base/circlebuf.cc

   1 /*
   2  * Copyright (c) 2003 The Regents of The University of Michigan
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #include <algorithm>
  30 #include <string>
  31
  32 #include <stdio.h>
  33 #include <string.h>
  34 #include <unistd.h>
  35
  36 #include "base/circlebuf.hh"
  37 #include "base/cprintf.hh"
  38 #include "base/intmath.hh"
  39
  40 using namespace std;
  41
  42 CircleBuf::CircleBuf(int l)
  43   : rollover(false), buflen(l), size(0), start(0), stop(0)
  44 { buf = new char[buflen]; }
  45
  46 CircleBuf::~CircleBuf()
  47 { if (buf) delete [] buf; }
  48
  49 void
  50 CircleBuf::dump()
  51 {
  52   cprintf("start = %10d, stop = %10d, buflen = %10d\n", start, stop, buflen);
  53   fflush(stdout);
  54   ::write(STDOUT_FILENO, buf, buflen);
  55   ::write(STDOUT_FILENO, "<\n", 2);
  56 }
  57
  58 void
  59 CircleBuf::flush()
  60 {
  61   start = 0;
  62   stop = 0;
  63   rollover = false;
  64 }
  65
  66 void
  67 CircleBuf::read(char *b, int len)
  68 {
  69   size -= len;
  70   if (size < 0)
  71     size = 0;
  72
  73   if (stop > start) {
  74     len = min(len, stop - start);
  75     memcpy(b, buf + start, len);
  76     start += len;
  77   }
  78   else {
  79     int endlen = buflen - start;
  80     if (endlen > len) {
  81       memcpy(b, buf + start, len);
  82       start += len;
  83     }
  84     else {
  85       memcpy(b, buf + start, endlen);
  86       start = min(len - endlen, stop);
  87       memcpy(b + endlen, buf, start);
  88     }
  89   }
  90 }
  91
  92 void
  93 CircleBuf::read(int fd, int len)
  94 {
  95   size -= len;
  96   if (size < 0)
  97     size = 0;
  98
  99   if (stop > start) {
 100     len = min(len, stop - start);
 101     ::write(fd, buf + start, len);
 102     start += len;
 103   }
 104   else {
 105     int endlen = buflen - start;
 106     if (endlen > len) {
 107       ::write(fd, buf + start, len);
 108       start += len;
 109     }
 110     else {
 111       ::write(fd, buf + start, endlen);
 112       start = min(len - endlen, stop);
 113       ::write(fd, buf, start);
 114     }
 115   }
 116 }
 117
 118 void
 119 CircleBuf::read(int fd)
 120 {
 121   size = 0;
 122
 123   if (stop > start) {
 124     ::write(fd, buf + start, stop - start);
 125   }
 126   else {
 127     ::write(fd, buf + start, buflen - start);
 128     ::write(fd, buf, stop);
 129   }
 130
 131   start = stop;
 132 }
 133
 134 void
 135 CircleBuf::readall(int fd)
 136 {
 137   if (rollover)
 138     ::write(fd, buf + stop, buflen - stop);
 139
 140   ::write(fd, buf, stop);
 141   start = stop;
 142 }
 143
 144 void
 145 CircleBuf::write(char b)
 146 { write(&b, 1); }
 147
 148 void
 149 CircleBuf::write(const char *b)
 150 { write(b, strlen(b)); }
 151
 152 void
 153 CircleBuf::write(const char *b, int len)
 154 {
 155   if (len <= 0)
 156     return;
 157
 158   size += len;
 159   if (size > buflen)
 160       size = buflen;
 161
 162   int old_start = start;
 163   int old_stop = stop;
 164
 165   if (len >= buflen) {
 166     start = 0;
 167     stop = buflen;
 168     rollover = true;
 169     memcpy(buf, b + (len - buflen), buflen);
 170     return;
 171   }
 172
 173   if (stop + len <= buflen) {
 174     memcpy(buf + stop, b, len);
 175     stop += len;
 176   } else {
 177     int end_len = buflen - old_stop;
 178     stop = len - end_len;
 179     memcpy(buf + old_stop, b, end_len);
 180     memcpy(buf, b + end_len, stop);
 181     rollover = true;
 182   }
 183
 184   if (old_start > old_stop && old_start < stop ||
 185       old_start < old_stop && stop < old_stop)
 186     start = stop + 1;
 187 }