#ifndef _VBUF_H_INCLUDED_ #define _VBUF_H_INCLUDED_ /*++ /* NAME /* vbuf 3h /* SUMMARY /* generic buffer /* SYNOPSIS /* #include <vbuf.h> /* DESCRIPTION /* .nf /* * The VBUF buffer is defined by 1) its structure, by 2) the VBUF_GET() and * 3) VBUF_PUT() operations that automatically handle buffer empty and * buffer full conditions, and 4) by the VBUF_SPACE() operation that allows * the user to reserve buffer space ahead of time, to allow for situations * where calling VBUF_PUT() is not possible or desirable. * * The VBUF buffer does not specify primitives for memory allocation or * deallocation. The purpose is to allow different applications to have * different strategies: a memory-resident buffer; a memory-mapped file; or * a stdio-like window to an open file. Each application provides its own * get(), put() and space() methods that perform the necessary magic. * * This interface is pretty normal. With one exception: the number of bytes * left to read is negated. This is done so that we can change direction * between reading and writing on the fly. The alternative would be to use * separate read and write counters per buffer. */ typedef struct VBUF VBUF; typedef int (*VBUF_GET_READY_FN) (VBUF *); typedef int (*VBUF_PUT_READY_FN) (VBUF *); typedef int (*VBUF_SPACE_FN) (VBUF *, ssize_t); struct VBUF { int flags; /* status, see below */ unsigned char *data; /* variable-length buffer */ ssize_t len; /* buffer length */ ssize_t cnt; /* bytes left to read/write */ unsigned char *ptr; /* read/write position */ VBUF_GET_READY_FN get_ready; /* read buffer empty action */ VBUF_PUT_READY_FN put_ready; /* write buffer full action */ VBUF_SPACE_FN space; /* request for buffer space */ }; /* * Typically, an application will embed a VBUF structure into a larger * structure that also contains application-specific members. This approach * gives us the best of both worlds. The application can still use the * generic VBUF primitives for reading and writing VBUFs. The macro below * transforms a pointer from VBUF structure to the structure that contains * it. */ #define VBUF_TO_APPL(vbuf_ptr,app_type,vbuf_member) \ ((app_type *) (((char *) (vbuf_ptr)) - offsetof(app_type,vbuf_member))) /* * Buffer status management. */ #define VBUF_FLAG_ERR (1<<0) /* some I/O error */ #define VBUF_FLAG_EOF (1<<1) /* end of data */ #define VBUF_FLAG_TIMEOUT (1<<2) /* timeout error */ #define VBUF_FLAG_BAD (VBUF_FLAG_ERR | VBUF_FLAG_EOF | VBUF_FLAG_TIMEOUT) #define VBUF_FLAG_FIXED (1<<3) /* fixed-size buffer */ #define vbuf_error(v) ((v)->flags & (VBUF_FLAG_ERR | VBUF_FLAG_TIMEOUT)) #define vbuf_eof(v) ((v)->flags & VBUF_FLAG_EOF) #define vbuf_timeout(v) ((v)->flags & VBUF_FLAG_TIMEOUT) #define vbuf_clearerr(v) ((v)->flags &= ~VBUF_FLAG_BAD) /* * Buffer I/O-like operations and results. */ #define VBUF_GET(v) ((v)->cnt < 0 ? ++(v)->cnt, \ (int) *(v)->ptr++ : vbuf_get(v)) #define VBUF_PUT(v,c) ((v)->cnt > 0 ? --(v)->cnt, \ (int) (*(v)->ptr++ = (c)) : vbuf_put((v),(c))) #define VBUF_SPACE(v,n) ((v)->space((v),(n))) #define VBUF_EOF (-1) /* no more space or data */ extern int vbuf_get(VBUF *); extern int vbuf_put(VBUF *, int); extern int vbuf_unget(VBUF *, int); extern ssize_t vbuf_read(VBUF *, char *, ssize_t); extern ssize_t vbuf_write(VBUF *, const char *, ssize_t); /* LICENSE /* .ad /* .fi /* The Secure Mailer license must be distributed with this software. /* AUTHOR(S) /* Wietse Venema /* IBM T.J. Watson Research /* P.O. Box 704 /* Yorktown Heights, NY 10598, USA /*--*/ #endif