! Basic! JSON Parser ! !ASCII Code Reference (decimal values): ! ! ยจ double quote 34 ! ' single quote 39 ! \ backslash 92 ! / forward slash 47 ! space 32 ! { left brace 123 ! } right brace 125 ! [ left bracket 91 ! ] right bracket 93 ! \b backspace 8 ! \f form feed 12 ! \n line feed 10 ! \r carriage return 13 ! \t horizontal tab 9 ! 0 numeral 0 48 ! 9 numeral 9 57 ! - minus 45 ! + plus 43 ! . period 46 ! e lower case e 101 ! E upper case E 69 ! !json_text1$ = "{\"coord\":{\"lon\":-80.34,\"lat\":39.28},\"sys\":{\"type\":1,\"id\":3051,\"message\":0.0303,\"country\":\"US\",\"sunrise\":1412248740,\"sunset\":1412290920}}" json_text2$ = "{\"coord\":{\"lon\":-80.34,\"lat\":39.28},\"sys\":{\"type\":1,\"id\":3051,\"message\":0.0303,\"country\":\"US\",\"sunrise\":1412248740,\"sunset\":1412290920},\"weather\":[{\"id\":741,\"main\":\"Fog\",\"description\":\"fog\",\"icon\":\"50n\"},{\"id\":701,\"main\":\"Mist\",\"description\":\"mist\",\"icon\":\"50n\"}],\"base\":\"cmc stations\",\"main\":{\"temp\":285.3,\"pressure\":1018,\"humidity\":100,\"temp_min\":284.15,\"temp_max\":287.15},\"wind\":{\"speed\":1.76,\"deg\":179.007},\"clouds\":{\"all\":90},\"dt\":1412228100,\"id\":4802316,\"name\":\"Clarksburg\",\"cod\":200}" ! Function definitions !=====FUNCTION: jsnp_next(c$,jsnpa[]) !Get the next char and advance the pointer. At EOF return 0. !If c$ parameter is provided, verify that it matches the current char. !c$ parameter must be a single character string or empty string. Fn.def jsnp_next(c$,jsnpa[]) a = ASCII(c$) If ((c$ <> "") & (a <> jsnpa[1])) Then Print "Error in jsnp_next. c$=";c$;", ch=";jsnpa[1];", at=";jsnpa[2] Goto jsnp_fail Endif If jsnpa[2] = jsnpa[4] jsnpa[1] = 0 %End of text. Set current char to NULL Fn.rtn 0 %Return NULL. Endif jsnpa[2] += 1 jsnpa[1] = jsnpa[jsnpa[2]] Fn.rtn jsnpa[1] Fn.end !=====FUNCTION: jsnp_white(jsnpa[]) !Skip whitespace, if any. !Returns nothing Fn.def jsnp_white(jsnpa[]) While ( (jsnpa[1] <> 0) & (jsnpa[1] <= 32) ) jsnp_next("",jsnpa[]) Repeat Fn.end !=====FUNCTION: jsnp_ishex(n) !n is an ASCII decimal character code. !Returns true if n is a valid hexadecimal character. Else false. Fn.def jsnp_ishex(n) If (n >= 48) & (n <= 57) Then %in range of ASCII 0 to 9 Fn.rtn 1 Endif If (n >= 65) & (n <= 70) Then %in range of ASCII A to F Fn.rtn 1 Endif If (n >= 97) & (n <= 102) Then %in range of ASCII a to f Fn.rtn 1 Else Fn.rtn 0 Endif Fn.end !=====FUNCTION: jsnp_pushkey(key$,jsnpa[]) !Pushes key$ onto the key stack. This is done by dot-concatenating key$ with whatever key is at the top !of the stack and pushing the result onto the stack. !Returns nothing Fn.def jsnp_pushkey(key$,jsnpa[]) sptr = jsnpa[6] Stack.IsEmpty sptr, empty If empty = 0 %stack is not empty Stack.peek sptr, t$ t$ = t$ + "." + key$ Stack.push sptr, t$ !PRINT "Push: ";t$ Else %stack is empty Stack.push sptr, key$ !PRINT "Push: ";key$ Endif Fn.rtn 0 Fn.end !=====FUNCTION: jsnp_word(jsnpa[]) !Parse the words true, false, null from the JSON string. !Returns 1 for true, 0 for false and null Fn.def jsnp_word(jsnpa[]) If jsnpa[1] = ASCII("t") Then jsnp_next("t",jsnpa[]) jsnp_next("r",jsnpa[]) jsnp_next("u",jsnpa[]) jsnp_next("e",jsnpa[]) Fn.rtn 1 %return true Endif If jsnpa[1] = ASCII("f") Then jsnp_next("f",jsnpa[]) jsnp_next("a",jsnpa[]) jsnp_next("l",jsnpa[]) jsnp_next("s",jsnpa[]) jsnp_next("e",jsnpa[]) Fn.rtn 0 %return false Endif If jsnpa[1] = ASCII("n") Then jsnp_next("n",jsnpa[]) jsnp_next("u",jsnpa[]) jsnp_next("l",jsnpa[]) jsnp_next("l",jsnpa[]) Fn.rtn 0 %return null/false Endif Print "Unexpected char in jsnp_word. ch=";jsnpa[1];", at=";jsnpa[2] Goto jsnp_fail Fn.end !=====END OF FUNCTION DEFINITIONS Goto startprog !=====SUBROUTINE: jsnp_parse !Parse an entire JSON string ! !Inputs: !jsnp_text$: JSON string !jsnp_bptr: pointer to bundle into which all the keys and values extracted from the JSON string will be placed. ! !If successful, this subroutine returns with jsnp_parse_retval == 1. If there is a recoverable failure, it !returns with jsnp_parse_retval == -1. If unrecoverable failure we jump to jsnp_fail: ! !This parser needs a few internally global variables that are accessible across different functions. Because !RFO Basic disallows access to global variables from within functions, the working values for this !parser are maintained in an internal numeric array. By passing a single array in each function call, !the effect of global variables can be achieved and without passing a dozen parameters in each function call. ! !The JSON text is initially extracted as ASCII and placed in the internal "globals" array mentioned above, !which also serves as a buffer, again minimizing the number of parameters that must be passed in each function call. ! !Regular expressions are not used. No switches are used. ! !Fixed array element values are: ! jsnpa[1] - current character ASCII value (ch) ! jsnpa[2] - current character pointer (at) ! jsnpa[3] - total number of chars in JSON string ! jsnpa[4] - array index of last character of JSON text ! jsnpa[5] - bundle pointer passed from caller, bptr ! jsnpa[6] - local key string stack pointer, sptr ! jsnpa[7] - extra space ! jsnpa[8...n] - JSON text characters as numeric ASCII values jsnp_parse: jsnp_l = Len(jsnp_text$) If jsnp_l = 0 Then Print "JSON string is empty" jsnp_parse_retval = -1 Return Endif Stack.create S, jsnp_sptr Dim jsnpa[7+jsnp_l] jsnpa[2] = 8 jsnpa[3] = jsnp_l jsnpa[4] = jsnp_l+7 jsnpa[5] = jsnp_bptr %output result bundle pointer passed from caller jsnpa[6] = jsnp_sptr %stack used locally for key strings !Extract JSON text and convert to numeric ASCII For i = 1 to jsnp_l jsnpa[i+7] = ASCII(Mid$(jsnp_text$, i, 1)) Next jsnpa[1] = jsnpa[jsnpa[2]] !Execute the parsing process by calling jsnp_value. Gosub jsnp_value jsnp_white(jsnpa[]) If jsnpa[1] <> 0 Then %we should have exhausted all chars in the JSON string Print "Extra chars found" Goto jsnp_fail Endif !Clean up after ourselves Stack.clear jsnp_sptr UnDim jsnpa[] jsnp_parse_retval = 1 Return !===== END OF SUBROUTINE jsnp_parse !=====SUBROUTINE: jsnp_value !Parse a JSON value. It could be an object, array, string, number, or word !Returns nothing jsnp_value: jsnp_value_s$ = "" jsnp_white(jsnpa[]) If jsnpa[1] = 123 %Left brace. An object? Gosub jsnp_object ElseIf jsnpa[1] = 91 Then %if left bracket then array Gosub jsnp_array ElseIf jsnpa[1] = 34 Then %Double quote. A string? Gosub jsnp_string jsnp_value_s$ = jsnp_string_retval$ Stack.pop jsnp_sptr, jsnp_key$ Bundle.put jsnp_bptr, jsnp_key$, jsnp_value_s$ ElseIf (jsnpa[1] = 45) | ((jsnpa[1] >= 48) & (jsnpa[1] <= 57)) Then %Minus sign or numeric 0-9. A number? Gosub jsnp_number jsnp_n = jsnp_number_retval Stack.IsEmpty jsnp_sptr, jsnp_empty If jsnp_empty <> 0 Then %empty stack is an error Print "Empty key stack" Goto jsnp_fail Endif Stack.pop jsnp_sptr, jsnp_key$ Bundle.put jsnp_bptr, jsnp_key$, jsnp_n Else %word? jnsp_n = jsnp_word(jsnpa[]) Stack.pop jsnp_sptr, jsnp_key$ Bundle.put jsnp_bptr, jsnp_key$, jsnp_n Endif Return !=====END OF SUBROUTINE jsnp_value !=====SUBROUTINE: jsnp_object !Parse an object value from the JSON string. !Returns nothing jsnp_object: If jsnpa[1] <> 123 %not a left brace? Print "Bad object" Goto jsnp_fail Endif jsnp_next("{",jsnpa[]) jsnp_white(jsnpa[]) If jsnpa[1] = 125 %if right brace then empty object. jsnp_next("}",jsnpa[]) Return Endif While jsnpa[1] <> 0 Gosub jsnp_string jsnp_key$ = jsnp_string_retval$ %key extracted jsnp_pushkey(jsnp_key$,jsnpa[]) jsnp_white(jsnpa[]) jsnp_next(":",jsnpa[]) Gosub jsnp_value %extracts the value and adds to the bundle jsnp_white(jsnpa[]) If jsnpa[1] = 125 %if right brace then done with this object jsnp_next("}",jsnpa[]) If jsnpa[1] <> 0 %if not at end of json string, the stack is not empty Stack.pop jsnp_sptr, jsnp_key$ %pop the object's name key and discard it. Endif W_R.break Endif jsnp_next(",",jsnpa[]) jsnp_white(jsnpa[]) Repeat Return !=====END OF SUBROUTINE jsnp_object !=====SUBROUTINE: jsnp_number !Parse a numeric value from the JSON string. !Returns a numeric value in jsnp_number_retval. !Builds a temporary string in jsnp_number_s$, then converts it to a number before returning it. jsnp_number: jsnp_number_s$ = "" %init If jsnpa[1] = 45 Then %minus sign? jsnp_number_s$ += "-" jsnp_next("",jsnpa[]) Endif While ((jsnpa[1] >= 48) & (jsnpa[1] <= 57)) %ch from 0 to 9 jsnp_number_s$ += CHR$(jsnpa[1]) jsnp_next("",jsnpa[]) Repeat If jsnpa[1] = 46 Then %dot or period jsnp_number_s$ += "." While (jsnp_next("",jsnpa[]) & (jsnpa[1] >= 48) & (jsnpa[1] <= 57)) jsnp_number_s$ += CHR$(jsnpa[1]) Repeat Endif If ((jsnpa[1] = 101) | (jsnpa[1] = 69)) Then %if lower or upper case E jsnp_number_s$ += CHR$(jsnpa[1]) jsnp_next("",jsnpa[]) If ((jsnpa[1] = 45) | (jsnpa[1] = 43)) Then %if plus or minus jsnp_number_s$ += CHR$(jsnpa[1]) jsnp_next("",jsnpa[]) Endif While ((jsnpa[1] >= 48) & (jsnpa[1] <= 57)) %while numeric 0-9 jsnp_number_s$ += CHR$(jsnpa[1]) jsnp_next("",jsnpa[]) Repeat Endif jsnp_number_retval = VAL(jsnp_number_s$) Return !=====END OF SUBROUTINE jsnp_number !=====SUBROUTINE: jsnp_string() !Parse a string value from the JSON string. !Builds and returns the string in jsnp_string_retval$ jsnp_string: jsnp_string_retval$ = "" %init !Parse and look for " and \ characters If jsnpa[1] = 34 %if double quote While jsnp_next("",jsnpa[]) If jsnpa[1] = 34 %if another double quote jsnp_next("",jsnpa[]) %skip the quote and return W_R.break Endif If jsnpa[1] = 92 %if backslash jsnp_next("",jsnpa[]) If jsnpa[1] = ASCII("u") %if we have \u then hex string For i = 1 to 4 If jsnp_ishex(jsnpa[1]) jsnp_string_retval$ += CHR$(jsnpa[1]) Else Print "Bad hex char in jsnp_string(). ch=";jsnpa[1];", at=";jsnpa[2] Goto jsnp_fail Endif Next i Else %we have a backslash. handle escape characters If jsnpa[1] = 34 %double quote jsnp_string_retval$ += CHR$(34) ElseIf jsnpa[1] = 92 %backslash jsnp_string_retval$ += CHR$(92) ElseIf jsnpa[1] = 47 %forward slash jsnp_string_retval$ += CHR$(47) ElseIf jsnpa[1] = 98 %b jsnp_string_retval$ += CHR$(92) + CHR$(98) ElseIf jsnpa[1] = 102 %f jsnp_string_retval$ += CHR$(92) + CHR$(102) ElseIf jsnpa[1] = 110 %n jsnp_string_retval$ += CHR$(92) + CHR$(110) ElseIf jsnpa[1] = 114 %r jsnp_string_retval$ += CHR$(92) + CHR$(114) ElseIf jsnpa[1] = 116 %t jsnp_string_retval$ += CHR$(92) + CHR$(116) Else Print "Bad escaped char in jsnp_string(). ch=";jsnpa[1];", at=";jsnpa[2] Goto jsnp_fail Endif Endif Else jsnp_string_retval$ += CHR$(jsnpa[1]) Endif Repeat Return Endif Print "Bad string in jsnp_string(). ch=";jsnpa[1];", at=";jsnpa[2] Goto jsnp_fail !=====END OF SUBROUTINE jsnp_string() !=====SUBROUTINE: jsnp_array !Parse an array from the JSON string. !Returns nothing jsnp_array: If jsnpa[1] <> 91 %if not a left bracket then bad array syntax Print "Bad array syntax" Goto jsnp_fail Endif jsnp_next("[",jsnpa[]) jsnp_white(jsnpa[]) If jsnpa[1] = 93 %if right bracket then empty array jsnp_next("]",jsnpa[]) Return Endif jsnp_ai = 1 %Initialize array index counter to 1 jsnp_key$ = FORMAT$("#####",jsnp_ai) jsnp_key$ = REPLACE$(jsnp_key$," ","") jsnp_pushkey(jsnp_key$,jsnpa[]) While jsnpa[1] <> 0 Gosub jsnp_value %extracts the value and adds to the bundle jsnp_white(jsnpa[]) If jsnpa[1] = 93 %if right bracket then done with this array jsnp_next("]",jsnpa[]) Stack.pop jsnp_sptr, jsnp_key$ %pop the name of the array and discard it. W_R.break Endif jsnp_white(jsnpa[]) If jsnpa[1] = ASCII(",") %must be another array element jsnp_next(",",jsnpa[]) jsnp_white(jsnpa[]) ! Array index has already been popped. Push the next one on the stack. jsnp_ai += 1 jsnp_key$ = FORMAT$("#####",jsnp_ai) jsnp_key$ = REPLACE$(jsnp_key$," ","") jsnp_pushkey(jsnp_key$,jsnpa[]) %push the next array index W_R.continue Else Print "Unexpected characters in JSON array" W_R.break Endif Repeat Return !=====END OF SUBROUTINE jsnp_array jsnp_fail: Print "Parser failure" End !=====MAIN PROGRAM startprog: Print "JSON Parser Test\n\n" jsnp_text$ = json_text2$ Print "Dump of original JSON text:" Print jsnp_text$ Print "Call the parser" Bundle.create jsnp_bptr Gosub jsnp_parse Debug.on Debug.dump.bundle jsnp_bptr Debug.off Console.save "json_parse_output.txt" End !=====END OF MAIN PROGRAM