rom/dos/readitem.c

   1 /*
   2     Copyright © 1995-2011, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc:
   6     Lang: english
   7 */
   8 #include <proto/exec.h>
   9 #include <dos/rdargs.h>
  10 #include <dos/dosasl.h>
  11 #include <dos/dosextens.h>
  12 #include "dos_intern.h"
  13
  14 /*****************************************************************************
  15
  16     NAME */
  17 #include <proto/dos.h>
  18
  19         AROS_LH3(LONG, ReadItem,
  20
  21 /*  SYNOPSIS */
  22         AROS_LHA(STRPTR,           buffer,   D1),
  23         AROS_LHA(LONG,             maxchars, D2),
  24         AROS_LHA(struct CSource *, input,    D3),
  25
  26 /*  LOCATION */
  27         struct DosLibrary *, DOSBase, 135, Dos)
  28
  29 /*  FUNCTION
  30         Read an item from a given character source. Items are words
  31         or quoted strings separated by whitespace or '=' just like on
  32         the commandline. The separator is unread and the output string
  33         is terminated by a NUL character.
  34
  35     INPUTS
  36         buffer   - Buffer to be filled.
  37         maxchars - Size of the buffer. Must be at least 1 (for the NUL
  38                    terminator).
  39         input    - A ready to use CSource structure or NULL which means
  40                    "read from the input stream".
  41
  42     RESULT
  43         One of ITEM_UNQUOTED - Normal word read.
  44                ITEM_QUOTED   - Quoted string read.
  45                ITEM_NOTHING  - End of line found. Nothing read.
  46                ITEM_EQUAL    - '=' read. Buffer is empty.
  47                ITEM_ERROR    - An error happened. IoErr() gives additional
  48                                information in that case.
  49
  50     NOTES
  51         This function handles conversion of '**', '*"', etc inside quotes.
  52
  53         This function has well known bugs, and should be avoided
  54         in new applications.
  55
  56     EXAMPLE
  57
  58     BUGS
  59         1. Forgets to unread a separator character (equal sign, whitespace or
  60            tabulation).
  61         2. Tries to unread an end-of-line, which actually causes unreading the
  62            last read character of CSource is supplied. Even if it's not a separator,
  63            but belongs to last read item.
  64         3. IoErr() is never modified by this function.
  65
  66         As AOS programs that use ReadItem() depend on this broken behaviour,
  67         it will not be fixed.
  68
  69         4. If maxchars == 0, buff[0] is set to 0 anyway.
  70
  71     SEE ALSO
  72
  73     INTERNALS
  74
  75 *****************************************************************************/
  76 {
  77     AROS_LIBFUNC_INIT
  78
  79 /*
  80  * WARNING!!!
  81  * As mentioned above, this code has some intentional (but not obvious) bugs.
  82  * They must not be fixed.
  83  * If you change something here, be sure that the code passes unit tests
  84  * in test/dos/readitem. Those unit tests are verified to pass on AmigaOS 3.1.
  85  */
  86
  87 /* Macro to get a character from the input source */
  88 #define GET(c)                                  \
  89 if(input!=NULL)                                 \
  90 {                                               \
  91     if(input->CS_CurChr>=input->CS_Length)      \
  92         c=EOF;                                  \
  93     else                                        \
  94         c=input->CS_Buffer[input->CS_CurChr++]; \
  95 }else                                           \
  96 {                                               \
  97     c=FGetC(Input());                           \
  98 }
  99
 100 /* Macro to push the character back */
 101 #define UNGET() {if(input!=NULL) input->CS_CurChr--; else UnGetC(Input(),-1);}
 102
 103     STRPTR b=buffer;
 104     LONG c;
 105
 106     /* No buffer? */
 107     if (buffer == NULL)
 108         return ITEM_NOTHING;
 109
 110     if (!maxchars) {
 111         *b = 0;
 112         return ITEM_NOTHING;
 113     }
 114
 115     /* Skip leading whitespace characters */
 116     do
 117     {
 118         GET(c);
 119     } while (c==' '||c=='\t');
 120
 121     if(!c||c=='\n'||c==EOF||c==';')
 122     {
 123         *b=0;
 124         if (c != EOF)
 125             UNGET();
 126         return ITEM_NOTHING;
 127     }else if(c=='=')
 128     {
 129         /* Found '='. Return it. */
 130         *b=0;
 131         return ITEM_EQUAL;
 132     }else if(c=='\"')
 133         /* Quoted item found. Convert Contents. */
 134         for(;;)
 135         {
 136             if(!maxchars)
 137             {
 138                 b[-1]=0;
 139                 return ITEM_NOTHING;
 140             }
 141             maxchars--;
 142             GET(c);
 143             /* Convert ** to *, *" to ", *n to \n and *e to 0x1b. */
 144             if(c=='*')
 145             {
 146                 GET(c);
 147                 /* Check for premature end of line. */
 148                 if(!c||c=='\n'||c==EOF)
 149                 {
 150                     UNGET();
 151                     *b=0;
 152                     return ITEM_ERROR;
 153                 }else if(c=='n'||c=='N')
 154                     c='\n';
 155                 else if(c=='e'||c=='E')
 156                     c=0x1b;
 157             }else if(!c||c=='\n'||c==EOF)
 158             {
 159                 UNGET();
 160                 *b=0;
 161                 return ITEM_ERROR;
 162             }else if(c=='\"')
 163             {
 164                 /* " ends the item. */
 165                 *b=0;
 166                 return ITEM_QUOTED;
 167             }
 168             *b++=c;
 169         }
 170     else
 171     {
 172         /* Unquoted item. Store first character. */
 173         if(!maxchars)
 174         {
 175             b[-1]=0;
 176             return ITEM_ERROR;
 177         }
 178         maxchars--;
 179         *b++=c;
 180         /* Read up to the next terminator. */
 181         for(;;)
 182         {
 183             if(!maxchars)
 184             {
 185                 b[-1]=0;
 186                 return ITEM_ERROR;
 187             }
 188             maxchars--;
 189             GET(c);
 190             /* Check for terminator */
 191             if(!c||c==' '||c=='\t'||c=='\n'||c=='='||c==EOF)
 192             {
 193                 /* To be compatible with AOS, we need
 194                  * to *not* UNGET() here if we see a space
 195                  * or equals sign.
 196                  *
 197                  * Yes, it's broken, but so are any programs
 198                  * that actually used ReadItem(), and relied
 199                  * on this behaviour.
 200                  */
 201                 if (c != '=' && c != ' ' && c != '\t')
 202                     UNGET();
 203                 *b=0;
 204                 return ITEM_UNQUOTED;
 205             }
 206             *b++=c;
 207         }
 208     }
 209     AROS_LIBFUNC_EXIT
 210 } /* ReadItem */