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| Next: <a href="Write-Other-Derived-Routines.html#Write-Other-Derived-Routines" accesskey="n" rel="next">Write Other Derived Routines</a>, Previous: <a href="Define-the-Derived-Structures.html#Define-the-Derived-Structures" accesskey="p" rel="prev">Define the Derived Structures</a>, Up: <a href="Deriving-a-New-Hash-Table-Type.html#Deriving-a-New-Hash-Table-Type" accesskey="u" rel="up">Deriving a New Hash Table Type</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="BFD-Index.html#BFD-Index" title="Index" rel="index">Index</a>]</p> |
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| <a name="Write-the-derived-creation-routine"></a> |
| <h4 class="subsubsection">2.18.4.2 Write the derived creation routine</h4> |
| <p>You must write a routine which will create and initialize an |
| entry in the hash table. This routine is passed as the |
| function argument to <code>bfd_hash_table_init</code>. |
| </p> |
| <p>In order to permit other hash tables to be derived from the |
| hash table you are creating, this routine must be written in a |
| standard way. |
| </p> |
| <p>The first argument to the creation routine is a pointer to a |
| hash table entry. This may be <code>NULL</code>, in which case the |
| routine should allocate the right amount of space. Otherwise |
| the space has already been allocated by a hash table type |
| derived from this one. |
| </p> |
| <p>After allocating space, the creation routine must call the |
| creation routine of the hash table type it is derived from, |
| passing in a pointer to the space it just allocated. This |
| will initialize any fields used by the base hash table. |
| </p> |
| <p>Finally the creation routine must initialize any local fields |
| for the new hash table type. |
| </p> |
| <p>Here is a boilerplate example of a creation routine. |
| <var>function_name</var> is the name of the routine. |
| <var>entry_type</var> is the type of an entry in the hash table you |
| are creating. <var>base_newfunc</var> is the name of the creation |
| routine of the hash table type your hash table is derived |
| from. |
| </p> |
| |
| <div class="example"> |
| <pre class="example">struct bfd_hash_entry * |
| <var>function_name</var> (struct bfd_hash_entry *entry, |
| struct bfd_hash_table *table, |
| const char *string) |
| { |
| struct <var>entry_type</var> *ret = (<var>entry_type</var> *) entry; |
| |
| /* Allocate the structure if it has not already been allocated by a |
| derived class. */ |
| if (ret == NULL) |
| { |
| ret = bfd_hash_allocate (table, sizeof (* ret)); |
| if (ret == NULL) |
| return NULL; |
| } |
| |
| /* Call the allocation method of the base class. */ |
| ret = ((<var>entry_type</var> *) |
| <var>base_newfunc</var> ((struct bfd_hash_entry *) ret, table, string)); |
| |
| /* Initialize the local fields here. */ |
| |
| return (struct bfd_hash_entry *) ret; |
| } |
| </pre></div> |
| <p><strong>Description</strong><br> |
| The creation routine for the linker hash table, which is in |
| <code>linker.c</code>, looks just like this example. |
| <var>function_name</var> is <code>_bfd_link_hash_newfunc</code>. |
| <var>entry_type</var> is <code>struct bfd_link_hash_entry</code>. |
| <var>base_newfunc</var> is <code>bfd_hash_newfunc</code>, the creation |
| routine for a basic hash table. |
| </p> |
| <p><code>_bfd_link_hash_newfunc</code> also initializes the local fields |
| in a linker hash table entry: <code>type</code>, <code>written</code> and |
| <code>next</code>. |
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