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      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 
     48 void
     49 dt_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 
     66 void
     67 dt_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 
     75 void
     76 dt_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 
     84 void
     85 dt_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 
    125 void
    126 dt_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 
    138 size_t
    139 dt_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 
    145 size_t
    146 dt_buf_len(const dt_buf_t *bp)
    147 {
    148 	return (bp->dbu_ptr - bp->dbu_buf);
    149 }
    150 
    151 int
    152 dt_buf_error(const dt_buf_t *bp)
    153 {
    154 	return (bp->dbu_err);
    155 }
    156 
    157 void *
    158 dt_buf_ptr(const dt_buf_t *bp)
    159 {
    160 	return (bp->dbu_buf);
    161 }
    162 
    163 void *
    164 dt_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