| /* |
| * Copyright 2016 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #ifndef SkRasterPipeline_DEFINED |
| #define SkRasterPipeline_DEFINED |
| |
| #include "SkNx.h" |
| #include "SkTArray.h" |
| #include "SkTypes.h" |
| |
| /** |
| * SkRasterPipeline provides a cheap way to chain together a pixel processing pipeline. |
| * |
| * It's particularly designed for situations where the potential pipeline is extremely |
| * combinatoric: {N dst formats} x {M source formats} x {K mask formats} x {C transfer modes} ... |
| * No one wants to write specialized routines for all those combinations, and if we did, we'd |
| * end up bloating our code size dramatically. SkRasterPipeline stages can be chained together |
| * at runtime, so we can scale this problem linearly rather than combinatorically. |
| * |
| * Each stage is represented by a function conforming to a common interface, SkRasterPipeline::Fn, |
| * and by an arbitrary context pointer. Fn's arguments, and sometimes custom calling convention, |
| * are designed to maximize the amount of data we can pass along the pipeline cheaply. |
| * On many machines all arguments stay in registers the entire time. |
| * |
| * The meaning of the arguments to Fn are sometimes fixed... |
| * - The Stage* always represents the current stage, mainly providing access to ctx(). |
| * - The size_t is always the destination x coordinate. If you need y, put it in your context. |
| * - By the time the shader's done, the first four vectors should hold source red, |
| * green, blue, and alpha, up to 4 pixels' worth each. |
| * |
| * ...and sometimes flexible: |
| * - In the shader, the first four vectors can be used for anything, e.g. sample coordinates. |
| * - The last four vectors are scratch registers that can be used to communicate between |
| * stages; transfer modes use these to hold the original destination pixel components. |
| * |
| * On some platforms the last four vectors are slower to work with than the other arguments. |
| * |
| * When done mutating its arguments and/or context, a stage can either: |
| * 1) call st->next() with its mutated arguments, chaining to the next stage of the pipeline; or |
| * 2) return, indicating the pipeline is complete for these pixels. |
| * |
| * Some obvious stages that typically return are those that write a color to a destination pointer, |
| * but any stage can short-circuit the rest of the pipeline by returning instead of calling next(). |
| */ |
| |
| class SkRasterPipeline { |
| public: |
| struct Stage; |
| using Fn = void(SK_VECTORCALL *)(Stage*, size_t, Sk4f,Sk4f,Sk4f,Sk4f, |
| Sk4f,Sk4f,Sk4f,Sk4f); |
| struct Stage { |
| template <typename T> |
| T ctx() { return static_cast<T>(fCtx); } |
| |
| void SK_VECTORCALL next(size_t x, Sk4f v0, Sk4f v1, Sk4f v2, Sk4f v3, |
| Sk4f v4, Sk4f v5, Sk4f v6, Sk4f v7) { |
| // Stages are logically a pipeline, and physically are contiguous in an array. |
| // To get to the next stage, we just increment our pointer to the next array element. |
| fNext(this+1, x, v0,v1,v2,v3, v4,v5,v6,v7); |
| } |
| |
| // It makes next() a good bit cheaper if we hold the next function to call here, |
| // rather than logically simpler choice of the function implementing this stage. |
| Fn fNext; |
| void* fCtx; |
| }; |
| |
| |
| SkRasterPipeline(); |
| |
| // Run the pipeline constructed with append(), walking x through [0,n), |
| // generally in 4 pixel steps, but sometimes 1 pixel at a time. |
| void run(size_t n); |
| |
| // Use this append() if your stage is sensitive to the number of pixels you're working with: |
| // - body will always be called for a full 4 pixels |
| // - tail will always be called for a single pixel |
| // Typically this is only an essential distintion for stages that read or write memory. |
| void append(Fn body, const void* body_ctx, |
| Fn tail, const void* tail_ctx); |
| |
| // Most stages don't actually care if they're working on 4 or 1 pixel. |
| void append(Fn fn, const void* ctx = nullptr) { |
| this->append(fn, ctx, fn, ctx); |
| } |
| |
| // Most 4 pixel or 1 pixel variants share the same context pointer. |
| void append(Fn body, Fn tail, const void* ctx = nullptr) { |
| this->append(body, ctx, tail, ctx); |
| } |
| |
| private: |
| using Stages = SkSTArray<10, Stage, /*MEM_COPY=*/true>; |
| |
| // This no-op default makes fBodyStart and fTailStart unconditionally safe to call, |
| // and is always the last stage's fNext as a sort of safety net to make sure even a |
| // buggy pipeline can't walk off its own end. |
| static void SK_VECTORCALL JustReturn(Stage*, size_t, Sk4f,Sk4f,Sk4f,Sk4f, |
| Sk4f,Sk4f,Sk4f,Sk4f); |
| |
| Stages fBody, |
| fTail; |
| Fn fBodyStart = &JustReturn, |
| fTailStart = &JustReturn; |
| }; |
| |
| #endif//SkRasterPipeline_DEFINED |