STATIC bool is_whitespace(mp_lexer_t *lex) {
return unichar_isspace(lex->chr0);
}
// This function implements a simple non-recursive JSON parser.
//
// The JSON specification is at http://www.ietf.org/rfc/rfc4627.txt
// The parser here will parse any valid JSON and return the correct
// corresponding Python object. It allows through a superset of JSON, since
// it treats commas and colons as "whitespace", and doesn't care if
// brackets/braces are correctly paired. It will raise a ValueError if the
// input is outside it's specs.
//
// Most of the work is parsing the primitives (null, false, true, numbers,
// strings). It does 1 pass over the input string and so is easily extended to
// being able to parse from a non-seekable stream. It tries to be fast and
// small in code size, while not using more RAM than necessary.
STATIC mp_obj_t mod_ujson_loads(mp_obj_t obj) {
mp_uint_t len;
const char *s = mp_obj_str_get_data(obj, &len);
const char *top = s + len;
vstr_t vstr;
vstr_init(&vstr, 8);
mp_obj_list_t stack; // we use a list as a simple stack for nested JSON
stack.len = 0;
stack.items = NULL;
mp_obj_t stack_top = MP_OBJ_NULL;
mp_obj_type_t *stack_top_type = NULL;
mp_obj_t stack_key = MP_OBJ_NULL;
for (;;) {
cont:
if (s == top) {
break;
}
mp_obj_t next = MP_OBJ_NULL;
bool enter = false;
switch (*s) {
case ',':
case ':':
case ' ':
s += 1;
goto cont;
case 'n':
if (s + 3 < top && s[1] == 'u' && s[2] == 'l' && s[3] == 'l') {
s += 4;
next = mp_const_none;
} else {
goto fail;
}
break;
case 'f':
if (s + 4 < top && s[1] == 'a' && s[2] == 'l' && s[3] == 's' && s[4] == 'e') {
s += 5;
next = mp_const_false;
} else {
goto fail;
}
break;
case 't':
if (s + 3 < top && s[1] == 'r' && s[2] == 'u' && s[3] == 'e') {
s += 4;
next = mp_const_true;
} else {
goto fail;
}
break;
case '"':
vstr_reset(&vstr);
for (s++; s < top && *s != '"';) {
byte c = *s;
if (c == '\\') {
s++;
c = *s;
switch (c) {
case 'b': c = 0x08; break;
case 'f': c = 0x0c; break;
case 'n': c = 0x0a; break;
case 'r': c = 0x0d; break;
case 't': c = 0x09; break;
case 'u': {
if (s + 4 >= top) { goto fail; }
mp_uint_t num = 0;
for (int i = 0; i < 4; i++) {
c = (*++s | 0x20) - '0';
if (c > 9) {
c -= ('a' - ('9' + 1));
}
num = (num << 4) | c;
}
vstr_add_char(&vstr, num);
goto str_cont;
}
}
}
vstr_add_byte(&vstr, c);
str_cont:
s++;
}
if (s == top) {
goto fail;
}
s++;
next = mp_obj_new_str(vstr.buf, vstr.len, false);
break;
case '-':
case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': {
bool flt = false;
vstr_reset(&vstr);
for (; s < top; s++) {
if (*s == '.' || *s == 'E' || *s == 'e') {
flt = true;
} else if (*s == '-' || unichar_isdigit(*s)) {
// pass
} else {
break;
}
vstr_add_byte(&vstr, *s);
}
if (flt) {
next = mp_parse_num_decimal(vstr.buf, vstr.len, false, false);
} else {
next = mp_parse_num_integer(vstr.buf, vstr.len, 10);
}
break;
}
case '[':
next = mp_obj_new_list(0, NULL);
enter = true;
s += 1;
break;
case '{':
next = mp_obj_new_dict(0);
enter = true;
s += 1;
break;
case '}':
case ']': {
s += 1;
if (stack_top == MP_OBJ_NULL) {
// no object at all
goto fail;
}
if (stack.len == 0) {
// finished; compound object
goto success;
}
stack.len -= 1;
stack_top = stack.items[stack.len];
stack_top_type = mp_obj_get_type(stack_top);
goto cont;
}
default:
goto fail;
}
if (stack_top == MP_OBJ_NULL) {
stack_top = next;
stack_top_type = mp_obj_get_type(stack_top);
if (!enter) {
// finished; single primitive only
goto success;
}
} else {
// append to list or dict
if (stack_top_type == &mp_type_list) {
mp_obj_list_append(stack_top, next);
} else {
if (stack_key == MP_OBJ_NULL) {
stack_key = next;
if (enter) {
goto fail;
}
} else {
mp_obj_dict_store(stack_top, stack_key, next);
stack_key = MP_OBJ_NULL;
}
}
if (enter) {
if (stack.items == NULL) {
mp_obj_list_init(&stack, 1);
stack.items[0] = stack_top;
} else {
mp_obj_list_append(&stack, stack_top);
}
stack_top = next;
stack_top_type = mp_obj_get_type(stack_top);
}
}
}
success:
// eat trailing whitespace
while (s < top && unichar_isspace(*s)) {
s++;
}
if (s < top) {
// unexpected chars
goto fail;
}
if (stack.len != 0) {
goto fail;
}
vstr_clear(&vstr);
return stack_top;
fail:
nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "syntax error in JSON"));
}
