buffer.c

   1 /* $OpenBSD: buffer.c,v 1.31 2006/08/03 03:34:41 deraadt Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Functions for manipulating fifo buffers (that can grow if needed).
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  */
  14
  15 #include "includes.h"
  16
  17 #include <sys/param.h>
  18
  19 #include <stdio.h>
  20 #include <string.h>
  21 #include <stdarg.h>
  22
  23 #include "xmalloc.h"
  24 #include "buffer.h"
  25 #include "log.h"
  26
  27 #define BUFFER_MAX_CHUNK        0x100000
  28 #define BUFFER_MAX_LEN          0xa00000
  29 #define BUFFER_ALLOCSZ          0x008000
  30
  31 /* Initializes the buffer structure. */
  32
  33 void
  34 buffer_init(Buffer *buffer)
  35 {
  36         const u_int len = 4096;
  37
  38         buffer->alloc = 0;
  39         buffer->buf = xmalloc(len);
  40         buffer->alloc = len;
  41         buffer->offset = 0;
  42         buffer->end = 0;
  43 }
  44
  45 /* Frees any memory used for the buffer. */
  46
  47 void
  48 buffer_free(Buffer *buffer)
  49 {
  50         if (buffer->alloc > 0) {
  51                 memset(buffer->buf, 0, buffer->alloc);
  52                 buffer->alloc = 0;
  53                 xfree(buffer->buf);
  54         }
  55 }
  56
  57 /*
  58  * Clears any data from the buffer, making it empty.  This does not actually
  59  * zero the memory.
  60  */
  61
  62 void
  63 buffer_clear(Buffer *buffer)
  64 {
  65         buffer->offset = 0;
  66         buffer->end = 0;
  67 }
  68
  69 /* Appends data to the buffer, expanding it if necessary. */
  70
  71 void
  72 buffer_append(Buffer *buffer, const void *data, u_int len)
  73 {
  74         void *p;
  75         p = buffer_append_space(buffer, len);
  76         memcpy(p, data, len);
  77 }
  78
  79 static int
  80 buffer_compact(Buffer *buffer)
  81 {
  82         /*
  83          * If the buffer is quite empty, but all data is at the end, move the
  84          * data to the beginning.
  85          */
  86         if (buffer->offset > MIN(buffer->alloc, BUFFER_MAX_CHUNK)) {
  87                 memmove(buffer->buf, buffer->buf + buffer->offset,
  88                         buffer->end - buffer->offset);
  89                 buffer->end -= buffer->offset;
  90                 buffer->offset = 0;
  91                 return (1);
  92         }
  93         return (0);
  94 }
  95
  96 /*
  97  * Appends space to the buffer, expanding the buffer if necessary. This does
  98  * not actually copy the data into the buffer, but instead returns a pointer
  99  * to the allocated region.
 100  */
 101
 102 void *
 103 buffer_append_space(Buffer *buffer, u_int len)
 104 {
 105         u_int newlen;
 106         void *p;
 107
 108         if (len > BUFFER_MAX_CHUNK)
 109                 fatal("buffer_append_space: len %u not supported", len);
 110
 111         /* If the buffer is empty, start using it from the beginning. */
 112         if (buffer->offset == buffer->end) {
 113                 buffer->offset = 0;
 114                 buffer->end = 0;
 115         }
 116 restart:
 117         /* If there is enough space to store all data, store it now. */
 118         if (buffer->end + len < buffer->alloc) {
 119                 p = buffer->buf + buffer->end;
 120                 buffer->end += len;
 121                 return p;
 122         }
 123
 124         /* Compact data back to the start of the buffer if necessary */
 125         if (buffer_compact(buffer))
 126                 goto restart;
 127
 128         /* Increase the size of the buffer and retry. */
 129         newlen = roundup(buffer->alloc + len, BUFFER_ALLOCSZ);
 130         if (newlen > BUFFER_MAX_LEN)
 131                 fatal("buffer_append_space: alloc %u not supported",
 132                     newlen);
 133         buffer->buf = xrealloc(buffer->buf, 1, newlen);
 134         buffer->alloc = newlen;
 135         goto restart;
 136         /* NOTREACHED */
 137 }
 138
 139 /*
 140  * Check whether an allocation of 'len' will fit in the buffer
 141  * This must follow the same math as buffer_append_space
 142  */
 143 int
 144 buffer_check_alloc(Buffer *buffer, u_int len)
 145 {
 146         if (buffer->offset == buffer->end) {
 147                 buffer->offset = 0;
 148                 buffer->end = 0;
 149         }
 150  restart:
 151         if (buffer->end + len < buffer->alloc)
 152                 return (1);
 153         if (buffer_compact(buffer))
 154                 goto restart;
 155         if (roundup(buffer->alloc + len, BUFFER_ALLOCSZ) <= BUFFER_MAX_LEN)
 156                 return (1);
 157         return (0);
 158 }
 159
 160 /* Returns the number of bytes of data in the buffer. */
 161
 162 u_int
 163 buffer_len(Buffer *buffer)
 164 {
 165         return buffer->end - buffer->offset;
 166 }
 167
 168 /* Gets data from the beginning of the buffer. */
 169
 170 int
 171 buffer_get_ret(Buffer *buffer, void *buf, u_int len)
 172 {
 173         if (len > buffer->end - buffer->offset) {
 174                 error("buffer_get_ret: trying to get more bytes %d than in buffer %d",
 175                     len, buffer->end - buffer->offset);
 176                 return (-1);
 177         }
 178         memcpy(buf, buffer->buf + buffer->offset, len);
 179         buffer->offset += len;
 180         return (0);
 181 }
 182
 183 void
 184 buffer_get(Buffer *buffer, void *buf, u_int len)
 185 {
 186         if (buffer_get_ret(buffer, buf, len) == -1)
 187                 fatal("buffer_get: buffer error");
 188 }
 189
 190 /* Consumes the given number of bytes from the beginning of the buffer. */
 191
 192 int
 193 buffer_consume_ret(Buffer *buffer, u_int bytes)
 194 {
 195         if (bytes > buffer->end - buffer->offset) {
 196                 error("buffer_consume_ret: trying to get more bytes than in buffer");
 197                 return (-1);
 198         }
 199         buffer->offset += bytes;
 200         return (0);
 201 }
 202
 203 void
 204 buffer_consume(Buffer *buffer, u_int bytes)
 205 {
 206         if (buffer_consume_ret(buffer, bytes) == -1)
 207                 fatal("buffer_consume: buffer error");
 208 }
 209
 210 /* Consumes the given number of bytes from the end of the buffer. */
 211
 212 int
 213 buffer_consume_end_ret(Buffer *buffer, u_int bytes)
 214 {
 215         if (bytes > buffer->end - buffer->offset)
 216                 return (-1);
 217         buffer->end -= bytes;
 218         return (0);
 219 }
 220
 221 void
 222 buffer_consume_end(Buffer *buffer, u_int bytes)
 223 {
 224         if (buffer_consume_end_ret(buffer, bytes) == -1)
 225                 fatal("buffer_consume_end: trying to get more bytes than in buffer");
 226 }
 227
 228 /* Returns a pointer to the first used byte in the buffer. */
 229
 230 void *
 231 buffer_ptr(Buffer *buffer)
 232 {
 233         return buffer->buf + buffer->offset;
 234 }
 235
 236 /* Dumps the contents of the buffer to stderr. */
 237
 238 void
 239 buffer_dump(Buffer *buffer)
 240 {
 241         u_int i;
 242         u_char *ucp = buffer->buf;
 243
 244         for (i = buffer->offset; i < buffer->end; i++) {
 245                 fprintf(stderr, "%02x", ucp[i]);
 246                 if ((i-buffer->offset)%16==15)
 247                         fprintf(stderr, "\r\n");
 248                 else if ((i-buffer->offset)%2==1)
 249                         fprintf(stderr, " ");
 250         }
 251         fprintf(stderr, "\r\n");
 252 }