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/* Copyright (C) 2000 MySQL AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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/* Routines to handle mallocing of results which will be freed the same time */
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#include "drizzled/internal/my_sys.h"
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#include "drizzled/internal/m_string.h"
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static const unsigned int MAX_BLOCK_TO_DROP= 4096;
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static const unsigned int MAX_BLOCK_USAGE_BEFORE_DROP= 10;
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Initialize memory root
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memory::init_alloc_root()
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mem_root - memory root to initialize
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block_size - size of chunks (blocks) used for memory allocation
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(It is external size of chunk i.e. it should include
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memory required for internal structures, thus it
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should be no less than memory::ROOT_MIN_BLOCK_SIZE)
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This function prepares memory root for further use, sets initial size of
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chunk for memory allocation and pre-allocates first block if specified.
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Altough error can happen during execution of this function if
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pre_alloc_size is non-0 it won't be reported. Instead it will be
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reported as error in first alloc_root() on this memory root.
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void memory::init_alloc_root(memory::Root *mem_root, size_t block_size)
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mem_root->free= mem_root->used= mem_root->pre_alloc= 0;
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mem_root->min_malloc= 32;
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mem_root->block_size= block_size - memory::ROOT_MIN_BLOCK_SIZE;
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mem_root->error_handler= 0;
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mem_root->block_num= 4; /* We shift this with >>2 */
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mem_root->first_block_usage= 0;
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mem_root memory root to change defaults of
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block_size new value of block size. Must be greater or equal
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than ALLOC_ROOT_MIN_BLOCK_SIZE (this value is about
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68 bytes and depends on platform and compilation flags)
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pre_alloc_size new size of preallocated block. If not zero,
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must be equal to or greater than block size,
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otherwise means 'no prealloc'.
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Function aligns and assigns new value to block size; then it tries to
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reuse one of existing blocks as prealloc block, or malloc new one of
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requested size. If no blocks can be reused, all unused blocks are freed
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void memory::reset_root_defaults(memory::Root *mem_root, size_t block_size,
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size_t pre_alloc_size)
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assert(alloc_root_inited(mem_root));
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mem_root->block_size= block_size - memory::ROOT_MIN_BLOCK_SIZE;
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size_t size= pre_alloc_size + ALIGN_SIZE(sizeof(memory::internal::UsedMemory));
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if (!mem_root->pre_alloc || mem_root->pre_alloc->size != size)
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memory::internal::UsedMemory *mem, **prev= &mem_root->free;
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Free unused blocks, so that consequent calls
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to reset_root_defaults won't eat away memory.
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if (mem->size == size)
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/* We found a suitable block, no need to do anything else */
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mem_root->pre_alloc= mem;
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if (mem->left + ALIGN_SIZE(sizeof(memory::internal::UsedMemory)) == mem->size)
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/* remove block from the list and free it */
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/* Allocate new prealloc block and add it to the end of free list */
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if ((mem= static_cast<memory::internal::UsedMemory *>(malloc(size))))
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mem->left= pre_alloc_size;
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*prev= mem_root->pre_alloc= mem;
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mem_root->pre_alloc= 0;
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mem_root->pre_alloc= 0;
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void *memory::alloc_root(memory::Root *mem_root, size_t length)
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size_t get_size, block_size;
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unsigned char* point;
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memory::internal::UsedMemory *next= NULL;
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memory::internal::UsedMemory **prev;
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assert(alloc_root_inited(mem_root));
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length= ALIGN_SIZE(length);
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if ((*(prev= &mem_root->free)) != NULL)
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if ((*prev)->left < length &&
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mem_root->first_block_usage++ >= MAX_BLOCK_USAGE_BEFORE_DROP &&
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(*prev)->left < MAX_BLOCK_TO_DROP)
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*prev= next->next; /* Remove block from list */
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next->next= mem_root->used;
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mem_root->used= next;
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mem_root->first_block_usage= 0;
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for (next= *prev ; next && next->left < length ; next= next->next)
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{ /* Time to alloc new block */
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block_size= mem_root->block_size * (mem_root->block_num >> 2);
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get_size= length+ALIGN_SIZE(sizeof(memory::internal::UsedMemory));
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get_size= max(get_size, block_size);
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if (!(next = static_cast<memory::internal::UsedMemory *>(malloc(get_size))))
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if (mem_root->error_handler)
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(*mem_root->error_handler)();
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mem_root->block_num++;
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next->size= get_size;
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next->left= get_size-ALIGN_SIZE(sizeof(memory::internal::UsedMemory));
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point= (unsigned char*) ((char*) next+ (next->size-next->left));
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/*TODO: next part may be unneded due to mem_root->first_block_usage counter*/
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if ((next->left-= length) < mem_root->min_malloc)
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*prev= next->next; /* Remove block from list */
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next->next= mem_root->used;
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mem_root->used= next;
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mem_root->first_block_usage= 0;
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return((void*) point);
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Allocate many pointers at the same time.
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ptr1, ptr2, etc all point into big allocated memory area.
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ptr1, length1 Multiple arguments terminated by a NULL pointer
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A pointer to the beginning of the allocated memory block
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in case of success or NULL if out of memory.
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void *memory::multi_alloc_root(memory::Root *root, ...)
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char **ptr, *start, *res;
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size_t tot_length, length;
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va_start(args, root);
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while ((ptr= va_arg(args, char **)))
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length= va_arg(args, uint);
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tot_length+= ALIGN_SIZE(length);
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if (!(start= (char*) memory::alloc_root(root, tot_length)))
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va_start(args, root);
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while ((ptr= va_arg(args, char **)))
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length= va_arg(args, uint);
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res+= ALIGN_SIZE(length);
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return((void*) start);
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#define TRASH_MEM(X) TRASH(((char*)(X) + ((X)->size-(X)->left)), (X)->left)
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/* Mark all data in blocks free for reusage */
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static inline void mark_blocks_free(memory::Root* root)
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memory::internal::UsedMemory *next;
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memory::internal::UsedMemory **last;
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/* iterate through (partially) free blocks, mark them free */
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for (next= root->free; next; next= *(last= &next->next))
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next->left= next->size - ALIGN_SIZE(sizeof(memory::internal::UsedMemory));
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/* Combine the free and the used list */
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*last= next=root->used;
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/* now go through the used blocks and mark them free */
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for (; next; next= next->next)
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next->left= next->size - ALIGN_SIZE(sizeof(memory::internal::UsedMemory));
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/* Now everything is set; Indicate that nothing is used anymore */
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root->first_block_usage= 0;
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Deallocate everything used by memory::alloc_root or just move
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used blocks to free list if called with MY_USED_TO_FREE
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MyFlags Flags for what should be freed:
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MARK_BLOCKS_FREED Don't free blocks, just mark them free
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KEEP_PREALLOC If this is not set, then free also the
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One can call this function either with root block initialised with
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init_alloc_root() or with a zero:ed block.
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It's also safe to call this multiple times with the same mem_root.
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void memory::free_root(memory::Root *root, myf MyFlags)
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memory::internal::UsedMemory *next,*old;
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if (MyFlags & memory::MARK_BLOCKS_FREE)
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mark_blocks_free(root);
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if (!(MyFlags & memory::KEEP_PREALLOC))
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for (next=root->used; next ;)
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old=next; next= next->next ;
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if (old != root->pre_alloc)
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for (next=root->free ; next ;)
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old=next; next= next->next;
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if (old != root->pre_alloc)
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root->used=root->free=0;
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root->free=root->pre_alloc;
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root->free->left=root->pre_alloc->size-ALIGN_SIZE(sizeof(memory::internal::UsedMemory));
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TRASH_MEM(root->pre_alloc);
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root->first_block_usage= 0;
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Find block that contains an object and set the pre_alloc to it
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void memory::set_prealloc_root(memory::Root *root, char *ptr)
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memory::internal::UsedMemory *next;
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for (next=root->used; next ; next=next->next)
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if ((char*) next <= ptr && (char*) next + next->size > ptr)
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root->pre_alloc=next;
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for (next=root->free ; next ; next=next->next)
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if ((char*) next <= ptr && (char*) next + next->size > ptr)
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root->pre_alloc=next;
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char *memory::strdup_root(memory::Root *root, const char *str)
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return strmake_root(root, str, strlen(str));
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char *memory::strmake_root(memory::Root *root, const char *str, size_t len)
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if ((pos=(char *)memory::alloc_root(root,len+1)))
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void *memory::memdup_root(memory::Root *root, const void *str, size_t len)
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if ((pos=memory::alloc_root(root,len)))
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} /* namespace drizzled */