types.h

一个简单的操作系统minix的核心代码

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				include/sys/types.h	 	 
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01600	/* The <sys/types.h> header contains important data type definitions.
01601	 * It is considered good programming practice to use these definitions, 
01602	 * instead of the underlying base type.  By convention, all type names end 
01603	 * with _t.
01604	 */
01605	
01606	#ifndef _TYPES_H
01607	#define _TYPES_H
01608	
01609	/* _ANSI is somehow used to determine whether or not the compiler is a
01610	 * 16 bit compiler
01611	 */
01612	#ifndef _ANSI
01613	#include <ansi.h>
01614	#endif
01615	
01616	/* The type size_t holds all results of the sizeof operator.  At first glance,
01617	 * it seems obvious that it should be an unsigned int, but this is not always 
01618	 * the case. For example, MINIX-ST (68000) has 32-bit pointers and 16-bit
01619	 * integers. When one asks for the size of a 70K struct or array, the result 
01620	 * requires 17 bits to express, so size_t must be a long type.  The type 
01621	 * ssize_t is the signed version of size_t.
01622	 */
01623	#ifndef _SIZE_T
01624	#define _SIZE_T
01625	typedef unsigned int size_t;
01626	#endif
01627	
01628	#ifndef _SSIZE_T
01629	#define _SSIZE_T
01630	typedef int ssize_t;
01631	#endif
01632	
01633	#ifndef _TIME_T
01634	#define _TIME_T
01635	typedef long time_t;               /* time in sec since 1 Jan 1970 0000 GMT */
01636	#endif
01637	
01638	#ifndef _CLOCK_T
01639	#define _CLOCK_T
01640	typedef long clock_t;              /* unit for system accounting */
01641	#endif
01642	
01643	#ifndef _SIGSET_T
01644	#define _SIGSET_T
01645	typedef unsigned long sigset_t;
01646	#endif
01647	
01648	/* Types used in disk, inode, etc. data structures. */
01649	typedef short          dev_t;      /* holds (major|minor) device pair */
01650	typedef char           gid_t;      /* group id */
01651	typedef unsigned short ino_t;      /* i-node number */
01652	typedef unsigned short mode_t;     /* file type and permissions bits */
01653	typedef char         nlink_t;      /* number of links to a file */
01654	typedef unsigned long  off_t;      /* offset within a file */
01655	typedef int            pid_t;      /* process id (must be signed) */
01656	typedef short          uid_t;      /* user id */
01657	typedef unsigned long zone_t;      /* zone number */
01658	typedef unsigned long block_t;     /* block number */
01659	typedef unsigned long  bit_t;      /* bit number in a bit map */
01660	typedef unsigned short zone1_t;    /* zone number for V1 file systems */
01661	typedef unsigned short bitchunk_t; /* collection of bits in a bitmap */
01662	
01663	typedef unsigned char   u8_t;      /* 8 bit type */
01664	typedef unsigned short u16_t;      /* 16 bit type */
01665	typedef unsigned long  u32_t;      /* 32 bit type */
01666	
01667	typedef char            i8_t;      /* 8 bit signed type */
01668	typedef short          i16_t;      /* 16 bit signed type */
01669	typedef long           i32_t;      /* 32 bit signed type */
01670	
01671	/* The following types are needed because MINIX uses K&R style function
01672	 * definitions (for maximum portability).  When a short, such as dev_t, is
01673	 * passed to a function with a K&R definition, the compiler automatically
01674	 * promotes it to an int.  The prototype must contain an int as the parameter,
01675	 * not a short, because an int is what an old-style function definition
01676	 * expects.  Thus using dev_t in a prototype would be incorrect.  It would be
01677	 * sufficient to just use int instead of dev_t in the prototypes, but Dev_t
01678	 * is clearer.
01679	 */
01680	typedef int            Dev_t;
01681	typedef int            Gid_t;
01682	typedef int          Nlink_t;
01683	typedef int            Uid_t;
01684	typedef int             U8_t;
01685	typedef unsigned long  U32_t;
01686	typedef int             I8_t;
01687	typedef int            I16_t;
01688	typedef long            I32_t;
01689	
01690	/* ANSI C makes writing down the promotion of unsigned types very messy.  When
01691	 * sizeof(short) == sizeof(int), there is no promotion, so the type stays
01692	 * unsigned.  When the compiler is not ANSI, there is usually no loss of
01693	 * unsignedness, and there are usually no prototypes so the promoted type
01694	 * doesn't matter.  The use of types like Ino_t is an attempt to use ints
01695	 * (which are not promoted) while providing information to the reader.
01696	 */
01697	
01698	#ifndef _ANSI_H
01699	#include <ansi.h>
01700	#endif
01701	
01702	#if _EM_WSIZE == 2 || !defined(_ANSI)
01703	typedef unsigned int      Ino_t;
01704	typedef unsigned int    Zone1_t;
01705	typedef unsigned int Bitchunk_t;
01706	typedef unsigned int      U16_t;
01707	typedef unsigned int  Mode_t;
01708	
01709	#else /* _EM_WSIZE == 4, or _EM_WSIZE undefined, or _ANSI defined */
01710	typedef int               Ino_t;
01711	typedef int             Zone1_t;
01712	typedef int          Bitchunk_t;
01713	typedef int               U16_t;
01714	typedef int           Mode_t;
01715	
01716	#endif /* _EM_WSIZE == 2, etc */
01717	 
01718	/* Signal handler type, e.g. SIG_IGN */
01719	#if defined(_ANSI)
01720	typedef void (*sighandler_t) (int);
01721	#else
01722	typedef void (*sighandler_t)();
01723	#endif
01724	
01725	#endif /* _TYPES_H */