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-rw-r--r--doc/Hash.3113
1 files changed, 101 insertions, 12 deletions
diff --git a/doc/Hash.3 b/doc/Hash.3
index d15b464..f9f4a39 100644
--- a/doc/Hash.3
+++ b/doc/Hash.3
@@ -5,19 +5,23 @@
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
-'\" RCS: @(#) $Id: Hash.3,v 1.4 2000/06/24 00:26:08 ericm Exp $
+'\" RCS: @(#) $Id: Hash.3,v 1.5 2000/07/19 22:15:28 ericm Exp $
'\"
.so man.macros
.TH Tcl_Hash 3 "" Tcl "Tcl Library Procedures"
.BS
.SH NAME
-Tcl_InitHashTable, Tcl_DeleteHashTable, Tcl_CreateHashEntry, Tcl_DeleteHashEntry, Tcl_FindHashEntry, Tcl_GetHashValue, Tcl_SetHashValue, Tcl_GetHashKey, Tcl_FirstHashEntry, Tcl_NextHashEntry, Tcl_HashStats \- procedures to manage hash tables
+Tcl_InitHashTable, Tcl_InitHashTableEx, Tcl_InitObjHashTable, Tcl_DeleteHashTable, Tcl_CreateHashEntry, Tcl_DeleteHashEntry, Tcl_FindHashEntry, Tcl_GetHashValue, Tcl_SetHashValue, Tcl_GetHashKey, Tcl_FirstHashEntry, Tcl_NextHashEntry, Tcl_HashStats \- procedures to manage hash tables
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
\fBTcl_InitHashTable\fR(\fItablePtr, keyType\fR)
.sp
+\fBTcl_InitHashTableEx\fR(\fItablePtr, keyType, typePtr\fR)
+.sp
+\fBTcl_InitObjHashTable\fR(\fItablePtr\fR)
+.sp
\fBTcl_DeleteHashTable\fR(\fItablePtr\fR)
.sp
Tcl_HashEntry *
@@ -52,8 +56,10 @@ Address of hash table structure (for all procedures but
previous call to \fBTcl_InitHashTable\fR).
.AP int keyType in
Kind of keys to use for new hash table. Must be either
-TCL_STRING_KEYS, TCL_OBJ_KEYS, TCL_ONE_WORD_KEYS, or an integer value
-greater than 1.
+TCL_STRING_KEYS, TCL_ONE_WORD_KEYS, TCL_CUSTOM_TYPE_KEYS,
+TCL_CUSTOM_PTR_KEYS, or an integer value greater than 1.
+.AP Tcl_HashKeyType *typePtr in
+Address of structure which defines the behaviour of the hash table.
.AP char *key in
Key to use for probe into table. Exact form depends on
\fIkeyType\fR used to create table.
@@ -96,7 +102,10 @@ on average.
This allows for fast lookups regardless of the number of entries
in a table.
.PP
-\fBTcl_InitHashTable\fR initializes a structure that describes
+\fBTcl_InitHashTable\fR calls the extended function
+\fBTcl_InitHashTableEx\fR with a NULL \fItypePtr\fR.
+.PP
+\fBTcl_InitHashTableEx\fR initializes a structure that describes
a new hash table.
The space for the structure is provided by the caller, not by
the hash module.
@@ -107,18 +116,22 @@ one of the following values:
Keys are null-terminated ASCII strings.
They are passed to hashing routines using the address of the
first character of the string.
-.IP \fBTCL_OBJ_KEYS\fR 25
-Keys are Tcl_Obj *. Hashing and comparison are done on the string
-representation of the object. The differences between this type and
-TCL_STRING_KEYS are: the key is not copied, instead the reference
-count is incremented; and the extra information associated with the
-Tcl_Obj * is used to optimize comparisons. The string is only
-compared if the two Tcl_Obj * are different and have the same length.
.IP \fBTCL_ONE_WORD_KEYS\fR 25
Keys are single-word values; they are passed to hashing routines
and stored in hash table entries as ``char *'' values.
The pointer value is the key; it need not (and usually doesn't)
actually point to a string.
+.IP \fBTCL_CUSTOM_TYPE_KEYS\fR 25
+Keys are of arbitrary type, and are stored in the entry. Hashing
+and comparison is determined by \fItypePtr\fR. The Tcl_HashKeyType
+structure is described in the section
+\fBTHE TCL_HASHKEYTYPE STRUCTURE\fR below.
+
+.IP \fBTCL_CUSTOM_TYPE_KEYS\fR 25
+Keys are pointers to arbitrary type, and the are stored in the entry. Hashing
+and comparison is determined by \fItypePtr\fR. The Tcl_HashKeyType
+structure is described in the section
+\fBTHE TCL_HASHKEYTYPE STRUCTURE\fR below.
.IP \fIother\fR 25
If \fIkeyType\fR is not one of the above,
then it must be an integer value greater than 1.
@@ -129,6 +142,9 @@ All keys must have the same size.
Array keys are passed into hashing functions using the address
of the first int in the array.
.PP
+\fBTcl_InitObjHashTable\fR uses \fBTcl_InitHashTableEx\fR to
+initialize a hash table whose keys are Tcl_Obj *.
+.PP
\fBTcl_DeleteHashTable\fR deletes all of the entries in a hash
table and frees up the memory associated with the table's
bucket array and entries.
@@ -211,5 +227,78 @@ However, users of the hashing routines should never refer directly
to any of the fields of any of the hash-related data structures;
use the procedures and macros defined here.
+.SH "THE TCL_HASHKEYTYPE STRUCTURE"
+.PP
+Extension writers can define new hash key types by defining four
+procedure, initializing a Tcl_HashKeyType structure to describe
+the type, and calling \fBTcl_InitHashTableEx\fR.
+The \fBTcl_HashKeyType\fR structure is defined as follows:
+.CS
+typedef struct Tcl_HashKeyType {
+ int \fIversion\fR;
+ int \fIflags\fR;
+ Tcl_HashKeyProc *\fIhashKeyProc\fR;
+ Tcl_CompareHashKeysProc *\fIcompareKeysProc\fR;
+ Tcl_AllocHashEntryProc *\fIallocEntryProc\fR;
+ Tcl_FreeHashEntryProc *\fIfreeEntryProc\fR;
+} Tcl_HashKeyType;
+.CE
+.PP
+The \fIversion\fR member is the version of the table. If this
+structure is extended in future then the version can be used
+to distinguish between different structures. It should be set
+to \fBTCL_HASH_KEY_TYPE_VERSION\fR.
+.PP
+The \fIflags\fR member is one or more of the following OR'ed together:
+.IP \fBTCL_HASH_KEY_RANDOMIZE_HASH\fR 25
+There are some things, pointers for example which don't hash well
+because they do not use the lower bits. If this flag is set then the
+hash table will attempt to rectify this by randomising the bits and
+then using the upper N bits as the index into the table.
+.PP
+The \fIhashKeyProc\fR member contains the address of a function
+called to calculate a hash value for the key.
+.CS
+typedef unsigned int (Tcl_HashKeyProc) (
+ Tcl_HashTable *\fItablePtr\fR,
+ VOID *\fIkeyPtr\fR);
+.CE
+If this is NULL then \fIkeyPtr\fR is used and
+\fBTCL_HASH_KEY_RANDOMIZE_HASH\fR is assumed.
+.PP
+The \fIcompareKeysProc\fR member contains the address of a function
+called to compare two keys.
+.CS
+typedef int (Tcl_CompareHashKeysProc) (VOID *\fIkeyPtr\fR,
+ Tcl_HashEntry *\fIhPtr\fR);
+.CE
+If this is NULL then the \fIkeyPtr\fR pointers are compared.
+If the keys don't match then the function returns 0, otherwise
+it returns 1.
+.PP
+The \fIallocEntryProc\fR member contains the address of a function
+called to allocate space for an entry and initialise the key.
+.CS
+typedef Tcl_HashEntry *(Tcl_AllocHashEntryProc) (
+ Tcl_HashTable *\fItablePtr\fR, VOID *\fIkeyPtr\fR);
+.CE
+If this is NULL then Tcl_Alloc is used to allocate enough space for a
+Tcl_HashEntry and the key pointer is assigned to key.oneWordValue.
+String keys and array keys use this function to allocate enough
+space for the entry and the key in one block, rather than doing
+it in two blocks. This saves space for a pointer to the key from
+the entry and another memory allocation. Tcl_Obj * keys use this
+function to allocate enough space for an entry and increment the
+reference count on the object.
+If
+.PP
+The \fIfreeEntryProc\fR member contains the address of a function
+called to free space for an entry.
+.CS
+typedef void (Tcl_FreeHashEntryProc) (Tcl_HashEntry *\fIhPtr\fR);
+.CE
+If this is NULL then Tcl_Free is used to free the space for the
+entry. Tcl_Obj * keys use this function to decrement the
+reference count on the object.
.SH KEYWORDS
hash table, key, lookup, search, value