buffer.c

   1 /*
   2  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   3  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   4  *                    All rights reserved
   5  * Functions for manipulating fifo buffers (that can grow if needed).
   6  *
   7  * As far as I am concerned, the code I have written for this software
   8  * can be used freely for any purpose.  Any derived versions of this
   9  * software must be clearly marked as such, and if the derived work is
  10  * incompatible with the protocol description in the RFC file, it must be
  11  * called by a name other than "ssh" or "Secure Shell".
  12  */
  13
  14 #include "includes.h"
  15 RCSID("$OpenBSD: buffer.c,v 1.23 2005/03/14 11:46:56 markus Exp $");
  16
  17 #include "xmalloc.h"
  18 #include "buffer.h"
  19 #include "log.h"
  20
  21 /* Initializes the buffer structure. */
  22
  23 void
  24 buffer_init(Buffer *buffer)
  25 {
  26         const u_int len = 4096;
  27
  28         buffer->alloc = 0;
  29         buffer->buf = xmalloc(len);
  30         buffer->alloc = len;
  31         buffer->offset = 0;
  32         buffer->end = 0;
  33 }
  34
  35 /* Frees any memory used for the buffer. */
  36
  37 void
  38 buffer_free(Buffer *buffer)
  39 {
  40         if (buffer->alloc > 0) {
  41                 memset(buffer->buf, 0, buffer->alloc);
  42                 buffer->alloc = 0;
  43                 xfree(buffer->buf);
  44         }
  45 }
  46
  47 /*
  48  * Clears any data from the buffer, making it empty.  This does not actually
  49  * zero the memory.
  50  */
  51
  52 void
  53 buffer_clear(Buffer *buffer)
  54 {
  55         buffer->offset = 0;
  56         buffer->end = 0;
  57 }
  58
  59 /* Appends data to the buffer, expanding it if necessary. */
  60
  61 void
  62 buffer_append(Buffer *buffer, const void *data, u_int len)
  63 {
  64         void *p;
  65         p = buffer_append_space(buffer, len);
  66         memcpy(p, data, len);
  67 }
  68
  69 /*
  70  * Appends space to the buffer, expanding the buffer if necessary. This does
  71  * not actually copy the data into the buffer, but instead returns a pointer
  72  * to the allocated region.
  73  */
  74
  75 void *
  76 buffer_append_space(Buffer *buffer, u_int len)
  77 {
  78         u_int newlen;
  79         void *p;
  80
  81         if (len > BUFFER_MAX_CHUNK)
  82                 fatal("buffer_append_space: len %u not supported", len);
  83
  84         /* If the buffer is empty, start using it from the beginning. */
  85         if (buffer->offset == buffer->end) {
  86                 buffer->offset = 0;
  87                 buffer->end = 0;
  88         }
  89 restart:
  90         /* If there is enough space to store all data, store it now. */
  91         if (buffer->end + len < buffer->alloc) {
  92                 p = buffer->buf + buffer->end;
  93                 buffer->end += len;
  94                 return p;
  95         }
  96         /*
  97          * If the buffer is quite empty, but all data is at the end, move the
  98          * data to the beginning and retry.
  99          */
 100         if (buffer->offset > MIN(buffer->alloc, BUFFER_MAX_CHUNK)) {
 101                 memmove(buffer->buf, buffer->buf + buffer->offset,
 102                         buffer->end - buffer->offset);
 103                 buffer->end -= buffer->offset;
 104                 buffer->offset = 0;
 105                 goto restart;
 106         }
 107         /* Increase the size of the buffer and retry. */
 108
 109         newlen = buffer->alloc + len + 32768;
 110         if (newlen > BUFFER_MAX_LEN)
 111                 fatal("buffer_append_space: alloc %u not supported",
 112                     newlen);
 113         buffer->buf = xrealloc(buffer->buf, newlen);
 114         buffer->alloc = newlen;
 115         goto restart;
 116         /* NOTREACHED */
 117 }
 118
 119 /* Returns the number of bytes of data in the buffer. */
 120
 121 u_int
 122 buffer_len(Buffer *buffer)
 123 {
 124         return buffer->end - buffer->offset;
 125 }
 126
 127 /* Gets data from the beginning of the buffer. */
 128
 129 int
 130 buffer_get_ret(Buffer *buffer, void *buf, u_int len)
 131 {
 132         if (len > buffer->end - buffer->offset) {
 133                 error("buffer_get_ret: trying to get more bytes %d than in buffer %d",
 134                     len, buffer->end - buffer->offset);
 135                 return (-1);
 136         }
 137         memcpy(buf, buffer->buf + buffer->offset, len);
 138         buffer->offset += len;
 139         return (0);
 140 }
 141
 142 void
 143 buffer_get(Buffer *buffer, void *buf, u_int len)
 144 {
 145         if (buffer_get_ret(buffer, buf, len) == -1)
 146                 fatal("buffer_get: buffer error");
 147 }
 148
 149 /* Consumes the given number of bytes from the beginning of the buffer. */
 150
 151 int
 152 buffer_consume_ret(Buffer *buffer, u_int bytes)
 153 {
 154         if (bytes > buffer->end - buffer->offset) {
 155                 error("buffer_consume_ret: trying to get more bytes than in buffer");
 156                 return (-1);
 157         }
 158         buffer->offset += bytes;
 159         return (0);
 160 }
 161
 162 void
 163 buffer_consume(Buffer *buffer, u_int bytes)
 164 {
 165         if (buffer_consume_ret(buffer, bytes) == -1)
 166                 fatal("buffer_consume: buffer error");
 167 }
 168
 169 /* Consumes the given number of bytes from the end of the buffer. */
 170
 171 int
 172 buffer_consume_end_ret(Buffer *buffer, u_int bytes)
 173 {
 174         if (bytes > buffer->end - buffer->offset)
 175                 return (-1);
 176         buffer->end -= bytes;
 177         return (0);
 178 }
 179
 180 void
 181 buffer_consume_end(Buffer *buffer, u_int bytes)
 182 {
 183         if (buffer_consume_end_ret(buffer, bytes) == -1)
 184                 fatal("buffer_consume_end: trying to get more bytes than in buffer");
 185 }
 186
 187 /* Returns a pointer to the first used byte in the buffer. */
 188
 189 void *
 190 buffer_ptr(Buffer *buffer)
 191 {
 192         return buffer->buf + buffer->offset;
 193 }
 194
 195 /* Dumps the contents of the buffer to stderr. */
 196
 197 void
 198 buffer_dump(Buffer *buffer)
 199 {
 200         u_int i;
 201         u_char *ucp = buffer->buf;
 202
 203         for (i = buffer->offset; i < buffer->end; i++) {
 204                 fprintf(stderr, "%02x", ucp[i]);
 205                 if ((i-buffer->offset)%16==15)
 206                         fprintf(stderr, "\r\n");
 207                 else if ((i-buffer->offset)%2==1)
 208                         fprintf(stderr, " ");
 209         }
 210         fprintf(stderr, "\r\n");
 211 }