buffer.c

   1 /* $OpenBSD: buffer.c,v 1.27 2006/04/16 00:48:52 djm 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 "xmalloc.h"
  18 #include "buffer.h"
  19 #include "log.h"
  20
  21 #define BUFFER_MAX_CHUNK        0x100000
  22 #define BUFFER_MAX_LEN          0xa00000
  23 #define BUFFER_ALLOCSZ          0x008000
  24
  25 /* Initializes the buffer structure. */
  26
  27 void
  28 buffer_init(Buffer *buffer)
  29 {
  30         const u_int len = 4096;
  31
  32         buffer->alloc = 0;
  33         buffer->buf = xmalloc(len);
  34         buffer->alloc = len;
  35         buffer->offset = 0;
  36         buffer->end = 0;
  37 }
  38
  39 /* Frees any memory used for the buffer. */
  40
  41 void
  42 buffer_free(Buffer *buffer)
  43 {
  44         if (buffer->alloc > 0) {
  45                 memset(buffer->buf, 0, buffer->alloc);
  46                 buffer->alloc = 0;
  47                 xfree(buffer->buf);
  48         }
  49 }
  50
  51 /*
  52  * Clears any data from the buffer, making it empty.  This does not actually
  53  * zero the memory.
  54  */
  55
  56 void
  57 buffer_clear(Buffer *buffer)
  58 {
  59         buffer->offset = 0;
  60         buffer->end = 0;
  61 }
  62
  63 /* Appends data to the buffer, expanding it if necessary. */
  64
  65 void
  66 buffer_append(Buffer *buffer, const void *data, u_int len)
  67 {
  68         void *p;
  69         p = buffer_append_space(buffer, len);
  70         memcpy(p, data, len);
  71 }
  72
  73 static int
  74 buffer_compact(Buffer *buffer)
  75 {
  76         /*
  77          * If the buffer is quite empty, but all data is at the end, move the
  78          * data to the beginning.
  79          */
  80         if (buffer->offset > MIN(buffer->alloc, BUFFER_MAX_CHUNK)) {
  81                 memmove(buffer->buf, buffer->buf + buffer->offset,
  82                         buffer->end - buffer->offset);
  83                 buffer->end -= buffer->offset;
  84                 buffer->offset = 0;
  85                 return (1);
  86         }
  87         return (0);
  88 }
  89
  90 /*
  91  * Appends space to the buffer, expanding the buffer if necessary. This does
  92  * not actually copy the data into the buffer, but instead returns a pointer
  93  * to the allocated region.
  94  */
  95
  96 void *
  97 buffer_append_space(Buffer *buffer, u_int len)
  98 {
  99         u_int newlen;
 100         void *p;
 101
 102         if (len > BUFFER_MAX_CHUNK)
 103                 fatal("buffer_append_space: len %u not supported", len);
 104
 105         /* If the buffer is empty, start using it from the beginning. */
 106         if (buffer->offset == buffer->end) {
 107                 buffer->offset = 0;
 108                 buffer->end = 0;
 109         }
 110 restart:
 111         /* If there is enough space to store all data, store it now. */
 112         if (buffer->end + len < buffer->alloc) {
 113                 p = buffer->buf + buffer->end;
 114                 buffer->end += len;
 115                 return p;
 116         }
 117
 118         /* Compact data back to the start of the buffer if necessary */
 119         if (buffer_compact(buffer))
 120                 goto restart;
 121
 122         /* Increase the size of the buffer and retry. */
 123         newlen = roundup(buffer->alloc + len, BUFFER_ALLOCSZ);
 124         if (newlen > BUFFER_MAX_LEN)
 125                 fatal("buffer_append_space: alloc %u not supported",
 126                     newlen);
 127         buffer->buf = xrealloc(buffer->buf, 1, newlen);
 128         buffer->alloc = newlen;
 129         goto restart;
 130         /* NOTREACHED */
 131 }
 132
 133 /*
 134  * Check whether an allocation of 'len' will fit in the buffer
 135  * This must follow the same math as buffer_append_space
 136  */
 137 int
 138 buffer_check_alloc(Buffer *buffer, u_int len)
 139 {
 140         if (buffer->offset == buffer->end) {
 141                 buffer->offset = 0;
 142                 buffer->end = 0;
 143         }
 144  restart:
 145         if (buffer->end + len < buffer->alloc)
 146                 return (1);
 147         if (buffer_compact(buffer))
 148                 goto restart;
 149         if (roundup(buffer->alloc + len, BUFFER_ALLOCSZ) <= BUFFER_MAX_LEN)
 150                 return (1);
 151         return (0);
 152 }
 153
 154 /* Returns the number of bytes of data in the buffer. */
 155
 156 u_int
 157 buffer_len(Buffer *buffer)
 158 {
 159         return buffer->end - buffer->offset;
 160 }
 161
 162 /* Gets data from the beginning of the buffer. */
 163
 164 int
 165 buffer_get_ret(Buffer *buffer, void *buf, u_int len)
 166 {
 167         if (len > buffer->end - buffer->offset) {
 168                 error("buffer_get_ret: trying to get more bytes %d than in buffer %d",
 169                     len, buffer->end - buffer->offset);
 170                 return (-1);
 171         }
 172         memcpy(buf, buffer->buf + buffer->offset, len);
 173         buffer->offset += len;
 174         return (0);
 175 }
 176
 177 void
 178 buffer_get(Buffer *buffer, void *buf, u_int len)
 179 {
 180         if (buffer_get_ret(buffer, buf, len) == -1)
 181                 fatal("buffer_get: buffer error");
 182 }
 183
 184 /* Consumes the given number of bytes from the beginning of the buffer. */
 185
 186 int
 187 buffer_consume_ret(Buffer *buffer, u_int bytes)
 188 {
 189         if (bytes > buffer->end - buffer->offset) {
 190                 error("buffer_consume_ret: trying to get more bytes than in buffer");
 191                 return (-1);
 192         }
 193         buffer->offset += bytes;
 194         return (0);
 195 }
 196
 197 void
 198 buffer_consume(Buffer *buffer, u_int bytes)
 199 {
 200         if (buffer_consume_ret(buffer, bytes) == -1)
 201                 fatal("buffer_consume: buffer error");
 202 }
 203
 204 /* Consumes the given number of bytes from the end of the buffer. */
 205
 206 int
 207 buffer_consume_end_ret(Buffer *buffer, u_int bytes)
 208 {
 209         if (bytes > buffer->end - buffer->offset)
 210                 return (-1);
 211         buffer->end -= bytes;
 212         return (0);
 213 }
 214
 215 void
 216 buffer_consume_end(Buffer *buffer, u_int bytes)
 217 {
 218         if (buffer_consume_end_ret(buffer, bytes) == -1)
 219                 fatal("buffer_consume_end: trying to get more bytes than in buffer");
 220 }
 221
 222 /* Returns a pointer to the first used byte in the buffer. */
 223
 224 void *
 225 buffer_ptr(Buffer *buffer)
 226 {
 227         return buffer->buf + buffer->offset;
 228 }
 229
 230 /* Dumps the contents of the buffer to stderr. */
 231
 232 void
 233 buffer_dump(Buffer *buffer)
 234 {
 235         u_int i;
 236         u_char *ucp = buffer->buf;
 237
 238         for (i = buffer->offset; i < buffer->end; i++) {
 239                 fprintf(stderr, "%02x", ucp[i]);
 240                 if ((i-buffer->offset)%16==15)
 241                         fprintf(stderr, "\r\n");
 242                 else if ((i-buffer->offset)%2==1)
 243                         fprintf(stderr, " ");
 244         }
 245         fprintf(stderr, "\r\n");
 246 }