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/* $Id: imagecache.c 2640 2012-09-09 01:49:16Z bird $ */
/** @file
* kBuild specific executable image cache for Windows.
*/
/*
* Copyright (c) 2012 knut st. osmundsen <bird-kBuild-spamx@anduin.net>
*
* This file is part of kBuild.
*
* kBuild is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* kBuild is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with kBuild. If not, see <http://www.gnu.org/licenses/>
*
*/
/* No GNU coding style here! */
/*******************************************************************************
* Header Files *
*******************************************************************************/
#include "make.h"
#include <Windows.h>
/*******************************************************************************
* Structures and Typedefs *
*******************************************************************************/
typedef struct EXECCACHEENTRY
{
/** The name hash value. */
unsigned uHash;
/** The name length. */
unsigned cchName;
/** Pointer to the next name with the same hash. */
struct EXECCACHEENTRY *pNext;
/** When it was last referenced. */
unsigned uLastRef;
/** The module handle. */
HMODULE hmod1;
/** The module handle. */
HMODULE hmod2;
/** The executable path. */
char szName[1];
} EXECCACHEENTRY;
typedef EXECCACHEENTRY *PEXECCACHEENTRY;
/*******************************************************************************
* Global Variables *
*******************************************************************************/
/** The number of cached images. */
static unsigned g_cCached;
/** Used noting when entries was last used.
* Increased on each kmk_cache_exec_image call. */
static unsigned g_uNow;
/** The size of the hash table. */
#define EXECCACHE_HASHTAB_SIZE 128
/** The hash table. */
static PEXECCACHEENTRY g_apHashTab[EXECCACHE_HASHTAB_SIZE];
/* sdbm:
This algorithm was created for sdbm (a public-domain reimplementation of
ndbm) database library. it was found to do well in scrambling bits,
causing better distribution of the keys and fewer splits. it also happens
to be a good general hashing function with good distribution. the actual
function is hash(i) = hash(i - 1) * 65599 + str[i]; what is included below
is the faster version used in gawk. [there is even a faster, duff-device
version] the magic constant 65599 was picked out of thin air while
experimenting with different constants, and turns out to be a prime.
this is one of the algorithms used in berkeley db (see sleepycat) and
elsewhere. */
static unsigned execcache_calc_hash(const char *psz, unsigned *pcch)
{
unsigned char *puch = (unsigned char *)psz;
unsigned hash = 0;
int ch;
while ((ch = *puch++))
hash = ch + (hash << 6) + (hash << 16) - hash;
*pcch = (unsigned)(puch - psz - 1);
return hash;
}
extern void kmk_cache_exec_image(const char *pszExec)
{
/*
* Lookup the name.
*/
unsigned cchName;
const unsigned uHash = execcache_calc_hash(pszExec, &cchName);
PEXECCACHEENTRY *ppCur = &g_apHashTab[uHash % EXECCACHE_HASHTAB_SIZE];
PEXECCACHEENTRY pCur = *ppCur;
while (pCur)
{
if ( pCur->uHash == uHash
&& pCur->cchName == cchName
&& !memcmp(pCur->szName, pszExec, cchName))
{
pCur->uLastRef = ++g_uNow;
return;
}
ppCur = &pCur->pNext;
pCur = pCur->pNext;
}
/*
* Not found, create a new entry.
*/
pCur = xmalloc(sizeof(*pCur) + cchName);
pCur->uHash = uHash;
pCur->cchName = cchName;
pCur->pNext = NULL;
pCur->uLastRef = ++g_uNow;
memcpy(pCur->szName, pszExec, cchName + 1);
pCur->hmod1 = LoadLibraryEx(pszExec, NULL, LOAD_LIBRARY_AS_DATAFILE);
if (pCur->hmod1 != NULL)
pCur->hmod2 = LoadLibraryEx(pszExec, NULL, DONT_RESOLVE_DLL_REFERENCES);
else
pCur->hmod2 = NULL;
*ppCur = pCur;
g_cCached++;
}
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