stdio.h

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/*
 * pANS stdio.h
 */
/*
 * According to X3J11, there is only one i/o buffer
 * and it must not be occupied by both input and output data.
 *	If rp<wp, we must have state==RD and
 *	if wp<rp, we must have state==WR, so that getc and putc work correctly.
 *	On open, rp, wp and buf are set to 0, so first getc or putc will call _IO_getc
 *	or _IO_putc, which will allocate the buffer.
 *	If setvbuf(., ., _IONBF, .) is called, bufl is set to 0 and
 *	buf, rp and wp are pointed at unbuf.
 *	If setvbuf(., ., _IOLBF, .) is called, _IO_putc leaves wp and rp pointed at the
 *	end of the buffer so that it can be called on each putc to check whether it's got
 *	a newline.  This nonsense is in order to avoid impacting performance of the other
 *	buffering modes more than necessary -- putting the test in putc adds many
 *	instructions that are wasted in non-_IOLBF mode:
 *	#define putc(c, f)	(_IO_ctmp=(c),\
 *				(f)->wp>=(f)->rp || (f)->flags&LINEBUF && _IO_ctmp=='\n'\
 *					?_IO_putc(_IO_ctmp, f)\
 *					:*(f)->wp++=_IO_ctmp)
 *				
 */
typedef struct{
	int fd;		/* UNIX file pointer */
	char flags;	/* bits for must free buffer on close, line-buffered */
	char state;	/* last operation was read, write, position, error, eof */
	char *buf;	/* pointer to i/o buffer */
	char *rp;	/* read pointer (or write end-of-buffer) */
	char *wp;	/* write pointer (or read end-of-buffer) */
	char *lp;	/* actual write pointer used when line-buffering */
	long bufl;	/* actual length of buffer */
	char unbuf[1];	/* tiny buffer for unbuffered io (used for ungetc?) */
}FILE;
typedef long fpos_t;
#ifndef NULL
#define	NULL	0
#endif
/*
 * Third arg of setvbuf
 */
#define	_IOFBF	1			/* block-buffered */
#define	_IOLBF	2			/* line-buffered */
#define	_IONBF	3			/* unbuffered */
#define	BUFSIZ	4096			/* size of setbuf buffer */
#define	EOF	(-1)			/* returned on end of file */
#define	FOPEN_MAX	128		/* max files open */
#define	FILENAME_MAX	BUFSIZ		/* silly filename length */
#define	L_tmpnam	20		/* sizeof "/tmp/abcdefghij9999 */
#define	SEEK_CUR	1
#define	SEEK_END	2
#define	SEEK_SET	0
#define	TMP_MAX		64		/* very hard to set correctly */
#define	stderr	(&_IO_stream[2])
#define	stdin	(&_IO_stream[0])
#define	stdout	(&_IO_stream[1])
#define	_IO_CHMASK	0377		/* mask for 8 bit characters */
FILE *tmpfile(void);
char *tmpnam(char *);
int fclose(FILE *);
int fflush(FILE *);
FILE *fopen(const char *, const char *);
FILE *freopen(const char *, const char *, FILE *);
void setbuf(FILE *, char *);
int setvbuf(FILE *, char *, int, long);
int fprintf(FILE *, const char *, ...);
int fscanf(FILE *, const char *, ...);
int printf(const char *, ...);
int scanf(const char *, ...);
int sprintf(char *, const char *, ...);
int sscanf(const char *, const char *, ...);
int vfprintf(FILE *, const char *, va_list);
int vprintf(const char *, va_list);
int vsprintf(char *, const char *, va_list);
int vfscanf(FILE *, const char *, va_list);
int fgetc(FILE *);
char *fgets(char *, int, FILE *);
int fputc(int, FILE *);
int fputs(const char *, FILE *);
int getc(FILE *);
#define	getc(f)	((f)->rp>=(f)->wp?_IO_getc(f):*(f)->rp++&_IO_CHMASK)
int _IO_getc(FILE *f);
int getchar(void);
#define	getchar()	getc(stdin)
char *gets(char *);
int putc(int, FILE *);
#define	putc(c, f) ((f)->wp>=(f)->rp?_IO_putc(c, f):(*(f)->wp++=c)&_IO_CHMASK)
int _IO_putc(int, FILE *);
int putchar(int);
#define	putchar(c)	putc(c, stdout)
int puts(const char *);
int ungetc(int, FILE *);
long fread(void *, long, long, FILE *);
long fwrite(const void *, long, long, FILE *);
int fgetpos(FILE *, fpos_t *);
int fseek(FILE *, long int, int);
int fsetpos(FILE *, const fpos_t *);
long int ftell(FILE *);
void rewind(FILE *);
void clearerr(FILE *);
int feof(FILE *);
int ferror(FILE *);
void perror(const char *);
extern FILE _IO_stream[FOPEN_MAX];
FILE *sopenr(const char *);
FILE *sopenw(void);
char *sclose(FILE *);
char	*dtoa(double, int, int, int*, int*, char**);
void	freedtoa(char*);