diff options
Diffstat (limited to 'NorthstarDLL/core')
| -rw-r--r-- | NorthstarDLL/core/structs.h | 49 |
1 files changed, 32 insertions, 17 deletions
diff --git a/NorthstarDLL/core/structs.h b/NorthstarDLL/core/structs.h index ac29f711..037233a6 100644 --- a/NorthstarDLL/core/structs.h +++ b/NorthstarDLL/core/structs.h @@ -35,28 +35,43 @@ OFFSET_STRUCT(Name) // Special case for a 0-offset field #define STRUCT_FIELD_NOOFFSET(offset, signature) signature; -// Based on: https://stackoverflow.com/questions/11632219/c-preprocessor-macro-specialisation-based-on-an-argument -// Yes, this is hacky, but it works quite well actually -// This basically makes sure that when the offset is 0x0, no padding field gets generated -#define OFFSET_0x0 () +// Just puts two tokens next to each other, but +// allows us to force the preprocessor to do another pass +#define FX(f, x) f x -#define IIF(c) CONCAT2(IIF_, c) -#define IIF_0(t, ...) __VA_ARGS__ -#define IIF_1(t, ...) t +// Macro used to detect if the given offset is 0 or not +#define TEST_0 , +// MSVC does no preprocessing of integer literals. +// On other compilers `0x0` gets processed into `0` +#define TEST_0x0 , -#define PROBE(x) x, 1 -#define MSVC_VA_ARGS_WORKAROUND(define, args) define args -#define CHECK(...) MSVC_VA_ARGS_WORKAROUND(CHECK_N, (__VA_ARGS__, 0)) -#define DO_PROBE(offset) PROBE_PROXY(OFFSET_##offset) // concatenate prefix with offset -#define PROBE_PROXY(...) PROBE_PRIMITIVE(__VA_ARGS__) // expand arguments -#define PROBE_PRIMITIVE(x) PROBE_COMBINE_##x // merge -#define PROBE_COMBINE_(...) PROBE(~) // if merge successful, expand to probe +// Concats the first and third argument and drops everything else +// Used with preprocessor expansion in later passes to move the third argument to the fourth and change the value +#define ZERO_P_I(a, b, c, ...) a##c -#define CHECK_N(x, n, ...) n +// We use FX to prepare to use ZERO_P_I. +// The right block contains 3 arguments: +// NIF_ +// CONCAT2(TEST_, offset) +// 1 +// +// If offset is not 0 (or 0x0) the preprocessor replaces +// it with nothing and the third argument stays 1 +// +// If the offset is 0, TEST_0 expands to , and 1 becomes the fourth argument +// +// With those arguments we call ZERO_P_I and the first and third arugment get concat. +// We either end up with: +// NIF_ (if offset is 0) or +// NIF_1 (if offset is not 0) +#define IF_ZERO(m) FX(ZERO_P_I, (NIF_, CONCAT2(TEST_, m), 1)) -#define IS_0(offset) CHECK(DO_PROBE(offset)) +// These macros are used to branch after we processed if the offset is zero or not +#define NIF_(t, ...) t +#define NIF_1(t, ...) __VA_ARGS__ -#define FIELD(offset, signature) IIF(IS_0(offset))(STRUCT_FIELD_NOOFFSET, STRUCT_FIELD_OFFSET)(offset, signature) +// FIELD(S), generates an anonymous struct when a non 0 offset is given, otherwise just a signature +#define FIELD(offset, signature) IF_ZERO(offset)(STRUCT_FIELD_NOOFFSET, STRUCT_FIELD_OFFSET)(offset, signature) #define FIELDS FIELD //clang-format on |