rom/dos/readitem.c

   1 /*
   2     Copyright © 1995-2014, 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.
  48
  49     NOTES
  50         This function handles conversion of '**', '*"', etc. inside quotes.
  51
  52         This function has well known bugs, and should be avoided
  53         in new applications.
  54
  55     EXAMPLE
  56
  57     BUGS
  58         1. Forgets to unread a separator character (equal sign, whitespace or
  59            tabulation).
  60         2. Tries to unread an end-of-line, which actually causes unreading the
  61            last read character of CSource if supplied. Even if it's not a
  62            separator, but belongs to the last read item.
  63         3. IoErr() is never modified by this function.
  64
  65         As AOS programs that use ReadItem() depend on this broken behaviour,
  66         it will not be fixed.
  67
  68         4. If maxchars == 0, buffer[0] is set to NUL anyway.
  69
  70     SEE ALSO
  71
  72     INTERNALS
  73
  74 *****************************************************************************/
  75 {
  76     AROS_LIBFUNC_INIT
  77
  78 /*
  79  * WARNING!!!
  80  * As mentioned above, this code has some intentional (but not obvious) bugs.
  81  * They must not be fixed.
  82  * If you change something here, be sure that the code passes unit tests
  83  * in test/dos/readitem. Those unit tests are verified to pass on AmigaOS 3.1.
  84  */
  85
  86 /* Macro to get a character from the input source */
  87 #define GET(c)                                  \
  88 if(input!=NULL)                                 \
  89 {                                               \
  90     if(input->CS_CurChr>=input->CS_Length)      \
  91         c=EOF;                                  \
  92     else                                        \
  93         c=input->CS_Buffer[input->CS_CurChr++]; \
  94 }else                                           \
  95 {                                               \
  96     c=FGetC(Input());                           \
  97 }
  98
  99 /* Macro to push the character back */
 100 #define UNGET() {if(input!=NULL) input->CS_CurChr--; else UnGetC(Input(),-1);}
 101
 102     STRPTR b=buffer;
 103     LONG c;
 104
 105     /* No buffer? */
 106     if (buffer == NULL)
 107         return ITEM_NOTHING;
 108
 109     if (!maxchars) {
 110         *b = 0;
 111         return ITEM_NOTHING;
 112     }
 113
 114     /* Skip leading whitespace characters */
 115     do
 116     {
 117         GET(c);
 118     } while (c==' '||c=='\t');
 119
 120     if(!c||c=='\n'||c==EOF||c==';')
 121     {
 122         *b=0;
 123         if (c != EOF)
 124             UNGET();
 125         return ITEM_NOTHING;
 126     }else if(c=='=')
 127     {
 128         /* Found '='. Return it. */
 129         *b=0;
 130         return ITEM_EQUAL;
 131     }else if(c=='\"')
 132         /* Quoted item found. Convert Contents. */
 133         for(;;)
 134         {
 135             if(!maxchars)
 136             {
 137                 b[-1]=0;
 138                 return ITEM_NOTHING;
 139             }
 140             maxchars--;
 141             GET(c);
 142             /* Convert ** to *, *" to ", *n to \n and *e to 0x1b. */
 143             if(c=='*')
 144             {
 145                 GET(c);
 146                 /* Check for premature end of line. */
 147                 if(!c||c=='\n'||c==EOF)
 148                 {
 149                     UNGET();
 150                     *b=0;
 151                     return ITEM_ERROR;
 152                 }else if(c=='n'||c=='N')
 153                     c='\n';
 154                 else if(c=='e'||c=='E')
 155                     c=0x1b;
 156             }else if(!c||c=='\n'||c==EOF)
 157             {
 158                 UNGET();
 159                 *b=0;
 160                 return ITEM_ERROR;
 161             }else if(c=='\"')
 162             {
 163                 /* " ends the item. */
 164                 *b=0;
 165                 return ITEM_QUOTED;
 166             }
 167             *b++=c;
 168         }
 169     else
 170     {
 171         /* Unquoted item. Store first character. */
 172         if(!maxchars)
 173         {
 174             b[-1]=0;
 175             return ITEM_ERROR;
 176         }
 177         maxchars--;
 178         *b++=c;
 179         /* Read up to the next terminator. */
 180         for(;;)
 181         {
 182             if(!maxchars)
 183             {
 184                 b[-1]=0;
 185                 return ITEM_ERROR;
 186             }
 187             maxchars--;
 188             GET(c);
 189             /* Check for terminator */
 190             if(!c||c==' '||c=='\t'||c=='\n'||c=='='||c==EOF)
 191             {
 192                 /* To be compatible with AOS, we need
 193                  * to *not* UNGET() here if we see a space
 194                  * or equals sign.
 195                  *
 196                  * Yes, it's broken, but so are any programs
 197                  * that actually used ReadItem(), and relied
 198                  * on this behaviour.
 199                  */
 200                 if (c != '=' && c != ' ' && c != '\t')
 201                     UNGET();
 202                 *b=0;
 203                 return ITEM_UNQUOTED;
 204             }
 205             *b++=c;
 206         }
 207     }
 208     AROS_LIBFUNC_EXIT
 209 } /* ReadItem */