lib/action/assembler.c

   1 /*
   2     Ming, an SWF output library
   3     Copyright (C) 2002  Opaque Industries - http://www.opaque.net/
   4
   5     This library is free software; you can redistribute it and/or
   6     modify it under the terms of the GNU Lesser General Public
   7     License as published by the Free Software Foundation; either
   8     version 2.1 of the License, or (at your option) any later version.
   9
  10     This library is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13     Lesser General Public License for more details.
  14
  15     You should have received a copy of the GNU Lesser General Public
  16     License along with this library; if not, write to the Free Software
  17     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18 */
  19
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include "assembler.h"
  24 #include "compile.h"
  25 #include "action.h"
  26
  27
  28 int len;
  29 Buffer asmBuffer;
  30 int nLabels;
  31
  32 struct label
  33 {
  34         char *name;
  35         int offset;
  36 };
  37
  38 struct label labels[256];
  39
  40
  41 static int
  42 findLabel(char *label)
  43 {
  44         int i;
  45
  46         for ( i=0; i<nLabels; ++i )
  47         {
  48                 if ( strcmp(label, labels[i].name) == 0 )
  49                         return i;
  50         }
  51
  52         return -1;
  53 }
  54
  55
  56 static void
  57 addLabel(char *label)
  58 {
  59         int i = findLabel(label);
  60
  61         if ( i == -1 )
  62         {
  63                 labels[nLabels].name = strdup(label);
  64                 labels[nLabels].offset = len;
  65                 ++nLabels;
  66         }
  67         else
  68                 labels[i].offset = len;
  69 }
  70
  71
  72 int
  73 bufferBranchTarget(Buffer output, char *label)
  74 {
  75         int i = findLabel(label);
  76
  77         if ( i == -1 )
  78         {
  79                 i = nLabels;
  80                 addLabel(label);
  81         }
  82
  83         return bufferWriteS16(output, i);
  84 }
  85
  86
  87 void
  88 bufferPatchTargets(Buffer buffer)
  89 {
  90         int l, i = 0;
  91         unsigned char *output = buffer->buffer;
  92
  93         while ( i < len )
  94         {
  95                 if ( output[i] & 0x80 ) /* then it's a multibyte instruction */
  96                 {
  97                         if ( output[i] == SWFACTION_BRANCHALWAYS ||
  98                                          output[i] == SWFACTION_BRANCHIFTRUE )
  99                         {
 100                                 int target, offset;
 101
 102                                 i += 3; /* plus instruction plus two-byte length */
 103
 104                                 target = output[i];
 105                                 offset = labels[target].offset - (i+2);
 106                                 output[i] = offset & 0xff;
 107                                 output[++i] = (offset>>8) & 0xff;
 108                                 ++i;
 109                         }
 110                         else
 111                         {
 112                                 ++i;
 113                                 l = output[i];
 114                                 ++i;
 115                                 l += output[i]<<8;
 116
 117                                 i += l+1;
 118                         }
 119                 }
 120                 else
 121                         ++i;
 122         }
 123 }
 124
 125
 126 /*
 127  * Local variables:
 128  * tab-width: 2
 129  * c-basic-offset: 2
 130  * End:
 131  */