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| <p> |
| Previous: <a rel="previous" accesskey="p" href="Parsing-a-Template-String.html#Parsing-a-Template-String">Parsing a Template String</a>, |
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| <h4 class="subsection">12.12.11 Example of Parsing a Template String</h4> |
| |
| <p>Here is an example of decoding argument types for a format string. We |
| assume this is part of an interpreter which contains arguments of type |
| <code>NUMBER</code>, <code>CHAR</code>, <code>STRING</code> and <code>STRUCTURE</code> (and |
| perhaps others which are not valid here). |
| |
| <pre class="smallexample"> /* <span class="roman">Test whether the </span><var>nargs</var><span class="roman"> specified objects</span> |
| <span class="roman">in the vector </span><var>args</var><span class="roman"> are valid</span> |
| <span class="roman">for the format string </span><var>format</var><span class="roman">:</span> |
| <span class="roman">if so, return 1.</span> |
| <span class="roman">If not, return 0 after printing an error message.</span> */ |
| |
| int |
| validate_args (char *format, int nargs, OBJECT *args) |
| { |
| int *argtypes; |
| int nwanted; |
| |
| /* <span class="roman">Get the information about the arguments.</span> |
| <span class="roman">Each conversion specification must be at least two characters</span> |
| <span class="roman">long, so there cannot be more specifications than half the</span> |
| <span class="roman">length of the string.</span> */ |
| |
| argtypes = (int *) alloca (strlen (format) / 2 * sizeof (int)); |
| nwanted = parse_printf_format (string, nelts, argtypes); |
| |
| /* <span class="roman">Check the number of arguments.</span> */ |
| if (nwanted > nargs) |
| { |
| error ("too few arguments (at least %d required)", nwanted); |
| return 0; |
| } |
| |
| /* <span class="roman">Check the C type wanted for each argument</span> |
| <span class="roman">and see if the object given is suitable.</span> */ |
| for (i = 0; i < nwanted; i++) |
| { |
| int wanted; |
| |
| if (argtypes[i] & PA_FLAG_PTR) |
| wanted = STRUCTURE; |
| else |
| switch (argtypes[i] & ~PA_FLAG_MASK) |
| { |
| case PA_INT: |
| case PA_FLOAT: |
| case PA_DOUBLE: |
| wanted = NUMBER; |
| break; |
| case PA_CHAR: |
| wanted = CHAR; |
| break; |
| case PA_STRING: |
| wanted = STRING; |
| break; |
| case PA_POINTER: |
| wanted = STRUCTURE; |
| break; |
| } |
| if (TYPE (args[i]) != wanted) |
| { |
| error ("type mismatch for arg number %d", i); |
| return 0; |
| } |
| } |
| return 1; |
| } |
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