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Add a new option decimal_as/1 to json_read to allow reading numbers w… #131

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49 changes: 40 additions & 9 deletions json.c
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,8 @@
#include <string.h>


static predicate_t PREDICATE_mk_rational3; /* +Integer, +NumberOfDecimals, -Rational */

/*******************************
* READ *
*******************************/
Expand Down Expand Up @@ -95,26 +97,45 @@ put_byte(text *t, int c)


static foreign_t
json_read_number(term_t stream, term_t c0, term_t number)
json_read_number(term_t stream, term_t c0, term_t use_rdiv, term_t number)
{ IOSTREAM *in;
text t;
int rc = FALSE;
int c;
term_t tmp;
int decimal_places = 0;
int is_decimal = 0;
int preserve_precision = FALSE;

if ( !PL_get_bool_ex(use_rdiv, &preserve_precision) )
return FALSE;
if ( !PL_get_stream(stream, &in, SIO_INPUT) ||
!PL_get_char_ex(c0, &c, FALSE) )
return FALSE;

init_text(&t);
put_byte(&t, c);
if (c == '.')
is_decimal = 1;

for(;;)
{ c = Speekcode(in);

if ( (c >= '0' && c <= '9') ||
c == '.' || c == '-' || c == '+' || c == 'e' || c == 'E' )
{ if ( put_byte(&t, c) != 0 )
{ if (preserve_precision && c == '.')
{ is_decimal = 1;
(void)Sgetcode(in);
continue;
}
else if (c == 'e' || c == 'E')
{ /* We cannot hope to have a perfect-precision result if the input contains an e
or E, so just give back a float in this case */
is_decimal = 0;
}
else if (preserve_precision && is_decimal)
{ decimal_places++;
}
if ( put_byte(&t, c) != 0 )
{ rc = PL_resource_error("memory");
break;
}
Expand All @@ -126,11 +147,19 @@ json_read_number(term_t stream, term_t c0, term_t number)
{ rc = PL_resource_error("memory");
break;
}

rc = ( (tmp = PL_new_term_ref()) &&
PL_chars_to_term(t.t, tmp) &&
PL_unify(tmp, number) );

if (is_decimal)
{ fid_t fid = PL_open_foreign_frame();
term_t av = PL_new_term_refs(3);
rc = (PL_chars_to_term(t.t, av+0) &&
PL_put_integer(av+1, decimal_places) &&
PL_call_predicate(NULL, PL_Q_NORMAL, PREDICATE_mk_rational3, av) &&
PL_unify(number, av+2));
PL_close_foreign_frame(fid);
} else
{ rc = ( (tmp = PL_new_term_ref()) &&
PL_chars_to_term(t.t, tmp) &&
PL_unify(tmp, number) );
}
break;
}
free_text(&t);
Expand Down Expand Up @@ -302,7 +331,9 @@ json_write_indent(term_t stream, term_t indent, term_t tab)

install_t
install_json()
{ PL_register_foreign("json_read_number", 3, json_read_number, 0);
{ PREDICATE_mk_rational3 = PL_predicate("mk_rational", 3, "json");

PL_register_foreign("json_read_number", 4, json_read_number, 0);
PL_register_foreign("json_skip_ws", 3, json_skip_ws, 0);
PL_register_foreign("json_write_string", 2, json_write_string, 0);
PL_register_foreign("json_write_indent", 3, json_write_indent, 0);
Expand Down
37 changes: 31 additions & 6 deletions json.pl
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -142,10 +142,11 @@
end_of_file:ground = error,
value_string_as:oneof([atom,string]) = atom,
tag:atom = '',
default_tag:atom).
default_tag:atom,
decimal_as:oneof([float, rdiv]) = float).

default_json_dict_options(
json_options(null, true, false, error, string, '', _)).
json_options(null, true, false, error, string, '', _, float)).


/*******************************
Expand Down Expand Up @@ -258,6 +259,10 @@
% The alternative is `string`, producing a packed string object.
% Please note that `codes` or `chars` would produce ambiguous
% output and are therefore not supported.
% - decimal_as(+Type)
% Prolog type used for non-integer numbers. Default is
% =float=. The alternative is =rdiv=, which produces a
% rdiv/2 term which guarantees no loss of precision.
%
% @see json_read_dict/3 to read a JSON term using the version 7
% extended data types.
Expand Down Expand Up @@ -313,13 +318,19 @@
json_string_codes(C1, Stream, Codes),
json_options_value_string_as(Options, Type),
codes_to_type(Type, Codes, String).
json_term_top(0'-, Stream, Number, _Options) :-
json_term_top(0'-, Stream, Number, Options) :-
!,
json_read_number(Stream, 0'-, Number).
json_term_top(D, Stream, Number, _Options) :-
( json_options_decimal_as(Options, rdiv)
-> json_read_number(Stream, 0'-, true, Number)
; json_read_number(Stream, 0'-, false, Number)
).
json_term_top(D, Stream, Number, Options) :-
between(0'0, 0'9, D),
!,
json_read_number(Stream, D, Number).
( json_options_decimal_as(Options, rdiv)
-> json_read_number(Stream, D, true, Number)
; json_read_number(Stream, D, false, Number)
).
json_term_top(C, Stream, Constant, Options) :-
json_read_constant(C, Stream, ID),
json_constant(ID, Constant, Options).
Expand Down Expand Up @@ -455,6 +466,11 @@
line_position(Read, LinePos),
line_count(Read, Line).

mk_rational(Integer, NumberOfDecimals, Rational):-
Rational is Integer rdiv (10 ** NumberOfDecimals).




/*******************************
* JSON OUTPUT *
Expand Down Expand Up @@ -960,6 +976,11 @@
% Prolog type used for strings used as value. Default
% is `string`. The alternative is `atom`, producing a
% packed string object.
% * decimal_as(+Type)
% Prolog type used for non-integer numbers. Default is
% =float=. The alternative is =rdiv=, which produces a
% rdiv/2 term which guarantees no loss of precision.


json_read_dict(Stream, Dict) :-
json_read_dict(Stream, Dict, []).
Expand Down Expand Up @@ -991,6 +1012,10 @@
atomic(Value0), Value0 \== [],
!,
Value = Value0.
term_to_dict(Rational0, Rational, _Options) :-
rational(Rational0),
!,
Rational = Rational0.
term_to_dict(List0, List, Options) :-
is_list(List0),
!,
Expand Down