Embed.cmake

find_program(EMBED_LD ld)
find_program(EMBED_OBJCOPY objcopy)

option(EMBED_USE_LD "Use ld to embed data files" ON)

function(wrap_string)
    set(options)
    set(oneValueArgs VARIABLE AT_COLUMN)
    set(multiValueArgs)
    cmake_parse_arguments(PARSE "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
    cmake_parse_arguments(WRAP_STRING "${options}" "${oneValueArgs}" "" ${ARGN})

    string(LENGTH ${${PARSE_VARIABLE}} string_length)
    math(EXPR offset "0")

    while(string_length GREATER 0)

        if(string_length GREATER ${PARSE_AT_COLUMN})
            math(EXPR length "${PARSE_AT_COLUMN}")
        else()
            math(EXPR length "${string_length}")
        endif()

        string(SUBSTRING ${${PARSE_VARIABLE}} ${offset} ${length} line)
        set(lines "${lines}\n${line}")

        math(EXPR string_length "${string_length} - ${length}")
        math(EXPR offset "${offset} + ${length}")
    endwhile()

    set(${PARSE_VARIABLE} "${lines}" PARENT_SCOPE)
endfunction()

function(generate_embed_source EMBED_NAME)
    set(options)
    set(oneValueArgs SRC HEADER RELATIVE)
    set(multiValueArgs OBJECTS SYMBOLS FILES)

    cmake_parse_arguments(PARSE "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})

    set(EXTERNS)
    set(INIT_KERNELS)

    list(LENGTH PARSE_SYMBOLS SYMBOLS_LEN)
    list(LENGTH PARSE_OBJECTS OBJECTS_LEN)
    if(NOT ${SYMBOLS_LEN} EQUAL ${OBJECTS_LEN})
        message(FATAL_ERROR "Symbols and objects dont match: ${SYMBOLS_LEN} != ${OBJECTS_LEN}")
    endif()
    math(EXPR LEN "${SYMBOLS_LEN} - 1")

    foreach(idx RANGE ${LEN})
        list(GET PARSE_SYMBOLS ${idx} SYMBOL)
        list(GET PARSE_OBJECTS ${idx} OBJECT)
        list(GET PARSE_FILES ${idx} FILE)

        set(START_SYMBOL "_binary_${SYMBOL}_start")
        set(END_SYMBOL "_binary_${SYMBOL}_end")
        if(EMBED_USE_LD)
            string(APPEND EXTERNS "
                extern const char ${START_SYMBOL}[];
                extern const char ${END_SYMBOL}[];
            ")
        else()
            string(APPEND EXTERNS "
                extern const char ${START_SYMBOL}[];
                extern const char* ${END_SYMBOL};
            ")
        endif()

        if(PARSE_RELATIVE)
            file(RELATIVE_PATH BASE_NAME ${PARSE_RELATIVE} "${FILE}")
        else()
            get_filename_component(BASE_NAME "${FILE}" NAME)
        endif()

        string(APPEND INIT_KERNELS "
            { \"${BASE_NAME}\", { ${START_SYMBOL}, ${END_SYMBOL}} },
        ")
    endforeach()

    file(WRITE "${PARSE_HEADER}" "
#include <unordered_map>
#include <string>
#include <utility>
const std::unordered_map<std::string, std::pair<const char*,const char*>>& ${EMBED_NAME}();
")

    file(WRITE "${PARSE_SRC}" "
#include <${EMBED_NAME}.hpp>
${EXTERNS}
const std::unordered_map<std::string, std::pair<const char*,const char*>>& ${EMBED_NAME}()
{
    static const std::unordered_map<std::string, std::pair<const char*,const char*>> result = {${INIT_KERNELS}};
    return result;
}
")
endfunction()

function(embed_file OUTPUT_FILE OUTPUT_SYMBOL FILE)
    set(WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
    # Glob is used to compute the relative path
    file(GLOB FILES RELATIVE ${WORKING_DIRECTORY} ${FILE})
    foreach(REL_FILE ${FILES})
        string(MAKE_C_IDENTIFIER "${REL_FILE}" SYMBOL)
        get_filename_component(OUTPUT_FILE_DIR "${REL_FILE}" DIRECTORY)
        file(MAKE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/embed")
        if(EMBED_USE_LD)
            set(OUT_FILE "${CMAKE_CURRENT_BINARY_DIR}/embed/${SYMBOL}.o")
        else()
            set(OUT_FILE "${CMAKE_CURRENT_BINARY_DIR}/embed/${SYMBOL}.cpp")
        endif()
        set(${OUTPUT_SYMBOL} ${SYMBOL} PARENT_SCOPE)
        set(${OUTPUT_FILE} "${OUT_FILE}" PARENT_SCOPE)
        if(EMBED_USE_LD)
            add_custom_command(
                OUTPUT "${OUT_FILE}"
                COMMAND ${EMBED_LD} -r -o "${OUT_FILE}" -z noexecstack --format=binary "${REL_FILE}" 
                COMMAND ${EMBED_OBJCOPY} --rename-section .data=.rodata,alloc,load,readonly,data,contents "${OUT_FILE}"
                WORKING_DIRECTORY ${WORKING_DIRECTORY}
                DEPENDS ${FILE}
                VERBATIM
            )
        else()
            set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS ${FILE})
            # reads source file contents as hex string
            file(READ ${FILE} HEX_STRING HEX)
            # wraps the hex string into multiple lines
            wrap_string(VARIABLE HEX_STRING AT_COLUMN 80)
            # adds '0x' prefix and comma suffix before and after every byte respectively
            string(REGEX REPLACE "([0-9a-f][0-9a-f])" "0x\\1, " ARRAY_VALUES ${HEX_STRING})
            # removes trailing comma
            string(REGEX REPLACE ", $" "" ARRAY_VALUES ${ARRAY_VALUES})
            file(WRITE "${OUT_FILE}" "
                extern const char _binary_${SYMBOL}_start[] = { ${ARRAY_VALUES} };
                extern const char* _binary_${SYMBOL}_end = _binary_${SYMBOL}_start + sizeof(_binary_${SYMBOL}_start);
            \n")
        endif()
    endforeach()
endfunction()

function(add_embed_library EMBED_NAME)
    set(options)
    set(oneValueArgs RELATIVE)
    set(multiValueArgs)
    cmake_parse_arguments(PARSE "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})

    file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/embed)
    file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/embed/${EMBED_NAME})
    set(EMBED_DIR ${CMAKE_CURRENT_BINARY_DIR}/embed/${EMBED_NAME})
    set(SRC_FILE "${EMBED_DIR}/${EMBED_NAME}.cpp")
    set(HEADER_FILE "${EMBED_DIR}/include/${EMBED_NAME}.hpp")
    set(WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
    set(OUTPUT_FILES)
    set(SYMBOLS)
    message(STATUS "Embedding files")
    foreach(FILE ${PARSE_UNPARSED_ARGUMENTS})
        embed_file(OUTPUT_FILE OUTPUT_SYMBOL ${FILE})
        list(APPEND OUTPUT_FILES ${OUTPUT_FILE})
        list(APPEND SYMBOLS ${OUTPUT_SYMBOL})
    endforeach()
    message(STATUS "Generating embedding library ${EMBED_NAME}")
    generate_embed_source(${EMBED_NAME} SRC ${SRC_FILE} HEADER ${HEADER_FILE} OBJECTS ${OUTPUT_FILES} SYMBOLS ${SYMBOLS} RELATIVE ${PARSE_RELATIVE} FILES ${PARSE_UNPARSED_ARGUMENTS})
    
    set(INTERNAL_EMBED_LIB embed_lib_${EMBED_NAME})
    add_library(${INTERNAL_EMBED_LIB} OBJECT "${SRC_FILE}")
    target_include_directories(${INTERNAL_EMBED_LIB} PRIVATE "${EMBED_DIR}/include")
    target_compile_options(${INTERNAL_EMBED_LIB} PRIVATE -Wno-reserved-identifier -Wno-extern-initializer -Wno-missing-variable-declarations)
    set_target_properties(${INTERNAL_EMBED_LIB} PROPERTIES POSITION_INDEPENDENT_CODE On)
    
    add_library(${EMBED_NAME} INTERFACE)
    if(EMBED_USE_LD)
        target_sources(${EMBED_NAME} INTERFACE ${OUTPUT_FILES})
    else()
        target_sources(${INTERNAL_EMBED_LIB} PRIVATE ${OUTPUT_FILES})
    endif()
    target_sources(${EMBED_NAME} INTERFACE $<TARGET_OBJECTS:${INTERNAL_EMBED_LIB}>)
    target_include_directories(${EMBED_NAME} INTERFACE "${EMBED_DIR}/include")
endfunction()