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      1 /*
      2  * Copyright 2014 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef GrProgramDesc_DEFINED
      9 #define GrProgramDesc_DEFINED
     10 
     11 #include "GrColor.h"
     12 #include "GrTypesPriv.h"
     13 #include "SkChecksum.h"
     14 
     15 /** This class describes a program to generate. It also serves as a program cache key. Very little
     16     of this is GL-specific. The GL-specific parts could be factored out into a subclass. */
     17 class GrProgramDesc {
     18 public:
     19     // Creates an uninitialized key that must be populated by GrGpu::buildProgramDesc()
     20     GrProgramDesc() {}
     21 
     22     // Returns this as a uint32_t array to be used as a key in the program cache.
     23     const uint32_t* asKey() const {
     24         return reinterpret_cast<const uint32_t*>(fKey.begin());
     25     }
     26 
     27     // Gets the number of bytes in asKey(). It will be a 4-byte aligned value. When comparing two
     28     // keys the size of either key can be used with memcmp() since the lengths themselves begin the
     29     // keys and thus the memcmp will exit early if the keys are of different lengths.
     30     uint32_t keyLength() const { return *this->atOffset<uint32_t, kLengthOffset>(); }
     31 
     32     // Gets the a checksum of the key. Can be used as a hash value for a fast lookup in a cache.
     33     uint32_t getChecksum() const { return *this->atOffset<uint32_t, kChecksumOffset>(); }
     34 
     35     GrProgramDesc& operator= (const GrProgramDesc& other) {
     36         uint32_t keyLength = other.keyLength();
     37         fKey.reset(SkToInt(keyLength));
     38         memcpy(fKey.begin(), other.fKey.begin(), keyLength);
     39         return *this;
     40     }
     41 
     42     bool operator== (const GrProgramDesc& other) const {
     43         // The length is masked as a hint to the compiler that the address will be 4 byte aligned.
     44         return 0 == memcmp(this->asKey(), other.asKey(), this->keyLength() & ~0x3);
     45     }
     46 
     47     bool operator!= (const GrProgramDesc& other) const {
     48         return !(*this == other);
     49     }
     50 
     51     static bool Less(const GrProgramDesc& a, const GrProgramDesc& b) {
     52         return memcmp(a.asKey(), b.asKey(), a.keyLength() & ~0x3) < 0;
     53     }
     54 
     55     struct KeyHeader {
     56         uint8_t                     fFragPosKey;   // set by GrGLShaderBuilder if there are
     57                                                    // effects that read the fragment position.
     58                                                    // Otherwise, 0.
     59         uint8_t                     fSnapVerticesToPixelCenters;
     60         int8_t                      fColorEffectCnt;
     61         int8_t                      fCoverageEffectCnt;
     62     };
     63     GR_STATIC_ASSERT(sizeof(KeyHeader) == 4);
     64 
     65     int numColorEffects() const {
     66         return this->header().fColorEffectCnt;
     67     }
     68 
     69     int numCoverageEffects() const {
     70         return this->header().fCoverageEffectCnt;
     71     }
     72 
     73     int numTotalEffects() const { return this->numColorEffects() + this->numCoverageEffects(); }
     74 
     75     // This should really only be used internally, base classes should return their own headers
     76     const KeyHeader& header() const { return *this->atOffset<KeyHeader, kHeaderOffset>(); }
     77 
     78 protected:
     79     template<typename T, size_t OFFSET> T* atOffset() {
     80         return reinterpret_cast<T*>(reinterpret_cast<intptr_t>(fKey.begin()) + OFFSET);
     81     }
     82 
     83     template<typename T, size_t OFFSET> const T* atOffset() const {
     84         return reinterpret_cast<const T*>(reinterpret_cast<intptr_t>(fKey.begin()) + OFFSET);
     85     }
     86 
     87     void finalize() {
     88         int keyLength = fKey.count();
     89         SkASSERT(0 == (keyLength % 4));
     90         *(this->atOffset<uint32_t, GrProgramDesc::kLengthOffset>()) = SkToU32(keyLength);
     91 
     92         uint32_t* checksum = this->atOffset<uint32_t, GrProgramDesc::kChecksumOffset>();
     93         *checksum = 0;
     94         *checksum = SkChecksum::Compute(reinterpret_cast<uint32_t*>(fKey.begin()), keyLength);
     95     }
     96 
     97     // The key, stored in fKey, is composed of four parts:
     98     // 1. uint32_t for total key length.
     99     // 2. uint32_t for a checksum.
    100     // 3. Header struct defined above.  Also room for extensions to the header
    101     // 4. A Backend specific payload.  Room is preallocated for this
    102     enum KeyOffsets {
    103         // Part 1.
    104         kLengthOffset = 0,
    105         // Part 2.
    106         kChecksumOffset = kLengthOffset + sizeof(uint32_t),
    107         // Part 3.
    108         kHeaderOffset = kChecksumOffset + sizeof(uint32_t),
    109         kHeaderSize = SkAlign4(2 * sizeof(KeyHeader)),
    110     };
    111 
    112     enum {
    113         kMaxPreallocProcessors = 8,
    114         kIntsPerProcessor      = 4,    // This is an overestimate of the average effect key size.
    115         kPreAllocSize = kHeaderOffset + kHeaderSize +
    116                         kMaxPreallocProcessors * sizeof(uint32_t) * kIntsPerProcessor,
    117     };
    118 
    119     SkSTArray<kPreAllocSize, uint8_t, true>& key() { return fKey; }
    120     const SkSTArray<kPreAllocSize, uint8_t, true>& key() const { return fKey; }
    121 
    122 private:
    123     SkSTArray<kPreAllocSize, uint8_t, true> fKey;
    124 };
    125 
    126 #endif
    127