ExternalProject: Re-implement download logic as a dedicated script

Move the content to a `ExternalProject-download.cmake.in` file and use
`configure_file` to generate the final script.

Retry logic was not working before because similar script trigger
FATAL_ERROR if 'file(DOWNLOAD ...)' exits with nonzero 'status_code'.
FATAL_ERROR makes the whole chain of commands stop and
'_ep_write_verifyfile_script' retry logic was not used in fact.

Default retry number set to 5 with pauses 0, 5, 5, 15, 60 seconds. Some
space left for future improvements if needed (90, 300, 1200=20min). Can
be controlled by user.

1 files changed, 161 insertions, 0 deletions

diff --git a/Modules/ExternalProject-download.cmake.in b/Modules/ExternalProject-download.cmake.in
new file mode 100644
index 0000000..5b73cd8
--- /dev/null
+++ b/Modules/ExternalProject-download.cmake.in
@@ -0,0 +1,161 @@
+#=============================================================================
+# Copyright 2008-2013 Kitware, Inc.
+# Copyright 2016 Ruslan Baratov
+#
+# Distributed under the OSI-approved BSD License (the "License");
+# see accompanying file Copyright.txt for details.
+#
+# This software is distributed WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the License for more information.
+#=============================================================================
+# (To distribute this file outside of CMake, substitute the full
+#  License text for the above reference.)
+
+cmake_minimum_required(VERSION 3.5)
+
+function(check_file_hash has_hash hash_is_good)
+  if("${has_hash}" STREQUAL "")
+    message(FATAL_ERROR "has_hash Can't be empty")
+  endif()
+
+  if("${hash_is_good}" STREQUAL "")
+    message(FATAL_ERROR "hash_is_good Can't be empty")
+  endif()
+
+  if("@ALGO@" STREQUAL "")
+    # No check
+    set("${has_hash}" FALSE PARENT_SCOPE)
+    set("${hash_is_good}" FALSE PARENT_SCOPE)
+    return()
+  endif()
+
+  set("${has_hash}" TRUE PARENT_SCOPE)
+
+  message(STATUS "verifying file...
+       file='@LOCAL@'")
+
+  file("@ALGO@" "@LOCAL@" actual_value)
+
+  if(NOT "${actual_value}" STREQUAL "@EXPECT_VALUE@")
+    set("${hash_is_good}" FALSE PARENT_SCOPE)
+    message(STATUS "@ALGO@ hash of
+    @LOCAL@
+  does not match expected value
+    expected: '@EXPECT_VALUE@'
+      actual: '${actual_value}'")
+  else()
+    set("${hash_is_good}" TRUE PARENT_SCOPE)
+  endif()
+endfunction()
+
+function(sleep_before_download attempt)
+  if(attempt EQUAL 0)
+    return()
+  endif()
+
+  if(attempt EQUAL 1)
+    message(STATUS "Retrying...")
+    return()
+  endif()
+
+  set(sleep_seconds 0)
+
+  if(attempt EQUAL 2)
+    set(sleep_seconds 5)
+  elseif(attempt EQUAL 3)
+    set(sleep_seconds 5)
+  elseif(attempt EQUAL 4)
+    set(sleep_seconds 15)
+  elseif(attempt EQUAL 5)
+    set(sleep_seconds 60)
+  elseif(attempt EQUAL 6)
+    set(sleep_seconds 90)
+  elseif(attempt EQUAL 7)
+    set(sleep_seconds 300)
+  else()
+    set(sleep_seconds 1200)
+  endif()
+
+  message(STATUS "Retry after ${sleep_seconds} seconds (attempt #${attempt}) ...")
+
+  execute_process(COMMAND "${CMAKE_COMMAND}" -E sleep "${sleep_seconds}")
+endfunction()
+
+if("@LOCAL@" STREQUAL "")
+  message(FATAL_ERROR "LOCAL can't be empty")
+endif()
+
+if("@REMOTE@" STREQUAL "")
+  message(FATAL_ERROR "REMOTE can't be empty")
+endif()
+
+if(EXISTS "@LOCAL@")
+  check_file_hash(has_hash hash_is_good)
+  if(has_hash)
+    if(hash_is_good)
+      message(STATUS "File already exists and hash match (skip download):
+  file='@LOCAL@'
+  @ALGO@='@EXPECT_VALUE@'"
+      )
+      return()
+    else()
+      message(STATUS "File already exists but hash mismatch. Removing...")
+      file(REMOVE "@LOCAL@")
+    endif()
+  else()
+    message(STATUS "File already exists but no hash specified (use URL_HASH):
+  file='@LOCAL@'
+Old file will be removed and new file downloaded from URL."
+    )
+    file(REMOVE "@LOCAL@")
+  endif()
+endif()
+
+set(retry_number 5)
+
+foreach(i RANGE ${retry_number})
+  sleep_before_download(${i})
+
+  message(STATUS "downloading...
+       src='@REMOTE@'
+       dst='@LOCAL@'
+       timeout='@TIMEOUT_MSG@'")
+
+  @TLS_VERIFY_CODE@
+  @TLS_CAINFO_CODE@
+
+  file(
+      DOWNLOAD
+      "@REMOTE@" "@LOCAL@"
+      @SHOW_PROGRESS@
+      @TIMEOUT_ARGS@
+      STATUS status
+      LOG log
+  )
+
+  list(GET status 0 status_code)
+  list(GET status 1 status_string)
+
+  if(status_code EQUAL 0)
+    check_file_hash(has_hash hash_is_good)
+    if(has_hash AND NOT hash_is_good)
+      message(STATUS "Hash mismatch, removing...")
+      file(REMOVE "@LOCAL@")
+    else()
+      message(STATUS "Downloading... done")
+      return()
+    endif()
+  else()
+    message("error: downloading '@REMOTE@' failed
+  status_code: ${status_code}
+  status_string: ${status_string}
+  log:
+  --- LOG BEGIN ---
+  ${log}
+  --- LOG END ---"
+    )
+  endif()
+endforeach()
+
+message(FATAL_ERROR "Downloading failed")