Thread: A size based variable header w/o dependencies.

I've asked here before about how to define a variable of a specific size, and I got a good answer for most situations, but unfortunately a bad answer for mine. I'm not in a position where porting all of libc to my OS is either practical or possible, so I made a highly configurable header to serve the same purpose as stdint, but w/o including a thousand other headers. Here it is. You're free to use it. Any suggestions? Can you think of a system which uses data sizes/types this couldn't be configured for by only modifying the lines directly under "/* All values are determined from these */"?

Code:

#ifndef STDVAR_H
#define STDVAR_H 1

/* All values are determined from these */
#define BYTE_BITS 8
#define BYTE_BYTES 1
#define WORD_BYTES BYTE_BYTES * 2
#define DWORD_BYTES WORD_BYTES * 2
#define QWORD_BYTES DWORD_BYTES * 2

/* Define a byte sized type */
#if WIDTH(unsigned char) == BYTE_WIDTH
typedef byte_t unsigned char;
#else 
#error No byte sized type available!
#endif

/* Define a word sized type */
#if WIDTH(unsigned wchar) == WORD_WIDTH
typedef word_t unsigned wchar;
#else 
#error No word sized type available!
#endif

/* Define a dword sized type */
#if WIDTH(unsigned int) == DWORD_WIDTH
typedef dword_t unsigned int;
#elif WIDTH(unsigned short) == DWORD_WIDTH
typedef dword_t unsigned short;
#else
#error No dword sized type available!
#endif

/* Define a qword sized type */
#if WIDTH(unsigned long long) == QWORD_WIDTH
typedef qword_t unsigned long long;
#elif WIDTH(unsigned int) == QWORD_WIDTH
typedef qword_t unsigned int;
#else 
#error No qword sized type available!
#endif

#define WIDTH(type) (sizeof(type) * BYTE_BITS)
#define MAX_VAL(type) ((1 << (WIDTH(TYPE)) - 1)

#define BYTE_WIDTH BYTE_BYTES * BYTE_BITS
#define WORD_WIDTH WORD_BYTES * BYTE_BITS
#define DWORD_WIDTH DWORD_BYTES * BYTE_BITS
#define QWORD_WIDTH QWORD_BYTES * BYTE_BITS


#define MAX_BYTE ((1 << (BYTE_WIDTH) - 1)
#define MAX_WORD ((1 << (WORD_WIDTH) - 1)
#define MAX_DWORD ((1 << (DWORD_WIDTH) - 1)
#define MAX_QWORD ((1 << (QWORD_WIDTH) - 1)

#endif /* STDVAR_H */

Is "typedef" correct, or should I use "#define"?

Also, this is a little different from stdint in that no variable has a system independent size. There is no x-bit variable mentioned. I may include that though, now that I thought of it. Thanks for kinda causing that brainstorm laserlight.

Uses the same guard words as gnu libc stdint w/o blocking stdint itself.

Code:

#ifndef SIZEVAR_H
#define SIZEVAR_H 1

/* All values are determined from these */
#define BYTE_BITS 8
#define BYTE_BYTES 1
#define WORD_BYTES BYTE_BYTES * 2
#define DWORD_BYTES WORD_BYTES * 2
#define QWORD_BYTES DWORD_BYTES * 2

/* Define a byte sized type */
#if WIDTH(unsigned char) == BYTE_WIDTH
typedef byte_t unsigned char;
#else 
#warning No byte sized type available!
#endif

/* Define a word sized type */
#if WIDTH(unsigned wchar_t) == WORD_WIDTH
typedef word_t unsigned wchar_t;
#else 
#warning No word sized type available!
#endif

/* Define a dword sized type */
#if WIDTH(unsigned int) == DWORD_WIDTH
typedef dword_t unsigned int;
#elif WIDTH(unsigned short) == DWORD_WIDTH
typedef dword_t unsigned short;
#else
#warning No dword sized type available!
#endif

/* Define a qword sized type */
#if WIDTH(unsigned long long) == QWORD_WIDTH
typedef qword_t unsigned long long;
#elif WIDTH(unsigned int) == QWORD_WIDTH
typedef qword_t unsigned int;
#else 
#warning No qword sized type available!
#endif


/* Define *int*_t variables */

/* Signed */
#ifndef __int8_t_defined
#define __int8_t_defined 1
#if WIDTH(char) == 8
typedef int8_t char;
#else
#warning No int8_t!
#endif
#endif

#ifndef __int16_t_defined
#define __int16_t_defined 1
#if WIDTH(wchar_t) == 16
typedef int16_t wchar_t;
#else
#warning No int16_t!
#endif
#endif

#ifndef __int32_t_defined
#define __int32_t_defined 1
#if WIDTH(int) == 32
typedef int32_t int;
#elif WIDTH(short) == 32
typedef int32_t short;
#else
#warning No int32_t!
#endif
#endif

#ifndef __int64_t_defined
#define __int64_t_defined 1
#if WIDTH(long long) == 64
typedef int64_t long long;
#elif WIDTH(int) == 64
typedef int64_t int;
#else
#warning No int64_t!
#endif
#endif

/* Usigned */
#ifndef __uint8_t_defined
#define __uint8_t_defined 1
#if WIDTH(unsigned char) == 8
typedef uint8_t unsigned char;
#else
#warning No uint8_t!
#endif
#endif

#ifndef __uint16_t_defined
#define __uint16_t_defined 1
#if WIDTH(unsigned wchar_t) == 16
typedef uint16_t unsigned wchar_t;
#else
#warning No uint16_t!
#endif
#endif

#ifndef __uint32_t_defined
#define __uint32_t_defined 1
#if WIDTH(unsigned int) == 32
typedef uint32_t unsigned int;
#elif WIDTH(unsigned short) == 32
typedef uint32_t unsigned short;
#else
#warning No uint32_t!
#endif
#endif

#ifndef __uint64_t_defined
#define __uint64_t_defined 1
#if WIDTH(unsigned long long) == 64
typedef uint64_t unsigned long long;
#elif WIDTH(unsigned int) == 64
typedef uint64_t unsigned int;
#else
#warning No uint64_t!
#endif
#endif


#define WIDTH(type) (sizeof(type) * BYTE_BITS)
#define MAX_VAL(type) ((1 << (WIDTH(TYPE)) - 1)

#define BYTE_WIDTH BYTE_BYTES * BYTE_BITS
#define WORD_WIDTH WORD_BYTES * BYTE_BITS
#define DWORD_WIDTH DWORD_BYTES * BYTE_BITS
#define QWORD_WIDTH QWORD_BYTES * BYTE_BITS


#define MAX_BYTE ((1 << (BYTE_WIDTH) - 1)
#define MAX_WORD ((1 << (WORD_WIDTH) - 1)
#define MAX_DWORD ((1 << (DWORD_WIDTH) - 1)
#define MAX_QWORD ((1 << (QWORD_WIDTH) - 1)

#endif /* SIZEVAR_H */

Thanks for pointing out the bugs, I've yet to get to a compilable version of what's using it, so I haven't taken the time to test it on a compiler(to get warning and error messages about the stuff you pointed out).

The sizeof thing is wrong though, all the uses of sizeof would be evaluated at compile time or before. All expressions in an preprocessor if get processed before the compiler sees the code. Every other use of sizeof is switched out for it's value at compile time.

I just tried it and I get what you mean now. Sorry Ronix.