Util.Counter: Speed up CTR mode using shortcut

This change allows CTR-mode ciphers to bypass the Python function call
mechanism when using counter objects created using Crypto.Util.Counter.

1 files changed, 44 insertions, 0 deletions

diff --git a/src/_counter.h b/src/_counter.h
new file mode 100644
index 0000000..3fc707f
--- /dev/null
+++ b/src/_counter.h
@@ -0,0 +1,44 @@
+/*
+ *  _counter.h: Fast counter for use with CTR-mode ciphers
+ *
+ * =======================================================================
+ * Copyright (C) 2008  Dwayne C. Litzenberger <dlitz@dlitz.net>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ * =======================================================================
+ */
+#ifndef PCT__COUNTER_H
+#define PCT__COUNTER_H
+
+#include <stdint.h>
+#include "Python.h"
+
+typedef struct {
+    PyObject_HEAD;
+    PyStringObject *prefix;     /* Prefix (useful for a nonce) */
+    PyStringObject *suffix;     /* Suffix (useful for a nonce) */
+    uint8_t *val;       /* Buffer for our output string */
+    uint32_t buf_size;  /* Size of the buffer */
+    uint8_t *p;         /* Pointer to the part of the buffer that we're allowed to update */
+    uint16_t nbytes;    /* The number of bytes that from .p that are part of the counter */
+    void (*inc_func)(void *);   /* Pointer to the counter increment function */
+} PCT_CounterObject;
+
+#endif /* PCT__COUNTER_H */