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Migrate jsonpull to unique_ptr ownership

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Replaces the shared_ptr-based json_object_ptr with a unique_ptr that
has a stateless custom deleter dispatching on json_object::type before
calling the right subclass destructor. Eliminates per-node atomic
reference-counting and the control-block allocation that shared_ptr
required for every node in the tree.

API now distinguishes owning and borrowing pointers explicitly:
- json_read / json_read_separators / json_hash_get return raw
  json_object * (borrowed from the parser-owned tree).
- json_read_tree / json_disconnect return json_object_ptr (caller
  takes ownership; back-pointers are cleared so the subtree can
  outlive the parser).
- json_free / json_context / json_stringify take raw pointers.
- The parser's container_stack holds raw pointers; jp->root keeps
  unique_ptr ownership of the most recent top-level value.

Internally, take_from_owner moves the unique_ptr out of whichever
parent vector / hash entry / parser root owned it, which both
json_free and json_disconnect rely on.

In the streaming parsers (parse_feature, parse_layers, the
geojson-loop callback), we are careful to free `j` only after we
have processed a complete Feature: json_read returns each token
as the tree is being built up, and freeing an intermediate node
would splice it out of the surrounding hash and corrupt the
in-progress feature.

Benchmark (tl_2022_us_county.json, -z0 --extend-zooms-if-still-dropping,
median of 5 runs on macOS arm64): 8.5s, vs 10.6s with shared_ptr
and 8.7s on the pre-refactor C baseline.

Co-authored-by: Cursor <cursoragent@cursor.com>
This commit is contained in:
Erica Fischer
2026-05-30 20:44:25 -07:00
co-authored by Cursor
parent 1a7075e3ab
commit 65beb3f0d7
23 changed files with 408 additions and 289 deletions
Download Patch File Download Diff File Expand all files Collapse all files
plugin.cpp
+26 -16
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@@ -143,16 +143,23 @@ std::vector<mvt_layer> parse_layers(int fd, int z, unsigned x, unsigned y, std::
}
// Reads from the prefilter
serial_feature parse_feature(json_pull_ptr jp, int z, unsigned x, unsigned y, std::vector<std::map<std::string, layermap_entry>> *layermaps, size_t tiling_seg, std::vector<std::vector<std::string>> *layer_unmaps, bool postfilter, key_pool &key_pool) {
serial_feature parse_feature(json_pull_ptr &jp, int z, unsigned x, unsigned y, std::vector<std::map<std::string, layermap_entry>> *layermaps, size_t tiling_seg, std::vector<std::vector<std::string>> *layer_unmaps, bool postfilter, key_pool &key_pool) {
serial_feature sf;
while (1) {
json_object_ptr j = json_read(jp);
// json_read returns each token as the parser produces it, including
// intermediate (still incomplete) container nodes. We must NOT free
// these intermediates here: they belong to the larger feature hash
// still being assembled, and freeing them would splice them out of
// the parent and corrupt the in-progress tree. We only free `j`
// after we have successfully processed a complete Feature hash
// (just before returning), or `jp->root` when the stream ends.
json_object *j = json_read(jp);
if (j == nullptr) {
if (jp->error != nullptr) {
fprintf(stderr, "Filter output:%d: %s: ", jp->line, jp->error);
if (jp->root != nullptr) {
json_context(jp->root);
json_context(jp->root.get());
} else {
fprintf(stderr, "\n");
}
@@ -164,7 +171,7 @@ serial_feature parse_feature(json_pull_ptr jp, int z, unsigned x, unsigned y, st
return sf;
}
json_object_ptr type = json_hash_get(j, "type");
json_object *type = json_hash_get(j, "type");
if (type == nullptr || type->type != JSON_STRING) {
continue;
}
@@ -172,21 +179,21 @@ serial_feature parse_feature(json_pull_ptr jp, int z, unsigned x, unsigned y, st
continue;
}
json_object_ptr geometry = json_hash_get(j, "geometry");
json_object *geometry = json_hash_get(j, "geometry");
if (geometry == nullptr) {
fprintf(stderr, "Filter output:%d: filtered feature with no geometry: ", jp->line);
json_context(j);
exit(EXIT_JSON);
}
json_object_ptr properties = json_hash_get(j, "properties");
json_object *properties = json_hash_get(j, "properties");
if (properties == nullptr || (properties->type != JSON_HASH && properties->type != JSON_NULL)) {
fprintf(stderr, "Filter output:%d: feature without properties hash: ", jp->line);
json_context(j);
exit(EXIT_JSON);
}
json_object_ptr geometry_type = json_hash_get(geometry, "type");
json_object *geometry_type = json_hash_get(geometry, "type");
if (geometry_type == nullptr) {
fprintf(stderr, "Filter output:%d: null geometry (additional not reported): ", jp->line);
json_context(j);
@@ -199,7 +206,7 @@ serial_feature parse_feature(json_pull_ptr jp, int z, unsigned x, unsigned y, st
exit(EXIT_JSON);
}
json_object_ptr coordinates = json_hash_get(geometry, "coordinates");
json_object *coordinates = json_hash_get(geometry, "coordinates");
if (coordinates == nullptr || coordinates->type != JSON_ARRAY) {
fprintf(stderr, "Filter output:%d: feature without coordinates array: ", jp->line);
json_context(j);
@@ -248,29 +255,29 @@ serial_feature parse_feature(json_pull_ptr jp, int z, unsigned x, unsigned y, st
sf.has_id = false;
std::string layername = "unknown";
json_object_ptr tippecanoe = json_hash_get(j, "tippecanoe");
json_object *tippecanoe = json_hash_get(j, "tippecanoe");
if (tippecanoe != nullptr) {
json_object_ptr layer = json_hash_get(tippecanoe, "layer");
json_object *layer = json_hash_get(tippecanoe, "layer");
if (layer != nullptr && layer->type == JSON_STRING) {
layername = layer->string();
}
json_object_ptr index = json_hash_get(tippecanoe, "index");
json_object *index = json_hash_get(tippecanoe, "index");
if (index != nullptr && index->type == JSON_NUMBER) {
sf.index = index->number();
}
json_object_ptr sequence = json_hash_get(tippecanoe, "sequence");
json_object *sequence = json_hash_get(tippecanoe, "sequence");
if (sequence != nullptr && sequence->type == JSON_NUMBER) {
sf.seq = sequence->number();
}
json_object_ptr extent = json_hash_get(tippecanoe, "extent");
json_object *extent = json_hash_get(tippecanoe, "extent");
if (extent != nullptr && extent->type == JSON_NUMBER) {
sf.extent = extent->number();
}
json_object_ptr dropped = json_hash_get(tippecanoe, "dropped");
json_object *dropped = json_hash_get(tippecanoe, "dropped");
if (dropped != nullptr && dropped->type == JSON_TRUE) {
sf.dropped = FEATURE_DROPPED; // dropped
} else {
@@ -295,7 +302,7 @@ serial_feature parse_feature(json_pull_ptr jp, int z, unsigned x, unsigned y, st
}
}
json_object_ptr id = json_hash_get(j, "id");
json_object *id = json_hash_get(j, "id");
if (id != nullptr && id->type == JSON_NUMBER) {
sf.id = id->number();
if (id->large_unsigned() > 0) {
@@ -345,7 +352,7 @@ serial_feature parse_feature(json_pull_ptr jp, int z, unsigned x, unsigned y, st
if (properties->type == JSON_HASH) {
for (const auto &e : properties->entries()) {
serial_val v = stringify_value(e.value, "Filter output", jp->line, j);
serial_val v = stringify_value(e.value.get(), "Filter output", jp->line, j);
// Nulls can be excluded here because the expression evaluation filter
// would have already run before prefiltering
@@ -361,8 +368,11 @@ serial_feature parse_feature(json_pull_ptr jp, int z, unsigned x, unsigned y, st
}
}
json_free(j);
return sf;
}
json_free(j);
}
}