From 74df7785f5779a6878932f2141a6a2db9e1d903e Mon Sep 17 00:00:00 2001
From: Sam Gross <colesbury@gmail.com>
Date: Mon, 6 Mar 2023 08:17:19 -0800
Subject: [PATCH] pyqueue: add internal queue data structure

---
 Include/cpython/pyqueue.h          | 18 +++++++++
 Include/internal/pycore_pyqueue.h  | 61 ++++++++++++++++++++++++++++++
 Makefile.pre.in                    |  1 +
 PCbuild/pythoncore.vcxproj         |  1 +
 PCbuild/pythoncore.vcxproj.filters |  3 ++
 5 files changed, 84 insertions(+)
 create mode 100644 Include/cpython/pyqueue.h
 create mode 100644 Include/internal/pycore_pyqueue.h

diff --git a/Include/cpython/pyqueue.h b/Include/cpython/pyqueue.h
new file mode 100644
index 0000000000..2f6a034698
--- /dev/null
+++ b/Include/cpython/pyqueue.h
@@ -0,0 +1,18 @@
+#ifndef Py_PYQUEUE_H
+#define Py_PYQUEUE_H
+/* Header excluded from the stable API */
+#ifndef Py_LIMITED_API
+
+// See pycore_pyqueue.h for the implementation of the queue API.
+
+struct _Py_queue_node {
+    struct _Py_queue_node *next;
+};
+
+struct _Py_queue_head {
+    struct _Py_queue_node first;
+    struct _Py_queue_node *tail;
+};
+
+#endif /* !defined(Py_LIMITED_API) */
+#endif /* !Py_PYQUEUE_H */
diff --git a/Include/internal/pycore_pyqueue.h b/Include/internal/pycore_pyqueue.h
new file mode 100644
index 0000000000..2a56497b00
--- /dev/null
+++ b/Include/internal/pycore_pyqueue.h
@@ -0,0 +1,61 @@
+#ifndef Py_INTERNAL_PYQUEUE_H
+#define Py_INTERNAL_PYQUEUE_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
+// Implementation of a queue that uses a singly linked list of
+// struct _Py_queue_node pointers. The queue is represented by a
+// struct _Py_queue_head which contains pointers to the first and
+// last node in the queue.
+
+static inline void
+_Py_queue_init(struct _Py_queue_head *head)
+{
+    head->first.next = head->tail = &head->first;
+}
+
+static inline bool
+_Py_queue_is_empty(struct _Py_queue_head *head)
+{
+    return head->first.next == &head->first;
+}
+
+static inline void
+_Py_queue_enqeue(struct _Py_queue_head *head, struct _Py_queue_node *node)
+{
+    node->next = &head->first;
+    head->tail->next = node;
+    head->tail = node;
+}
+
+static inline struct _Py_queue_node *
+_Py_queue_dequeue(struct _Py_queue_head *head)
+{
+    if (_Py_queue_is_empty(head)) {
+        return NULL;
+    }
+    struct _Py_queue_node *node = head->first.next;
+    head->first.next = node->next;
+    if (node->next == &head->first) {
+        head->tail = &head->first;
+    }
+    return node;
+}
+
+#define _Py_queue_data(node, type, member) \
+    (type*)((char*)node - offsetof(type, member))
+
+#define _Py_queue_first(head, type, member) (_Py_queue_data(((head)->first.next), type, member))
+
+#define _Py_queue_last(head, type, member) (_Py_queue_data(((head)->tail), type, member))
+
+
+#ifdef __cplusplus
+}
+#endif
+#endif  // !Py_INTERNAL_PYQUEUE_H
diff --git a/Makefile.pre.in b/Makefile.pre.in
index f00a82a809..cb6f5e8b9c 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -1706,6 +1706,7 @@ PYTHON_HEADERS= \
 		$(srcdir)/Include/internal/pycore_pylifecycle.h \
 		$(srcdir)/Include/internal/pycore_pymem.h \
 		$(srcdir)/Include/internal/pycore_pymem_init.h \
+		$(srcdir)/Include/internal/pycore_pyqueue.h \
 		$(srcdir)/Include/internal/pycore_pystate.h \
 		$(srcdir)/Include/internal/pycore_pythread.h \
 		$(srcdir)/Include/internal/pycore_range.h \
diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
index 0b6b3a96be..6c44f7be24 100644
--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -251,6 +251,7 @@
     <ClInclude Include="..\Include\internal\pycore_pylifecycle.h" />
     <ClInclude Include="..\Include\internal\pycore_pymem.h" />
     <ClInclude Include="..\Include\internal\pycore_pymem_init.h" />
+    <ClInclude Include="..\Include\internal\pycore_pyqueue.h" />
     <ClInclude Include="..\Include\internal\pycore_pystate.h" />
     <ClInclude Include="..\Include\internal\pycore_pythread.h" />
     <ClInclude Include="..\Include\internal\pycore_qsbr.h" />
diff --git a/PCbuild/pythoncore.vcxproj.filters b/PCbuild/pythoncore.vcxproj.filters
index 71ac510d2a..9b4b4dcc31 100644
--- a/PCbuild/pythoncore.vcxproj.filters
+++ b/PCbuild/pythoncore.vcxproj.filters
@@ -663,6 +663,9 @@
     <ClInclude Include="..\Include\internal\pycore_pymem_init.h">
       <Filter>Include\internal</Filter>
     </ClInclude>
+    <ClInclude Include="..\Include\internal\pycore_pyqueue.h">
+      <Filter>Include\internal</Filter>
+    </ClInclude>
     <ClInclude Include="..\Include\internal\pycore_pystate.h">
       <Filter>Include\internal</Filter>
     </ClInclude>