src/Packer.cc

   1
   2 /*
   3  * DEBUG: section 60    Packer: A uniform interface to store-like modules
   4  * AUTHOR: Alex Rousskov
   5  *
   6  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   7  * ----------------------------------------------------------
   8  *
   9  *  Squid is the result of efforts by numerous individuals from
  10  *  the Internet community; see the CONTRIBUTORS file for full
  11  *  details.   Many organizations have provided support for Squid's
  12  *  development; see the SPONSORS file for full details.  Squid is
  13  *  Copyrighted (C) 2001 by the Regents of the University of
  14  *  California; see the COPYRIGHT file for full details.  Squid
  15  *  incorporates software developed and/or copyrighted by other
  16  *  sources; see the CREDITS file for full details.
  17  *
  18  *  This program is free software; you can redistribute it and/or modify
  19  *  it under the terms of the GNU General Public License as published by
  20  *  the Free Software Foundation; either version 2 of the License, or
  21  *  (at your option) any later version.
  22  *
  23  *  This program is distributed in the hope that it will be useful,
  24  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  25  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  26  *  GNU General Public License for more details.
  27  *
  28  *  You should have received a copy of the GNU General Public License
  29  *  along with this program; if not, write to the Free Software
  30  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  31  *
  32  */
  33
  34 /*
  35  * Rationale:
  36  * ----------
  37  *
  38  * OK, we have to major interfaces comm.c and store.c.
  39  *
  40  * Store.c has a nice storeAppend[Printf] capability which makes "storing"
  41  * things easy and painless.
  42  *
  43  * Comm.c lacks commAppend[Printf] because comm does not handle its own
  44  * buffers (no mem_obj equivalent for comm.c).
  45  *
  46  * Thus, if one wants to be able to store _and_ Comm::Write an object, s/he
  47  * has to implement two almost identical functions.
  48  *
  49  * Packer
  50  * ------
  51  *
  52  * Packer provides for a more uniform interface to store and comm modules.
  53  * Packer has its own append and printf routines that "know" where to send
  54  * incoming data. In case of store interface, Packer sends data to
  55  * storeAppend.  Otherwise, Packer uses a MemBuf that can be flushed later to
  56  * Comm::Write.
  57  *
  58  * Thus, one can write just one function that will either "pack" things for
  59  * Comm::Write or "append" things to store, depending on actual packer
  60  * supplied.
  61  *
  62  * It is amazing how much work a tiny object can save. :)
  63  *
  64  */
  65
  66 /*
  67  * To-Do:
  68  */
  69
  70 #include "squid.h"
  71 #include "MemBuf.h"
  72 #include "Store.h"
  73
  74 /* local types */
  75
  76 /* local routines */
  77
  78 /* local constants and vars */
  79
  80 /*
  81  * We do have one potential problem here. Both append_f and vprintf_f types
  82  * cannot match real functions precisely (at least because of the difference in
  83  * the type of the first parameter). Thus, we have to use type cast. If somebody
  84  * changes the prototypes of real functions, Packer will not notice that because
  85  * of the type cast.
  86  *
  87  * Solution: we use the constants below to *hard code* current prototypes of
  88  * real functions. If real prototypes change, these constants will produce a
  89  * warning (e.g., "warning: assignment from incompatible pointer type").
  90  */
  91
  92 static void
  93 memBufAppend(MemBuf *mb, const char *buf, mb_size_t len)
  94 {
  95     mb->append(buf, len);
  96 }
  97
  98 static void
  99 memBufVPrintf(MemBuf * mb, const char *fmt, va_list vargs)
 100 {
 101     mb->vPrintf(fmt, vargs);
 102 }
 103
 104 static void
 105 storeEntryAppend(StoreEntry *e, const char *buf, int len)
 106 {
 107     e->append(buf, len);
 108 }
 109
 110 /* append()'s */
 111 static void (*const store_append) (StoreEntry *, const char *, int) = &storeEntryAppend;
 112 static void (*const memBuf_append) (MemBuf *, const char *, mb_size_t) = &memBufAppend;
 113
 114 /* vprintf()'s */
 115 static void (*const store_vprintf) (StoreEntry *, const char *, va_list ap) = &storeAppendVPrintf;
 116 static void (*const memBuf_vprintf) (MemBuf *, const char *, va_list ap) = &memBufVPrintf;
 117
 118 /* init/clean */
 119
 120 /* init with this to forward data to StoreEntry */
 121 void
 122 packerToStoreInit(Packer * p, StoreEntry * e)
 123 {
 124     assert(p && e);
 125     p->append = (append_f) store_append;
 126     p->packer_vprintf = (vprintf_f) store_vprintf;
 127     p->real_handler = e;
 128     e->buffer();
 129 }
 130
 131 /* init with this to accumulate data in MemBuf */
 132 void
 133 packerToMemInit(Packer * p, MemBuf * mb)
 134 {
 135     assert(p && mb);
 136     p->append = (append_f) memBuf_append;
 137     p->packer_vprintf = (vprintf_f) memBuf_vprintf;
 138     p->real_handler = mb;
 139 }
 140
 141 /* call this when you are done */
 142 void
 143 packerClean(Packer * p)
 144 {
 145     assert(p);
 146
 147     if (p->append == (append_f) store_append && p->real_handler)
 148         static_cast<StoreEntry*>(p->real_handler)->flush();
 149
 150     /* it is not really necessary to do this, but, just in case... */
 151     p->append = NULL;
 152     p->packer_vprintf = NULL;
 153     p->real_handler = NULL;
 154 }
 155
 156 void
 157 packerAppend(Packer * p, const char *buf, int sz)
 158 {
 159     assert(p);
 160     assert(p->real_handler && p->append);
 161     p->append(p->real_handler, buf, sz);
 162 }
 163
 164 void
 165 packerPrintf(Packer * p, const char *fmt,...)
 166 {
 167     va_list args;
 168     va_start(args, fmt);
 169
 170     assert(p);
 171     assert(p->real_handler && p->packer_vprintf);
 172     p->packer_vprintf(p->real_handler, fmt, args);
 173     va_end(args);
 174 }