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* Copyright 2022 Google LLC
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkPaintParamsKey_DEFINED
#define SkPaintParamsKey_DEFINED
#include <array>
#include <limits>
#include "include/core/SkTypes.h"
// TODO: this needs to be expanded into a more flexible dictionary (esp. for user-supplied SkSL)
// TODO: should this enum actually be in ShaderCodeDictionary.h?
enum class CodeSnippetID : uint8_t {
// TODO: It seems like this requires some refinement. Fundamentally this doesn't seem like a
// draw that originated from a PaintParams.
// SkShader code snippets
// BlendMode code snippets
kLast = kSimpleBlendMode
static constexpr int kCodeSnippetIDCount = static_cast<int>(CodeSnippetID::kLast) + 1;
// This class is a compact representation of the shader needed to implement a given
// PaintParams. Its structure is a series of blocks where each block has a
// header that consists of 2-bytes - a 1-byte code-snippet ID and a 1-byte number-of-bytes-in-the-
// block field. The rest of the data in the block is dependent on the individual code snippet.
class SkPaintParamsKey {
// Block headers have the following structure:
// 1st byte: codeSnippetID
// 2nd byte: total blockSize in bytes
// Returns the header's offset in the key - to be passed back into endBlock
int beginBlock(CodeSnippetID codeSnippetID) {
SkASSERT(fNumBytes < kMaxKeySize);
this->addByte((uint8_t) codeSnippetID);
this->addByte(0); // this needs to be patched up with a call to endBlock
return fNumBytes - 2;
// Update the size byte of a block header
void endBlock(int headerOffset, CodeSnippetID codeSnippetID) {
SkASSERT(fData[headerOffset] == (uint32_t) codeSnippetID);
int blockSize = fNumBytes - headerOffset;
SkASSERT(blockSize <= kMaxBlockSize);
fData[headerOffset+1] = blockSize;
std::pair<CodeSnippetID, uint8_t> readCodeSnippetID(int headerOffset) const {
SkASSERT(headerOffset < kMaxKeySize - 2);
CodeSnippetID id = static_cast<CodeSnippetID>(fData[headerOffset]);
uint8_t blockSize = fData[headerOffset+1];
SkASSERT(headerOffset + blockSize <= this->sizeInBytes());
return { id, blockSize };
void addByte(uint8_t byte) {
SkASSERT(fNumBytes < kMaxKeySize);
fData[fNumBytes++] = byte;
#ifdef SK_DEBUG
void dump() const;
uint8_t byte(int offset) const { SkASSERT(offset < fNumBytes); return fData[offset]; }
const void* data() const { return; }
int sizeInBytes() const { return fNumBytes; }
bool operator==(const SkPaintParamsKey& that) const;
bool operator!=(const SkPaintParamsKey& that) const { return !(*this == that); }
// TODO: need to make it so the key can can dynamically grow
static const int kMaxKeySize = 32;
static const int kMaxBlockSize = std::numeric_limits<uint8_t>::max();
int fNumBytes = 0;
std::array<uint8_t, kMaxKeySize> fData;
#endif // SkPaintParamsKey_DEFINED