From 405f9537d22e077b88967ee64dd11a8315ac7fca Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Tue, 12 Nov 2024 20:29:23 +0200
Subject: [PATCH] Add example/compile_time.cpp

---
 doc/hash2/examples.adoc  | 12 ++++++++++
 example/Jamfile          |  1 +
 example/compile_time.cpp | 48 ++++++++++++++++++++++++++++++++++++++++
 test/Jamfile             |  1 +
 4 files changed, 62 insertions(+)
 create mode 100644 example/compile_time.cpp

diff --git a/doc/hash2/examples.adoc b/doc/hash2/examples.adoc
index 0c89a26..439cfe9 100644
--- a/doc/hash2/examples.adoc
+++ b/doc/hash2/examples.adoc
@@ -43,6 +43,8 @@ of a list of files, using a specified hash algorithm.
 The hash algorithm is passed as the first command
 line argument.
 
+This example requires {cpp}14.
+
 [source]
 ----
 include::../../example/hash2sum.cpp[lines=7..-1]
@@ -64,3 +66,13 @@ b07e42587d10ec323a25fd8fc3eef2213fb0997beb7950350f4e8a4b *canada.json
 4ceee5a83ad320fedb0dfddfb6f80af50b99677e87158e2d039aa168 *citm_catalog.json
 854ebe0da98cadd426ea0fa3218d60bb52cf6494e435d2f385a37d48 *twitter.json
 ----
+
+## Compile Time Hashing
+
+This example demonstrates calculating the MD5 digest of a data array, embedded in the program source, at compile time. It requires {cpp}14.
+
+[source]
+----
+include::../../example/compile_time.cpp[lines=5..-1]
+----
+
diff --git a/example/Jamfile b/example/Jamfile
index d584355..8001c2a 100644
--- a/example/Jamfile
+++ b/example/Jamfile
@@ -5,3 +5,4 @@ project : default-build release <link>static ;
 
 exe md5sum : md5sum.cpp ;
 exe hash2sum : hash2sum.cpp ;
+exe compile_time : compile_time.cpp ;
diff --git a/example/compile_time.cpp b/example/compile_time.cpp
new file mode 100644
index 0000000..cd4db31
--- /dev/null
+++ b/example/compile_time.cpp
@@ -0,0 +1,48 @@
+// Copyright 2024 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/hash2/md5.hpp>
+#include <iostream>
+
+// xxd -i resource
+constexpr unsigned char resource[] = {
+  0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x03, 0x6d, 0x90,
+  0xcf, 0x6e, 0x83, 0x30, 0x0c, 0xc6, 0xcf, 0x45, 0xea, 0x3b, 0x78, 0x9c,
+  0x4b, 0x02, 0x3d, 0x6e, 0xd0, 0x43, 0xff, 0x1c, 0x26, 0x55, 0x3b, 0x14,
+  0x6d, 0xd7, 0x2a, 0x04, 0x43, 0x22, 0x95, 0x84, 0x25, 0x66, 0x8c, 0x47,
+  0xda, 0x5b, 0x2e, 0x91, 0xd6, 0xcb, 0xd4, 0x93, 0x2d, 0xdb, 0xdf, 0xef,
+  0xb3, 0x5d, 0x2a, 0x1a, 0x6e, 0xbb, 0x75, 0x52, 0x2a, 0x14, 0x6d, 0x8c,
+  0x03, 0x92, 0x00, 0x45, 0x34, 0x66, 0xf8, 0x39, 0xe9, 0xaf, 0x2a, 0x75,
+  0xd8, 0x39, 0xf4, 0x2a, 0x05, 0x69, 0x0d, 0xa1, 0xa1, 0x2a, 0xcd, 0x5f,
+  0xe0, 0xfd, 0x72, 0xae, 0x5a, 0x2b, 0x79, 0x54, 0x73, 0x25, 0xbc, 0xda,
+  0xb2, 0x98, 0xa6, 0x91, 0xc0, 0xef, 0xa8, 0xc6, 0xb6, 0x4b, 0x88, 0x17,
+  0x6c, 0xb5, 0x43, 0x49, 0xda, 0xf4, 0x40, 0x16, 0xca, 0x80, 0x0f, 0xcc,
+  0x2a, 0x7d, 0xa8, 0x7f, 0x50, 0x2c, 0xb9, 0xd8, 0x31, 0xc6, 0x22, 0xf9,
+  0x8f, 0x58, 0xf2, 0xfb, 0xd6, 0x4f, 0x59, 0xb6, 0x4e, 0x56, 0x3f, 0x70,
+  0xb0, 0xe3, 0xe2, 0x74, 0xaf, 0x08, 0xf6, 0x38, 0x08, 0x03, 0x47, 0x31,
+  0xa3, 0xdf, 0xc0, 0x36, 0xcf, 0x8b, 0xd0, 0x3f, 0x6a, 0x4f, 0x4e, 0x37,
+  0x13, 0x61, 0x0b, 0x93, 0x69, 0xd1, 0x01, 0x29, 0x84, 0xbd, 0xb5, 0x9e,
+  0xa0, 0xb6, 0x1d, 0xcd, 0xc2, 0x21, 0x9c, 0xb5, 0x44, 0xe3, 0x71, 0x03,
+  0x1f, 0xe8, 0xbc, 0xb6, 0x06, 0x0a, 0x96, 0x07, 0xd3, 0x55, 0x8d, 0x08,
+  0x42, 0x4a, 0x3b, 0x8c, 0xc2, 0x2c, 0xf1, 0x86, 0x4e, 0xdf, 0xc2, 0xf4,
+  0xeb, 0xe1, 0xf4, 0x56, 0x9f, 0xae, 0xc5, 0x35, 0x67, 0xf4, 0x4d, 0x60,
+  0x5d, 0xf8, 0xcf, 0xb8, 0x80, 0xa0, 0x20, 0x89, 0xef, 0x7b, 0xe6, 0x7c,
+  0x9e, 0x67, 0xd6, 0x44, 0x13, 0x66, 0x5d, 0xcf, 0xff, 0x29, 0xd6, 0x49,
+  0x96, 0x85, 0x0b, 0x7e, 0x01, 0x36, 0x66, 0x95, 0x6b, 0x80, 0x01, 0x00,
+  0x00
+};
+
+template<std::size_t N> constexpr auto md5( unsigned char const(&a)[ N ] )
+{
+    boost::hash2::md5_128 hash;
+    hash.update( a, N );
+    return hash.result();
+}
+
+constexpr auto resource_digest = md5( resource );
+
+int main()
+{
+    std::cout << "Resource digest: " << resource_digest << std::endl;
+}
diff --git a/test/Jamfile b/test/Jamfile
index 8c28bdc..19895c1 100644
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -148,3 +148,4 @@ link ../benchmark/keys.cpp ;
 
 link ../example/md5sum.cpp ;
 link ../example/hash2sum.cpp : <cxxstd>11:<build>no <toolset>msvc-14.0:<build>no ;
+link ../example/compile_time.cpp : <cxxstd>11:<build>no <toolset>msvc-14.0:<build>no ;