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+ .rn '' }`
+ ''' $RCSfile$$Revision$$Date$
+ '''
+ ''' $Log$
+ '''
+ .de Sh
+ .br
+ .if t .Sp
+ .ne 5
+ .PP
+ \fB\\$1\fR
+ .PP
+ ..
+ .de Sp
+ .if t .sp .5v
+ .if n .sp
+ ..
+ .de Ip
+ .br
+ .ie \\n(.$>=3 .ne \\$3
+ .el .ne 3
+ .IP "\\$1" \\$2
+ ..
+ .de Vb
+ .ft CW
+ .nf
+ .ne \\$1
+ ..
+ .de Ve
+ .ft R
+
+ .fi
+ ..
+ '''
+ '''
+ ''' Set up \*(-- to give an unbreakable dash;
+ ''' string Tr holds user defined translation string.
+ ''' Bell System Logo is used as a dummy character.
+ '''
+ .tr \(*W-|\(bv\*(Tr
+ .ie n \{\
+ .ds -- \(*W-
+ .ds PI pi
+ .if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
+ .if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
+ .ds L" ""
+ .ds R" ""
+ ''' \*(M", \*(S", \*(N" and \*(T" are the equivalent of
+ ''' \*(L" and \*(R", except that they are used on ".xx" lines,
+ ''' such as .IP and .SH, which do another additional levels of
+ ''' double-quote interpretation
+ .ds M" """
+ .ds S" """
+ .ds N" """""
+ .ds T" """""
+ .ds L' '
+ .ds R' '
+ .ds M' '
+ .ds S' '
+ .ds N' '
+ .ds T' '
+ 'br\}
+ .el\{\
+ .ds -- \(em\|
+ .tr \*(Tr
+ .ds L" ``
+ .ds R" ''
+ .ds M" ``
+ .ds S" ''
+ .ds N" ``
+ .ds T" ''
+ .ds L' `
+ .ds R' '
+ .ds M' `
+ .ds S' '
+ .ds N' `
+ .ds T' '
+ .ds PI \(*p
+ 'br\}
+ .\" If the F register is turned on, we'll generate
+ .\" index entries out stderr for the following things:
+ .\" TH Title
+ .\" SH Header
+ .\" Sh Subsection
+ .\" Ip Item
+ .\" X<> Xref (embedded
+ .\" Of course, you have to process the output yourself
+ .\" in some meaninful fashion.
+ .if \nF \{
+ .de IX
+ .tm Index:\\$1\t\\n%\t"\\$2"
+ ..
+ .nr % 0
+ .rr F
+ .\}
+ .TH mm 3 "20-Jun-2000" "MM 1.1.2" "Shared Memory Library"
+ .UC
+ .if n .hy 0
+ .if n .na
+ .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
+ .de CQ \" put $1 in typewriter font
+ .ft CW
+ 'if n "\c
+ 'if t \\&\\$1\c
+ 'if n \\&\\$1\c
+ 'if n \&"
+ \\&\\$2 \\$3 \\$4 \\$5 \\$6 \\$7
+ '.ft R
+ ..
+ .\" @(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2
+ . \" AM - accent mark definitions
+ .bd B 3
+ . \" fudge factors for nroff and troff
+ .if n \{\
+ . ds #H 0
+ . ds #V .8m
+ . ds #F .3m
+ . ds #[ \f1
+ . ds #] \fP
+ .\}
+ .if t \{\
+ . ds #H ((1u-(\\\\n(.fu%2u))*.13m)
+ . ds #V .6m
+ . ds #F 0
+ . ds #[ \&
+ . ds #] \&
+ .\}
+ . \" simple accents for nroff and troff
+ .if n \{\
+ . ds ' \&
+ . ds ` \&
+ . ds ^ \&
+ . ds , \&
+ . ds ~ ~
+ . ds ? ?
+ . ds ! !
+ . ds /
+ . ds q
+ .\}
+ .if t \{\
+ . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
+ . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
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+ . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
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+ . ds ? \s-2c\h'-\w'c'u*7/10'\u\h'\*(#H'\zi\d\s+2\h'\w'c'u*8/10'
+ . ds ! \s-2\(or\s+2\h'-\w'\(or'u'\v'-.8m'.\v'.8m'
+ . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
+ . ds q o\h'-\w'o'u*8/10'\s-4\v'.4m'\z\(*i\v'-.4m'\s+4\h'\w'o'u*8/10'
+ .\}
+ . \" troff and (daisy-wheel) nroff accents
+ .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
+ .ds 8 \h'\*(#H'\(*b\h'-\*(#H'
+ .ds v \\k:\h'-(\\n(.wu*9/10-\*(#H)'\v'-\*(#V'\*(#[\s-4v\s0\v'\*(#V'\h'|\\n:u'\*(#]
+ .ds _ \\k:\h'-(\\n(.wu*9/10-\*(#H+(\*(#F*2/3))'\v'-.4m'\z\(hy\v'.4m'\h'|\\n:u'
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+ .ds 3 \*(#[\v'.2m'\s-2\&3\s0\v'-.2m'\*(#]
+ .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
+ .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
+ .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
+ .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
+ .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
+ .ds ae a\h'-(\w'a'u*4/10)'e
+ .ds Ae A\h'-(\w'A'u*4/10)'E
+ .ds oe o\h'-(\w'o'u*4/10)'e
+ .ds Oe O\h'-(\w'O'u*4/10)'E
+ . \" corrections for vroff
+ .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
+ .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
+ . \" for low resolution devices (crt and lpr)
+ .if \n(.H>23 .if \n(.V>19 \
+ \{\
+ . ds : e
+ . ds 8 ss
+ . ds v \h'-1'\o'\(aa\(ga'
+ . ds _ \h'-1'^
+ . ds . \h'-1'.
+ . ds 3 3
+ . ds o a
+ . ds d- d\h'-1'\(ga
+ . ds D- D\h'-1'\(hy
+ . ds th \o'bp'
+ . ds Th \o'LP'
+ . ds ae ae
+ . ds Ae AE
+ . ds oe oe
+ . ds Oe OE
+ .\}
+ .rm #[ #] #H #V #F C
+ .SH "NAME"
+ \fBMM \- Shared Memory Library\fR
+ .SH "VERSION"
+ MM 1.1.2 (20-Jun-2000)
+ .SH "SYNOPSIS"
+ .PP
+ .Vb 1
+ \& #include "mm.h"
+ .Ve
+ \fB Global Malloc-Replacement API\fR
+ .PP
+ .Vb 14
+ \& int \fBMM_create\fR(size_t size, const char *file);
+ \& int \fBMM_permission\fR(mode_t mode, uid_t owner, gid_t group);
+ \& void \fBMM_destroy\fR(void);
+ \& int \fBMM_lock\fR(mm_lock_mode mode);
+ \& int \fBMM_unlock\fR(void);
+ \& void *\fBMM_malloc\fR(size_t size);
+ \& void *\fBMM_realloc\fR(void *ptr, size_t size);
+ \& void \fBMM_free\fR(void *ptr);
+ \& void *\fBMM_calloc\fR(size_t number, size_t size);
+ \& char *\fBMM_strdup\fR(const char *str);
+ \& size_t \fBMM_sizeof\fR(void *ptr);
+ \& size_t \fBMM_maxsize\fR(void);
+ \& size_t \fBMM_available\fR(void);
+ \& char *\fBMM_error\fR(void);
+ .Ve
+ \fB Standard Malloc-Style API\fR
+ .PP
+ .Vb 15
+ \& MM *\fBmm_create\fR(size_t size, char *file);
+ \& int \fBmm_permission\fR(MM *mm, mode_t mode, uid_t owner, gid_t group);
+ \& void \fBmm_destroy\fR(MM *mm);
+ \& int \fBmm_lock\fR(MM *mm, mm_lock_mode mode);
+ \& int \fBmm_unlock\fR(MM *mm);
+ \& void *\fBmm_malloc\fR(MM *mm, size_t size);
+ \& void *\fBmm_realloc\fR(MM *mm, void *ptr, size_t size);
+ \& void \fBmm_free\fR(MM *mm, void *ptr);
+ \& void *\fBmm_calloc\fR(MM *mm, size_t number, size_t size);
+ \& char *\fBmm_strdup\fR(MM *mm, const char *str);
+ \& size_t \fBmm_sizeof\fR(void *ptr);
+ \& size_t \fBmm_maxsize\fR(void);
+ \& size_t \fBmm_available\fR(MM *mm);
+ \& char *\fBmm_error\fR(void);
+ \& void \fBmm_display_info\fR(MM *mm);
+ .Ve
+ \fB Low-level Shared Memory API\fR
+ .PP
+ .Vb 9
+ \& void *\fBmm_core_create\fR(size_t size, char *file);
+ \& int \fBmm_core_permission\fR(void *core, mode_t mode, uid_t owner, gid_t group);
+ \& void \fBmm_core_delete\fR(void *core);
+ \& int \fBmm_core_lock\fR(void *core, mm_lock_mode mode);
+ \& int \fBmm_core_unlock\fR(void *core);
+ \& size_t \fBmm_core_size\fR(void *core);
+ \& size_t \fBmm_core_maxsegsize\fR(void);
+ \& size_t \fBmm_core_align2page\fR(size_t size);
+ \& size_t \fBmm_core_align2click\fR(size_t size);
+ .Ve
+ \fB Internal Library API\fR
+ .PP
+ .Vb 3
+ \& void \fBmm_lib_error_set\fR(unsigned int, const char *str);
+ \& char *\fBmm_lib_error_get\fR(void);
+ \& int \fBmm_lib_version\fR(void);
+ .Ve
+ .SH "DESCRIPTION"
+ The \fBMM\fR library is a 2-layer abstraction library which simplifies the usage
+ of shared memory between forked (and this way strongly related) processes
+ under Unix platforms. On the first (lower) layer it hides all platform
+ dependent implementation details (allocation and locking) when dealing with
+ shared memory segments and on the second (higher) layer it provides a
+ high-level \fImalloc\fR\|(3)\-style API for a convenient and well known way to work
+ with data-structures inside those shared memory segments.
+ .PP
+ The abbreviation \fBMM\fR is historically and originally comes from the phrase
+ ``\fImemory mapped\fR'\*(R' as used by the POSIX.1 \fImmap\fR\|(2) function. Because this
+ facility is internally used by this library on most platforms to establish the
+ shared memory segments.
+ .Sh "\s-1LIBRARY\s0 \s-1STRUCTURE\s0"
+ This library is structured into three main APIs which are internally based on
+ each other:
+ .Ip "\fBGlobal Malloc-Replacement \s-1API\s0\fR" 4
+ This is the most high-level \s-1API\s0 which directly can be used as replacement \s-1API\s0
+ for the \s-1POSIX\s0.1 memory allocation \s-1API\s0 (\fImalloc\fR\|(2) and friends). This is
+ useful when converting \fIheap\fR based data structures to \fIshared memory\fR
+ based data structures without the need to change the code dramatically. All
+ which is needed is to prefix the \s-1POSIX\s0.1 memory allocation functions with
+ `\f(CWMM_\fR\*(R', i.e. `\f(CWmalloc\fR\*(R' becomes `\f(CWMM_malloc\fR\*(R', `\f(CWstrdup\fR\*(R' becomes
+ `\f(CWMM_strdup\fR\*(R', etc. This \s-1API\s0 internally uses just a global `\f(CWMM *\fR\*(R' pool for
+ calling the corresponding functions (those with prefix `\f(CWmm_\fR') of the
+ \fIStandard Malloc-Style \s-1API\s0\fR.
+ .Ip "\fBStandard Malloc-Style \s-1API\s0\fR" 4
+ This is the standard high-level memory allocation \s-1API\s0. Its interface is
+ similar to the \fIGlobal Malloc-Replacement \s-1API\s0\fR but it uses an explicit `\f(CWMM *\fR\*(R'
+ pool to operate on. That is why every function of this \s-1API\s0 has an argument of
+ type `\f(CWMM *\fR\*(R' as its first argument. This \s-1API\s0 provides a comfortable way to
+ work with small dynamically allocated shared memory chunks inside large
+ statically allocated shared memory segments. It is internally based on the
+ \fILow-Level Shared Memory \s-1API\s0\fR for creating the underlaying shared memory
+ segment.
+ .Ip "\fBLow-Level Shared Memory \s-1API\s0\fR" 4
+ This is the basis of the whole \fB\s-1MM\s0\fR library. It provides low-level functions
+ for creating shared memory segments with mutual exclusion (in short \fImutex\fR)
+ capabilities in a portable way. Internally the shared memory and mutex
+ facility is implemented in various platform-dependent ways. A list of
+ implementation variants follows under the next topic.
+ .Sh "\s-1SHARED\s0 \s-1MEMORY\s0 \s-1IMPLEMENTATION\s0"
+ Internally the shared memory facility is implemented in various
+ platform-dependent ways. Each way has its own advantages and disadvantages
+ (in addition to the fact that some variants aren't available at all on some
+ platforms). The \fB\s-1MM\s0\fR library's configuration procedure tries hard to make a
+ good decision. The implemented variants are now given for overview and
+ background reasons with their advantages and disadvantages and in an ascending
+ order, i.e. the \fB\s-1MM\s0\fR configuration mechanism chooses the last available one
+ in the list as the preferred variant.
+ .Ip "Classical mmap(2) on temporary file (\s-1MMFILE\s0)" 4
+ \fIAdvantage:\fR maximum portable.
+ \fIDisadvantage:\fR needs a temporary file on the filesystem.
+ .Ip "mmap(2) via \s-1POSIX\s0.1 shm_open(3) on temporary file (\s-1MMPOSX\s0)" 4
+ \fIAdvantage:\fR standardized by \s-1POSIX\s0.1 and theoretically portable.
+ \fIDisadvantage:\fR needs a temporary file on the filesystem and is
+ is usually not available on existing Unix platform.
+ .Ip "\s-1SVR4-\s0style mmap(2) on \f(CW/dev/zero\fR device (\s-1MMZERO\s0)" 4
+ \fIAdvantage:\fR widely available and mostly portable on \s-1SVR4\s0 platforms.
+ \fIDisadvantage:\fR needs the \f(CW/dev/zero\fR device and a \fImmap\fR\|(2)
+ which supports memory mapping through this device.
+ .Ip "SysV \s-1IPC\s0 shmget(2) (\s-1IPCSHM\s0)" 4
+ \fIAdvantage:\fR does not need a temporary file or external device.
+ \fIDisadvantage:\fR although available on mostly all modern Unix platforms, it has
+ strong restrictions like the maximum size of a single shared memory segment (can
+ be as small as 100KB, but depends on the platform).
+ .Ip "4.4BSD\-style mmap(2) via \f(CWMAP_ANON\fR facility (\s-1MMANON\s0)" 4
+ \fIAdvantage:\fR does not need a temporary file or external device.
+ \fIDisadvantage:\fR usually only available on \s-1BSD\s0 platforms and derivatives.
+ .Sh "\s-1LOCKING\s0 \s-1IMPLEMENTATION\s0"
+ As for the shared memory facility, internally the locking facility is
+ implemented in various platform-dependent ways. They are again listed
+ in ascending order, i.e. the \fB\s-1MM\s0\fR configuration mechanism chooses the
+ last available one in the list as the preferred variant. The list of
+ implemented variants is:
+ .Ip "4.2BSD\-style flock(2) on temporary file (\s-1FLOCK\s0)" 4
+ \fIAdvantage:\fR exists on a lot of platforms, especially on older Unix
+ derivates. \fIDisadvantage:\fR needs a temporary file on the filesystem and has
+ to re-open file-descriptors to it in \fIeach\fR\|(!) \fIfork\fR\|(2)'ed child process.
+ .Ip "SysV \s-1IPC\s0 semget(2) (\s-1IPCSEM\s0)" 4
+ \fIAdvantage:\fR exists on a lot of platforms and does not need a temporary file.
+ \fIDisadvantage:\fR an unmeant termination of the application leads to a
+ semaphore leak because the facility does not allow a ``remove in advance'\*(R'
+ trick (as the \s-1IPC\s0 shared memory facility does) for safe cleanups.
+ .Ip "\s-1SVR4-\s0style fcntl(2) on temporary file (\s-1FCNTL\s0)" 4
+ \fIAdvantage:\fR exists on a lot of platforms and is also the most powerful
+ variant (although not always the fastest one). \fIDisadvantage:\fR needs a
+ temporary file.
+ .Sh "\s-1MEMORY\s0 \s-1ALLOCATION\s0 \s-1STRATEGY\s0"
+ The memory allocation strategy the \fIStandard Malloc-Style \s-1API\s0\fR functions use
+ internally is the following:
+ .Ip "\fBAllocation\fR" 4
+ If a chunk of memory has to be allocated, the internal list of free chunks
+ is searched for a minimal-size chunk which is larger or equal than the size of
+ the to be allocated chunk (a \fIbest fit\fR strategy).
+ .Sp
+ If a chunk is found which matches this best-fit criteria, but is still a lot
+ larger than the requested size, it is split into two chunks: One with exactly
+ the requested size (which is the resulting chunk given back) and one with the
+ remaining size (which is immediately re-inserted into the list of free
+ chunks).
+ .Sp
+ If no fitting chunk is found at all in the list of free chunks, a new one is
+ created from the spare area of the shared memory segment until the segment is
+ full (in which case an \fIout of memory\fR error occurs).
+ .Ip "\fBDeallocation\fR" 4
+ If a chunk of memory has to be deallocated, it is inserted in sorted manner
+ into the internal list of free chunks. The insertion operation automatically
+ merges the chunk with a previous and/or a next free chunk if possible, i.e.
+ if the free chunks stay physically seamless (one after another) in memory, to
+ automatically form larger free chunks out of smaller ones.
+ .Sp
+ This way the shared memory segment is automatically defragmented when memory
+ is deallocated.
+ .PP
+ This strategy reduces memory waste and fragmentation caused by small and
+ frequent allocations and deallocations to a minimum.
+ .PP
+ The internal implementation of the list of free chunks is not specially
+ optimized (for instance by using binary search trees or even \fIsplay\fR trees,
+ etc), because it is assumed that the total amount of entries in the list of
+ free chunks is always small (caused both by the fact that shared memory
+ segments are usually a lot smaller than heaps and the fact that we always
+ defragment by merging the free chunks if possible).
+ .SH "API FUNCTIONS"
+ In the following, all API functions are described in detail The order .
+ directly follows the one in the \fBSYNOPSIS\fR section above .
+ .Sh "Global Malloc-Replacement \s-1API\s0"
+ .Ip "int \fBMM_create\fR(size_t \fIsize\fR, const char *\fIfile\fR);" 4
+ This initializes the global shared memory pool with \fIsize\fR and \fIfile\fR and
+ has to be called \fIbefore\fR any \fIfork\fR\|(2) operations are performed by the
+ application.
+ .Ip "int \fBMM_permission\fR(mode_t \fImode\fR, uid_t \fIowner\fR, gid_t \fIgroup\fR);" 4
+ This sets the filesystem \fImode\fR, \fIowner\fR and \fIgroup\fR for the global shared
+ memory pool (has effects only if the underlaying shared memory segment
+ implementation is actually based on external auxiliary files). The arguments
+ are directly passed through to \fIchmod\fR\|(2) and \fIchown\fR\|(2).
+ .Ip "void \fBMM_destroy\fR(void);" 4
+ This destroys the global shared memory pool and should be called \fIafter\fR all
+ child processes were killed.
+ .Ip "int \fBMM_lock\fR(mm_lock_mode \fImode\fR);" 4
+ This locks the global shared memory pool for the current process in order to
+ perform either shared/read-only (\fImode\fR is \f(CWMM_LOCK_RD\fR) or
+ exclusive/read-write (\fImode\fR is \f(CWMM_LOCK_RW\fR) critical operations inside the
+ global shared memory pool.
+ .Ip "int \fBMM_unlock\fR(void);" 4
+ This unlocks the global shared memory pool for the current process after the
+ critical operations were performed inside the global shared memory pool.
+ .Ip "void *\fBMM_malloc\fR(size_t \fIsize\fR);" 4
+ Identical to the \s-1POSIX\s0.1 \fImalloc\fR\|(3) function but instead of allocating
+ memory from the \fIheap\fR it allocates it from the global shared memory pool.
+ .Ip "void \fBMM_free\fR(void *\fIptr\fR);" 4
+ Identical to the \s-1POSIX\s0.1 \fIfree\fR\|(3) function but instead of deallocating
+ memory in the \fIheap\fR it deallocates it in the global shared memory pool.
+ .Ip "void *\fBMM_realloc\fR(void *\fIptr\fR, size_t \fIsize\fR);" 4
+ Identical to the \s-1POSIX\s0.1 \fIrealloc\fR\|(3) function but instead of reallocating
+ memory in the \fIheap\fR it reallocates it inside the global shared memory pool.
+ .Ip "void *\fBMM_calloc\fR(size_t \fInumber\fR, size_t \fIsize\fR);" 4
+ Identical to the \s-1POSIX\s0.1 \fIcalloc\fR\|(3) function but instead of allocating and
+ initializing memory from the \fIheap\fR it allocates and initializes it from the
+ global shared memory pool.
+ .Ip "char *\fBMM_strdup\fR(const char *\fIstr\fR);" 4
+ Identical to the \s-1POSIX\s0.1 \fIstrdup\fR\|(3) function but instead of creating the
+ string copy in the \fIheap\fR it creates it in the global shared memory pool.
+ .Ip "size_t \fBMM_sizeof\fR(const void *\fIptr\fR);" 4
+ This function returns the size in bytes of the chunk starting at \fIptr\fR when
+ \fIptr\fR was previously allocated with \fIMM_malloc\fR\|(3). The result is undefined
+ if \fIptr\fR was not previously allocated with \fIMM_malloc\fR\|(3).
+ .Ip "size_t \fBMM_maxsize\fR(void);" 4
+ This function returns the maximum size which is allowed
+ as the first argument to the \fIMM_create\fR\|(3) function.
+ .Ip "size_t \fBMM_available\fR(void);" 4
+ Returns the amount in bytes of still available (free) memory in the global
+ shared memory pool.
+ .Ip "char *\fBMM_error\fR(void);" 4
+ Returns the last error message which occurred inside the \fB\s-1MM\s0\fR library.
+ .Sh "Standard Malloc-Style \s-1API\s0"
+ .Ip "\s-1MM\s0 *\fBmm_create\fR(size_t \fIsize\fR, const char *\fIfile\fR);" 4
+ This creates a shared memory pool which has space for approximately a total of
+ \fIsize\fR bytes with the help of \fIfile\fR. Here \fIfile\fR is a filesystem path to a
+ file which need not to exist (and perhaps is never created because this
+ depends on the platform and chosen shared memory and mutex implementation).
+ The return value is a pointer to a \f(CWMM\fR structure which should be treated as
+ opaque by the application. It describes the internals of the created shared
+ memory pool. In case of an error \f(CWNULL\fR is returned. A \fIsize\fR of 0 means to
+ allocate the maximum allowed size which is platform dependent and is between a
+ few \s-1KB\s0 and the soft limit of 64MB.
+ .Ip "int \fBmm_permission\fR(\s-1MM\s0 *\fImm\fR, mode_t \fImode\fR, uid_t \fIowner\fR, gid_t \fIgroup\fR);" 4
+ This sets the filesystem \fImode\fR, \fIowner\fR and \fIgroup\fR for the shared memory
+ pool \fImm\fR (has effects only when the underlaying shared memory segment
+ implementation is actually based on external auxiliary files). The arguments
+ are directly passed through to \fIchmod\fR\|(2) and \fIchown\fR\|(2).
+ .Ip "void \fBmm_destroy\fR(\s-1MM\s0 *\fImm\fR);" 4
+ This destroys the complete shared memory pool \fImm\fR and with it all chunks
+ which were allocated in this pool. Additionally any created files on the
+ filesystem corresponding the to shared memory pool are unlinked.
+ .Ip "int \fBmm_lock\fR(\s-1MM\s0 *\fImm\fR, mm_lock_mode \fImode\fR);" 4
+ This locks the shared memory pool \fImm\fR for the current process in order to
+ perform either shared/read-only (\fImode\fR is \f(CWMM_LOCK_RD\fR) or
+ exclusive/read-write (\fImode\fR is \f(CWMM_LOCK_RW\fR) critical operations inside the
+ global shared memory pool.
+ .Ip "int \fBmm_unlock\fR(\s-1MM\s0 *\fImm\fR);" 4
+ This unlocks the shared memory pool \fImm\fR for the current process after
+ critical operations were performed inside the global shared memory pool.
+ .Ip "void *\fBmm_malloc\fR(\s-1MM\s0 *\fImm\fR, size_t \fIsize\fR);" 4
+ This function allocates \fIsize\fR bytes from the shared memory pool \fImm\fR and
+ returns either a (virtual memory word aligned) pointer to it or \f(CWNULL\fR in
+ case of an error (out of memory). It behaves like the \s-1POSIX\s0.1 \fImalloc\fR\|(3)
+ function but instead of allocating memory from the \fIheap\fR it allocates it
+ from the shared memory segment underlaying \fImm\fR.
+ .Ip "void \fBmm_free\fR(\s-1MM\s0 *\fImm\fR, void *\fIptr\fR);" 4
+ This deallocates the chunk starting at \fIptr\fR in the shared memory pool \fImm\fR.
+ It behaves like the \s-1POSIX\s0.1 \fIfree\fR\|(3) function but instead of deallocating
+ memory from the \fIheap\fR it deallocates it from the shared memory segment
+ underlaying \fImm\fR.
+ .Ip "void *\fBmm_realloc\fR(\s-1MM\s0 *\fImm\fR, void *\fIptr\fR, size_t \fIsize\fR);" 4
+ This function reallocates the chunk starting at \fIptr\fR inside the shared
+ memory pool \fImm\fR with the new size of \fIsize\fR bytes. It behaves like the
+ \s-1POSIX\s0.1 \fIrealloc\fR\|(3) function but instead of reallocating memory in the
+ \fIheap\fR it reallocates it in the shared memory segment underlaying \fImm\fR.
+ .Ip "void *\fBmm_calloc\fR(\s-1MM\s0 *\fImm\fR, size_t \fInumber\fR, size_t \fIsize\fR);" 4
+ This is similar to \fImm_malloc\fR\|(3), but additionally clears the chunk. It behaves
+ like the \s-1POSIX\s0.1 \fIcalloc\fR\|(3) function. It allocates space for \fInumber\fR
+ objects, each \fIsize\fR bytes in length from the shared memory pool \fImm\fR. The
+ result is identical to calling \fImm_malloc\fR\|(3) with an argument of ``\fInumber\fR *
+ \fIsize\fR'\*(R', with the exception that the allocated memory is initialized to nul
+ bytes.
+ .Ip "char *\fBmm_strdup\fR(\s-1MM\s0 *\fImm\fR, const char *\fIstr\fR);" 4
+ This function behaves like the \s-1POSIX\s0.1 \fIstrdup\fR\|(3) function. It allocates
+ sufficient memory inside the shared memory pool \fImm\fR for a copy of the string
+ \fIstr\fR, does the copy, and returns a pointer to it. The pointer may
+ subsequently be used as an argument to the function \fImm_free\fR\|(3). If
+ insufficient shared memory is available, \f(CWNULL\fR is returned.
+ .Ip "size_t \fBmm_sizeof\fR(const void *\fIptr\fR);" 4
+ This function returns the size in bytes of the chunk starting at \fIptr\fR when
+ \fIptr\fR was previously allocated with \fImm_malloc\fR\|(3). The result is undefined
+ when \fIptr\fR was not previously allocated with \fImm_malloc\fR\|(3).
+ .Ip "size_t \fBmm_maxsize\fR(void);" 4
+ This function returns the maximum size which is allowed as the first argument
+ to the \fImm_create\fR\|(3) function.
+ .Ip "size_t \fBmm_available\fR(\s-1MM\s0 *\fImm\fR);" 4
+ Returns the amount in bytes of still available (free) memory in the
+ shared memory pool \fImm\fR.
+ .Ip "char *\fBmm_error\fR(void);" 4
+ Returns the last error message which occurred inside the \fB\s-1MM\s0\fR library.
+ .Ip "void \fBmm_display_info\fR(\s-1MM\s0 *\fImm\fR);" 4
+ This is debugging function which displays a summary page for the shared memory
+ pool \fImm\fR describing various internal sizes and counters.
+ .Sh "Low-Level Shared Memory \s-1API\s0"
+ .Ip "void *\fBmm_core_create\fR(size_t \fIsize\fR, const char *\fIfile\fR);" 4
+ This creates a shared memory area which is at least \fIsize\fR bytes in size with
+ the help of \fIfile\fR. The value \fIsize\fR has to be greater than 0 and less or
+ equal the value returned by \fImm_core_maxsegsize\fR\|(3). Here \fIfile\fR is a
+ filesystem path to a file which need not to exist (and perhaps is never
+ created because this depends on the platform and chosen shared memory and
+ mutex implementation). The return value is either a (virtual memory word
+ aligned) pointer to the shared memory segment or \f(CWNULL\fR in case of an error.
+ The application is guaranteed to be able to access the shared memory segment
+ from byte 0 to byte \fIsize\fR\-1 starting at the returned address.
+ .Ip "int \fBmm_core_permission\fR(void *\fIcore\fR, mode_t \fImode\fR, uid_t \fIowner\fR, gid_t \fIgroup\fR);" 4
+ This sets the filesystem \fImode\fR, \fIowner\fR and \fIgroup\fR for the shared memory
+ segment \fIcode\fR (has effects only when the underlaying shared memory segment
+ implementation is actually based on external auxiliary files). The arguments
+ are directly passed through to \fIchmod\fR\|(2) and \fIchown\fR\|(2).
+ .Ip "void \fBmm_core_delete\fR(void *\fIcore\fR);" 4
+ This deletes a shared memory segment \fIcore\fR (as previously returned by a
+ \fImm_core_create\fR\|(3) call). After this operation, accessing the segment starting
+ at \fIcore\fR is no longer allowed and will usually lead to a segmentation fault.
+ .Ip "int \fBmm_core_lock\fR(const void *\fIcore\fR, mm_lock_mode \fImode\fR);" 4
+ This function acquires an advisory lock for the current process on the shared
+ memory segment \fIcore\fR for either shared/read-only (\fImode\fR is \f(CWMM_LOCK_RD\fR)
+ or exclusive/read-write (\fImode\fR is \f(CWMM_LOCK_RW\fR) critical operations between
+ \fIfork\fR\|(2)'ed child processes.
+ .Ip "int \fBmm_core_unlock\fR(const void *\fIcore\fR);" 4
+ This function releases a previously acquired advisory lock for the current
+ process on the shared memory segment \fIcore\fR.
+ .Ip "size_t \fBmm_core_size\fR(const void *\fIcore\fR);" 4
+ This returns the size in bytes of \fIcore\fR. This size is exactly the size which
+ was used for creating the shared memory area via \fImm_core_create\fR\|(3). The
+ function is provided just for convenience reasons to not require the
+ application to remember the memory size behind \fIcore\fR itself.
+ .Ip "size_t \fBmm_core_maxsegsize\fR(void);" 4
+ This returns the number of bytes of a maximum-size shared memory segment which
+ is allowed to allocate via the \s-1MM\s0 library. It is between a few \s-1KB\s0 and the soft
+ limit of 64MB.
+ .Ip "size_t \fBmm_core_align2page\fR(size_t \fIsize\fR);" 4
+ This is just a utility function which can be used to align the number \fIsize\fR
+ to the next virtual memory \fIpage\fR boundary used by the underlaying platform.
+ The memory page boundary under Unix platforms is usually somewhere between
+ 2048 and 16384 bytes. You do not have to align the \fIsize\fR arguments of other
+ \fB\s-1MM\s0\fR library functions yourself, because this is already done internally.
+ This function is exported by the \fB\s-1MM\s0\fR library just for convenience reasons in
+ case an application wants to perform similar calculations for other purposes.
+ .Ip "size_t \fBmm_core_align2word\fR(size_t \fIsize\fR);" 4
+ This is another utility function which can be used to align the number \fIsize\fR
+ to the next virtual memory \fIword\fR boundary used by the underlaying platform.
+ The memory word boundary under Unix platforms is usually somewhere between 4
+ and 16 bytes. You do not have to align the \fIsize\fR arguments of other \fB\s-1MM\s0\fR
+ library functions yourself, because this is already done internally. This
+ function is exported by the \fB\s-1MM\s0\fR library just for convenience reasons in case
+ an application wants to perform simular calculations for other purposes.
+ .Sh "Low-Level Shared Memory \s-1API\s0"
+ .Ip "void \fBmm_lib_error_set\fR(unsigned int, const char *str);" 4
+ This is a function which is used internally by the various \s-1MM\s0 function to set
+ an error string. It's usually not called directly from applications.
+ .Ip "char *\fBmm_lib_error_get\fR(void);" 4
+ This is a function which is used internally by \fIMM_error\fR\|(3) and \fImm_error\fR\|(3)
+ functions to get the current error string. It is usually not called directly
+ from applications.
+ .Ip "int \fBmm_lib_version\fR(void);" 4
+ This function returns a hex-value ``0x\fIV\fR\fI\s-1RR\s0\fR\fIT\fR\fI\s-1LL\s0\fR'\*(R' which describes the
+ current \fB\s-1MM\s0\fR library version. \fIV\fR is the version, \fI\s-1RR\s0\fR the revisions, \fI\s-1LL\s0\fR
+ the level and \fIT\fR the type of the level (alphalevel=0, betalevel=1,
+ patchlevel=2, etc). For instance \fB\s-1MM\s0\fR version 1.0.4 is encoded as 0x100204.
+ The reason for this unusual mapping is that this way the version number is
+ steadily \fIincreasing\fR.
+ .SH "RESTRICTIONS"
+ The maximum size of a continuous shared memory segment one can allocate
+ depends on the underlaying platform. This cannot be changed, of course. But
+ currently the high-level \fImalloc\fR\|(3)\-style API just uses a single shared memory
+ segment as the underlaying data structure for an \f(CWMM\fR object which means that
+ the maximum amount of memory an \f(CWMM\fR object represents also depends on the
+ platform.
+ .PP
+ This could be changed in later versions by allowing at least the
+ high-level \fImalloc\fR\|(3)\-style API to internally use multiple shared memory
+ segments to form the \f(CWMM\fR object. This way \f(CWMM\fR objects could have
+ arbitrary sizes, although the maximum size of an allocatable continous
+ chunk still is bounded by the maximum size of a shared memory segment.
+ .SH "SEE ALSO"
+ mm-\fIconfig\fR\|(1).
+ .PP
+ \fImalloc\fR\|(3), \fIcalloc\fR\|(3), \fIrealloc\fR\|(3), \fIstrdup\fR\|(3), \fIfree\fR\|(3), \fImmap\fR\|(2), \fIshmget\fR\|(2),
+ \fIshmctl\fR\|(2), \fIflock\fR\|(2), \fIfcntl\fR\|(2), \fIsemget\fR\|(2), \fIsemctl\fR\|(2), \fIsemop\fR\|(2).
+ .SH "HOME"
+ http://www.engelschall.com/sw/mm/
+
+ .SH "HISTORY"
+ This library was originally written in January 1999 by \fIRalf S.
+ Engelschall\fR <rse@engelschall.com> for use in the \fBExtended API\fR (EAPI)
+ of the \fBApache\fR HTTP server project (see http://www.apache.org/), which
+ was originally invented for \fBmod_ssl\fR (see http://www.modssl.org/).
+ .PP
+ Its base idea (a malloc-style API for handling shared memory) was originally
+ derived from the non-publically available \fImm_malloc\fR library written in
+ October 1997 by \fICharles Randall\fR <crandall@matchlogic.com> for MatchLogic,
+ Inc.
+ .SH "AUTHOR"
+ .PP
+ .Vb 3
+ \& Ralf S. Engelschall
+ \& rse@engelschall.com
+ \& www.engelschall.com
+ .Ve
+
+ .rn }` ''
+ .IX Title "mm 3"
+ .IX Name "B<MM - Shared Memory Library>"
+
+ .IX Header "NAME"
+
+ .IX Header "VERSION"
+
+ .IX Header "SYNOPSIS"
+
+ .IX Header "DESCRIPTION"
+
+ .IX Subsection "\s-1LIBRARY\s0 \s-1STRUCTURE\s0"
+
+ .IX Item "\fBGlobal Malloc-Replacement \s-1API\s0\fR"
+
+ .IX Item "\fBStandard Malloc-Style \s-1API\s0\fR"
+
+ .IX Item "\fBLow-Level Shared Memory \s-1API\s0\fR"
+
+ .IX Subsection "\s-1SHARED\s0 \s-1MEMORY\s0 \s-1IMPLEMENTATION\s0"
+
+ .IX Item "Classical mmap(2) on temporary file (\s-1MMFILE\s0)"
+
+ .IX Item "mmap(2) via \s-1POSIX\s0.1 shm_open(3) on temporary file (\s-1MMPOSX\s0)"
+
+ .IX Item "\s-1SVR4-\s0style mmap(2) on \f(CW/dev/zero\fR device (\s-1MMZERO\s0)"
+
+ .IX Item "SysV \s-1IPC\s0 shmget(2) (\s-1IPCSHM\s0)"
+
+ .IX Item "4.4BSD\-style mmap(2) via \f(CWMAP_ANON\fR facility (\s-1MMANON\s0)"
+
+ .IX Subsection "\s-1LOCKING\s0 \s-1IMPLEMENTATION\s0"
+
+ .IX Item "4.2BSD\-style flock(2) on temporary file (\s-1FLOCK\s0)"
+
+ .IX Item "SysV \s-1IPC\s0 semget(2) (\s-1IPCSEM\s0)"
+
+ .IX Item "\s-1SVR4-\s0style fcntl(2) on temporary file (\s-1FCNTL\s0)"
+
+ .IX Subsection "\s-1MEMORY\s0 \s-1ALLOCATION\s0 \s-1STRATEGY\s0"
+
+ .IX Item "\fBAllocation\fR"
+
+ .IX Item "\fBDeallocation\fR"
+
+ .IX Header "API FUNCTIONS"
+
+ .IX Subsection "Global Malloc-Replacement \s-1API\s0"
+
+ .IX Item "int \fBMM_create\fR(size_t \fIsize\fR, const char *\fIfile\fR);"
+
+ .IX Item "int \fBMM_permission\fR(mode_t \fImode\fR, uid_t \fIowner\fR, gid_t \fIgroup\fR);"
+
+ .IX Item "void \fBMM_destroy\fR(void);"
+
+ .IX Item "int \fBMM_lock\fR(mm_lock_mode \fImode\fR);"
+
+ .IX Item "int \fBMM_unlock\fR(void);"
+
+ .IX Item "void *\fBMM_malloc\fR(size_t \fIsize\fR);"
+
+ .IX Item "void \fBMM_free\fR(void *\fIptr\fR);"
+
+ .IX Item "void *\fBMM_realloc\fR(void *\fIptr\fR, size_t \fIsize\fR);"
+
+ .IX Item "void *\fBMM_calloc\fR(size_t \fInumber\fR, size_t \fIsize\fR);"
+
+ .IX Item "char *\fBMM_strdup\fR(const char *\fIstr\fR);"
+
+ .IX Item "size_t \fBMM_sizeof\fR(const void *\fIptr\fR);"
+
+ .IX Item "size_t \fBMM_maxsize\fR(void);"
+
+ .IX Item "size_t \fBMM_available\fR(void);"
+
+ .IX Item "char *\fBMM_error\fR(void);"
+
+ .IX Subsection "Standard Malloc-Style \s-1API\s0"
+
+ .IX Item "\s-1MM\s0 *\fBmm_create\fR(size_t \fIsize\fR, const char *\fIfile\fR);"
+
+ .IX Item "int \fBmm_permission\fR(\s-1MM\s0 *\fImm\fR, mode_t \fImode\fR, uid_t \fIowner\fR, gid_t \fIgroup\fR);"
+
+ .IX Item "void \fBmm_destroy\fR(\s-1MM\s0 *\fImm\fR);"
+
+ .IX Item "int \fBmm_lock\fR(\s-1MM\s0 *\fImm\fR, mm_lock_mode \fImode\fR);"
+
+ .IX Item "int \fBmm_unlock\fR(\s-1MM\s0 *\fImm\fR);"
+
+ .IX Item "void *\fBmm_malloc\fR(\s-1MM\s0 *\fImm\fR, size_t \fIsize\fR);"
+
+ .IX Item "void \fBmm_free\fR(\s-1MM\s0 *\fImm\fR, void *\fIptr\fR);"
+
+ .IX Item "void *\fBmm_realloc\fR(\s-1MM\s0 *\fImm\fR, void *\fIptr\fR, size_t \fIsize\fR);"
+
+ .IX Item "void *\fBmm_calloc\fR(\s-1MM\s0 *\fImm\fR, size_t \fInumber\fR, size_t \fIsize\fR);"
+
+ .IX Item "char *\fBmm_strdup\fR(\s-1MM\s0 *\fImm\fR, const char *\fIstr\fR);"
+
+ .IX Item "size_t \fBmm_sizeof\fR(const void *\fIptr\fR);"
+
+ .IX Item "size_t \fBmm_maxsize\fR(void);"
+
+ .IX Item "size_t \fBmm_available\fR(\s-1MM\s0 *\fImm\fR);"
+
+ .IX Item "char *\fBmm_error\fR(void);"
+
+ .IX Item "void \fBmm_display_info\fR(\s-1MM\s0 *\fImm\fR);"
+
+ .IX Subsection "Low-Level Shared Memory \s-1API\s0"
+
+ .IX Item "void *\fBmm_core_create\fR(size_t \fIsize\fR, const char *\fIfile\fR);"
+
+ .IX Item "int \fBmm_core_permission\fR(void *\fIcore\fR, mode_t \fImode\fR, uid_t \fIowner\fR, gid_t \fIgroup\fR);"
+
+ .IX Item "void \fBmm_core_delete\fR(void *\fIcore\fR);"
+
+ .IX Item "int \fBmm_core_lock\fR(const void *\fIcore\fR, mm_lock_mode \fImode\fR);"
+
+ .IX Item "int \fBmm_core_unlock\fR(const void *\fIcore\fR);"
+
+ .IX Item "size_t \fBmm_core_size\fR(const void *\fIcore\fR);"
+
+ .IX Item "size_t \fBmm_core_maxsegsize\fR(void);"
+
+ .IX Item "size_t \fBmm_core_align2page\fR(size_t \fIsize\fR);"
+
+ .IX Item "size_t \fBmm_core_align2word\fR(size_t \fIsize\fR);"
+
+ .IX Subsection "Low-Level Shared Memory \s-1API\s0"
+
+ .IX Item "void \fBmm_lib_error_set\fR(unsigned int, const char *str);"
+
+ .IX Item "char *\fBmm_lib_error_get\fR(void);"
+
+ .IX Item "int \fBmm_lib_version\fR(void);"
+
+ .IX Header "RESTRICTIONS"
+
+ .IX Header "SEE ALSO"
+
+ .IX Header "HOME"
+
+ .IX Header "HISTORY"
+
+ .IX Header "AUTHOR"
+
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