+++ /dev/null
-This is Info file ./mmalloc.info, produced by Makeinfo version 1.68
-from the input file mmalloc.texi.
-
-START-INFO-DIR-ENTRY
-* Mmalloc: (mmalloc). The GNU mapped-malloc package.
-END-INFO-DIR-ENTRY
-
- This file documents the GNU mmalloc (mapped-malloc) package, written
-by fnf@cygnus.com, based on GNU malloc written by mike@ai.mit.edu.
-
- Copyright (C) 1992 Free Software Foundation, Inc.
-
- Permission is granted to make and distribute verbatim copies of this
-manual provided the copyright notice and this permission notice are
-preserved on all copies.
-
- Permission is granted to copy and distribute modified versions of
-this manual under the conditions for verbatim copying, provided also
-that the entire resulting derived work is distributed under the terms
-of a permission notice identical to this one.
-
- Permission is granted to copy and distribute translations of this
-manual into another language, under the above conditions for modified
-versions.
-
-\1f
-File: mmalloc.info, Node: Top, Next: Overview, Prev: (dir), Up: (dir)
-
-mmalloc
-*******
-
- This file documents the GNU memory-mapped malloc package mmalloc.
-
-* Menu:
-
-* Overview:: Overall Description
-* Implementation:: Implementation
-
- -- The Detailed Node Listing --
-
-Implementation
-
-* Compatibility:: Backwards Compatibility
-* Functions:: Function Descriptions
-
-\1f
-File: mmalloc.info, Node: Overview, Next: Implementation, Prev: Top, Up: Top
-
-Overall Description
-*******************
-
- This is a heavily modified version of GNU `malloc'. It uses `mmap'
-as the basic mechanism for obtaining memory from the system, rather
-than `sbrk'. This gives it several advantages over the more
-traditional malloc:
-
- * Several different heaps can be used, each of them growing or
- shinking under control of `mmap', with the `mmalloc' functions
- using a specific heap on a call by call basis.
-
- * By using `mmap', it is easy to create heaps which are intended to
- be persistent and exist as a filesystem object after the creating
- process has gone away.
-
- * Because multiple heaps can be managed, data used for a specific
- purpose can be allocated into its own heap, making it easier to
- allow applications to "dump" and "restore" initialized
- malloc-managed memory regions. For example, the "unexec" hack
- popularized by GNU Emacs could potentially go away.
-
-\1f
-File: mmalloc.info, Node: Implementation, Prev: Overview, Up: Top
-
-Implementation
-**************
-
- The `mmalloc' functions contain no internal static state. All
-`mmalloc' internal data is allocated in the mapped in region, along
-with the user data that it manages. This allows it to manage multiple
-such regions and to "pick up where it left off" when such regions are
-later dynamically mapped back in.
-
- In some sense, malloc has been "purified" to contain no internal
-state information and generalized to use multiple memory regions rather
-than a single region managed by `sbrk'. However the new routines now
-need an extra parameter which informs `mmalloc' which memory region it
-is dealing with (along with other information). This parameter is
-called the "malloc descriptor".
-
- The functions initially provided by `mmalloc' are:
-
- void *mmalloc_attach (int fd, void *baseaddr);
- void *mmalloc_detach (void *md);
- int mmalloc_errno (void *md);
- int mmalloc_setkey (void *md, int keynum, void *key);
- void *mmalloc_getkey (void *md, int keynum);
-
- void *mmalloc (void *md, size_t size);
- void *mrealloc (void *md, void *ptr, size_t size);
- void *mvalloc (void *md, size_t size);
- void mfree (void *md, void *ptr);
-
-* Menu:
-
-* Compatibility:: Backwards Compatibility
-* Functions:: Function Descriptions
-
-\1f
-File: mmalloc.info, Node: Compatibility, Next: Functions, Prev: Implementation, Up: Implementation
-
-Backwards Compatibility
-=======================
-
- To allow a single malloc package to be used in a given application,
-provision is made for the traditional `malloc', `realloc', and `free'
-functions to be implemented as special cases of the `mmalloc'
-functions. In particular, if any of the functions that expect malloc
-descriptors are called with a `NULL' pointer rather than a valid malloc
-descriptor, then they default to using an `sbrk' managed region. The
-`mmalloc' package provides compatible `malloc', `realloc', and `free'
-functions using this mechanism internally. Applications can avoid this
-extra interface layer by simply including the following defines:
-
- #define malloc(size) mmalloc ((void *)0, (size))
- #define realloc(ptr,size) mrealloc ((void *)0, (ptr), (size));
- #define free(ptr) mfree ((void *)0, (ptr))
-
-or replace the existing `malloc', `realloc', and `free' calls with the
-above patterns if using `#define' causes problems.
-
-\1f
-File: mmalloc.info, Node: Functions, Prev: Compatibility, Up: Implementation
-
-Function Descriptions
-=====================
-
- These are the details on the functions that make up the `mmalloc'
-package.
-
-`void *mmalloc_attach (int FD, void *BASEADDR);'
- Initialize access to a `mmalloc' managed region.
-
- If FD is a valid file descriptor for an open file, then data for
- the `mmalloc' managed region is mapped to that file. Otherwise
- `/dev/zero' is used and the data will not exist in any filesystem
- object.
-
- If the open file corresponding to FD is from a previous use of
- `mmalloc' and passes some basic sanity checks to ensure that it is
- compatible with the current `mmalloc' package, then its data is
- mapped in and is immediately accessible at the same addresses in
- the current process as the process that created the file.
-
- If BASEADDR is not `NULL', the mapping is established starting at
- the specified address in the process address space. If BASEADDR
- is `NULL', the `mmalloc' package chooses a suitable address at
- which to start the mapped region, which will be the value of the
- previous mapping if opening an existing file which was previously
- built by `mmalloc', or for new files will be a value chosen by
- `mmap'.
-
- Specifying BASEADDR provides more control over where the regions
- start and how big they can be before bumping into existing mapped
- regions or future mapped regions.
-
- On success, returns a malloc descriptor which is used in subsequent
- calls to other `mmalloc' package functions. It is explicitly
- `void *' (`char *' for systems that don't fully support `void') so
- that users of the package don't have to worry about the actual
- implementation details.
-
- On failure returns `NULL'.
-
-`void *mmalloc_detach (void *MD);'
- Terminate access to a `mmalloc' managed region identified by the
- descriptor MD, by closing the base file and unmapping all memory
- pages associated with the region.
-
- Returns `NULL' on success.
-
- Returns the malloc descriptor on failure, which can subsequently
- be used for further action (such as obtaining more information
- about the nature of the failure).
-
-`void *mmalloc (void *MD, size_t SIZE);'
- Given an `mmalloc' descriptor MD, allocate additional memory of
- SIZE bytes in the associated mapped region.
-
-`*mrealloc (void *MD, void *PTR, size_t SIZE);'
- Given an `mmalloc' descriptor MD and a pointer to memory
- previously allocated by `mmalloc' in PTR, reallocate the memory to
- be SIZE bytes long, possibly moving the existing contents of
- memory if necessary.
-
-`void *mvalloc (void *MD, size_t SIZE);'
- Like `mmalloc' but the resulting memory is aligned on a page
- boundary.
-
-`void mfree (void *MD, void *PTR);'
- Given an `mmalloc' descriptor MD and a pointer to memory previously
- allocated by `mmalloc' in PTR, free the previously allocated
- memory.
-
-`int mmalloc_errno (void *MD);'
- Given a `mmalloc' descriptor, if the last `mmalloc' operation
- failed for some reason due to a system call failure, then returns
- the associated `errno'. Returns 0 otherwise. (This function is
- not yet implemented).
-
-
-\1f
-Tag Table:
-Node: Top\7f963
-Node: Overview\7f1397
-Node: Implementation\7f2425
-Node: Compatibility\7f3818
-Node: Functions\7f4892
-\1f
-End Tag Table
projects / deliverable / binutils-gdb.git / commitdiff
