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/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef SkDescriptor_DEFINED
#define SkDescriptor_DEFINED
#include "SkTypes.h"
class SkDescriptor : SkNoncopyable {
public:
static size_t ComputeOverhead(int entryCount)
{
SkASSERT(entryCount >= 0);
return sizeof(SkDescriptor) + entryCount * sizeof(Entry);
}
static SkDescriptor* Alloc(size_t length)
{
SkASSERT(SkAlign4(length) == length);
SkDescriptor* desc = (SkDescriptor*)sk_malloc_throw(length);
return desc;
}
static void Free(SkDescriptor* desc)
{
sk_free(desc);
}
void init()
{
fLength = sizeof(SkDescriptor);
fCount = 0;
}
uint32_t getLength() const { return fLength; }
void* addEntry(uint32_t tag, uint32_t length, const void* data = NULL)
{
SkASSERT(tag);
SkASSERT(SkAlign4(length) == length);
SkASSERT(this->findEntry(tag, NULL) == NULL);
Entry* entry = (Entry*)((char*)this + fLength);
entry->fTag = tag;
entry->fLen = length;
if (data)
memcpy(entry + 1, data, length);
fCount += 1;
fLength += sizeof(Entry) + length;
return (entry + 1); // return its data
}
void computeChecksum()
{
fChecksum = SkDescriptor::ComputeChecksum(this);
}
#ifdef SK_DEBUG
void assertChecksum() const
{
SkASSERT(fChecksum == SkDescriptor::ComputeChecksum(this));
}
#endif
const void* findEntry(uint32_t tag, uint32_t* length) const
{
const Entry* entry = (const Entry*)(this + 1);
int count = fCount;
while (--count >= 0)
{
if (entry->fTag == tag)
{
if (length)
*length = entry->fLen;
return entry + 1;
}
entry = (const Entry*)((const char*)(entry + 1) + entry->fLen);
}
return NULL;
}
SkDescriptor* copy() const
{
SkDescriptor* desc = SkDescriptor::Alloc(fLength);
memcpy(desc, this, fLength);
return desc;
}
bool equals(const SkDescriptor& other) const
{
// probe to see if we have a good checksum algo
// SkASSERT(a.fChecksum != b.fChecksum || memcmp(&a, &b, a.fLength) == 0);
// the first value we should look at is the checksum, so this loop
// should terminate early if they descriptors are different.
// NOTE: if we wrote a sentinel value at the end of each, we chould
// remove the aa < stop test in the loop...
const uint32_t* aa = (const uint32_t*)this;
const uint32_t* bb = (const uint32_t*)&other;
const uint32_t* stop = (const uint32_t*)((const char*)aa + fLength);
do {
if (*aa++ != *bb++)
return false;
} while (aa < stop);
return true;
}
uint32_t getChecksum() const { return fChecksum; }
struct Entry {
uint32_t fTag;
uint32_t fLen;
};
#ifdef SK_DEBUG
uint32_t getCount() const { return fCount; }
#endif
private:
uint32_t fChecksum; // must be first
uint32_t fLength; // must be second
uint32_t fCount;
static uint32_t ComputeChecksum(const SkDescriptor* desc)
{
const uint32_t* ptr = (const uint32_t*)desc + 1; // skip the checksum field
const uint32_t* stop = (const uint32_t*)((const char*)desc + desc->fLength);
uint32_t sum = 0;
SkASSERT(ptr < stop);
do {
sum = (sum << 1) | (sum >> 31);
sum ^= *ptr++;
} while (ptr < stop);
return sum;
}
// private so no one can create one except our factories
SkDescriptor() {}
};
#include "SkScalerContext.h"
class SkAutoDescriptor : SkNoncopyable {
public:
SkAutoDescriptor(size_t size)
{
if (size <= sizeof(fStorage))
fDesc = (SkDescriptor*)(void*)fStorage;
else
fDesc = SkDescriptor::Alloc(size);
}
~SkAutoDescriptor()
{
if (fDesc != (SkDescriptor*)(void*)fStorage)
SkDescriptor::Free(fDesc);
}
SkDescriptor* getDesc() const { return fDesc; }
private:
enum {
kStorageSize = sizeof(SkDescriptor)
+ sizeof(SkDescriptor::Entry) + sizeof(SkScalerContext::Rec) // for rec
+ sizeof(SkDescriptor::Entry) + sizeof(void*) // for typeface
+ 32 // slop for occational small extras
};
SkDescriptor* fDesc;
uint32_t fStorage[(kStorageSize + 3) >> 2];
};
#endif
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