int buflib_alloc_ex(struct buflib_context *ctx, size_t size, const char *name, struct buflib_callbacks *ops) { union buflib_data *handle, *block; size_t name_len = name ? B_ALIGN_UP(strlen(name)+1) : 0; bool last; /* This really is assigned a value before use */ int block_len; size += name_len; size = (size + sizeof(union buflib_data) - 1) / sizeof(union buflib_data) /* add 4 objects for alloc len, pointer to handle table entry and * name length, and the ops pointer */ + 4; handle_alloc: handle = handle_alloc(ctx); if (!handle) { /* If allocation has failed, and compaction has succeded, it may be * possible to get a handle by trying again. */ union buflib_data* last_block = find_block_before(ctx, ctx->alloc_end, false); struct buflib_callbacks* ops = last_block[2].ops; unsigned hints = 0; if (!ops || !ops->shrink_callback) { /* the last one isn't shrinkable * make room in front of a shrinkable and move this alloc */ hints = BUFLIB_SHRINK_POS_FRONT; hints |= last_block->val * sizeof(union buflib_data); } else if (ops && ops->shrink_callback) { /* the last is shrinkable, make room for handles directly */ hints = BUFLIB_SHRINK_POS_BACK; hints |= 16*sizeof(union buflib_data); } /* buflib_compact_and_shrink() will compact and move last_block() * if possible */ if (buflib_compact_and_shrink(ctx, hints)) goto handle_alloc; return -1; } buffer_alloc: /* need to re-evaluate last before the loop because the last allocation * possibly made room in its front to fit this, so last would be wrong */ last = false; for (block = find_first_free(ctx);;block += block_len) { /* If the last used block extends all the way to the handle table, the * block "after" it doesn't have a header. Because of this, it's easier * to always find the end of allocation by saving a pointer, and always * calculate the free space at the end by comparing it to the * last_handle pointer. */ if(block == ctx->alloc_end) { last = true; block_len = ctx->last_handle - block; if ((size_t)block_len < size) block = NULL; break; } block_len = block->val; /* blocks with positive length are already allocated. */ if(block_len > 0) continue; block_len = -block_len; /* The search is first-fit, any fragmentation this causes will be * handled at compaction. */ if ((size_t)block_len >= size) break; } if (!block) { /* Try compacting if allocation failed */ unsigned hint = BUFLIB_SHRINK_POS_FRONT | ((size*sizeof(union buflib_data))&BUFLIB_SHRINK_SIZE_MASK); if (buflib_compact_and_shrink(ctx, hint)) { goto buffer_alloc; } else { handle->val=1; handle_free(ctx, handle); return -2; } } /* Set up the allocated block, by marking the size allocated, and storing * a pointer to the handle. */ union buflib_data *name_len_slot; block->val = size; block[1].handle = handle; block[2].ops = ops; strcpy(block[3].name, name); name_len_slot = (union buflib_data*)B_ALIGN_UP(block[3].name + name_len); name_len_slot->val = 1 + name_len/sizeof(union buflib_data); handle->alloc = (char*)(name_len_slot + 1); block += size; /* alloc_end must be kept current if we're taking the last block. */ if (last) ctx->alloc_end = block; /* Only free blocks *before* alloc_end have tagged length. */ else if ((size_t)block_len > size) block->val = size - block_len; /* Return the handle index as a positive integer. */ return ctx->handle_table - handle; }
int buflib_alloc_ex(struct buflib_context *ctx, size_t size, const char *name, struct buflib_callbacks *ops) { /* busy wait if there's a thread owning the lock */ while (ctx->handle_lock != 0) YIELD(); union buflib_data *handle, *block; size_t name_len = name ? B_ALIGN_UP(strlen(name)+1) : 0; bool last; /* This really is assigned a value before use */ int block_len; size += name_len; size = (size + sizeof(union buflib_data) - 1) / sizeof(union buflib_data) /* add 4 objects for alloc len, pointer to handle table entry and * name length, and the ops pointer */ + 4; handle_alloc: handle = handle_alloc(ctx); if (!handle) { /* If allocation has failed, and compaction has succeded, it may be * possible to get a handle by trying again. */ if (!ctx->compact && buflib_compact(ctx)) goto handle_alloc; else { /* first try to shrink the alloc before the handle table * to make room for new handles */ int handle = ctx->handle_table - ctx->last_handle; union buflib_data* last_block = handle_to_block(ctx, handle); struct buflib_callbacks* ops = last_block[2].ops; if (ops && ops->shrink_callback) { char *data = buflib_get_data(ctx, handle); unsigned hint = BUFLIB_SHRINK_POS_BACK | 10*sizeof(union buflib_data); if (ops->shrink_callback(handle, hint, data, (char*)(last_block+last_block->val)-data) == BUFLIB_CB_OK) { /* retry one more time */ goto handle_alloc; } } return 0; } } buffer_alloc: /* need to re-evaluate last before the loop because the last allocation * possibly made room in its front to fit this, so last would be wrong */ last = false; for (block = ctx->first_free_block;;block += block_len) { /* If the last used block extends all the way to the handle table, the * block "after" it doesn't have a header. Because of this, it's easier * to always find the end of allocation by saving a pointer, and always * calculate the free space at the end by comparing it to the * last_handle pointer. */ if(block == ctx->alloc_end) { last = true; block_len = ctx->last_handle - block; if ((size_t)block_len < size) block = NULL; break; } block_len = block->val; /* blocks with positive length are already allocated. */ if(block_len > 0) continue; block_len = -block_len; /* The search is first-fit, any fragmentation this causes will be * handled at compaction. */ if ((size_t)block_len >= size) break; } if (!block) { /* Try compacting if allocation failed */ if (buflib_compact_and_shrink(ctx, (size*sizeof(union buflib_data))&BUFLIB_SHRINK_SIZE_MASK)) { goto buffer_alloc; } else { handle->val=1; handle_free(ctx, handle); return 0; } } /* Set up the allocated block, by marking the size allocated, and storing * a pointer to the handle. */ union buflib_data *name_len_slot; block->val = size; block[1].handle = handle; block[2].ops = ops ?: &default_callbacks; strcpy(block[3].name, name); name_len_slot = (union buflib_data*)B_ALIGN_UP(block[3].name + name_len); name_len_slot->val = 1 + name_len/sizeof(union buflib_data); handle->alloc = (char*)(name_len_slot + 1); /* If we have just taken the first free block, the next allocation search * can save some time by starting after this block. */ if (block == ctx->first_free_block) ctx->first_free_block += size; block += size; /* alloc_end must be kept current if we're taking the last block. */ if (last) ctx->alloc_end = block; /* Only free blocks *before* alloc_end have tagged length. */ else if ((size_t)block_len > size) block->val = size - block_len; /* Return the handle index as a positive integer. */ return ctx->handle_table - handle; }