Create ParseConfigHeader.cmake

This script parses the config.h file to automate the process of exposing the configuration flags and configuration values found in the latter.

cmake/ParseConfigHeader.cmake

@@ -0,0 +1,17 @@
+file(READ "${CMAKE_CURRENT_SOURCE_DIR}/src/config.h" CONFIG_HEADER_CONTENT)
+
+set(BLANK_OR_BACKSLASH_PATTERN "[ \t\r\n\\]+")
+set(VALID_IDENTIFIER_PATTERN "[A-Za-z_]+[A-Za-z_0-9]*")
+set(VALID_VALUE_PATTERN [=["?[A-Za-z_0-9.-]+"?]=]) # not really correct but does the job since the config.h file hopefully will have been checked by a C preprocessor.
+set(MACRO_REGEX "(// )?\#define${BLANK_OR_BACKSLASH_PATTERN}(${VALID_IDENTIFIER_PATTERN})${BLANK_OR_BACKSLASH_PATTERN}(${VALID_VALUE_PATTERN})")
+
+string(REGEX MATCHALL ${MACRO_REGEX} MACRO_LIST ${CONFIG_HEADER_CONTENT})
+
+set(CONFIG_HEADER_FLAGS ${MACRO_LIST})
+list(FILTER CONFIG_HEADER_FLAGS INCLUDE REGEX "^.+SUPPORT_")
+list(TRANSFORM CONFIG_HEADER_FLAGS REPLACE ${MACRO_REGEX} [[\2=OFF]] REGEX "^//")
+list(TRANSFORM CONFIG_HEADER_FLAGS REPLACE ${MACRO_REGEX} [[\2=ON]])
+
+set(CONFIG_HEADER_VALUES ${MACRO_LIST})
+list(FILTER CONFIG_HEADER_VALUES EXCLUDE REGEX "(^.+SUPPORT_)|(^//)")
+list(TRANSFORM CONFIG_HEADER_VALUES REPLACE ${MACRO_REGEX} [[\2=\3]])