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37 :
38 : #ifndef nsSegmentedBuffer_h__
39 : #define nsSegmentedBuffer_h__
40 :
41 : #include "nsMemory.h"
42 : #include "prclist.h"
43 :
44 : class nsSegmentedBuffer
45 : {
46 : public:
47 26452 : nsSegmentedBuffer()
48 : : mSegmentSize(0), mMaxSize(0),
49 : mSegAllocator(nsnull), mSegmentArray(nsnull),
50 : mSegmentArrayCount(0),
51 26452 : mFirstSegmentIndex(0), mLastSegmentIndex(0) {}
52 :
53 26437 : ~nsSegmentedBuffer() {
54 26437 : Empty();
55 26437 : NS_IF_RELEASE(mSegAllocator);
56 26437 : }
57 :
58 :
59 : nsresult Init(PRUint32 segmentSize, PRUint32 maxSize,
60 : nsIMemory* allocator = nsnull);
61 :
62 : char* AppendNewSegment(); // pushes at end
63 :
64 : // returns true if no more segments remain:
65 : bool DeleteFirstSegment(); // pops from beginning
66 :
67 : // returns true if no more segments remain:
68 : bool DeleteLastSegment(); // pops from beginning
69 :
70 : // Call Realloc() on last segment. This is used to reduce memory
71 : // consumption when data is not an exact multiple of segment size.
72 : bool ReallocLastSegment(size_t newSize);
73 :
74 : void Empty(); // frees all segments
75 :
76 7591639 : inline PRUint32 GetSegmentCount() {
77 7591639 : if (mFirstSegmentIndex <= mLastSegmentIndex)
78 7591282 : return mLastSegmentIndex - mFirstSegmentIndex;
79 : else
80 357 : return mSegmentArrayCount + mLastSegmentIndex - mFirstSegmentIndex;
81 : }
82 :
83 40112 : inline PRUint32 GetSegmentSize() { return mSegmentSize; }
84 1148 : inline PRUint32 GetMaxSize() { return mMaxSize; }
85 3684177 : inline PRUint32 GetSize() { return GetSegmentCount() * mSegmentSize; }
86 :
87 3694576 : inline char* GetSegment(PRUint32 indx) {
88 3694576 : NS_ASSERTION(indx < GetSegmentCount(), "index out of bounds");
89 3694576 : PRInt32 i = ModSegArraySize(mFirstSegmentIndex + (PRInt32)indx);
90 3694576 : return mSegmentArray[i];
91 : }
92 :
93 : protected:
94 11071095 : inline PRInt32 ModSegArraySize(PRInt32 n) {
95 11071095 : PRUint32 result = n & (mSegmentArrayCount - 1);
96 11071095 : NS_ASSERTION(result == n % mSegmentArrayCount,
97 : "non-power-of-2 mSegmentArrayCount");
98 11071095 : return result;
99 : }
100 :
101 3682998 : inline bool IsFull() {
102 3682998 : return ModSegArraySize(mLastSegmentIndex + 1) == mFirstSegmentIndex;
103 : }
104 :
105 : protected:
106 : PRUint32 mSegmentSize;
107 : PRUint32 mMaxSize;
108 : nsIMemory* mSegAllocator;
109 : char** mSegmentArray;
110 : PRUint32 mSegmentArrayCount;
111 : PRInt32 mFirstSegmentIndex;
112 : PRInt32 mLastSegmentIndex;
113 : };
114 :
115 : // NS_SEGMENTARRAY_INITIAL_SIZE: This number needs to start out as a
116 : // power of 2 given how it gets used. We double the segment array
117 : // when we overflow it, and use that fact that it's a power of 2
118 : // to compute a fast modulus operation in IsFull.
119 : //
120 : // 32 segment array entries can accommodate 128k of data if segments
121 : // are 4k in size. That seems like a reasonable amount that will avoid
122 : // needing to grow the segment array.
123 : #define NS_SEGMENTARRAY_INITIAL_COUNT 32
124 :
125 : #endif // nsSegmentedBuffer_h__
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