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Subclass json_object so primitives shrink from 168 to 24 bytes

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The previous "every member in a struct" layout cost 168 bytes per
json_object, even for JSON_NULL / JSON_TRUE / JSON_FALSE nodes that
have no payload. Splitting json_object into a small base class plus
json_number / json_string / json_array / json_hash subclasses brings
each instance down to just the size of its actual contents:

  json_object (base, TRUE / FALSE / NULL)   24 bytes
  json_number                                48 bytes
  json_string                                48 bytes
  json_array  (empty)                        48 bytes
  json_hash   (empty)                        72 bytes

Other size wins along the way:

* Drop enable_shared_from_this<json_object> (its embedded weak_ptr
  was 16 bytes per node). json_pull now keeps an explicit
  container_stack and the parser no longer needs to resurrect a
  shared_ptr from a raw `parent` walk.
* Remove the unused `refcon` slot from the string variant.
* No virtual destructor: shared_ptr keeps the deleter from the
  original std::make_shared<json_xxx> call, so destroying a
  shared_ptr<json_object> still runs the right subclass dtor.

The base class exposes type-tagged accessors (o->string(),
o->number(), o->array(), o->keys(), o->values(), o->large_signed(),
o->large_unsigned()) that assert the type matches and downcast to
the appropriate subclass storage. All call sites were swept from
the old `o->value.X.Y` field paths to these accessors. A raw-pointer
overload of json_hash_get() replaces the few external uses of
shared_from_this() that survived in geojson-loop.cpp.

Co-authored-by: Cursor <cursoragent@cursor.com>
This commit is contained in:
Erica Fischer
2026-05-30 17:49:08 -07:00
co-authored by Cursor
parent 3da03c6075
commit f366b2c4aa
14 changed files with 424 additions and 291 deletions
Download Patch File Download Diff File Expand all files Collapse all files
evaluator.cpp
+28 -28
View File
@@ -17,7 +17,7 @@ int compare(mvt_value const &one, json_object_ptr two, bool &fail) {
return false; // string vs non-string
}
return strcmp(one.c_str(), two->value.string.string.c_str());
return strcmp(one.c_str(), two->string().c_str());
case mvt_double:
case mvt_float:
@@ -52,9 +52,9 @@ int compare(mvt_value const &one, json_object_ptr two, bool &fail) {
exit(EXIT_IMPOSSIBLE);
}
if (v < two->value.number.number) {
if (v < two->number()) {
return -1;
} else if (v > two->value.number.number) {
} else if (v > two->number()) {
return 1;
} else {
return 0;
@@ -102,7 +102,7 @@ static int eval(std::function<mvt_value(std::string const &)> feature, json_obje
}
if (f->type == JSON_NUMBER) {
if (f->value.number.number == 0) {
if (f->number() == 0) {
return 0;
} else {
return 1;
@@ -110,7 +110,7 @@ static int eval(std::function<mvt_value(std::string const &)> feature, json_obje
}
if (f->type == JSON_STRING) {
if (f->value.string.string.empty()) {
if (f->string().empty()) {
return 0;
} else {
return 1;
@@ -123,39 +123,39 @@ static int eval(std::function<mvt_value(std::string const &)> feature, json_obje
exit(EXIT_FILTER);
}
if (f->value.array.array.size() < 1) {
if (f->array().size() < 1) {
fprintf(stderr, "Array too small in filter: %s\n", json_stringify(f).c_str());
exit(EXIT_FILTER);
}
if (f->value.array.array[0]->type != JSON_STRING) {
if (f->array()[0]->type != JSON_STRING) {
fprintf(stderr, "Filter operation is not a string: %s\n", json_stringify(f).c_str());
exit(EXIT_FILTER);
}
const std::string &op = f->value.array.array[0]->value.string.string;
const std::string &op = f->array()[0]->string();
if (op == "has" ||
op == "!has") {
if (f->value.array.array.size() != 2) {
if (f->array().size() != 2) {
fprintf(stderr, "Wrong number of array elements in filter: %s\n", json_stringify(f).c_str());
exit(EXIT_FILTER);
}
if (op == "has") {
if (f->value.array.array[1]->type != JSON_STRING) {
if (f->array()[1]->type != JSON_STRING) {
fprintf(stderr, "\"has\" key is not a string: %s\n", json_stringify(f).c_str());
exit(EXIT_FILTER);
}
return feature(f->value.array.array[1]->value.string.string).type != mvt_no_such_key;
return feature(f->array()[1]->string()).type != mvt_no_such_key;
}
if (op == "!has") {
if (f->value.array.array[1]->type != JSON_STRING) {
if (f->array()[1]->type != JSON_STRING) {
fprintf(stderr, "\"!has\" key is not a string: %s\n", json_stringify(f).c_str());
exit(EXIT_FILTER);
}
return feature(f->value.array.array[1]->value.string.string).type == mvt_no_such_key;
return feature(f->array()[1]->string()).type == mvt_no_such_key;
}
}
@@ -165,16 +165,16 @@ static int eval(std::function<mvt_value(std::string const &)> feature, json_obje
op == ">=" ||
op == "<" ||
op == "<=") {
if (f->value.array.array.size() != 3) {
if (f->array().size() != 3) {
fprintf(stderr, "Wrong number of array elements in filter: %s\n", json_stringify(f).c_str());
exit(EXIT_FILTER);
}
if (f->value.array.array[1]->type != JSON_STRING) {
if (f->array()[1]->type != JSON_STRING) {
fprintf(stderr, "comparison key is not a string: %s\n", json_stringify(f).c_str());
exit(EXIT_FILTER);
}
mvt_value ff = feature(f->value.array.array[1]->value.string.string);
mvt_value ff = feature(f->array()[1]->string());
if (ff.type == mvt_no_such_key) {
static bool warned = false;
if (!warned) {
@@ -188,7 +188,7 @@ static int eval(std::function<mvt_value(std::string const &)> feature, json_obje
}
bool fail = false;
int cmp = compare(ff, f->value.array.array[2], fail);
int cmp = compare(ff, f->array()[2], fail);
if (fail) {
static bool warned = false;
@@ -236,8 +236,8 @@ static int eval(std::function<mvt_value(std::string const &)> feature, json_obje
v = false;
}
for (size_t i = 1; i < f->value.array.array.size(); i++) {
int out = eval(feature, f->value.array.array[i], exclude_attributes, unidecode_data);
for (size_t i = 1; i < f->array().size(); i++) {
int out = eval(feature, f->array()[i], exclude_attributes, unidecode_data);
if (out >= 0) { // nulls are ignored in boolean and/or expressions
if (op == "all") {
@@ -263,17 +263,17 @@ static int eval(std::function<mvt_value(std::string const &)> feature, json_obje
if (op == "in" ||
op == "!in") {
if (f->value.array.array.size() < 2) {
if (f->array().size() < 2) {
fprintf(stderr, "Array too small in filter: %s\n", json_stringify(f).c_str());
exit(EXIT_FILTER);
}
if (f->value.array.array[1]->type != JSON_STRING) {
if (f->array()[1]->type != JSON_STRING) {
fprintf(stderr, "\"!in\" key is not a string: %s\n", json_stringify(f).c_str());
exit(EXIT_FILTER);
}
mvt_value ff = feature(f->value.array.array[1]->value.string.string);
mvt_value ff = feature(f->array()[1]->string());
if (ff.type == mvt_no_such_key) {
static bool warned = false;
if (!warned) {
@@ -287,9 +287,9 @@ static int eval(std::function<mvt_value(std::string const &)> feature, json_obje
}
bool found = false;
for (size_t i = 2; i < f->value.array.array.size(); i++) {
for (size_t i = 2; i < f->array().size(); i++) {
bool fail = false;
int cmp = compare(ff, f->value.array.array[i], fail);
int cmp = compare(ff, f->array()[i], fail);
if (fail) {
static bool warned = false;
@@ -314,19 +314,19 @@ static int eval(std::function<mvt_value(std::string const &)> feature, json_obje
}
if (op == "attribute-filter") {
if (f->value.array.array.size() != 3) {
if (f->array().size() != 3) {
fprintf(stderr, "Wrong number of array elements in filter: %s\n", json_stringify(f).c_str());
exit(EXIT_FILTER);
}
if (f->value.array.array[1]->type != JSON_STRING) {
if (f->array()[1]->type != JSON_STRING) {
fprintf(stderr, "\"attribute-filter\" key is not a string: %s\n", json_stringify(f).c_str());
exit(EXIT_FILTER);
}
bool ok = eval(feature, f->value.array.array[2], exclude_attributes, unidecode_data) > 0;
bool ok = eval(feature, f->array()[2], exclude_attributes, unidecode_data) > 0;
if (!ok) {
exclude_attributes.insert(f->value.array.array[1]->value.string.string);
exclude_attributes.insert(f->array()[1]->string());
}
return true;