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Comment updates most. Also some small changes to the VDBE. (CVS 339)

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FossilOrigin-Name: 9b0be4fcc1cbca69f5fee906f86dfb36a323fe84
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drh
2002-01-06 17:07:40 +00:00
parent c6b52df32d
commit aacc543e23
12 changed files with 99 additions and 74 deletions
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42
src/hash.c
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@@ -12,13 +12,22 @@
** This is the implementation of generic hash-tables
** used in SQLite.
**
** $Id: hash.c,v 1.4 2001/11/21 02:21:12 drh Exp $
** $Id: hash.c,v 1.5 2002/01/06 17:07:40 drh Exp $
*/
#include "sqliteInt.h"
#include <assert.h>
/* Turn bulk memory into a hash table object by initializing the
** fields of the Hash structure.
**
** "new" is a pointer to the hash table that is to be initialized.
** keyClass is one of the constants SQLITE_HASH_INT, SQLITE_HASH_POINTER,
** SQLITE_HASH_BINARY, or SQLITE_HASH_STRING. The value of keyClass
** determines what kind of key the hash table will use. "copyKey" is
** true if the hash table should make its own private copy of keys and
** false if it should just use the supplied pointer. CopyKey only makes
** sense for SQLITE_HASH_STRING and SQLITE_HASH_BINARY and is ignored
** for other key classes.
*/
void sqliteHashInit(Hash *new, int keyClass, int copyKey){
assert( new!=0 );
@@ -33,6 +42,8 @@ void sqliteHashInit(Hash *new, int keyClass, int copyKey){
}
/* Remove all entries from a hash table. Reclaim all memory.
** Call this routine to delete a hash table or to reset a hash table
** to the empty state.
*/
void sqliteHashClear(Hash *pH){
HashElem *elem; /* For looping over all elements of the table */
@@ -107,6 +118,15 @@ static int binCompare(const void *pKey1, int n1, const void *pKey2, int n2){
/*
** Return a pointer to the appropriate hash function given the key class.
**
** The C syntax in this function definition may be unfamilar to some
** programmers, so we provide the following additional explanation:
**
** The name of the function is "hashFunction". The function takes a
** single parameter "keyClass". The return value of hashFunction()
** is a pointer to another function. Specifically, the return value
** of hashFunction() is a pointer to a function that takes two parameters
** with types "const void*" and "int" and returns an "int".
*/
static int (*hashFunction(int keyClass))(const void*,int){
switch( keyClass ){
@@ -121,6 +141,9 @@ static int (*hashFunction(int keyClass))(const void*,int){
/*
** Return a pointer to the appropriate hash function given the key class.
**
** For help in interpreted the obscure C code in the function definition,
** see the header comment on the previous function.
*/
static int (*compareFunction(int keyClass))(const void*,int,const void*,int){
switch( keyClass ){
@@ -134,8 +157,9 @@ static int (*compareFunction(int keyClass))(const void*,int,const void*,int){
}
/* Resize the hash table. new_size must be a power of 2.
** The hash table might fail to resize if sqliteMalloc() fails.
/* Resize the hash table so that it cantains "new_size" buckets.
** "new_size" must be a power of 2. The hash table might fail
** to resize if sqliteMalloc() fails.
*/
static void rehash(Hash *pH, int new_size){
struct _ht *new_ht; /* The new hash table */
@@ -172,8 +196,8 @@ static void rehash(Hash *pH, int new_size){
}
/* This function (for internal use only) locates an element in an
** pH that matches the given key. The hash for this key has
** already been computed and is passed as the 3rd parameter.
** hash table that matches the given key. The hash for this key has
** already been computed and is passed as the 4th parameter.
*/
static HashElem *findElementGivenHash(
const Hash *pH, /* The pH to be searched */
@@ -205,7 +229,7 @@ static HashElem *findElementGivenHash(
static void removeElementGivenHash(
Hash *pH, /* The pH containing "elem" */
HashElem* elem, /* The element to be removed from the pH */
int h /* Hash value for the element */
int h /* Hash value for the element */
){
if( elem->prev ){
elem->prev->next = elem->next;
@@ -229,9 +253,9 @@ static void removeElementGivenHash(
pH->count--;
}
/* Attempt to locate an element of the associative pH with a key
/* Attempt to locate an element of the hash table pH with a key
** that matches pKey,nKey. Return the data for this element if it is
** found, or NULL if no match is found.
** found, or NULL if there is no match.
*/
void *sqliteHashFind(const Hash *pH, const void *pKey, int nKey){
int h; /* A hash on key */
@@ -257,7 +281,7 @@ void *sqliteHashFind(const Hash *pH, const void *pKey, int nKey){
** If another element already exists with the same key, then the
** new data replaces the old data and the old data is returned.
** The key is not copied in this instance. If a malloc fails, then
** new data is returned.
** the new data is returned and the hash table is unchanged.
**
** If the "data" parameter to this function is NULL, then the
** element corresponding to "key" is removed from the hash table.