unescape_string Subroutine

public subroutine unescape_string(str_in, str_out, error_message)

Remove the escape characters from a JSON string and return it.

The escaped characters are denoted by the \ character:

  • \" - quotation mark
  • \\ - reverse solidus
  • \/ - solidus
  • \b - backspace
  • \f - formfeed
  • \n - newline (LF)
  • \r - carriage return (CR)
  • \t - horizontal tab
  • \uXXXX - 4 hexadecimal digits

Arguments

Type IntentOptional AttributesName
character(kind=CK,len=*), intent(in) :: str_in

string as stored in a json_value

character(kind=CK,len=:), intent(out), allocatable:: str_out

decoded string

character(kind=CK,len=:), intent(out), allocatable:: error_message

will be allocated if there was an error


Calls

proc~~unescape_string~~CallsGraph proc~unescape_string unescape_string interface~to_unicode to_unicode proc~unescape_string->interface~to_unicode proc~to_uni to_uni interface~to_unicode->proc~to_uni proc~to_uni_vec to_uni_vec interface~to_unicode->proc~to_uni_vec

Called by

proc~~unescape_string~~CalledByGraph proc~unescape_string unescape_string proc~parse_string parse_string proc~parse_string->proc~unescape_string

Contents

Source Code


Source Code

    subroutine unescape_string(str_in, str_out, error_message)

    implicit none

    character(kind=CK,len=*),intent(in)              :: str_in  !! string as stored in a [[json_value]]
    character(kind=CK,len=:),allocatable,intent(out) :: str_out !! decoded string
    character(kind=CK,len=:),allocatable,intent(out) :: error_message !! will be allocated if there was an error

    integer :: i   !! counter
    integer :: n   !! length of str_in
    integer :: m   !! length of str_out
    character(kind=CK,len=1) :: c  !! for scanning each character in string

#if defined __GFORTRAN__
    character(kind=CK,len=:),allocatable :: tmp  !! for GFortran bug workaround
#endif

    if (scan(str_in,backslash)>0) then

        !there is at least one escape character, so process this string:

        n = len(str_in)
        str_out = repeat(space,n) !size the output string (will be trimmed later)
        m = 0  !counter in str_out
        i = 0  !counter in str_in

        do

            i = i + 1
            if (i>n) exit ! finished
            c = str_in(i:i) ! get next character in the string

            if (c == backslash) then

                if (i<n) then

                    i = i + 1
                    c = str_in(i:i) !character after the escape

                    if (any(c == [quotation_mark,backslash,slash, &
                         to_unicode(['b','f','n','r','t'])])) then

                        select case(c)
                        case (quotation_mark,backslash,slash)
                            !use d as is
                        case (CK_'b')
                             c = bspace
                        case (CK_'f')
                             c = formfeed
                        case (CK_'n')
                             c = newline
                        case (CK_'r')
                             c = carriage_return
                        case (CK_'t')
                             c = horizontal_tab
                        end select

                        m = m + 1
                        str_out(m:m) = c

                    else if (c == 'u') then !expecting 4 hexadecimal digits after
                                            !the escape character    [\uXXXX]

                        !for now, we are just returning them as is
                        ![not checking to see if it is a valid hex value]
                        !
                        ! Example:
                        !   123456
                        !   \uXXXX

                        if (i+4<=n) then
                            m = m + 1
                            str_out(m:m+5) = str_in(i-1:i+4)
                            i = i + 4
                            m = m + 5
                        else
                            error_message = 'Error in unescape_string:'//&
                                                 ' Invalid hexadecimal sequence'//&
                                                 ' in string: '//str_in(i-1:)
                            if (allocated(str_out)) deallocate(str_out)
                            return
                        end if

                    else
                        !unknown escape character
                        error_message = 'Error in unescape_string:'//&
                                             ' unknown escape sequence in string "'//&
                                             trim(str_in)//'" ['//backslash//c//']'
                        if (allocated(str_out)) deallocate(str_out)
                        return
                    end if

                else
                    !an escape character is the last character in
                    ! the string [this may not be valid syntax,
                    ! but just keep it]
                    m = m + 1
                    str_out(m:m) = c
                end if

            else
                m = m + 1
                str_out(m:m) = c
            end if

        end do

        !trim trailing space:
#if defined __GFORTRAN__
        ! workaround for Gfortran 6.1.0 bug
        tmp = str_out(1:m)
        str_out = tmp
#else
        str_out = str_out(1:m)
#endif

    else
        !there are no escape characters, so return as is:
        str_out = str_in
    end if

    end subroutine unescape_string