Current Path :
/
opt
/
cpanel
/
ea-openssl11
/
share
/
man
/
man3
/
Or
Select Your Path :
Upload File :
New :
File
Dir
//opt/cpanel/ea-openssl11/share/man/man3/OPENSSL_LH_HASHFUNC.3
.\" Automatically generated by Pod::Man 2.27 (Pod::Simple 3.28) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. Capital omega is used to do unbreakable dashes and .\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff, .\" nothing in troff, for use with C<>. .tr \(*W- .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' .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" "" . ds C` "" . ds C' "" 'br\} .el\{\ . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\} .\" .\" Escape single quotes in literal strings from groff's Unicode transform. .ie \n(.g .ds Aq \(aq .el .ds Aq ' .\" .\" If the F register is turned on, we'll generate index entries on stderr for .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index .\" entries marked with X<> in POD. Of course, you'll have to process the .\" output yourself in some meaningful fashion. .\" .\" Avoid warning from groff about undefined register 'F'. .de IX .. .nr rF 0 .if \n(.g .if rF .nr rF 1 .if (\n(rF:(\n(.g==0)) \{ . if \nF \{ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{ . nr % 0 . nr F 2 . \} . \} .\} .rr rF .\" .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). .\" Fear. Run. Save yourself. No user-serviceable parts. . \" 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 / .\} .if t \{\ . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' .\} . \" 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 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 . \" 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 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 .\} .rm #[ #] #H #V #F C .\" ======================================================================== .\" .IX Title "OPENSSL_LH_COMPFUNC 3" .TH OPENSSL_LH_COMPFUNC 3 "2023-09-11" "1.1.1w" "OpenSSL" .\" For nroff, turn off justification. Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" LHASH, DECLARE_LHASH_OF, OPENSSL_LH_COMPFUNC, OPENSSL_LH_HASHFUNC, OPENSSL_LH_DOALL_FUNC, LHASH_DOALL_ARG_FN_TYPE, IMPLEMENT_LHASH_HASH_FN, IMPLEMENT_LHASH_COMP_FN, lh_TYPE_new, lh_TYPE_free, lh_TYPE_insert, lh_TYPE_delete, lh_TYPE_retrieve, lh_TYPE_doall, lh_TYPE_doall_arg, lh_TYPE_error \- dynamic hash table .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include <openssl/lhash.h> \& \& DECLARE_LHASH_OF(TYPE); \& \& LHASH *lh_TYPE_new(OPENSSL_LH_HASHFUNC hash, OPENSSL_LH_COMPFUNC compare); \& void lh_TYPE_free(LHASH_OF(TYPE) *table); \& \& TYPE *lh_TYPE_insert(LHASH_OF(TYPE) *table, TYPE *data); \& TYPE *lh_TYPE_delete(LHASH_OF(TYPE) *table, TYPE *data); \& TYPE *lh_TYPE_retrieve(LHASH_OF(TYPE) *table, TYPE *data); \& \& void lh_TYPE_doall(LHASH_OF(TYPE) *table, OPENSSL_LH_DOALL_FUNC func); \& void lh_TYPE_doall_arg(LHASH_OF(TYPE) *table, OPENSSL_LH_DOALL_FUNCARG func, \& TYPE *arg); \& \& int lh_TYPE_error(LHASH_OF(TYPE) *table); \& \& typedef int (*OPENSSL_LH_COMPFUNC)(const void *, const void *); \& typedef unsigned long (*OPENSSL_LH_HASHFUNC)(const void *); \& typedef void (*OPENSSL_LH_DOALL_FUNC)(const void *); \& typedef void (*LHASH_DOALL_ARG_FN_TYPE)(const void *, const void *); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" This library implements type-checked dynamic hash tables. The hash table entries can be arbitrary structures. Usually they consist of key and value fields. In the description here, \fI\s-1TYPE\s0\fR is used a placeholder for any of the OpenSSL datatypes, such as \fI\s-1SSL_SESSION\s0\fR. .PP \&\fIlh_TYPE_new()\fR creates a new \fB\s-1LHASH_OF\s0(\s-1TYPE\s0)\fR structure to store arbitrary data entries, and specifies the 'hash' and 'compare' callbacks to be used in organising the table's entries. The \fBhash\fR callback takes a pointer to a table entry as its argument and returns an unsigned long hash value for its key field. The hash value is normally truncated to a power of 2, so make sure that your hash function returns well mixed low order bits. The \fBcompare\fR callback takes two arguments (pointers to two hash table entries), and returns 0 if their keys are equal, nonzero otherwise. .PP If your hash table will contain items of some particular type and the \fBhash\fR and \&\fBcompare\fR callbacks hash/compare these types, then the \&\fB\s-1IMPLEMENT_LHASH_HASH_FN\s0\fR and \fB\s-1IMPLEMENT_LHASH_COMP_FN\s0\fR macros can be used to create callback wrappers of the prototypes required by \&\fIlh_TYPE_new()\fR as shown in this example: .PP .Vb 11 \& /* \& * Implement the hash and compare functions; "stuff" can be any word. \& */ \& static unsigned long stuff_hash(const TYPE *a) \& { \& ... \& } \& static int stuff_cmp(const TYPE *a, const TYPE *b) \& { \& ... \& } \& \& /* \& * Implement the wrapper functions. \& */ \& static IMPLEMENT_LHASH_HASH_FN(stuff, TYPE) \& static IMPLEMENT_LHASH_COMP_FN(stuff, TYPE) .Ve .PP If the type is going to be used in several places, the following macros can be used in a common header file to declare the function wrappers: .PP .Vb 2 \& DECLARE_LHASH_HASH_FN(stuff, TYPE) \& DECLARE_LHASH_COMP_FN(stuff, TYPE) .Ve .PP Then a hash table of \s-1TYPE\s0 objects can be created using this: .PP .Vb 1 \& LHASH_OF(TYPE) *htable; \& \& htable = lh_TYPE_new(LHASH_HASH_FN(stuff), LHASH_COMP_FN(stuff)); .Ve .PP \&\fIlh_TYPE_free()\fR frees the \fB\s-1LHASH_OF\s0(\s-1TYPE\s0)\fR structure \&\fBtable\fR. Allocated hash table entries will not be freed; consider using \fIlh_TYPE_doall()\fR to deallocate any remaining entries in the hash table (see below). .PP \&\fIlh_TYPE_insert()\fR inserts the structure pointed to by \fBdata\fR into \&\fBtable\fR. If there already is an entry with the same key, the old value is replaced. Note that \fIlh_TYPE_insert()\fR stores pointers, the data are not copied. .PP \&\fIlh_TYPE_delete()\fR deletes an entry from \fBtable\fR. .PP \&\fIlh_TYPE_retrieve()\fR looks up an entry in \fBtable\fR. Normally, \fBdata\fR is a structure with the key field(s) set; the function will return a pointer to a fully populated structure. .PP \&\fIlh_TYPE_doall()\fR will, for every entry in the hash table, call \&\fBfunc\fR with the data item as its parameter. For example: .PP .Vb 2 \& /* Cleans up resources belonging to \*(Aqa\*(Aq (this is implemented elsewhere) */ \& void TYPE_cleanup_doall(TYPE *a); \& \& /* Implement a prototype\-compatible wrapper for "TYPE_cleanup" */ \& IMPLEMENT_LHASH_DOALL_FN(TYPE_cleanup, TYPE) \& \& /* Call "TYPE_cleanup" against all items in a hash table. */ \& lh_TYPE_doall(hashtable, LHASH_DOALL_FN(TYPE_cleanup)); \& \& /* Then the hash table itself can be deallocated */ \& lh_TYPE_free(hashtable); .Ve .PP When doing this, be careful if you delete entries from the hash table in your callbacks: the table may decrease in size, moving the item that you are currently on down lower in the hash table \- this could cause some entries to be skipped during the iteration. The second best solution to this problem is to set hash\->down_load=0 before you start (which will stop the hash table ever decreasing in size). The best solution is probably to avoid deleting items from the hash table inside a \*(L"doall\*(R" callback! .PP \&\fIlh_TYPE_doall_arg()\fR is the same as \fIlh_TYPE_doall()\fR except that \&\fBfunc\fR will be called with \fBarg\fR as the second argument and \fBfunc\fR should be of type \fB\s-1LHASH_DOALL_ARG_FN_TYPE\s0\fR (a callback prototype that is passed both the table entry and an extra argument). As with \&\fIlh_doall()\fR, you can instead choose to declare your callback with a prototype matching the types you are dealing with and use the declare/implement macros to create compatible wrappers that cast variables before calling your type-specific callbacks. An example of this is demonstrated here (printing all hash table entries to a \s-1BIO\s0 that is provided by the caller): .PP .Vb 2 \& /* Prints item \*(Aqa\*(Aq to \*(Aqoutput_bio\*(Aq (this is implemented elsewhere) */ \& void TYPE_print_doall_arg(const TYPE *a, BIO *output_bio); \& \& /* Implement a prototype\-compatible wrapper for "TYPE_print" */ \& static IMPLEMENT_LHASH_DOALL_ARG_FN(TYPE, const TYPE, BIO) \& \& /* Print out the entire hashtable to a particular BIO */ \& lh_TYPE_doall_arg(hashtable, LHASH_DOALL_ARG_FN(TYPE_print), BIO, \& logging_bio); .Ve .PP \&\fIlh_TYPE_error()\fR can be used to determine if an error occurred in the last operation. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fIlh_TYPE_new()\fR returns \fB\s-1NULL\s0\fR on error, otherwise a pointer to the new \&\fB\s-1LHASH\s0\fR structure. .PP When a hash table entry is replaced, \fIlh_TYPE_insert()\fR returns the value being replaced. \fB\s-1NULL\s0\fR is returned on normal operation and on error. .PP \&\fIlh_TYPE_delete()\fR returns the entry being deleted. \fB\s-1NULL\s0\fR is returned if there is no such value in the hash table. .PP \&\fIlh_TYPE_retrieve()\fR returns the hash table entry if it has been found, \&\fB\s-1NULL\s0\fR otherwise. .PP \&\fIlh_TYPE_error()\fR returns 1 if an error occurred in the last operation, 0 otherwise. It's meaningful only after non-retrieve operations. .PP \&\fIlh_TYPE_free()\fR, \fIlh_TYPE_doall()\fR and \fIlh_TYPE_doall_arg()\fR return no values. .SH "NOTE" .IX Header "NOTE" The \s-1LHASH\s0 code is not thread safe. All updating operations, as well as lh_TYPE_error call must be performed under a write lock. All retrieve operations should be performed under a read lock, \fIunless\fR accurate usage statistics are desired. In which case, a write lock should be used for retrieve operations as well. For output of the usage statistics, using the functions from \fIOPENSSL_LH_stats\fR\|(3), a read lock suffices. .PP The \s-1LHASH\s0 code regards table entries as constant data. As such, it internally represents \fIlh_insert()\fR'd items with a \*(L"const void *\*(R" pointer type. This is why callbacks such as those used by \fIlh_doall()\fR and \fIlh_doall_arg()\fR declare their prototypes with \*(L"const\*(R", even for the parameters that pass back the table items' data pointers \- for consistency, user-provided data is \*(L"const\*(R" at all times as far as the \&\s-1LHASH\s0 code is concerned. However, as callers are themselves providing these pointers, they can choose whether they too should be treating all such parameters as constant. .PP As an example, a hash table may be maintained by code that, for reasons of encapsulation, has only \*(L"const\*(R" access to the data being indexed in the hash table (i.e. it is returned as \*(L"const\*(R" from elsewhere in their code) \- in this case the \s-1LHASH\s0 prototypes are appropriate as-is. Conversely, if the caller is responsible for the life-time of the data in question, then they may well wish to make modifications to table item passed back in the \fIlh_doall()\fR or \&\fIlh_doall_arg()\fR callbacks (see the \*(L"TYPE_cleanup\*(R" example above). If so, the caller can either cast the \*(L"const\*(R" away (if they're providing the raw callbacks themselves) or use the macros to declare/implement the wrapper functions without \*(L"const\*(R" types. .PP Callers that only have \*(L"const\*(R" access to data they're indexing in a table, yet declare callbacks without constant types (or cast the \&\*(L"const\*(R" away themselves), are therefore creating their own risks/bugs without being encouraged to do so by the \s-1API. \s0 On a related note, those auditing code should pay special attention to any instances of DECLARE/IMPLEMENT_LHASH_DOALL_[\s-1ARG_\s0]_FN macros that provide types without any \*(L"const\*(R" qualifiers. .SH "BUGS" .IX Header "BUGS" \&\fIlh_TYPE_insert()\fR returns \fB\s-1NULL\s0\fR both for success and error. .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fIOPENSSL_LH_stats\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" In OpenSSL 1.0.0, the lhash interface was revamped for better type checking. .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2000\-2022 The OpenSSL Project Authors. All Rights Reserved. .PP Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.
