buff.h

#ifdef __cplusplus
extern "C" {
#endif

#ifdef B_SFIO   --------------------这个宏在何定义未知
#include "sfio.h"
#endif

#include <stdarg.h>

/* Reading is buffered */
#define B_RD     (1)
/* Writing is buffered */
#define B_WR     (2)
#define B_RDWR   (3)
/* At end of file, or closed stream; no further input allowed */
#define B_EOF    (4)
/* No further output possible */
#define B_EOUT   (8)
/* A read error has occurred */
#define B_RDERR (16)
/* A write error has occurred */
#define B_WRERR (32)
#ifdef B_ERROR  /* in SVR4: sometimes defined in /usr/include/sys/buf.h */
#undef B_ERROR
#endif
#define B_ERROR (48)
/* Use chunked writing */
#define B_CHUNK (64)
/* bflush() if a read would block */
#define B_SAFEREAD (128)
/* buffer is a socket */
#define B_SOCKET (256)
#ifdef CHARSET_EBCDIC
#define B_ASCII2EBCDIC 0x40000000  /* Enable conversion for this buffer */
#define B_EBCDIC2ASCII 0x80000000  /* Enable conversion for this buffer */
#endif /*CHARSET_EBCDIC*/

typedef struct buff_struct BUFF;

struct buff_struct {
    int flags;   /* flags */
    unsigned char *inptr; /* pointer to next location to read */
    int incnt;   /* number of bytes left to read from input buffer;
     * always 0 if had a read error  */
    int outchunk;  /* location of chunk header when chunking */
    int outcnt;   /* number of byte put in output buffer */
    unsigned char *inbase;
    unsigned char *outbase;
    int bufsiz;
    void (*error) (BUFF *fb, int op, void *data);
    void *error_data;
    long int bytes_sent; /* number of bytes actually written */

    ap_pool *pool;

/* could also put pointers to the basic I/O routines here */
    int fd;   /* the file descriptor */
    int fd_in;   /* input file descriptor, if different */
#ifdef WIN32
    HANDLE hFH;   /* Windows filehandle */
#endif

    /* transport handle, for RPC binding handle or some such */
    void *t_handle;

#ifdef B_SFIO
    Sfio_t *sf_in;
    Sfio_t *sf_out;
#endif
};

#ifdef B_SFIO
typedef struct {
    Sfdisc_t disc;
    BUFF *buff;
} apache_sfio;

extern Sfdisc_t *bsfio_new(pool *p, BUFF *b);
#endif

/* Options to bset/getopt */
#define BO_BYTECT (1)

/* Stream creation and modification */
API_EXPORT(BUFF *) ap_bcreate(pool *p, int flags);
API_EXPORT(void) ap_bpushfd(BUFF *fb, int fd_in, int fd_out);
#ifdef WIN32
API_EXPORT(void) ap_bpushh(BUFF *fb, HANDLE hFH);
#endif
API_EXPORT(int) ap_bsetopt(BUFF *fb, int optname, const void *optval);
API_EXPORT(int) ap_bgetopt(BUFF *fb, int optname, void *optval);
API_EXPORT(int) ap_bsetflag(BUFF *fb, int flag, int value);
API_EXPORT(int) ap_bclose(BUFF *fb);

#define ap_bgetflag(fb, flag) ((fb)->flags & (flag))

/* Error handling */
API_EXPORT(void) ap_bonerror(BUFF *fb, void (*error) (BUFF *, int, void *),
     void *data);

/* I/O */
API_EXPORT(int) ap_bread(BUFF *fb, void *buf, int nbyte);
API_EXPORT(int) ap_bgets(char *s, int n, BUFF *fb);
API_EXPORT(int) ap_blookc(char *buff, BUFF *fb);
API_EXPORT(int) ap_bskiplf(BUFF *fb);
API_EXPORT(int) ap_bwrite(BUFF *fb, const void *buf, int nbyte);
API_EXPORT(int) ap_bflush(BUFF *fb);
API_EXPORT(int) ap_bputs(const char *x, BUFF *fb);
API_EXPORT(int) ap_bvputs(BUFF *fb,...);
API_EXPORT_NONSTD(int) ap_bprintf(BUFF *fb, const char *fmt,...)
    __attribute__((format(printf,2,3)));
API_EXPORT(int) ap_vbprintf(BUFF *fb, const char *fmt, va_list vlist);

/* Internal routines */
API_EXPORT(int) ap_bflsbuf(int c, BUFF *fb);
API_EXPORT(int) ap_bfilbuf(BUFF *fb);

#ifndef CHARSET_EBCDIC    -----------------------在何处定义以及意义未知

#define ap_bgetc(fb)   ( ((fb)->incnt == 0) ? ap_bfilbuf(fb) : /
      ((fb)->incnt--, *((fb)->inptr++)) )

#define ap_bputc(c, fb) ((((fb)->flags & (B_EOUT|B_WRERR|B_WR)) != B_WR || /
       (fb)->outcnt == (fb)->bufsiz) ? ap_bflsbuf(c, (fb)) : /
       ((fb)->outbase[(fb)->outcnt++] = (c), 0))

#else /*CHARSET_EBCDIC*/

#define ap_bgetc(fb)   ( ((fb)->incnt == 0) ? ap_bfilbuf(fb) : /
      ((fb)->incnt--, (fb->flags & B_ASCII2EBCDIC)/
      ?os_toebcdic[(unsigned char)*((fb)->inptr++)]:*((fb)->inptr++)) )

#define ap_bputc(c, fb) ((((fb)->flags & (B_EOUT|B_WRERR|B_WR)) != B_WR || /
       (fb)->outcnt == (fb)->bufsiz) ? ap_bflsbuf(c, (fb)) : /
       ((fb)->outbase[(fb)->outcnt++] = (fb->flags & B_EBCDIC2ASCII)/
       ?os_toascii[(unsigned char)c]:(c), 0))

#endif /*CHARSET_EBCDIC*/
struct child_info {
#ifdef WIN32
    /*
     *  These handles are used by ap_call_exec to call
     *  create process with pipe handles.
     */
    HANDLE hPipeInputRead;
    HANDLE hPipeOutputWrite;
    HANDLE hPipeErrorWrite;
#else
    /*
     * We need to put a dummy member in here to avoid compilation
     * errors under certain Unix compilers, like SGI's and HPUX's,
     * which fail to compile a zero-sized struct.  Of course
     * it would be much nicer if there was actually a use for this
     * structure under Unix.  Aah the joys of x-platform code.
     */
    int dummy;
#endif
};
API_EXPORT(int) ap_bspawn_child(pool *, int (*)(void *, child_info *), void *,
     enum kill_conditions, BUFF **pipe_in, BUFF **pipe_out,
     BUFF **pipe_err);

/* enable non-blocking operations */
API_EXPORT(int) ap_bnonblock(BUFF *fb, int direction);
/* and get an fd to select() on */
API_EXPORT(int) ap_bfileno(BUFF *fb, int direction);

/* bflush() if a read now would block, but don't actually read anything */
API_EXPORT(void) ap_bhalfduplex(BUFF *fb);

#ifdef __cplusplus
}
#endif

这个文件主要是在内存管理的基础上定义了apache应用层的文件读取缓存结构和API接口。