michael@0: 
michael@0: /*
michael@0:  * Copyright 2006 The Android Open Source Project
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: 
michael@0: #ifndef SkDescriptor_DEFINED
michael@0: #define SkDescriptor_DEFINED
michael@0: 
michael@0: #include "SkChecksum.h"
michael@0: #include "SkTypes.h"
michael@0: 
michael@0: class SkDescriptor : SkNoncopyable {
michael@0: public:
michael@0:     static size_t ComputeOverhead(int entryCount) {
michael@0:         SkASSERT(entryCount >= 0);
michael@0:         return sizeof(SkDescriptor) + entryCount * sizeof(Entry);
michael@0:     }
michael@0: 
michael@0:     static SkDescriptor* Alloc(size_t length) {
michael@0:         SkASSERT(SkAlign4(length) == length);
michael@0:         SkDescriptor* desc = (SkDescriptor*)sk_malloc_throw(length);
michael@0:         return desc;
michael@0:     }
michael@0: 
michael@0:     static void Free(SkDescriptor* desc) {
michael@0:         sk_free(desc);
michael@0:     }
michael@0: 
michael@0:     void init() {
michael@0:         fLength = sizeof(SkDescriptor);
michael@0:         fCount  = 0;
michael@0:     }
michael@0: 
michael@0:     uint32_t getLength() const { return fLength; }
michael@0: 
michael@0:     void* addEntry(uint32_t tag, uint32_t length, const void* data = NULL) {
michael@0:         SkASSERT(tag);
michael@0:         SkASSERT(SkAlign4(length) == length);
michael@0:         SkASSERT(this->findEntry(tag, NULL) == NULL);
michael@0: 
michael@0:         Entry*  entry = (Entry*)((char*)this + fLength);
michael@0:         entry->fTag = tag;
michael@0:         entry->fLen = length;
michael@0:         if (data) {
michael@0:             memcpy(entry + 1, data, length);
michael@0:         }
michael@0: 
michael@0:         fCount += 1;
michael@0:         fLength += sizeof(Entry) + length;
michael@0:         return (entry + 1); // return its data
michael@0:     }
michael@0: 
michael@0:     void computeChecksum() {
michael@0:         fChecksum = SkDescriptor::ComputeChecksum(this);
michael@0:     }
michael@0: 
michael@0: #ifdef SK_DEBUG
michael@0:     void assertChecksum() const {
michael@0:         SkASSERT(SkDescriptor::ComputeChecksum(this) == fChecksum);
michael@0:     }
michael@0: #endif
michael@0: 
michael@0:     const void* findEntry(uint32_t tag, uint32_t* length) const {
michael@0:         const Entry* entry = (const Entry*)(this + 1);
michael@0:         int          count = fCount;
michael@0: 
michael@0:         while (--count >= 0) {
michael@0:             if (entry->fTag == tag) {
michael@0:                 if (length) {
michael@0:                     *length = entry->fLen;
michael@0:                 }
michael@0:                 return entry + 1;
michael@0:             }
michael@0:             entry = (const Entry*)((const char*)(entry + 1) + entry->fLen);
michael@0:         }
michael@0:         return NULL;
michael@0:     }
michael@0: 
michael@0:     SkDescriptor* copy() const {
michael@0:         SkDescriptor* desc = SkDescriptor::Alloc(fLength);
michael@0:         memcpy(desc, this, fLength);
michael@0:         return desc;
michael@0:     }
michael@0: 
michael@0:     bool equals(const SkDescriptor& other) const {
michael@0:         // probe to see if we have a good checksum algo
michael@0: //        SkASSERT(a.fChecksum != b.fChecksum || memcmp(&a, &b, a.fLength) == 0);
michael@0: 
michael@0:         // the first value we should look at is the checksum, so this loop
michael@0:         // should terminate early if they descriptors are different.
michael@0:         // NOTE: if we wrote a sentinel value at the end of each, we chould
michael@0:         //       remove the aa < stop test in the loop...
michael@0:         const uint32_t* aa = (const uint32_t*)this;
michael@0:         const uint32_t* bb = (const uint32_t*)&other;
michael@0:         const uint32_t* stop = (const uint32_t*)((const char*)aa + fLength);
michael@0:         do {
michael@0:             if (*aa++ != *bb++)
michael@0:                 return false;
michael@0:         } while (aa < stop);
michael@0:         return true;
michael@0:     }
michael@0: 
michael@0:     uint32_t getChecksum() const { return fChecksum; }
michael@0: 
michael@0:     struct Entry {
michael@0:         uint32_t fTag;
michael@0:         uint32_t fLen;
michael@0:     };
michael@0: 
michael@0: #ifdef SK_DEBUG
michael@0:     uint32_t getCount() const { return fCount; }
michael@0: #endif
michael@0: 
michael@0: private:
michael@0:     uint32_t fChecksum;  // must be first
michael@0:     uint32_t fLength;    // must be second
michael@0:     uint32_t fCount;
michael@0: 
michael@0:     static uint32_t ComputeChecksum(const SkDescriptor* desc) {
michael@0:         const uint32_t* ptr = (const uint32_t*)desc + 1; // skip the checksum field
michael@0:         size_t len = desc->fLength - sizeof(uint32_t);
michael@0:         return SkChecksum::Compute(ptr, len);
michael@0:     }
michael@0: 
michael@0:     // private so no one can create one except our factories
michael@0:     SkDescriptor() {}
michael@0: };
michael@0: 
michael@0: #include "SkScalerContext.h"
michael@0: 
michael@0: class SkAutoDescriptor : SkNoncopyable {
michael@0: public:
michael@0:     SkAutoDescriptor(size_t size) {
michael@0:         if (size <= sizeof(fStorage)) {
michael@0:             fDesc = (SkDescriptor*)(void*)fStorage;
michael@0:         } else {
michael@0:             fDesc = SkDescriptor::Alloc(size);
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     ~SkAutoDescriptor() {
michael@0:         if (fDesc != (SkDescriptor*)(void*)fStorage) {
michael@0:             SkDescriptor::Free(fDesc);
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     SkDescriptor* getDesc() const { return fDesc; }
michael@0: private:
michael@0:     enum {
michael@0:         kStorageSize =  sizeof(SkDescriptor)
michael@0:                         + sizeof(SkDescriptor::Entry) + sizeof(SkScalerContext::Rec)    // for rec
michael@0:                         + sizeof(SkDescriptor::Entry) + sizeof(void*)                   // for typeface
michael@0:                         + 32   // slop for occational small extras
michael@0:     };
michael@0:     SkDescriptor*   fDesc;
michael@0:     uint32_t        fStorage[(kStorageSize + 3) >> 2];
michael@0: };
michael@0: #define SkAutoDescriptor(...) SK_REQUIRE_LOCAL_VAR(SkAutoDescriptor)
michael@0: 
michael@0: 
michael@0: #endif