SkVertices.cpp

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/*
 * Copyright 2017 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
#include "include/core/SkVertices.h"
 
#include "include/core/SkTypes.h"
#include "include/private/base/SkMalloc.h"
#include "include/private/base/SkTo.h"
#include "src/base/SkSafeMath.h"
#include "src/core/SkPicturePriv.h"
#include "src/core/SkReadBuffer.h"
#include "src/core/SkSafeRange.h"
#include "src/core/SkVerticesPriv.h"
#include "src/core/SkWriteBuffer.h"
 
#include <atomic>
#include <new>
#include <utility>
 
static uint32_t next_id() {
    static std::atomic<uint32_t> nextID{1};
 
    uint32_t id;
    do {
        id = nextID.fetch_add(1, std::memory_order_relaxed);
    } while (id == SK_InvalidGenID);
    return id;
}
 
struct SkVertices::Desc {
    VertexMode  fMode;
    int         fVertexCount,
                fIndexCount;
    bool        fHasTexs,
                fHasColors;
};
 
struct SkVertices::Sizes {
    Sizes(const Desc& desc) {
        SkSafeMath safe;
 
        fVSize = safe.mul(desc.fVertexCount, sizeof(SkPoint));
        fTSize = desc.fHasTexs ? safe.mul(desc.fVertexCount, sizeof(SkPoint)) : 0;
        fCSize = desc.fHasColors ? safe.mul(desc.fVertexCount, sizeof(SkColor)) : 0;
 
        fBuilderTriFanISize = 0;
        fISize = safe.mul(desc.fIndexCount, sizeof(uint16_t));
        if (kTriangleFan_VertexMode == desc.fMode) {
            int numFanTris = 0;
            if (desc.fIndexCount) {
                fBuilderTriFanISize = fISize;
                numFanTris = desc.fIndexCount - 2;
            } else {
                numFanTris = desc.fVertexCount - 2;
                // By forcing this to become indexed we are adding a constraint to the maximum
                // number of vertices.
                if (desc.fVertexCount > (SkTo<int>(UINT16_MAX) + 1)) {
                    sk_bzero(this, sizeof(*this));
                    return;
                }
            }
            if (numFanTris <= 0) {
                sk_bzero(this, sizeof(*this));
                return;
            }
            fISize = safe.mul(numFanTris, 3 * sizeof(uint16_t));
        }
 
        fTotal = safe.add(sizeof(SkVertices),
                 safe.add(fVSize,
                 safe.add(fTSize,
                 safe.add(fCSize,
                          fISize))));
 
        if (safe.ok()) {
            fArrays = fVSize + fTSize + fCSize + fISize;  // just the sum of the arrays
        } else {
            sk_bzero(this, sizeof(*this));
        }
    }
 
    bool isValid() const { return fTotal != 0; }
 
    size_t fTotal = 0;  // size of entire SkVertices allocation (obj + arrays)
    size_t fArrays; // size of all the data arrays (V + D + T + C + I)
    size_t fVSize;
    size_t fTSize;
    size_t fCSize;
    size_t fISize;
 
    // For indexed tri-fans this is the number of amount of space fo indices needed in the builder
    // before conversion to indexed triangles (or zero if not indexed or not a triangle fan).
    size_t fBuilderTriFanISize;
};
 
SkVertices::Builder::Builder(VertexMode mode, int vertexCount, int indexCount,
                             uint32_t builderFlags) {
    bool hasTexs = SkToBool(builderFlags & SkVertices::kHasTexCoords_BuilderFlag);
    bool hasColors = SkToBool(builderFlags & SkVertices::kHasColors_BuilderFlag);
    this->init({mode, vertexCount, indexCount, hasTexs, hasColors});
}
 
SkVertices::Builder::Builder(const Desc& desc) {
    this->init(desc);
}
 
void SkVertices::Builder::init(const Desc& desc) {
    Sizes sizes(desc);
    if (!sizes.isValid()) {
        SkASSERT(!this->isValid());
        return;
    }
 
    void* storage = ::operator new (sizes.fTotal);
    if (sizes.fBuilderTriFanISize) {
        fIntermediateFanIndices.reset(new uint8_t[sizes.fBuilderTriFanISize]);
    }
 
    fVertices.reset(new (storage) SkVertices);
 
    // need to point past the object to store the arrays
    char* ptr = (char*)storage + sizeof(SkVertices);
 
    // return the original ptr (or null), but then advance it by size
    auto advance = [&ptr](size_t size) {
        char* new_ptr = size ? ptr : nullptr;
        ptr += size;
        return new_ptr;
    };
 
    fVertices->fPositions      = (SkPoint*) advance(sizes.fVSize);
    fVertices->fTexs           = (SkPoint*) advance(sizes.fTSize);
    fVertices->fColors         = (SkColor*) advance(sizes.fCSize);
    fVertices->fIndices        = (uint16_t*)advance(sizes.fISize);
 
    fVertices->fVertexCount    = desc.fVertexCount;
    fVertices->fIndexCount     = desc.fIndexCount;
    fVertices->fMode           = desc.fMode;
 
    // We defer assigning fBounds and fUniqueID until detach() is called
}
 
sk_sp<SkVertices> SkVertices::Builder::detach() {
    if (fVertices) {
        fVertices->fBounds.setBounds(fVertices->fPositions, fVertices->fVertexCount);
        if (fVertices->fMode == kTriangleFan_VertexMode) {
            if (fIntermediateFanIndices) {
                SkASSERT(fVertices->fIndexCount);
                auto tempIndices = this->indices();
                for (int t = 0; t < fVertices->fIndexCount - 2; ++t) {
                    fVertices->fIndices[3 * t + 0] = tempIndices[0];
                    fVertices->fIndices[3 * t + 1] = tempIndices[t + 1];
                    fVertices->fIndices[3 * t + 2] = tempIndices[t + 2];
                }
                fVertices->fIndexCount = 3 * (fVertices->fIndexCount - 2);
            } else {
                SkASSERT(!fVertices->fIndexCount);
                for (int t = 0; t < fVertices->fVertexCount - 2; ++t) {
                    fVertices->fIndices[3 * t + 0] = 0;
                    fVertices->fIndices[3 * t + 1] = SkToU16(t + 1);
                    fVertices->fIndices[3 * t + 2] = SkToU16(t + 2);
                }
                fVertices->fIndexCount = 3 * (fVertices->fVertexCount - 2);
            }
            fVertices->fMode = kTriangles_VertexMode;
        }
        fVertices->fUniqueID = next_id();
        return std::move(fVertices);        // this will null fVertices after the return
    }
    return nullptr;
}
 
SkPoint* SkVertices::Builder::positions() {
    return fVertices ? const_cast<SkPoint*>(fVertices->fPositions) : nullptr;
}
 
SkPoint* SkVertices::Builder::texCoords() {
    return fVertices ? const_cast<SkPoint*>(fVertices->fTexs) : nullptr;
}
 
SkColor* SkVertices::Builder::colors() {
    return fVertices ? const_cast<SkColor*>(fVertices->fColors) : nullptr;
}
 
uint16_t* SkVertices::Builder::indices() {
    if (!fVertices) {
        return nullptr;
    }
    if (fIntermediateFanIndices) {
        return reinterpret_cast<uint16_t*>(fIntermediateFanIndices.get());
    }
    return const_cast<uint16_t*>(fVertices->fIndices);
}
 
///////////////////////////////////////////////////////////////////////////////////////////////////
 
sk_sp<SkVertices> SkVertices::MakeCopy(VertexMode mode, int vertexCount,
                                       const SkPoint pos[], const SkPoint texs[],
                                       const SkColor colors[],
                                       int indexCount, const uint16_t indices[]) {
    auto desc = Desc{mode, vertexCount, indexCount, !!texs, !!colors};
    Builder builder(desc);
    if (!builder.isValid()) {
        return nullptr;
    }
 
    Sizes sizes(desc);
    SkASSERT(sizes.isValid());
    sk_careful_memcpy(builder.positions(), pos, sizes.fVSize);
    sk_careful_memcpy(builder.texCoords(), texs, sizes.fTSize);
    sk_careful_memcpy(builder.colors(), colors, sizes.fCSize);
    size_t isize = (mode == kTriangleFan_VertexMode) ? sizes.fBuilderTriFanISize : sizes.fISize;
    sk_careful_memcpy(builder.indices(), indices, isize);
 
    return builder.detach();
}
 
size_t SkVertices::approximateSize() const {
    return this->getSizes().fTotal;
}
 
SkVertices::Sizes SkVertices::getSizes() const {
    Sizes sizes({fMode, fVertexCount, fIndexCount, !!fTexs, !!fColors});
    SkASSERT(sizes.isValid());
    return sizes;
}
 
///////////////////////////////////////////////////////////////////////////////////////////////////
 
// storage = packed | vertex_count | index_count | attr_count
//           | pos[] | custom[] | texs[] | colors[] | indices[]
 
#define kMode_Mask          0x0FF
#define kHasTexs_Mask       0x100
#define kHasColors_Mask     0x200
 
void SkVerticesPriv::encode(SkWriteBuffer& buffer) const {
    // packed has room for additional flags in the future
    uint32_t packed = static_cast<uint32_t>(fVertices->fMode);
    SkASSERT((packed & ~kMode_Mask) == 0);  // our mode fits in the mask bits
    if (fVertices->fTexs) {
        packed |= kHasTexs_Mask;
    }
    if (fVertices->fColors) {
        packed |= kHasColors_Mask;
    }
 
    SkVertices::Sizes sizes = fVertices->getSizes();
    SkASSERT(!sizes.fBuilderTriFanISize);
 
    // Header
    buffer.writeUInt(packed);
    buffer.writeInt(fVertices->fVertexCount);
    buffer.writeInt(fVertices->fIndexCount);
 
    // Data arrays
    buffer.writeByteArray(fVertices->fPositions, sizes.fVSize);
    buffer.writeByteArray(fVertices->fTexs, sizes.fTSize);
    buffer.writeByteArray(fVertices->fColors, sizes.fCSize);
    // if index-count is odd, we won't be 4-bytes aligned, so we call the pad version
    buffer.writeByteArray(fVertices->fIndices, sizes.fISize);
}
 
sk_sp<SkVertices> SkVerticesPriv::Decode(SkReadBuffer& buffer) {
    auto decode = [](SkReadBuffer& buffer) -> sk_sp<SkVertices> {
        SkSafeRange safe;
        bool hasCustomData = buffer.isVersionLT(SkPicturePriv::kVerticesRemoveCustomData_Version);
 
        const uint32_t packed = buffer.readUInt();
        const int vertexCount = safe.checkGE(buffer.readInt(), 0);
        const int indexCount = safe.checkGE(buffer.readInt(), 0);
        const int attrCount = hasCustomData ? safe.checkGE(buffer.readInt(), 0) : 0;
        const SkVertices::VertexMode mode = safe.checkLE<SkVertices::VertexMode>(
                packed & kMode_Mask, SkVertices::kLast_VertexMode);
        const bool hasTexs = SkToBool(packed & kHasTexs_Mask);
        const bool hasColors = SkToBool(packed & kHasColors_Mask);
 
        // Check that the header fields and buffer are valid. If this is data with the experimental
        // custom attributes feature - we don't support that any more.
        // We also don't support serialized triangle-fan data. We stopped writing that long ago,
        // so it should never appear in valid encoded data.
        if (!safe || !buffer.isValid() || attrCount ||
            mode == SkVertices::kTriangleFan_VertexMode) {
            return nullptr;
        }
 
        const SkVertices::Desc desc{mode, vertexCount, indexCount, hasTexs, hasColors};
        SkVertices::Sizes sizes(desc);
        if (!sizes.isValid() || sizes.fArrays > buffer.available()) {
            return nullptr;
        }
 
        SkVertices::Builder builder(desc);
        if (!builder.isValid()) {
            return nullptr;
        }
 
        buffer.readByteArray(builder.positions(), sizes.fVSize);
        if (hasCustomData) {
            size_t customDataSize = 0;
            buffer.skipByteArray(&customDataSize);
            if (customDataSize != 0) {
                return nullptr;
            }
        }
        buffer.readByteArray(builder.texCoords(), sizes.fTSize);
        buffer.readByteArray(builder.colors(), sizes.fCSize);
        buffer.readByteArray(builder.indices(), sizes.fISize);
 
        if (!buffer.isValid()) {
            return nullptr;
        }
 
        if (indexCount > 0) {
            // validate that the indices are in range
            const uint16_t* indices = builder.indices();
            for (int i = 0; i < indexCount; ++i) {
                if (indices[i] >= (unsigned)vertexCount) {
                    return nullptr;
                }
            }
        }
 
        return builder.detach();
    };
 
    if (auto verts = decode(buffer)) {
        return verts;
    }
    buffer.validate(false);
    return nullptr;
}
 
void SkVertices::operator delete(void* p) {
    ::operator delete(p);
}