decode~3->proc~b64_decode_r8~3 interface~b64_decode~3->proc~b64_decode_i8~3 interface~b64_decode~3->proc~b64_decode_i2~3 interface~b64_decode~3->proc~b64_decode_string~3 interface~b64_decode~3->proc~b64_decode_r8_a~3 interface~b64_decode~3->proc~b64_decode_i8_a~3 interface~b64_decode~3->proc~b64_decode_i2_a~3 interface~b64_decode~3->proc~b64_decode_string_a~3 interface~b64_decode_up~3 b64_decode_up interface~b64_decode_up~3->proc~b64_decode_up_a~3 interface~b64_decode_up~3->proc~b64_decode_up_a~3 interface~b64_decode_up~3->interface~b64_decode_up~3 interface~b64_decode_up~3->interface~b64_decode_up~3

Contents

Source Code

decode_bits

Source Code

   pure subroutine decode_bits(code, bits)
   !< Decode a base64 string into a sequence of bits stream.
   !<
   !< The base64 string must be parsed with a strike of 4 characters and converted into a 3 bytes stream. Considering the base64 code
   !< `QUJD` the decoding process must do
   !<```
   !< +-b64 char--+-b64 char--+-b64 char--+-b64 char--+
   !< |      Q    |      U    |      J    |      D    |
   !< +-b64 index-+-b64 index-+-b64 index-+-b64 index-+
   !< !      16   |      20   |      9    |      3    |
   !< +-6 bits----+-6 bits----+-6 bits----+-6 bits----+
   !< |0 1 0 0 0 0|0 1 0 1 0 0|0 0 1 0 0 1|0 0 0 0 1 1|
   !< +-----------+---+-------+-------+---+-----------+
   !< |0 1 0 0 0 0 0 1|0 1 0 0 0 0 1 0|0 1 0 0 0 0 1 1|
   !< +-----8 bits----+-----8 bits----+-----8 bits----+
   !<```
   !< @note The bits pattern is returned as a 1-byte element array, the dimension of witch must be computed outside this procedure.
   !<
   !< @warning This procedure is the backend of decoding, thus it must be never called outside the module.
   character(*), intent(in)  :: code      !< Characters code.
   integer(I1P), intent(out) :: bits(1:)  !< Bits decoded.
   integer(I1P)              :: sixb(1:4) !< 6 bits slices (stored into 8 bits integer) of 24 bits input.
   integer(I8P)              :: c         !< Counter.
   integer(I8P)              :: e         !< Counter.
   integer(I8P)              :: Nb        !< Length of bits array.

   Nb=size(bits,dim=1,kind=I8P)
   e = 1_I8P
   do c=1_I8P,len(code),4_I8P ! loop over code characters: 3 bytes (24 bits) scanning
      sixb = 0_I1P
      sixb(1) = index(base64,code(c  :c  )) - 1
      sixb(2) = index(base64,code(c+1:c+1)) - 1
      sixb(3) = index(base64,code(c+2:c+2)) - 1
      sixb(4) = index(base64,code(c+3:c+3)) - 1
         call mvbits(sixb(1),0,6,bits(e  ),2) ; call mvbits(sixb(2),4,2,bits(e  ),0)
      if (e+1<=Nb) then
         call mvbits(sixb(2),0,4,bits(e+1),4) ; call mvbits(sixb(3),2,4,bits(e+1),0)
      endif
      if (e+2<=Nb) then
         call mvbits(sixb(3),0,2,bits(e+2),6) ; call mvbits(sixb(4),0,6,bits(e+2),0)
      endif
      e = e + 3_I8P
   enddo
   endsubroutine decode_bits