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common: enhance json_scan with simple array helpers.

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In several places we want to access the first element of an array.
This uses a '[indexnum:xxx]' form which is a bit weird, but works similarly
to the way we specify member matches.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2021-01-06 16:11:19 +10:30 • committed by Christian Decker
parent 553daf17e0
commit a5befb0072
2 changed files with 110 additions and 4 deletions
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90
common/json.c
View file

@ -782,11 +782,14 @@ static bool handle_percent(const char *buffer,
}
}
/* GUIDE := OBJ | '%'
/* GUIDE := OBJ | ARRAY | '%'
* OBJ := '{' FIELDLIST '}'
* FIELDLIST := FIELD [',' FIELD]*
* FIELD := LITERAL ':' FIELDVAL
* FIELDVAL := OBJ | LITERAL | '%'
* FIELDVAL := OBJ | ARRAY | LITERAL | '%'
* ARRAY := '[' ARRLIST ']'
* ARRLIST := ARRELEM [',' ARRELEM]*
* ARRELEM := NUMBER ':' FIELDVAL
*/
/* Returns NULL on failure, or offset into guide */
@ -803,12 +806,34 @@ static const char *parse_literal(const char *guide,
return guide + *len;
}
static const char *parse_number(const char *guide, u32 *number)
{
char *endp;
long int l;
l = strtol(guide, &endp, 10);
if (endp == guide || errno == ERANGE)
return NULL;
/* Test for overflow */
*number = l;
if (*number != l)
return NULL;
return endp;
}
/* Recursion */
static const char *parse_obj(const char *buffer,
const jsmntok_t *tok,
const char *guide,
va_list *ap);
static const char *parse_arr(const char *buffer,
const jsmntok_t *tok,
const char *guide,
va_list *ap);
static const char *parse_guide(const char *buffer,
const jsmntok_t *tok,
const char *guide,
@ -820,6 +845,12 @@ static const char *parse_guide(const char *buffer,
return NULL;
assert(*guide == '}');
return guide + 1;
} else if (*guide == '[') {
guide = parse_arr(buffer, tok, guide, ap);
if (!guide)
return NULL;
assert(*guide == ']');
return guide + 1;
} else {
assert(*guide == '%');
if (!handle_percent(buffer, tok, ap))
@ -839,6 +870,12 @@ static const char *parse_fieldval(const char *buffer,
return NULL;
assert(*guide == '}');
return guide + 1;
} else if (*guide == '[') {
guide = parse_arr(buffer, tok, guide, ap);
if (!guide)
return NULL;
assert(*guide == ']');
return guide + 1;
} else if (*guide == '%') {
if (!handle_percent(buffer, tok, ap))
return NULL;
@ -907,6 +944,55 @@ static const char *parse_obj(const char *buffer,
return guide;
}
static const char *parse_arrelem(const char *buffer,
const jsmntok_t *tok,
const char *guide,
va_list *ap)
{
const jsmntok_t *member;
u32 idx;
guide = parse_number(guide, &idx);
assert(*guide == ':');
member = json_get_arr(tok, idx);
if (!member)
return NULL;
return parse_fieldval(buffer, member, guide + 1, ap);
}
static const char *parse_arrlist(const char *buffer,
const jsmntok_t *tok,
const char *guide,
va_list *ap)
{
for (;;) {
guide = parse_arrelem(buffer, tok, guide, ap);
if (!guide)
return NULL;
if (*guide != ',')
break;
guide++;
}
return guide;
}
static const char *parse_arr(const char *buffer,
const jsmntok_t *tok,
const char *guide,
va_list *ap)
{
assert(*guide == '[');
if (tok->type != JSMN_ARRAY)
return NULL;
guide = parse_arrlist(buffer, tok, guide + 1, ap);
if (!guide)
return NULL;
return guide;
}
bool json_scanv(const char *buffer,
const jsmntok_t *tok,
const char *guide,

24
common/test/run-json_scan.c
View file

@ -140,16 +140,19 @@ int main(int argc, char *argv[])
common_setup(argv[0]);
buf = tal_strdup(tmpctx, "{\"1\":\"one\", \"2\":\"two\", \"3\":{\"three\": {\"deeper\": 17}}}");
buf = tal_strdup(tmpctx, "{\"1\":\"one\", \"2\":\"two\", \"3\":{\"three\": {\"deeper\": 17}}, \"arr\": [{\"1\": \"arrone\"}, 2, [3, 4]]}");
toks = json_parse_simple(tmpctx, buf, strlen(buf));
assert(toks);
assert(toks->size == 3);
assert(toks->size == 4);
/* These are direct matches, and they work. */
assert(json_scan(buf, toks, "{1:one}"));
assert(json_scan(buf, toks, "{1:one,2:two}"));
assert(json_scan(buf, toks, "{2:two,1:one}"));
assert(json_scan(buf, toks, "{2:two,1:one,3:{three:{deeper:17}}}"));
assert(json_scan(buf, toks, "{2:two,1:one,3:{three:{deeper:17}},arr:[0:{1:arrone}]}"));
assert(json_scan(buf, toks, "{2:two,1:one,3:{three:{deeper:17}},arr:[1:2]}"));
assert(json_scan(buf, toks, "{2:two,1:one,3:{three:{deeper:17}},arr:[1:2,2:[0:3,1:4]]}"));
/* These do not match */
assert(!json_scan(buf, toks, "{2:one}"));
@ -159,6 +162,12 @@ int main(int argc, char *argv[])
assert(!json_scan(buf, toks, "{2:two,1:one,3:three}"));
assert(!json_scan(buf, toks, "{3:{three:deeper}}"));
assert(!json_scan(buf, toks, "{3:{three:{deeper:{}}}}"));
assert(!json_scan(buf, toks, "{arr:{}}"));
assert(!json_scan(buf, toks, "{arr:[0:1]}"));
assert(!json_scan(buf, toks, "{arr:[4:0]}"));
assert(!json_scan(buf, toks, "{arr:[0:{1:arrtwo}]}"));
assert(!json_scan(buf, toks, "{arr:[1:3]}"));
assert(!json_scan(buf, toks, "{arr:[2:[0:1]]}"));
/* These capture simple values. */
assert(json_scan(buf, toks, "{3:{three:{deeper:%}}}",
@ -177,5 +186,16 @@ int main(int argc, char *argv[])
assert(json_scan(buf, toks, "{3:%}", JSON_SCAN(json_to_tok, &t)));
assert(t == &toks[6]);
assert(json_scan(buf, toks, "{arr:%}", JSON_SCAN(json_to_tok, &t)));
assert(t == &toks[12]);
assert(json_scan(buf, toks, "{arr:[1:%]}",
JSON_SCAN(json_to_number, &u32val)));
assert(u32val == 2);
assert(json_scan(buf, toks, "{arr:[2:[1:%]]}",
JSON_SCAN(json_to_number, &u32val)));
assert(u32val == 4);
common_shutdown();
}