Add custom error creator function

This commit add the tg_geom_new_error() function, which allows for creating custom error geometries outside of the TG library.
tidwall · Dec 3, 2024 · 1f494a5 · 1f494a5
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commit 1f494a5
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diff --git a/docs/API.md b/docs/API.md
@@ -142,6 +142,7 @@ Functions for creating and freeing geometries.
 - [tg_geom_new_multilinestring()](#group___geometry_constructors_1gaccfd80de48f1e5c7de38cbf515d3bf9f)
 - [tg_geom_new_multipolygon()](#group___geometry_constructors_1gad57b01099788e21a5103cd8293f4e364)
 - [tg_geom_new_geometrycollection()](#group___geometry_constructors_1ga39569ef55606b8d54ed7cf14a4382bdd)
+- [tg_geom_new_error()](#group___geometry_constructors_1ga53823d8d5f2f77ba2ac14b4f8a77700c)
 - [tg_geom_clone()](#group___geometry_constructors_1ga76f55846aa97188b1840b9ad07dae000)
 - [tg_geom_copy()](#group___geometry_constructors_1ga389a890d60908d3e2b448a0e2b3d558e)
 - [tg_geom_free()](#group___geometry_constructors_1gaf6f400f624b9f3e9052ac26ab17d72ae)
@@ -871,6 +872,14 @@ Creates a GeometryCollection geometry.
 
 
 
+<a name='group___geometry_constructors_1ga53823d8d5f2f77ba2ac14b4f8a77700c'></a>
+## tg_geom_new_error()
+```c
+struct tg_geom *tg_geom_new_error(const char *errmsg);
+```
+Utility for returning an error message wrapped in a geometry. This operation does not return a real geometry, only an error message, which may be useful for generating custom errors from operations outside of the TG library. 
+
+
 <a name='group___geometry_constructors_1ga76f55846aa97188b1840b9ad07dae000'></a>
 ## tg_geom_clone()
 ```c

diff --git a/tests/test_geom.c b/tests/test_geom.c
@@ -981,6 +981,21 @@ void test_geom_chaos(void) {
 
 }
 
+void test_geom_error(void) {
+    struct tg_geom *geom;
+    geom = tg_geom_new_error(0);
+    assert(strcmp(tg_geom_error(geom), "no memory") == 0);
+    tg_geom_free(geom);
+
+    geom = tg_geom_new_error("");
+    assert(strcmp(tg_geom_error(geom), "") == 0);
+    tg_geom_free(geom);
+
+    geom = tg_geom_new_error("hello");
+    assert(strcmp(tg_geom_error(geom), "hello") == 0);
+    tg_geom_free(geom);
+
+}
 
 int main(int argc, char **argv) {
     do_test(test_geom_point);
@@ -996,5 +1011,6 @@ int main(int argc, char **argv) {
     do_test(test_geom_various);
     do_test(test_geom_copy);
     do_chaos_test(test_geom_chaos);
+    do_test(test_geom_error);
     return 0;
 }
diff --git a/tg.c b/tg.c
@@ -14344,3 +14344,11 @@ struct tg_geom *tg_parse_ix(const void *data, size_t len, enum tg_index ix) {
 wkb:
     return tg_parse_wkb_ix((uint8_t*)src, len, ix);
 }
+
+/// Utility for returning an error message wrapped in a geometry.
+/// This operation does not return a real geometry, only an error message,
+/// which may be useful for generating custom errors from operations 
+/// outside of the TG library.
+struct tg_geom *tg_geom_new_error(const char *error) {
+    return error?make_parse_error("%s", error):0;
+}
diff --git a/tg.h b/tg.h
@@ -82,6 +82,7 @@ struct tg_geom *tg_geom_new_multipoint(const struct tg_point *points, int npoint
 struct tg_geom *tg_geom_new_multilinestring(const struct tg_line *const lines[], int nlines);
 struct tg_geom *tg_geom_new_multipolygon(const struct tg_poly *const polys[], int npolys);
 struct tg_geom *tg_geom_new_geometrycollection(const struct tg_geom *const geoms[], int ngeoms);
+struct tg_geom *tg_geom_new_error(const char *errmsg);
 struct tg_geom *tg_geom_clone(const struct tg_geom *geom);
 struct tg_geom *tg_geom_copy(const struct tg_geom *geom);
 void tg_geom_free(struct tg_geom *geom);