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      1 
      2 /*
      3  * Copyright 2006 The Android Open Source Project
      4  *
      5  * Use of this source code is governed by a BSD-style license that can be
      6  * found in the LICENSE file.
      7  */
      8 
      9 
     10 #ifndef SkRegionPriv_DEFINED
     11 #define SkRegionPriv_DEFINED
     12 
     13 #include "SkRegion.h"
     14 #include "SkThread.h"
     15 
     16 #define assert_sentinel(value, isSentinel) \
     17     SkASSERT(((value) == SkRegion::kRunTypeSentinel) == isSentinel)
     18 
     19 //SkDEBUGCODE(extern int32_t gRgnAllocCounter;)
     20 
     21 #ifdef SK_DEBUG
     22 // Given the first interval (just past the interval-count), compute the
     23 // interval count, by search for the x-sentinel
     24 //
     25 static int compute_intervalcount(const SkRegion::RunType runs[]) {
     26     const SkRegion::RunType* curr = runs;
     27     while (*curr < SkRegion::kRunTypeSentinel) {
     28         SkASSERT(curr[0] < curr[1]);
     29         SkASSERT(curr[1] < SkRegion::kRunTypeSentinel);
     30         curr += 2;
     31     }
     32     return SkToInt((curr - runs) >> 1);
     33 }
     34 #endif
     35 
     36 struct SkRegion::RunHead {
     37 private:
     38 
     39 public:
     40     int32_t fRefCnt;
     41     int32_t fRunCount;
     42 
     43     /**
     44      *  Number of spans with different Y values. This does not count the initial
     45      *  Top value, nor does it count the final Y-Sentinel value. In the logical
     46      *  case of a rectangle, this would return 1, and an empty region would
     47      *  return 0.
     48      */
     49     int getYSpanCount() const {
     50         return fYSpanCount;
     51     }
     52 
     53     /**
     54      *  Number of intervals in the entire region. This equals the number of
     55      *  rects that would be returned by the Iterator. In the logical case of
     56      *  a rect, this would return 1, and an empty region would return 0.
     57      */
     58     int getIntervalCount() const {
     59         return fIntervalCount;
     60     }
     61 
     62     static RunHead* Alloc(int count) {
     63         //SkDEBUGCODE(sk_atomic_inc(&gRgnAllocCounter);)
     64         //SkDEBUGF(("************** gRgnAllocCounter::alloc %d\n", gRgnAllocCounter));
     65 
     66         SkASSERT(count >= SkRegion::kRectRegionRuns);
     67 
     68         RunHead* head = (RunHead*)sk_malloc_throw(sizeof(RunHead) + count * sizeof(RunType));
     69         head->fRefCnt = 1;
     70         head->fRunCount = count;
     71         // these must be filled in later, otherwise we will be invalid
     72         head->fYSpanCount = 0;
     73         head->fIntervalCount = 0;
     74         return head;
     75     }
     76 
     77     static RunHead* Alloc(int count, int yspancount, int intervalCount) {
     78         SkASSERT(yspancount > 0);
     79         SkASSERT(intervalCount > 1);
     80 
     81         RunHead* head = Alloc(count);
     82         head->fYSpanCount = yspancount;
     83         head->fIntervalCount = intervalCount;
     84         return head;
     85     }
     86 
     87     SkRegion::RunType* writable_runs() {
     88         SkASSERT(fRefCnt == 1);
     89         return (SkRegion::RunType*)(this + 1);
     90     }
     91 
     92     const SkRegion::RunType* readonly_runs() const {
     93         return (const SkRegion::RunType*)(this + 1);
     94     }
     95 
     96     RunHead* ensureWritable() {
     97         RunHead* writable = this;
     98         if (fRefCnt > 1) {
     99             // We need to alloc & copy the current region before we call
    100             // sk_atomic_dec because it could be freed in the meantime,
    101             // otherwise.
    102             writable = Alloc(fRunCount, fYSpanCount, fIntervalCount);
    103             memcpy(writable->writable_runs(), this->readonly_runs(),
    104                    fRunCount * sizeof(RunType));
    105 
    106             // fRefCount might have changed since we last checked.
    107             // If we own the last reference at this point, we need to
    108             // free the memory.
    109             if (sk_atomic_dec(&fRefCnt) == 1) {
    110                 sk_free(this);
    111             }
    112         }
    113         return writable;
    114     }
    115 
    116     /**
    117      *  Given a scanline (including its Bottom value at runs[0]), return the next
    118      *  scanline. Asserts that there is one (i.e. runs[0] < Sentinel)
    119      */
    120     static SkRegion::RunType* SkipEntireScanline(const SkRegion::RunType runs[]) {
    121         // we are not the Y Sentinel
    122         SkASSERT(runs[0] < SkRegion::kRunTypeSentinel);
    123 
    124         const int intervals = runs[1];
    125         SkASSERT(runs[2 + intervals * 2] == SkRegion::kRunTypeSentinel);
    126 #ifdef SK_DEBUG
    127         {
    128             int n = compute_intervalcount(&runs[2]);
    129             SkASSERT(n == intervals);
    130         }
    131 #endif
    132 
    133         // skip the entire line [B N [L R] S]
    134         runs += 1 + 1 + intervals * 2 + 1;
    135         return const_cast<SkRegion::RunType*>(runs);
    136     }
    137 
    138 
    139     /**
    140      *  Return the scanline that contains the Y value. This requires that the Y
    141      *  value is already known to be contained within the bounds of the region,
    142      *  and so this routine never returns NULL.
    143      *
    144      *  It returns the beginning of the scanline, starting with its Bottom value.
    145      */
    146     SkRegion::RunType* findScanline(int y) const {
    147         const RunType* runs = this->readonly_runs();
    148 
    149         // if the top-check fails, we didn't do a quick check on the bounds
    150         SkASSERT(y >= runs[0]);
    151 
    152         runs += 1;  // skip top-Y
    153         for (;;) {
    154             int bottom = runs[0];
    155             // If we hit this, we've walked off the region, and our bounds check
    156             // failed.
    157             SkASSERT(bottom < SkRegion::kRunTypeSentinel);
    158             if (y < bottom) {
    159                 break;
    160             }
    161             runs = SkipEntireScanline(runs);
    162         }
    163         return const_cast<SkRegion::RunType*>(runs);
    164     }
    165 
    166     // Copy src runs into us, computing interval counts and bounds along the way
    167     void computeRunBounds(SkIRect* bounds) {
    168         RunType* runs = this->writable_runs();
    169         bounds->fTop = *runs++;
    170 
    171         int bot;
    172         int ySpanCount = 0;
    173         int intervalCount = 0;
    174         int left = SK_MaxS32;
    175         int rite = SK_MinS32;
    176 
    177         do {
    178             bot = *runs++;
    179             SkASSERT(bot < SkRegion::kRunTypeSentinel);
    180             ySpanCount += 1;
    181 
    182             const int intervals = *runs++;
    183             SkASSERT(intervals >= 0);
    184             SkASSERT(intervals < SkRegion::kRunTypeSentinel);
    185 
    186             if (intervals > 0) {
    187 #ifdef SK_DEBUG
    188                 {
    189                     int n = compute_intervalcount(runs);
    190                     SkASSERT(n == intervals);
    191                 }
    192 #endif
    193                 RunType L = runs[0];
    194                 SkASSERT(L < SkRegion::kRunTypeSentinel);
    195                 if (left > L) {
    196                     left = L;
    197                 }
    198 
    199                 runs += intervals * 2;
    200                 RunType R = runs[-1];
    201                 SkASSERT(R < SkRegion::kRunTypeSentinel);
    202                 if (rite < R) {
    203                     rite = R;
    204                 }
    205 
    206                 intervalCount += intervals;
    207             }
    208             SkASSERT(SkRegion::kRunTypeSentinel == *runs);
    209             runs += 1;  // skip x-sentinel
    210 
    211             // test Y-sentinel
    212         } while (SkRegion::kRunTypeSentinel > *runs);
    213 
    214 #ifdef SK_DEBUG
    215         // +1 to skip the last Y-sentinel
    216         int runCount = SkToInt(runs - this->writable_runs() + 1);
    217         SkASSERT(runCount == fRunCount);
    218 #endif
    219 
    220         fYSpanCount = ySpanCount;
    221         fIntervalCount = intervalCount;
    222 
    223         bounds->fLeft = left;
    224         bounds->fRight = rite;
    225         bounds->fBottom = bot;
    226     }
    227 
    228 private:
    229     int32_t fYSpanCount;
    230     int32_t fIntervalCount;
    231 };
    232 
    233 #endif
    234