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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
geojson.cpp
+25 -25
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@@ -68,12 +68,12 @@ int serialize_geojson_feature(struct serialization_state *sst, json_object_ptr g
int t;
for (t = 0; t < GEOM_TYPES; t++) {
if (geometry_type->value.string.string == geometry_names[t]) {
if (geometry_type->string() == geometry_names[t]) {
break;
}
}
if (t >= GEOM_TYPES) {
fprintf(stderr, "%s:%d: Can't handle geometry type %s: ", sst->fname, sst->line, geometry_type->value.string.string.c_str());
fprintf(stderr, "%s:%d: Can't handle geometry type %s: ", sst->fname, sst->line, geometry_type->string().c_str());
json_context(feature);
return 0;
}
@@ -85,17 +85,17 @@ int serialize_geojson_feature(struct serialization_state *sst, json_object_ptr g
if (tippecanoe != nullptr) {
json_object_ptr min = json_hash_get(tippecanoe, "minzoom");
if (min != nullptr && (min->type == JSON_NUMBER)) {
tippecanoe_minzoom = integer_zoom(sst->fname, milo::dtoa_milo(min->value.number.number));
tippecanoe_minzoom = integer_zoom(sst->fname, milo::dtoa_milo(min->number()));
}
json_object_ptr max = json_hash_get(tippecanoe, "maxzoom");
if (max != nullptr && (max->type == JSON_NUMBER)) {
tippecanoe_maxzoom = integer_zoom(sst->fname, milo::dtoa_milo(max->value.number.number));
tippecanoe_maxzoom = integer_zoom(sst->fname, milo::dtoa_milo(max->number()));
}
json_object_ptr ln = json_hash_get(tippecanoe, "layer");
if (ln != nullptr && (ln->type == JSON_STRING)) {
tippecanoe_layername = ln->value.string.string;
tippecanoe_layername = ln->string();
}
}
@@ -103,27 +103,27 @@ int serialize_geojson_feature(struct serialization_state *sst, json_object_ptr g
unsigned long long id_value = 0;
if (id != nullptr) {
if (id->type == JSON_NUMBER) {
if (id->value.number.number >= 0) {
if (id->number() >= 0) {
char *err = NULL;
std::string id_number = milo::dtoa_milo(id->value.number.number);
std::string id_number = milo::dtoa_milo(id->number());
id_value = strtoull(id_number.c_str(), &err, 10);
if (id->value.number.large_unsigned != 0) {
id_value = id->value.number.large_unsigned;
if (id->large_unsigned() != 0) {
id_value = id->large_unsigned();
}
if (err != NULL && *err != '\0') {
static bool warned_frac = false;
if (!warned_frac) {
fprintf(stderr, "Warning: Can't represent non-integer feature ID %s\n", milo::dtoa_milo(id->value.number.number).c_str());
fprintf(stderr, "Warning: Can't represent non-integer feature ID %s\n", milo::dtoa_milo(id->number()).c_str());
warned_frac = true;
}
} else if (id->value.number.large_unsigned == 0 && std::to_string(id_value) != milo::dtoa_milo(id->value.number.number)) {
} else if (id->large_unsigned() == 0 && std::to_string(id_value) != milo::dtoa_milo(id->number())) {
static bool warned = false;
if (!warned) {
fprintf(stderr, "Warning: Can't represent too-large feature ID %s\n", milo::dtoa_milo(id->value.number.number).c_str());
fprintf(stderr, "Warning: Can't represent too-large feature ID %s\n", milo::dtoa_milo(id->number()).c_str());
warned = true;
}
} else {
@@ -133,7 +133,7 @@ int serialize_geojson_feature(struct serialization_state *sst, json_object_ptr g
static bool warned_neg = false;
if (!warned_neg) {
fprintf(stderr, "Warning: Can't represent negative feature ID %s\n", milo::dtoa_milo(id->value.number.number).c_str());
fprintf(stderr, "Warning: Can't represent negative feature ID %s\n", milo::dtoa_milo(id->number()).c_str());
warned_neg = true;
}
}
@@ -142,20 +142,20 @@ int serialize_geojson_feature(struct serialization_state *sst, json_object_ptr g
if (additional[A_CONVERT_NUMERIC_IDS] && id->type == JSON_STRING) {
char *err = NULL;
id_value = strtoull(id->value.string.string.c_str(), &err, 10);
id_value = strtoull(id->string().c_str(), &err, 10);
if (err != NULL && *err != '\0') {
static bool warned_frac = false;
if (!warned_frac) {
fprintf(stderr, "Warning: Can't represent non-integer feature ID %s\n", id->value.string.string.c_str());
fprintf(stderr, "Warning: Can't represent non-integer feature ID %s\n", id->string().c_str());
warned_frac = true;
}
} else if (std::to_string(id_value) != id->value.string.string) {
} else if (std::to_string(id_value) != id->string()) {
static bool warned = false;
if (!warned) {
fprintf(stderr, "Warning: Can't represent too-large feature ID %s\n", id->value.string.string.c_str());
fprintf(stderr, "Warning: Can't represent too-large feature ID %s\n", id->string().c_str());
warned = true;
}
} else {
@@ -177,7 +177,7 @@ int serialize_geojson_feature(struct serialization_state *sst, json_object_ptr g
size_t nprop = 0;
if (properties != nullptr && properties->type == JSON_HASH) {
nprop = properties->value.object.keys.size();
nprop = properties->keys().size();
}
std::vector<std::shared_ptr<std::string>> full_keys;
@@ -188,10 +188,10 @@ int serialize_geojson_feature(struct serialization_state *sst, json_object_ptr g
key_pool key_pool;
for (size_t i = 0; i < nprop; i++) {
if (properties->value.object.keys[i]->type == JSON_STRING) {
serial_val sv = stringify_value(properties->value.object.values[i], sst->fname, sst->line, feature);
if (properties->keys()[i]->type == JSON_STRING) {
serial_val sv = stringify_value(properties->values()[i], sst->fname, sst->line, feature);
full_keys.emplace_back(key_pool.pool(properties->value.object.keys[i]->value.string.string.c_str()));
full_keys.emplace_back(key_pool.pool(properties->keys()[i]->string().c_str()));
values.push_back(std::move(sv));
}
}
@@ -223,9 +223,9 @@ void check_crs(json_object_ptr j, const char *reading) {
if (properties != nullptr) {
json_object_ptr name = json_hash_get(properties, "name");
if (name != nullptr && name->type == JSON_STRING) {
if (name->value.string.string != projection->alias) {
if (name->string() != projection->alias) {
if (!quiet) {
fprintf(stderr, "%s: Warning: GeoJSON specified projection \"%s\", not the expected \"%s\".\n", reading, name->value.string.string.c_str(), projection->alias);
fprintf(stderr, "%s: Warning: GeoJSON specified projection \"%s\", not the expected \"%s\".\n", reading, name->string().c_str(), projection->alias);
fprintf(stderr, "%s: If \"%s\" is not the expected projection, use -s to specify the right one.\n", reading, projection->alias);
}
}
@@ -243,8 +243,8 @@ struct json_serialize_action : json_feature_action {
sst->line = geometry->parser->line;
if (geometrycollection) {
int ret = 1;
for (size_t g = 0; g < geometry->value.array.array.size(); g++) {
ret &= serialize_geojson_feature(sst, geometry->value.array.array[g], properties, id, layer, tippecanoe, feature, layername);
for (size_t g = 0; g < geometry->array().size(); g++) {
ret &= serialize_geojson_feature(sst, geometry->array()[g], properties, id, layer, tippecanoe, feature, layername);
}
return ret;
} else {