fix fast string creation for pypy (#75)

Co-authored-by: David Hewitt <mail@davidhewitt.dev>

Cargo.toml

@@ -19,7 +19,7 @@ pyo3 = { version = "0.21.0", default-features=false, features = ["num-bigint"],
 lexical-parse-float = { version = "0.8.5", features =  ["format"] }
 
 [features]
-python = ["dep:pyo3"]
+python = ["dep:pyo3", "dep:pyo3-build-config"]
 
 [dev-dependencies]
 bencher = "0.1.5"
@@ -29,6 +29,9 @@ serde = "1.0.147"
 pyo3 = { version = "0.21.0", default-features=false, features = ["num-bigint", "auto-initialize"] }
 codspeed-bencher-compat = "2.3.1"
 
+[build-dependencies]
+pyo3-build-config = { version = "0.21.0", optional = true }
+
 [profile.bench]
 debug = true
 lto = true

build.rs

@@ -0,0 +1,4 @@
+fn main() {
+    #[cfg(feature = "python")]
+    pyo3_build_config::use_pyo3_cfgs();
+}

src/py_string_cache.rs

@@ -195,6 +195,7 @@ pub fn pystring_fast_new<'py>(py: Python<'py>, s: &str, ascii_only: bool) -> Bou
 
 /// Faster creation of PyString from an ASCII string, inspired by
 /// https://github.com/ijl/orjson/blob/3.10.0/src/str/create.rs#L41
+#[cfg(not(PyPy))]
 unsafe fn pystring_ascii_new<'py>(py: Python<'py>, s: &str) -> Bound<'py, PyString> {
     let ptr = ffi::PyUnicode_New(s.len() as isize, 127);
     // see https://github.com/pydantic/jiter/pull/72#discussion_r1545485907
@@ -204,3 +205,9 @@ unsafe fn pystring_ascii_new<'py>(py: Python<'py>, s: &str) -> Bound<'py, PyStri
     core::ptr::write(data_ptr.add(s.len()), 0);
     Bound::from_owned_ptr(py, ptr).downcast_into_unchecked()
 }
+
+// ffi::PyUnicode_DATA seems to be broken for pypy, hence this
+#[cfg(PyPy)]
+fn pystring_ascii_new<'py>(py: Python<'py>, s: &str) -> Bound<'py, PyString> {
+    PyString::new_bound(py, s)
+}