Improve FILE(DOWNLOAD) and ExternalProject.

Improve FILE(DOWNLOAD ...):

- Add percent complete progress output to the FILE DOWNLOAD
  command. This progress output is off by default to
  preserve existing behavior. To turn it on, pass
  SHOW_PROGRESS as an argument.

- Add EXPECTED_MD5 argument. Verify that the downloaded
  file has the expected md5 sum after download is complete.

- Add documentation for SHOW_PROGRESS and EXPECTED_MD5.

  When the destination file exists already and has the
  expected md5 sum, then do not bother re-downloading
  the file. ("Short circuit" return.)

  Also, add a test that checks for the status output
  indicating that the short circuit behavior is actually
  occurring. Use a binary file for the test so that the
  md5 sum is guaranteed to be the same on all platforms
  regardless of "shifting text file line ending" issues.

Improve ExternalProject:

- Add argument URL_MD5.

- Add verify step that compares md5 sum of .tar.gz file
  before extracting it.

- Add md5 check to download step, too, to prevent
  unnecessary downloads.

- Emit a warning message when a file is not verified.
  Indicate that the file may be corrupt or that no
  checksum was specified.

4 files changed, 54 insertions, 0 deletions

diff --git a/Tests/CMakeTests/CMakeLists.txt b/Tests/CMakeTests/CMakeLists.txt
index 7a176e9..3e5f08c 100644
--- a/Tests/CMakeTests/CMakeLists.txt
+++ b/Tests/CMakeTests/CMakeLists.txt
@@ -28,6 +28,11 @@ AddCMakeTest(Math "")
 AddCMakeTest(CMakeMinimumRequired "")
 AddCMakeTest(CompilerIdVendor "")
 
+AddCMakeTest(FileDownload "")
+set_property(TEST CMake.FileDownload PROPERTY
+  PASS_REGULAR_EXPRESSION "file already exists with expected MD5 sum"
+  )
+
 if(HAVE_ELF_H)
   AddCMakeTest(ELF "")
 endif()
diff --git a/Tests/CMakeTests/FileDownloadInput.png b/Tests/CMakeTests/FileDownloadInput.png
new file mode 100644
index 0000000..7bbcee4
--- /dev/null
+++ b/Tests/CMakeTests/FileDownloadInput.png
diff --git a/Tests/CMakeTests/FileDownloadTest.cmake.in b/Tests/CMakeTests/FileDownloadTest.cmake.in
new file mode 100644
index 0000000..578f510
--- /dev/null
+++ b/Tests/CMakeTests/FileDownloadTest.cmake.in
@@ -0,0 +1,41 @@
+set(url "file://@CMAKE_CURRENT_SOURCE_DIR@/FileDownloadInput.png")
+set(dir "@CMAKE_CURRENT_BINARY_DIR@/downloads")
+
+message(STATUS "FileDownload:1")
+file(DOWNLOAD
+  ${url}
+  ${dir}/file1.png
+  TIMEOUT 2
+  )
+
+message(STATUS "FileDownload:2")
+file(DOWNLOAD
+  ${url}
+  ${dir}/file2.png
+  TIMEOUT 2
+  SHOW_PROGRESS
+  )
+
+# Two calls in a row, exactly the same arguments.
+# Since downloaded file should exist already for 2nd call,
+# the 2nd call will short-circuit and return early...
+#
+if(EXISTS ${dir}/file3.png)
+  file(REMOVE ${dir}/file3.png)
+endif()
+
+message(STATUS "FileDownload:3")
+file(DOWNLOAD
+  ${url}
+  ${dir}/file3.png
+  TIMEOUT 2
+  EXPECTED_MD5 d16778650db435bda3a8c3435c3ff5d1
+  )
+
+message(STATUS "FileDownload:4")
+file(DOWNLOAD
+  ${url}
+  ${dir}/file3.png
+  TIMEOUT 2
+  EXPECTED_MD5 d16778650db435bda3a8c3435c3ff5d1
+  )
diff --git a/Tests/ExternalProject/CMakeLists.txt b/Tests/ExternalProject/CMakeLists.txt
index f02f2f7..4ae04d3 100644
--- a/Tests/ExternalProject/CMakeLists.txt
+++ b/Tests/ExternalProject/CMakeLists.txt
@@ -65,7 +65,9 @@ ExternalProject_Add(${proj}
   SVN_REPOSITORY ""
   SVN_REVISION ""
   TEST_COMMAND ""
+  TIMEOUT ""
   URL ""
+  URL_MD5 ""
   UPDATE_COMMAND ""
 )
 
@@ -96,6 +98,7 @@ endif()
 set(proj TutorialStep1-LocalTAR)
 ExternalProject_Add(${proj}
   URL "${CMAKE_CURRENT_SOURCE_DIR}/Step1.tar"
+  URL_MD5 a87c5b47c0201c09ddfe1d5738fdb1e3
   LIST_SEPARATOR ::
   PATCH_COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_SOURCE_DIR}/Step1Patch.cmake
   CMAKE_GENERATOR "${CMAKE_GENERATOR}"
@@ -107,6 +110,7 @@ ExternalProject_Add(${proj}
 set(proj TutorialStep1-LocalNoDirTAR)
 ExternalProject_Add(${proj}
   URL "${CMAKE_CURRENT_SOURCE_DIR}/Step1NoDir.tar"
+  URL_MD5 d09e3d370c5c908fa035c30939ee438e
   LIST_SEPARATOR @@
   CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR> -G ${CMAKE_GENERATOR} <SOURCE_DIR>
              -DTEST_LIST:STRING=1@@2@@3
@@ -126,6 +130,7 @@ ExternalProject_Add_Step(${proj} mypatch
 set(proj TutorialStep1-LocalTGZ)
 ExternalProject_Add(${proj}
   URL "${CMAKE_CURRENT_SOURCE_DIR}/Step1.tgz"
+  URL_MD5 38c648e817339c356f6be00eeed79bd0
   CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR> -G ${CMAKE_GENERATOR} <SOURCE_DIR>
   INSTALL_COMMAND ""
 )
@@ -133,6 +138,7 @@ ExternalProject_Add(${proj}
 set(proj TutorialStep1-LocalNoDirTGZ)
 ExternalProject_Add(${proj}
   URL "${CMAKE_CURRENT_SOURCE_DIR}/Step1NoDir.tgz"
+  URL_MD5 0b8182edcecdf40bf1c9d71d7d259f78
   CMAKE_GENERATOR "${CMAKE_GENERATOR}"
   CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
   INSTALL_COMMAND ""
@@ -161,6 +167,7 @@ if(do_cvs_tests)
   ExternalProject_Add(${proj}
     SOURCE_DIR ${local_cvs_repo}
     URL ${CMAKE_CURRENT_SOURCE_DIR}/cvsrepo.tgz
+    URL_MD5 55fc85825ffdd9ed2597123c68b79f7e
     BUILD_COMMAND ""
     CONFIGURE_COMMAND ${CVS_EXECUTABLE} --version
     INSTALL_COMMAND ""
@@ -257,6 +264,7 @@ if(do_svn_tests)
   ExternalProject_Add(${proj}
     SOURCE_DIR ${local_svn_repo}
     URL ${CMAKE_CURRENT_SOURCE_DIR}/svnrepo.tgz
+    URL_MD5 2f468be4ed1fa96377fca0cc830819c4
     BUILD_COMMAND ""
     CONFIGURE_COMMAND ${Subversion_SVN_EXECUTABLE} --version
     INSTALL_COMMAND ""