1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License").  You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22/*
23 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
24 * Use is subject to license terms.
25 */
26
27#pragma ident	"%Z%%M%	%I%	%E% SMI"
28
29/*
30 * DTrace Memory Buffer Routines
31 *
32 * The routines in this file are used to create an automatically resizing
33 * memory buffer that can be written to like a file.  Memory buffers are
34 * used to construct DOF to ioctl() to dtrace(7D), and provide semantics that
35 * simplify caller code.  Specifically, any allocation errors result in an
36 * error code being set inside the buffer which is maintained persistently and
37 * propagates to another buffer if the buffer in error is concatenated.  These
38 * semantics permit callers to execute a large series of writes without needing
39 * to check for errors and then perform a single check before using the buffer.
40 */
41
42#include <sys/sysmacros.h>
43#include <strings.h>
44
45#include <dt_impl.h>
46#include <dt_buf.h>
47
48void
49dt_buf_create(dtrace_hdl_t *dtp, dt_buf_t *bp, const char *name, size_t len)
50{
51	if (len == 0)
52		len = _dtrace_bufsize;
53
54	bp->dbu_buf = bp->dbu_ptr = dt_zalloc(dtp, len);
55	bp->dbu_len = len;
56
57	if (bp->dbu_buf == NULL)
58		bp->dbu_err = dtrace_errno(dtp);
59	else
60		bp->dbu_err = 0;
61
62	bp->dbu_resizes = 0;
63	bp->dbu_name = name;
64}
65
66void
67dt_buf_destroy(dtrace_hdl_t *dtp, dt_buf_t *bp)
68{
69	dt_dprintf("dt_buf_destroy(%s): size=%lu resizes=%u\n",
70	    bp->dbu_name, (ulong_t)bp->dbu_len, bp->dbu_resizes);
71
72	dt_free(dtp, bp->dbu_buf);
73}
74
75void
76dt_buf_reset(dtrace_hdl_t *dtp, dt_buf_t *bp)
77{
78	if ((bp->dbu_ptr = bp->dbu_buf) != NULL)
79		bp->dbu_err = 0;
80	else
81		dt_buf_create(dtp, bp, bp->dbu_name, bp->dbu_len);
82}
83
84void
85dt_buf_write(dtrace_hdl_t *dtp, dt_buf_t *bp,
86    const void *buf, size_t len, size_t align)
87{
88	size_t off = (size_t)(bp->dbu_ptr - bp->dbu_buf);
89	size_t adj = roundup(off, align) - off;
90
91	if (bp->dbu_err != 0) {
92		(void) dt_set_errno(dtp, bp->dbu_err);
93		return; /* write silently fails */
94	}
95
96	if (bp->dbu_ptr + adj + len > bp->dbu_buf + bp->dbu_len) {
97		size_t new_len = bp->dbu_len * 2;
98		uchar_t *new_buf;
99		uint_t r = 1;
100
101		while (bp->dbu_ptr + adj + len > bp->dbu_buf + new_len) {
102			new_len *= 2;
103			r++;
104		}
105
106		if ((new_buf = dt_zalloc(dtp, new_len)) == NULL) {
107			bp->dbu_err = dtrace_errno(dtp);
108			return;
109		}
110
111		bcopy(bp->dbu_buf, new_buf, off);
112		dt_free(dtp, bp->dbu_buf);
113
114		bp->dbu_buf = new_buf;
115		bp->dbu_ptr = new_buf + off;
116		bp->dbu_len = new_len;
117		bp->dbu_resizes += r;
118	}
119
120	bp->dbu_ptr += adj;
121	bcopy(buf, bp->dbu_ptr, len);
122	bp->dbu_ptr += len;
123}
124
125void
126dt_buf_concat(dtrace_hdl_t *dtp, dt_buf_t *dst,
127    const dt_buf_t *src, size_t align)
128{
129	if (dst->dbu_err == 0 && src->dbu_err != 0) {
130		(void) dt_set_errno(dtp, src->dbu_err);
131		dst->dbu_err = src->dbu_err;
132	} else {
133		dt_buf_write(dtp, dst, src->dbu_buf,
134		    (size_t)(src->dbu_ptr - src->dbu_buf), align);
135	}
136}
137
138size_t
139dt_buf_offset(const dt_buf_t *bp, size_t align)
140{
141	size_t off = (size_t)(bp->dbu_ptr - bp->dbu_buf);
142	return (roundup(off, align));
143}
144
145size_t
146dt_buf_len(const dt_buf_t *bp)
147{
148	return (bp->dbu_ptr - bp->dbu_buf);
149}
150
151int
152dt_buf_error(const dt_buf_t *bp)
153{
154	return (bp->dbu_err);
155}
156
157void *
158dt_buf_ptr(const dt_buf_t *bp)
159{
160	return (bp->dbu_buf);
161}
162
163void *
164dt_buf_claim(dtrace_hdl_t *dtp, dt_buf_t *bp)
165{
166	void *buf = bp->dbu_buf;
167
168	if (bp->dbu_err != 0) {
169		dt_free(dtp, buf);
170		buf = NULL;
171	}
172
173	bp->dbu_buf = bp->dbu_ptr = NULL;
174	bp->dbu_len = 0;
175
176	return (buf);
177}
178