picolibrary

ROM Facilities

ROM facilities are defined in the include/picolibrary/rom.h/source/picolibrary/rom.cc header/source file pair.

Table of Contents

1. Null-Terminated Strings

Null-Terminated Strings

The ::picolibrary::ROM::String type is used for handles to null-terminated strings that may be stored in ROM. This type defaults to char const *. A HIL can replace this type with a HIL specific version by doing the following:

• Provide a picolibrary-hil library that provides picolibrary/hil/rom.h
• Define PICOLIBRARY_ROM_STRING_IS_HIL_DEFINED in picolibrary/hil/rom.h
• Define the HIL specific version of ::picolibrary::ROM::String in picolibrary/hil/rom.h

If a function is being overloaded to work with null-terminated strings stored in RAM and null-terminated strings that may be stored in ROM, the ::picolibrary::ROM::String overload must only be defined if PICOLIBRARY_ROM_STRING_IS_HIL_DEFINED is defined since ::picolibrary::ROM::String defaults to char const *:

void foo( char const * string ) noexcept
{
}

#ifdef PICOLIBRARY_ROM_STRING_IS_HIL_DEFINED
void foo( ::picolibrary::ROM::String string ) noexcept;
{
}
#endif // PICOLIBRARY_ROM_STRING_IS_HIL_DEFINED

To create a string literal that can be stored in ROM, use the PICOLIBRARY_ROM_STRING() macro:

auto foo() noexcept -> ::picolibrary::ROM::String
{
    return PICOLIBRARY_ROM_STRING( "string" );
}

If a toolchain does not store string literals in ROM automatically, a HIL can replace the PICOLIBRARY_ROM_STRING() macro by doing the following:

• Provide a picolibrary-hil library that provides picolibrary/hil/rom.h
• Define the macro replacement in picolibrary/hil/rom.h

To get the length of a null-terminated string that may be stored in ROM, use the ::picolibrary::ROM::strlen() function:

void foo( ::picolibrary::ROM::String string ) noexcept
{
    auto const length = ::picolibrary::ROM::strlen( string );
}

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