_item_buffer.h Source File

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# _item_buffer.h

    00001 /*
    00002     Copyright 2005-2011 Intel Corporation.  All Rights Reserved.
    00003
    00004     The source code contained or described herein and all documents related
    00005     to the source code ("Material") are owned by Intel Corporation or its
    00006     suppliers or licensors.  Title to the Material remains with Intel
    00007     Corporation or its suppliers and licensors.  The Material is protected
    00008     by worldwide copyright laws and treaty provisions.  No part of the
    00009     Material may be used, copied, reproduced, modified, published, uploaded,
    00010     posted, transmitted, distributed, or disclosed in any way without
    00011     Intel's prior express written permission.
    00012
    00013     No license under any patent, copyright, trade secret or other
    00014     intellectual property right is granted to or conferred upon you by
    00015     disclosure or delivery of the Materials, either expressly, by
    00016     implication, inducement, estoppel or otherwise.  Any license under such
    00017     intellectual property rights must be express and approved by Intel in
    00018     writing.
    00019 */
    00020
    00021 #ifndef __TBB_item_buffer_H
    00022 #define __TBB_item_buffer_H
    00023
    00025     //* tests for empty and so forth.  No mutual exclusion is built in.
    00026     template <typename T>
    00027     class item_buffer {
    00028     public:
    00029         typedef T input_type;
    00030         typedef T output_type;
    00031     protected:
    00032         typedef size_t size_type;
    00033         typedef std::pair< T, bool > item_type;
    00034
    00035         item_type *my_array;
    00036         size_type my_array_size;
    00037         static const size_type initial_buffer_size = 4;
    00038         size_type my_head;
    00039         size_type my_tail;
    00040
    00041         bool buffer_empty() { return my_head == my_tail; }
    00042
    00043         item_type &item(size_type i) { return my_array[i & (my_array_size - 1) ]; } // may not be marked valid
    00044
    00045         bool item_valid(size_type i) { return item(i).second; }
    00046
    00047         void fetch_front(T &v) { __TBB_ASSERT(item_valid(my_head), "front not valid"); v = item(my_head).first; }
    00048         void fetch_back(T &v) { __TBB_ASSERT(item_valid(my_tail-1), "back not valid"); v = item(my_tail-1).first; }
    00049
    00050         void invalidate(size_type i) { __TBB_ASSERT(item_valid(i), "Item not valid"); item(i).second = false; }
    00051         void validate(size_type i) { __TBB_ASSERT(!item_valid(i), "Item already valid"); item(i).second = true; }
    00052
    00053         void invalidate_front() { invalidate(my_head); }
    00054         void validate_front() { validate(my_head); }
    00055         void invalidate_back() { invalidate(my_tail-1); }
    00056
    00057         size_type size() { return my_tail - my_head; }
    00058         size_type capacity() { return my_array_size; }
    00059         bool buffer_full() { return size() == capacity(); }
    00060
    00062         void grow_my_array( size_t minimum_size ) {
    00063             size_type old_size = my_array_size;
    00064             size_type new_size = old_size ? 2*old_size : initial_buffer_size;
    00065             while( new_size<minimum_size )
    00066                 new_size*=2;
    00067
    00068             item_type* new_array = cache_aligned_allocator<item_type>().allocate(new_size);
    00069             item_type* old_array = my_array;
    00070
    00071             for( size_type i=0; i<new_size; ++i )
    00072                 new_array[i].second = false;
    00073
    00074             size_t t=my_head;
    00075             for( size_type i=0; i<old_size; ++i, ++t )
    00076                 new_array[t&(new_size-1)] = old_array[t&(old_size-1)];
    00077             my_array = new_array;
    00078             my_array_size = new_size;
    00079             if( old_array )
    00080                 cache_aligned_allocator<item_type>().deallocate(old_array,old_size);
    00081         }
    00082
    00083         bool push_back(T &v) {
    00084             if(buffer_full()) {
    00085                 grow_my_array(size() + 1);
    00086             }
    00087             item(my_tail) = std::make_pair( v, true );
    00088             ++my_tail;
    00089             return true;
    00090         }
    00091
    00092         bool pop_back(T &v) {
    00093             if (!item_valid(my_tail-1)) {
    00094                 return false;
    00095             }
    00096             fetch_back(v);
    00097             invalidate_back();
    00098             --my_tail;
    00099             return true;
    00100         }
    00101
    00102         bool pop_front(T &v) {
    00103             if(!item_valid(my_head)) {
    00104                 return false;
    00105             }
    00106             fetch_front(v);
    00107             invalidate_front();
    00108             ++my_head;
    00109             return true;
    00110         }
    00111
    00112     public:
    00114         item_buffer( ) : my_array(NULL), my_array_size(0),
    00115             my_head(0), my_tail(0) {
    00116             grow_my_array(initial_buffer_size);
    00117         }
    00118
    00119         ~item_buffer() {if(my_array) cache_aligned_allocator<item_type>().deallocate(my_array,my_array_size); }
    00120
    00121     };
    00122
    00124     //* complete operation with pop_front(); use consume_front().
    00125     //* No synchronization built-in.
    00126     template<typename T>
    00127     class reservable_item_buffer : public item_buffer<T> {
    00128     protected:
    00129         using item_buffer<T>::buffer_empty;
    00130         using item_buffer<T>::fetch_front;
    00131         using item_buffer<T>::invalidate_front;
    00132         using item_buffer<T>::validate_front;
    00133         using item_buffer<T>::item_valid;
    00134         using item_buffer<T>::my_head;
    00135
    00136     public:
    00137         reservable_item_buffer() : item_buffer<T>(), my_reserved(false) {}
    00138     protected:
    00139
    00140         bool reserve_front(T &v) {
    00141             if(my_reserved || !item_valid(my_head)) return false;
    00142             my_reserved = true;
    00143             // reserving the head
    00144             fetch_front(v);
    00145             // invalidate the head, but don't commit until consume is called
    00146             invalidate_front();
    00147             return true;
    00148         }
    00149
    00150         void consume_front() {
    00151             __TBB_ASSERT(my_reserved, "Attempt to consume a non-reserved item");
    00152             ++my_head;
    00153             my_reserved = false;
    00154         }
    00155
    00156         void release_front() {
    00157             __TBB_ASSERT(my_reserved, "Attempt to release a non-reserved item");
    00158             validate_front();
    00159             my_reserved = false;
    00160         }
    00161
    00162         bool my_reserved;
    00163     };
    00164
    00165 #endif // __TBB_item_buffer_H

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