bpo-47012: speed up iteration of bytes and bytearray (GH-31867)

4 files changed, 13 insertions, 9 deletions

diff --git a/Include/internal/pycore_long.h b/Include/internal/pycore_long.h
index 436bf08..a337624 100644
--- a/Include/internal/pycore_long.h
+++ b/Include/internal/pycore_long.h
@@ -23,8 +23,9 @@ extern void _PyLong_FiniTypes(PyInterpreterState *interp);
 #define _PyLong_SMALL_INTS _Py_SINGLETON(small_ints)
 
 // _PyLong_GetZero() and _PyLong_GetOne() must always be available
-#if _PY_NSMALLPOSINTS < 2
-#  error "_PY_NSMALLPOSINTS must be greater than 1"
+// _PyLong_FromUnsignedChar must always be available
+#if _PY_NSMALLPOSINTS < 257
+#  error "_PY_NSMALLPOSINTS must be greater than or equal to 257"
 #endif
 
 // Return a borrowed reference to the zero singleton.
@@ -37,6 +38,11 @@ static inline PyObject* _PyLong_GetZero(void)
 static inline PyObject* _PyLong_GetOne(void)
 { return (PyObject *)&_PyLong_SMALL_INTS[_PY_NSMALLNEGINTS+1]; }
 
+static inline PyObject* _PyLong_FromUnsignedChar(unsigned char i)
+{
+    return Py_NewRef((PyObject *)&_PyLong_SMALL_INTS[_PY_NSMALLNEGINTS+i]);
+}
+
 PyObject *_PyLong_Add(PyLongObject *left, PyLongObject *right);
 PyObject *_PyLong_Multiply(PyLongObject *left, PyLongObject *right);
 PyObject *_PyLong_Subtract(PyLongObject *left, PyLongObject *right);
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-03-14-11-15-11.bpo-47012.5L6NoE.rst b/Misc/NEWS.d/next/Core and Builtins/2022-03-14-11-15-11.bpo-47012.5L6NoE.rst
new file mode 100644
index 0000000..f85487f
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-03-14-11-15-11.bpo-47012.5L6NoE.rst
@@ -0,0 +1 @@
+Speed up iteration of :class:`bytes` and :class:`bytearray` by 30%. Patch by Kumar Aditya.
diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
index ba2d347..cbe673a 100644
--- a/Objects/bytearrayobject.c
+++ b/Objects/bytearrayobject.c
@@ -6,6 +6,7 @@
 #include "pycore_bytes_methods.h"
 #include "pycore_object.h"        // _PyObject_GC_UNTRACK()
 #include "pycore_strhex.h"        // _Py_strhex_with_sep()
+#include "pycore_long.h"          // _PyLong_FromUnsignedChar()
 #include "bytesobject.h"
 
 /*[clinic input]
@@ -2428,7 +2429,6 @@ static PyObject *
 bytearrayiter_next(bytesiterobject *it)
 {
     PyByteArrayObject *seq;
-    PyObject *item;
 
     assert(it != NULL);
     seq = it->it_seq;
@@ -2437,11 +2437,8 @@ bytearrayiter_next(bytesiterobject *it)
     assert(PyByteArray_Check(seq));
 
     if (it->it_index < PyByteArray_GET_SIZE(seq)) {
-        item = PyLong_FromLong(
-            (unsigned char)PyByteArray_AS_STRING(seq)[it->it_index]);
-        if (item != NULL)
-            ++it->it_index;
-        return item;
+        return _PyLong_FromUnsignedChar(
+            (unsigned char)PyByteArray_AS_STRING(seq)[it->it_index++]);
     }
 
     it->it_seq = NULL;
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index fd1c58c..0039532 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -3133,7 +3133,7 @@ striter_next(striterobject *it)
     assert(PyBytes_Check(seq));
 
     if (it->it_index < PyBytes_GET_SIZE(seq)) {
-        return PyLong_FromLong(
+        return _PyLong_FromUnsignedChar(
             (unsigned char)seq->ob_sval[it->it_index++]);
     }