summaryrefslogtreecommitdiffstats
path: root/src/util/vbuf.h
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--src/util/vbuf.h110
1 files changed, 110 insertions, 0 deletions
diff --git a/src/util/vbuf.h b/src/util/vbuf.h
new file mode 100644
index 0000000..149fe0c
--- /dev/null
+++ b/src/util/vbuf.h
@@ -0,0 +1,110 @@
+#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_RD_ERR (1<<0) /* read error */
+#define VBUF_FLAG_WR_ERR (1<<1) /* write error */
+#define VBUF_FLAG_ERR (VBUF_FLAG_RD_ERR | VBUF_FLAG_WR_ERR)
+#define VBUF_FLAG_EOF (1<<2) /* end of data */
+#define VBUF_FLAG_RD_TIMEOUT (1<<3) /* read timeout */
+#define VBUF_FLAG_WR_TIMEOUT (1<<4) /* write timeout */
+#define VBUF_FLAG_TIMEOUT (VBUF_FLAG_RD_TIMEOUT | VBUF_FLAG_WR_TIMEOUT)
+#define VBUF_FLAG_BAD (VBUF_FLAG_ERR | VBUF_FLAG_EOF | VBUF_FLAG_TIMEOUT)
+#define VBUF_FLAG_FIXED (1<<5) /* fixed-size buffer */
+
+#define vbuf_rd_error(v) ((v)->flags & (VBUF_FLAG_RD_ERR | VBUF_FLAG_RD_TIMEOUT))
+#define vbuf_wr_error(v) ((v)->flags & (VBUF_FLAG_WR_ERR | VBUF_FLAG_WR_TIMEOUT))
+#define vbuf_rd_timeout(v) ((v)->flags & VBUF_FLAG_RD_TIMEOUT)
+#define vbuf_wr_timeout(v) ((v)->flags & VBUF_FLAG_WR_TIMEOUT)
+
+#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 *, void *, ssize_t);
+extern ssize_t vbuf_write(VBUF *, const void *, 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