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author | dim <dim@FreeBSD.org> | 2010-11-01 19:35:33 +0000 |
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committer | dim <dim@FreeBSD.org> | 2010-11-01 19:35:33 +0000 |
commit | 3f5c947f4453c6016a2a6a9636367ee3f48fc6fc (patch) | |
tree | 461aafc934d462eb9b9221308f8e25238c0ada62 /contrib/binutils/bfd/doc/hash.texi | |
parent | e6be3e7867eb43d220575baee2ce5662fb03e46c (diff) | |
parent | d0f678fa0ff3f08a4eca29daf4d1ac39797b6326 (diff) | |
download | FreeBSD-src-3f5c947f4453c6016a2a6a9636367ee3f48fc6fc.zip FreeBSD-src-3f5c947f4453c6016a2a6a9636367ee3f48fc6fc.tar.gz |
Merge ^/vendor/binutils/dist@214571 into contrib/binutils, which brings
us up to version 2.17.50.20070703, at the last GPLv2 commit.
Amongst others, this added upstream support for some FreeBSD-specific
things that we previously had to manually hack in, such as the OSABI
label support, and so on.
There are also quite a number of new files, some for cpu's (e.g. SPU)
that we may or may not be interested in, but those can be cleaned up
later on, if needed.
Diffstat (limited to 'contrib/binutils/bfd/doc/hash.texi')
-rw-r--r-- | contrib/binutils/bfd/doc/hash.texi | 247 |
1 files changed, 0 insertions, 247 deletions
diff --git a/contrib/binutils/bfd/doc/hash.texi b/contrib/binutils/bfd/doc/hash.texi deleted file mode 100644 index 88d9585..0000000 --- a/contrib/binutils/bfd/doc/hash.texi +++ /dev/null @@ -1,247 +0,0 @@ -@section Hash Tables -@cindex Hash tables -BFD provides a simple set of hash table functions. Routines -are provided to initialize a hash table, to free a hash table, -to look up a string in a hash table and optionally create an -entry for it, and to traverse a hash table. There is -currently no routine to delete an string from a hash table. - -The basic hash table does not permit any data to be stored -with a string. However, a hash table is designed to present a -base class from which other types of hash tables may be -derived. These derived types may store additional information -with the string. Hash tables were implemented in this way, -rather than simply providing a data pointer in a hash table -entry, because they were designed for use by the linker back -ends. The linker may create thousands of hash table entries, -and the overhead of allocating private data and storing and -following pointers becomes noticeable. - -The basic hash table code is in @code{hash.c}. - -@menu -* Creating and Freeing a Hash Table:: -* Looking Up or Entering a String:: -* Traversing a Hash Table:: -* Deriving a New Hash Table Type:: -@end menu - -@node Creating and Freeing a Hash Table, Looking Up or Entering a String, Hash Tables, Hash Tables -@subsection Creating and freeing a hash table -@findex bfd_hash_table_init -@findex bfd_hash_table_init_n -To create a hash table, create an instance of a @code{struct -bfd_hash_table} (defined in @code{bfd.h}) and call -@code{bfd_hash_table_init} (if you know approximately how many -entries you will need, the function @code{bfd_hash_table_init_n}, -which takes a @var{size} argument, may be used). -@code{bfd_hash_table_init} returns @code{FALSE} if some sort of -error occurs. - -@findex bfd_hash_newfunc -The function @code{bfd_hash_table_init} take as an argument a -function to use to create new entries. For a basic hash -table, use the function @code{bfd_hash_newfunc}. @xref{Deriving -a New Hash Table Type}, for why you would want to use a -different value for this argument. - -@findex bfd_hash_allocate -@code{bfd_hash_table_init} will create an objalloc which will be -used to allocate new entries. You may allocate memory on this -objalloc using @code{bfd_hash_allocate}. - -@findex bfd_hash_table_free -Use @code{bfd_hash_table_free} to free up all the memory that has -been allocated for a hash table. This will not free up the -@code{struct bfd_hash_table} itself, which you must provide. - -@findex bfd_hash_set_default_size -Use @code{bfd_hash_set_default_size} to set the default size of -hash table to use. - -@node Looking Up or Entering a String, Traversing a Hash Table, Creating and Freeing a Hash Table, Hash Tables -@subsection Looking up or entering a string -@findex bfd_hash_lookup -The function @code{bfd_hash_lookup} is used both to look up a -string in the hash table and to create a new entry. - -If the @var{create} argument is @code{FALSE}, @code{bfd_hash_lookup} -will look up a string. If the string is found, it will -returns a pointer to a @code{struct bfd_hash_entry}. If the -string is not found in the table @code{bfd_hash_lookup} will -return @code{NULL}. You should not modify any of the fields in -the returns @code{struct bfd_hash_entry}. - -If the @var{create} argument is @code{TRUE}, the string will be -entered into the hash table if it is not already there. -Either way a pointer to a @code{struct bfd_hash_entry} will be -returned, either to the existing structure or to a newly -created one. In this case, a @code{NULL} return means that an -error occurred. - -If the @var{create} argument is @code{TRUE}, and a new entry is -created, the @var{copy} argument is used to decide whether to -copy the string onto the hash table objalloc or not. If -@var{copy} is passed as @code{FALSE}, you must be careful not to -deallocate or modify the string as long as the hash table -exists. - -@node Traversing a Hash Table, Deriving a New Hash Table Type, Looking Up or Entering a String, Hash Tables -@subsection Traversing a hash table -@findex bfd_hash_traverse -The function @code{bfd_hash_traverse} may be used to traverse a -hash table, calling a function on each element. The traversal -is done in a random order. - -@code{bfd_hash_traverse} takes as arguments a function and a -generic @code{void *} pointer. The function is called with a -hash table entry (a @code{struct bfd_hash_entry *}) and the -generic pointer passed to @code{bfd_hash_traverse}. The function -must return a @code{boolean} value, which indicates whether to -continue traversing the hash table. If the function returns -@code{FALSE}, @code{bfd_hash_traverse} will stop the traversal and -return immediately. - -@node Deriving a New Hash Table Type, , Traversing a Hash Table, Hash Tables -@subsection Deriving a new hash table type -Many uses of hash tables want to store additional information -which each entry in the hash table. Some also find it -convenient to store additional information with the hash table -itself. This may be done using a derived hash table. - -Since C is not an object oriented language, creating a derived -hash table requires sticking together some boilerplate -routines with a few differences specific to the type of hash -table you want to create. - -An example of a derived hash table is the linker hash table. -The structures for this are defined in @code{bfdlink.h}. The -functions are in @code{linker.c}. - -You may also derive a hash table from an already derived hash -table. For example, the a.out linker backend code uses a hash -table derived from the linker hash table. - -@menu -* Define the Derived Structures:: -* Write the Derived Creation Routine:: -* Write Other Derived Routines:: -@end menu - -@node Define the Derived Structures, Write the Derived Creation Routine, Deriving a New Hash Table Type, Deriving a New Hash Table Type -@subsubsection Define the derived structures -You must define a structure for an entry in the hash table, -and a structure for the hash table itself. - -The first field in the structure for an entry in the hash -table must be of the type used for an entry in the hash table -you are deriving from. If you are deriving from a basic hash -table this is @code{struct bfd_hash_entry}, which is defined in -@code{bfd.h}. The first field in the structure for the hash -table itself must be of the type of the hash table you are -deriving from itself. If you are deriving from a basic hash -table, this is @code{struct bfd_hash_table}. - -For example, the linker hash table defines @code{struct -bfd_link_hash_entry} (in @code{bfdlink.h}). The first field, -@code{root}, is of type @code{struct bfd_hash_entry}. Similarly, -the first field in @code{struct bfd_link_hash_table}, @code{table}, -is of type @code{struct bfd_hash_table}. - -@node Write the Derived Creation Routine, Write Other Derived Routines, Define the Derived Structures, Deriving a New Hash Table Type -@subsubsection Write the derived creation routine -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}. - -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. - -The first argument to the creation routine is a pointer to a -hash table entry. This may be @code{NULL}, 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. - -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. - -Finally the creation routine must initialize any local fields -for the new hash table type. - -Here is a boilerplate example of a creation routine. -@var{function_name} is the name of the routine. -@var{entry_type} is the type of an entry in the hash table you -are creating. @var{base_newfunc} is the name of the creation -routine of the hash table type your hash table is derived -from. - - -@example -struct bfd_hash_entry * -@var{function_name} (struct bfd_hash_entry *entry, - struct bfd_hash_table *table, - const char *string) -@{ - struct @var{entry_type} *ret = (@var{entry_type} *) 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{base_newfunc} ((struct bfd_hash_entry *) ret, table, string)); - - /* Initialize the local fields here. */ - - return (struct bfd_hash_entry *) ret; -@} -@end example -@strong{Description}@* -The creation routine for the linker hash table, which is in -@code{linker.c}, looks just like this example. -@var{function_name} is @code{_bfd_link_hash_newfunc}. -@var{entry_type} is @code{struct bfd_link_hash_entry}. -@var{base_newfunc} is @code{bfd_hash_newfunc}, the creation -routine for a basic hash table. - -@code{_bfd_link_hash_newfunc} also initializes the local fields -in a linker hash table entry: @code{type}, @code{written} and -@code{next}. - -@node Write Other Derived Routines, , Write the Derived Creation Routine, Deriving a New Hash Table Type -@subsubsection Write other derived routines -You will want to write other routines for your new hash table, -as well. - -You will want an initialization routine which calls the -initialization routine of the hash table you are deriving from -and initializes any other local fields. For the linker hash -table, this is @code{_bfd_link_hash_table_init} in @code{linker.c}. - -You will want a lookup routine which calls the lookup routine -of the hash table you are deriving from and casts the result. -The linker hash table uses @code{bfd_link_hash_lookup} in -@code{linker.c} (this actually takes an additional argument which -it uses to decide how to return the looked up value). - -You may want a traversal routine. This should just call the -traversal routine of the hash table you are deriving from with -appropriate casts. The linker hash table uses -@code{bfd_link_hash_traverse} in @code{linker.c}. - -These routines may simply be defined as macros. For example, -the a.out backend linker hash table, which is derived from the -linker hash table, uses macros for the lookup and traversal -routines. These are @code{aout_link_hash_lookup} and -@code{aout_link_hash_traverse} in aoutx.h. - |