src/Packer.cc

   1
   2 /*
   3  * $Id$
   4  *
   5  * DEBUG: section 60    Packer: A uniform interface to store-like modules
   6  * AUTHOR: Alex Rousskov
   7  *
   8  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   9  * ----------------------------------------------------------
  10  *
  11  *  Squid is the result of efforts by numerous individuals from
  12  *  the Internet community; see the CONTRIBUTORS file for full
  13  *  details.   Many organizations have provided support for Squid's
  14  *  development; see the SPONSORS file for full details.  Squid is
  15  *  Copyrighted (C) 2001 by the Regents of the University of
  16  *  California; see the COPYRIGHT file for full details.  Squid
  17  *  incorporates software developed and/or copyrighted by other
  18  *  sources; see the CREDITS file for full details.
  19  *
  20  *  This program is free software; you can redistribute it and/or modify
  21  *  it under the terms of the GNU General Public License as published by
  22  *  the Free Software Foundation; either version 2 of the License, or
  23  *  (at your option) any later version.
  24  *
  25  *  This program is distributed in the hope that it will be useful,
  26  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  27  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  28  *  GNU General Public License for more details.
  29  *
  30  *  You should have received a copy of the GNU General Public License
  31  *  along with this program; if not, write to the Free Software
  32  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  33  *
  34  */
  35
  36 /*
  37  * Rationale:
  38  * ----------
  39  *
  40  * OK, we have to major interfaces comm.c and store.c.
  41  *
  42  * Store.c has a nice storeAppend[Printf] capability which makes "storing"
  43  * things easy and painless.
  44  *
  45  * Comm.c lacks commAppend[Printf] because comm does not handle its own
  46  * buffers (no mem_obj equivalent for comm.c).
  47  *
  48  * Thus, if one wants to be able to store _and_ Comm::Write an object, s/he
  49  * has to implement two almost identical functions.
  50  *
  51  * Packer
  52  * ------
  53  *
  54  * Packer provides for a more uniform interface to store and comm modules.
  55  * Packer has its own append and printf routines that "know" where to send
  56  * incoming data. In case of store interface, Packer sends data to
  57  * storeAppend.  Otherwise, Packer uses a MemBuf that can be flushed later to
  58  * Comm::Write.
  59  *
  60  * Thus, one can write just one function that will either "pack" things for
  61  * Comm::Write or "append" things to store, depending on actual packer
  62  * supplied.
  63  *
  64  * It is amazing how much work a tiny object can save. :)
  65  *
  66  */
  67
  68
  69 /*
  70  * To-Do:
  71  */
  72
  73
  74 #include "squid-old.h"
  75 #include "Store.h"
  76 #include "MemBuf.h"
  77
  78 /* local types */
  79
  80 /* local routines */
  81
  82 /* local constants and vars */
  83
  84 /*
  85  * We do have one potential problem here. Both append_f and vprintf_f types
  86  * cannot match real functions precisely (at least because of the difference in
  87  * the type of the first parameter). Thus, we have to use type cast. If somebody
  88  * changes the prototypes of real functions, Packer will not notice that because
  89  * of the type cast.
  90  *
  91  * Solution: we use the constants below to *hard code* current prototypes of
  92  * real functions. If real prototypes change, these constants will produce a
  93  * warning (e.g., "warning: assignment from incompatible pointer type").
  94  */
  95
  96 static void
  97 memBufAppend(MemBuf *mb, const char *buf, mb_size_t len)
  98 {
  99     mb->append(buf, len);
 100 }
 101
 102 static void
 103 memBufVPrintf(MemBuf * mb, const char *fmt, va_list vargs)
 104 {
 105     mb->vPrintf(fmt, vargs);
 106 }
 107
 108 static void
 109 storeEntryAppend(StoreEntry *e, const char *buf, int len)
 110 {
 111     e->append(buf, len);
 112 }
 113
 114
 115 /* append()'s */
 116 static void (*const store_append) (StoreEntry *, const char *, int) = &storeEntryAppend;
 117 static void (*const memBuf_append) (MemBuf *, const char *, mb_size_t) = &memBufAppend;
 118
 119 /* vprintf()'s */
 120 static void (*const store_vprintf) (StoreEntry *, const char *, va_list ap) = &storeAppendVPrintf;
 121 static void (*const memBuf_vprintf) (MemBuf *, const char *, va_list ap) = &memBufVPrintf;
 122
 123
 124 /* init/clean */
 125
 126 /* init with this to forward data to StoreEntry */
 127 void
 128 packerToStoreInit(Packer * p, StoreEntry * e)
 129 {
 130     assert(p && e);
 131     p->append = (append_f) store_append;
 132     p->packer_vprintf = (vprintf_f) store_vprintf;
 133     p->real_handler = e;
 134     e->buffer();
 135 }
 136
 137 /* init with this to accumulate data in MemBuf */
 138 void
 139 packerToMemInit(Packer * p, MemBuf * mb)
 140 {
 141     assert(p && mb);
 142     p->append = (append_f) memBuf_append;
 143     p->packer_vprintf = (vprintf_f) memBuf_vprintf;
 144     p->real_handler = mb;
 145 }
 146
 147 /* call this when you are done */
 148 void
 149 packerClean(Packer * p)
 150 {
 151     assert(p);
 152
 153     if (p->append == (append_f) store_append && p->real_handler)
 154         static_cast<StoreEntry*>(p->real_handler)->flush();
 155
 156     /* it is not really necessary to do this, but, just in case... */
 157     p->append = NULL;
 158     p->packer_vprintf = NULL;
 159     p->real_handler = NULL;
 160 }
 161
 162 void
 163 packerAppend(Packer * p, const char *buf, int sz)
 164 {
 165     assert(p);
 166     assert(p->real_handler && p->append);
 167     p->append(p->real_handler, buf, sz);
 168 }
 169
 170 void
 171 packerPrintf(Packer * p, const char *fmt,...)
 172 {
 173     va_list args;
 174     va_start(args, fmt);
 175
 176     assert(p);
 177     assert(p->real_handler && p->packer_vprintf);
 178     p->packer_vprintf(p->real_handler, fmt, args);
 179     va_end(args);
 180 }