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|    1 /* |  | 
|    2 ** 2007 August 14 |  | 
|    3 ** |  | 
|    4 ** The author disclaims copyright to this source code.  In place of |  | 
|    5 ** a legal notice, here is a blessing: |  | 
|    6 ** |  | 
|    7 **    May you do good and not evil. |  | 
|    8 **    May you find forgiveness for yourself and forgive others. |  | 
|    9 **    May you share freely, never taking more than you give. |  | 
|   10 ** |  | 
|   11 ************************************************************************* |  | 
|   12 ** |  | 
|   13 ** This file contains low-level memory allocation drivers for when |  | 
|   14 ** SQLite will use the standard C-library malloc/realloc/free interface |  | 
|   15 ** to obtain the memory it needs. |  | 
|   16 ** |  | 
|   17 ** This file contains implementations of the low-level memory allocation |  | 
|   18 ** routines specified in the sqlite3_mem_methods object. |  | 
|   19 ** |  | 
|   20 ** $Id: mem1.c,v 1.30 2009/03/23 04:33:33 danielk1977 Exp $ |  | 
|   21 */ |  | 
|   22 #include "sqliteInt.h" |  | 
|   23  |  | 
|   24 /* |  | 
|   25 ** This version of the memory allocator is the default.  It is |  | 
|   26 ** used when no other memory allocator is specified using compile-time |  | 
|   27 ** macros. |  | 
|   28 */ |  | 
|   29 #ifdef SQLITE_SYSTEM_MALLOC |  | 
|   30  |  | 
|   31 /* |  | 
|   32 ** Like malloc(), but remember the size of the allocation |  | 
|   33 ** so that we can find it later using sqlite3MemSize(). |  | 
|   34 ** |  | 
|   35 ** For this low-level routine, we are guaranteed that nByte>0 because |  | 
|   36 ** cases of nByte<=0 will be intercepted and dealt with by higher level |  | 
|   37 ** routines. |  | 
|   38 */ |  | 
|   39 static void *sqlite3MemMalloc(int nByte){ |  | 
|   40   sqlite3_int64 *p; |  | 
|   41   assert( nByte>0 ); |  | 
|   42   nByte = ROUND8(nByte); |  | 
|   43   p = malloc( nByte+8 ); |  | 
|   44   if( p ){ |  | 
|   45     p[0] = nByte; |  | 
|   46     p++; |  | 
|   47   } |  | 
|   48   return (void *)p; |  | 
|   49 } |  | 
|   50  |  | 
|   51 /* |  | 
|   52 ** Like free() but works for allocations obtained from sqlite3MemMalloc() |  | 
|   53 ** or sqlite3MemRealloc(). |  | 
|   54 ** |  | 
|   55 ** For this low-level routine, we already know that pPrior!=0 since |  | 
|   56 ** cases where pPrior==0 will have been intecepted and dealt with |  | 
|   57 ** by higher-level routines. |  | 
|   58 */ |  | 
|   59 static void sqlite3MemFree(void *pPrior){ |  | 
|   60   sqlite3_int64 *p = (sqlite3_int64*)pPrior; |  | 
|   61   assert( pPrior!=0 ); |  | 
|   62   p--; |  | 
|   63   free(p); |  | 
|   64 } |  | 
|   65  |  | 
|   66 /* |  | 
|   67 ** Like realloc().  Resize an allocation previously obtained from |  | 
|   68 ** sqlite3MemMalloc(). |  | 
|   69 ** |  | 
|   70 ** For this low-level interface, we know that pPrior!=0.  Cases where |  | 
|   71 ** pPrior==0 while have been intercepted by higher-level routine and |  | 
|   72 ** redirected to xMalloc.  Similarly, we know that nByte>0 becauses |  | 
|   73 ** cases where nByte<=0 will have been intercepted by higher-level |  | 
|   74 ** routines and redirected to xFree. |  | 
|   75 */ |  | 
|   76 static void *sqlite3MemRealloc(void *pPrior, int nByte){ |  | 
|   77   sqlite3_int64 *p = (sqlite3_int64*)pPrior; |  | 
|   78   assert( pPrior!=0 && nByte>0 ); |  | 
|   79   nByte = ROUND8(nByte); |  | 
|   80   p = (sqlite3_int64*)pPrior; |  | 
|   81   p--; |  | 
|   82   p = realloc(p, nByte+8 ); |  | 
|   83   if( p ){ |  | 
|   84     p[0] = nByte; |  | 
|   85     p++; |  | 
|   86   } |  | 
|   87   return (void*)p; |  | 
|   88 } |  | 
|   89  |  | 
|   90 /* |  | 
|   91 ** Report the allocated size of a prior return from xMalloc() |  | 
|   92 ** or xRealloc(). |  | 
|   93 */ |  | 
|   94 static int sqlite3MemSize(void *pPrior){ |  | 
|   95   sqlite3_int64 *p; |  | 
|   96   if( pPrior==0 ) return 0; |  | 
|   97   p = (sqlite3_int64*)pPrior; |  | 
|   98   p--; |  | 
|   99   return (int)p[0]; |  | 
|  100 } |  | 
|  101  |  | 
|  102 /* |  | 
|  103 ** Round up a request size to the next valid allocation size. |  | 
|  104 */ |  | 
|  105 static int sqlite3MemRoundup(int n){ |  | 
|  106   return ROUND8(n); |  | 
|  107 } |  | 
|  108  |  | 
|  109 /* |  | 
|  110 ** Initialize this module. |  | 
|  111 */ |  | 
|  112 static int sqlite3MemInit(void *NotUsed){ |  | 
|  113   UNUSED_PARAMETER(NotUsed); |  | 
|  114   return SQLITE_OK; |  | 
|  115 } |  | 
|  116  |  | 
|  117 /* |  | 
|  118 ** Deinitialize this module. |  | 
|  119 */ |  | 
|  120 static void sqlite3MemShutdown(void *NotUsed){ |  | 
|  121   UNUSED_PARAMETER(NotUsed); |  | 
|  122   return; |  | 
|  123 } |  | 
|  124  |  | 
|  125 /* |  | 
|  126 ** This routine is the only routine in this file with external linkage. |  | 
|  127 ** |  | 
|  128 ** Populate the low-level memory allocation function pointers in |  | 
|  129 ** sqlite3GlobalConfig.m with pointers to the routines in this file. |  | 
|  130 */ |  | 
|  131 void sqlite3MemSetDefault(void){ |  | 
|  132   static const sqlite3_mem_methods defaultMethods = { |  | 
|  133      sqlite3MemMalloc, |  | 
|  134      sqlite3MemFree, |  | 
|  135      sqlite3MemRealloc, |  | 
|  136      sqlite3MemSize, |  | 
|  137      sqlite3MemRoundup, |  | 
|  138      sqlite3MemInit, |  | 
|  139      sqlite3MemShutdown, |  | 
|  140      0 |  | 
|  141   }; |  | 
|  142   sqlite3_config(SQLITE_CONFIG_MALLOC, &defaultMethods); |  | 
|  143 } |  | 
|  144  |  | 
|  145 #endif /* SQLITE_SYSTEM_MALLOC */ |  | 
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