usr/src/lib/smbsrv/libsmb/common/smb_ctxbuf.c

   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 (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25
  26 /*
  27  * Buffer manipulation routines. These routines can be used to format
  28  * data within a data buffer without worrying about overrunning the
  29  * buffer.
  30  *
  31  * A ctxbuf_t structure is used to track the current location within
  32  * the buffer. The ctxbuf_init() must be called first to initialize the
  33  * context structure. ctxbuf_printf() can then be called to fill the buffer.
  34  * ctxbuf_printf will discard any data that would overrun the buffer and
  35  * the buffer will always be null terminated.
  36  */
  37
  38 #pragma ident   "%Z%%M% %I%     %E% SMI"
  39
  40 #include <stdio.h>
  41 #include <stdarg.h>
  42 #include <smbsrv/libsmb.h>
  43
  44 /*
  45  * smb_ctxbuf_init
  46  *
  47  * Initialize the buffer context structure.
  48  * This must be called before any of the other
  49  * buffer routines can be used.
  50  *
  51  * Returns -1 if invalid parameters, 0 otherwise
  52  */
  53 int
  54 smb_ctxbuf_init(smb_ctxbuf_t *ctx, unsigned char *buf, size_t buflen)
  55 {
  56         if (ctx == 0 || buf == 0 || buflen == 0)
  57                 return (-1);
  58
  59         buf[0] = '\0';
  60
  61         ctx->basep = buf;
  62         ctx->curp = buf;
  63         ctx->endp = &buf[buflen];
  64
  65         return (0);
  66 }
  67
  68 /*
  69  * smb_ctxbuf_len
  70  *
  71  * Return the amount of data stored in the buffer,
  72  * excluding the terminating null character. Similar
  73  * to strlen()
  74  *
  75  * Returns 0 if the ctx is invalid.
  76  */
  77 int
  78 smb_ctxbuf_len(smb_ctxbuf_t *ctx)
  79 {
  80         if (ctx == 0 || ctx->basep == 0 ||
  81             ctx->curp == 0 || ctx->endp == 0)
  82                 return (0);
  83         else
  84                 /*LINTED E_PTRDIFF_OVERFLOW*/
  85                 return (ctx->curp - ctx->basep);
  86 }
  87
  88 /*
  89  * smb_ctxbuf_printf
  90  *
  91  * Move formatted output (based on fmt string) to the buffer
  92  * identified in ctxbuf.  Any output characters beyond the buffer
  93  * are discarded and a null character is written at the end of the
  94  * characters actually written.
  95  *
  96  * Returns
  97  * Always return the number of bytes actually written (excluding the
  98  * terminating null).
  99  */
 100 int
 101 smb_ctxbuf_printf(smb_ctxbuf_t   *ctx, const char *fmt, ...)
 102 {
 103         int n;
 104         va_list args;
 105
 106         if (ctx == 0 || ctx->basep == 0 ||
 107             ctx->curp == 0 || ctx->endp == 0)
 108                 return (-1);
 109
 110         va_start(args, fmt);
 111         /*LINTED E_PTRDIFF_OVERFLOW*/
 112         n = vsnprintf((char *)ctx->curp, ctx->endp-ctx->curp, fmt, args);
 113         ctx->curp += n;
 114         va_end(args);
 115
 116         /*
 117          * return the number of bytes moved into the buffer.
 118          */
 119         return (n);
 120 }