Add varint implementation

.gitignore

@@ -28,3 +28,4 @@
 /Makefile.in
 /missing
 /stamp-h1
+/test/varint

Makefile.am

@@ -51,6 +51,7 @@ libmacaroons_la_SOURCES += base64.c
 libmacaroons_la_SOURCES += macaroons.c
 libmacaroons_la_SOURCES += packet.c
 libmacaroons_la_SOURCES += port.c
+libmacaroons_la_SOURCES += varint.c
 libmacaroons_la_SOURCES += explicit_bzero.c
 libmacaroons_la_SOURCES += timingsafe_bcmp.c
 libmacaroons_la_SOURCES += tweetnacl.c
@@ -69,6 +70,7 @@ EXTRA_DIST += test/python-hmac-sanity-check.sh
 EXTRA_DIST += test/readme.sh
 
 check_LTLIBRARIES = libmacaroons-shim.la
+check_PROGRAMS = test/varint
 
 libmacaroons_shim_la_SOURCES = shim.c explicit_bzero.c
 libmacaroons_shim_la_LDFLAGS = -module -avoid-version -rpath /evil/libtool/hack/to/force/shared/lib/creation
@@ -78,6 +80,10 @@ if ENABLE_PYTHON_BINDINGS
 TESTS += test/python-hmac-sanity-check.sh
 TESTS += test/readme.sh
 endif
+TESTS += test/varint
+
+test_varint_SOURCES = test/varint.c varint.c
+test_varint_CFLAGS = $(AM_CFLAGS) $(CFLAGS)
 
 #################################### Python ####################################
 

test/varint.c

@@ -0,0 +1,79 @@
+/* Copyright (c) 2016, Robert Escriva
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *     * Redistributions of source code must retain the above copyright notice,
+ *       this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of this project nor the names of its contributors may
+ *       be used to endorse or promote products derived from this software
+ *       without specific prior written permission.
+ *
+ * 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.
+ */
+
+/* need to rely upon assert always asserting */
+#ifdef NDEBUG
+#undef NDEBUG
+#endif
+
+/* C */
+#include <assert.h>
+#include <stdint.h>
+#include <string.h>
+
+/* macaroons */
+#include "varint.h"
+
+void
+varint_verify(uint64_t value, const char* representation)
+{
+    const unsigned sz = strlen(representation);
+    assert(sz % 2 == 0);
+    unsigned char buf[VARINT_MAX_SIZE];
+    uint64_t eulav;
+    assert(packvarint(value, buf) == buf + sz / 2);
+    assert(unpackvarint(buf, buf + VARINT_MAX_SIZE, &eulav) == buf + sz / 2);
+    assert(value == eulav);
+
+    for (unsigned i = 0; i < sz / 2; ++i)
+    {
+        char hex[3];
+        snprintf(hex, 3, "%02x", buf[i] & 0xff);
+        assert(hex[0] == representation[2 * i]);
+        assert(hex[1] == representation[2 * i + 1]);
+    }
+}
+
+int
+main(int argc, const char* argv[])
+{
+    (void)argc;
+    (void)argv;
+    varint_verify(0ULL, "00");
+    varint_verify(5ULL, "05");
+    varint_verify(127ULL, "7f");
+    varint_verify(128ULL, "8001");
+    varint_verify(16383ULL, "ff7f");
+    varint_verify(16384ULL, "808001");
+    varint_verify(16385ULL, "818001");
+    varint_verify(16386ULL, "828001");
+    varint_verify(16387ULL, "838001");
+    varint_verify(16388ULL, "848001");
+    varint_verify(3735928559ULL, "effdb6f50d");
+    varint_verify(18446744073709551615ULL, "ffffffffffffffffff01");
+}

varint.c

@@ -0,0 +1,58 @@
+// This code is derived from code distributed as part of Google LevelDB.
+// The original is available in leveldb as util/coding.cc.
+// This file was retrieved Jul 15, 2013 by Robert Escriva and imported into
+// libe.  This code is copied/modified from libe.
+
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+/* C */
+#include <stdint.h>
+#include <stdlib.h>
+
+/* macaroons */
+#include "varint.h"
+
+unsigned char*
+packvarint(uint64_t v, unsigned char* ptr)
+{
+    const unsigned B = 128;
+
+    while (v >= B)
+    {
+        *(ptr++) = (v & (B-1)) | B;
+        v >>= 7;
+    }
+
+    *(ptr++) = (unsigned char)(v);
+    return ptr;
+}
+
+const unsigned char*
+unpackvarint(const unsigned char* ptr,
+             const unsigned char* end,
+             uint64_t* value)
+{
+    uint64_t result = 0;
+
+    for (unsigned shift = 0; shift <= 63 && ptr < end; shift += 7)
+    {
+        uint64_t byte = *ptr & 0xff;
+        ptr++;
+
+        if (byte & 128)
+        {
+            // More bytes are present
+            result |= ((byte & 127) << shift);
+        }
+        else
+        {
+            result |= (byte << shift);
+            *value = result;
+            return ptr;
+        }
+    }
+
+    return NULL;
+}

varint.h

@@ -0,0 +1,28 @@
+// This code is derived from code distributed as part of Google LevelDB.
+// The original is available in leveldb as util/coding.h.
+// This file was retrieved Jul 15, 2013 by Robert Escriva and imported into
+// libe.  This code is copied/modified from libe.
+
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Endian-neutral encoding:
+// * Fixed-length numbers are encoded with least-significant byte first
+// * In addition we support variable length "varint" encoding
+// * Strings are encoded prefixed by their length in varint format
+
+#ifndef macaroons_varint_h_
+#define macaroons_varint_h_
+
+#define VARINT_MAX_SIZE 10
+
+unsigned char*
+packvarint(uint64_t value, unsigned char* ptr);
+
+const unsigned char*
+unpackvarint(const unsigned char* ptr,
+             const unsigned char* end,
+             uint64_t* value);
+
+#endif /* macaroons_varint_h_ */