parse_string Subroutine

private subroutine parse_string(json, unit, str, string)

Parses a string while reading a JSON file.


  • Jacob Williams : 6/16/2014 : Added hex validation.
  • Jacob Williams : 12/3/2015 : Fixed some bugs.
  • Jacob Williams : 8/23/2015 : string is now returned unescaped.
  • Jacob Williams : 7/21/2018 : moved hex validate to unescape_string.


Type IntentOptional AttributesName
class(json_core), intent(inout) :: json
integer(kind=IK), intent(in) :: unit

file unit number (if parsing from a file)

character(kind=CK,len=*), intent(in) :: str

JSON string (if parsing from a string)

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

the string (unescaped if necessary)


proc~~parse_string~~CallsGraph proc~parse_string parse_string proc~unescape_string unescape_string proc~parse_string->proc~unescape_string proc~valid_json_hex valid_json_hex proc~unescape_string->proc~valid_json_hex


Source Code

Source Code

    subroutine parse_string(json, unit, str, string)

    implicit none

    class(json_core),intent(inout)                   :: json
    integer(IK),intent(in)                           :: unit   !! file unit number (if
                                                               !! parsing from a file)
    character(kind=CK,len=*),intent(in)              :: str    !! JSON string (if parsing
                                                               !! from a string)
    character(kind=CK,len=:),allocatable,intent(out) :: string !! the string (unescaped
                                                               !! if necessary)

    logical(LK)              :: eof      !! end of file flag
    logical(LK)              :: escape   !! for escape string parsing
    character(kind=CK,len=1) :: c        !! character returned by [[pop_char]]
    integer(IK)              :: ip       !! index to put next character,
                                         !! to speed up by reducing the number
                                         !! of character string reallocations.
    character(kind=CK,len=:),allocatable :: error_message !! for string unescaping

    !at least return a blank string if there is a problem:
    string = repeat(space, chunk_size)

    if (.not. json%exception_thrown) then

        escape = .false.
        ip     = 1


            !get the next character from the file:
            call json%pop_char(unit, str=str, eof=eof, skip_ws=.false., popped=c)

            if (eof) then

                call json%throw_exception('Error in parse_string: Expecting end of string')

            else if (c==quotation_mark .and. .not. escape) then  !end of string



                !if the string is not big enough, then add another chunk:
                if (ip>len(string)) string = string // repeat(space, chunk_size)

                !append to string:
                string(ip:ip) = c
                ip = ip + 1

                ! check for escape character, so we don't
                ! exit prematurely if escaping a quotation
                ! character:
                if (escape) then
                    escape = .false.
                    escape = (c==backslash)
                end if

            end if

        end do

        !trim the string if necessary:
        if (ip<len(string)+1) then
            if (ip==1) then
                string = CK_''
                string = string(1:ip-1)
            end if
        end if

        ! string is returned unescaped:
        ! (this will also validate any hex strings present)
        call unescape_string(string,error_message)
        if (allocated(error_message)) then
            call json%throw_exception(error_message)
            deallocate(error_message)  !cleanup
        end if

    end if

    end subroutine parse_string