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 "(//${BLANK_OR_BACKSLASH_PATTERN}*)?\#define${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]])