SkSLIndexExpression.h revision e92badc3ffce83668f76fcfa33a49784346cab1e 
1/*
2 * Copyright 2016 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SKSL_INDEX
9#define SKSL_INDEX
10
11#include "SkSLExpression.h"
12#include "SkSLUtil.h"
13
14namespace SkSL {
15
16/**
17 * Given a type, returns the type that will result from extracting an array value from it.
18 */
19static std::shared_ptr<Type> index_type(const Type& type) {
20    if (type.kind() == Type::kMatrix_Kind) {
21        if (type.componentType() == kFloat_Type) {
22            switch (type.columns()) {
23                case 2: return kVec2_Type;
24                case 3: return kVec3_Type;
25                case 4: return kVec4_Type;
26                default: ASSERT(false);
27            }
28        } else {
29            ASSERT(type.componentType() == kDouble_Type);
30            switch (type.columns()) {
31                case 2: return kDVec2_Type;
32                case 3: return kDVec3_Type;
33                case 4: return kDVec4_Type;
34                default: ASSERT(false);
35            }
36        }
37    }
38    return type.componentType();
39}
40
41/**
42 * An expression which extracts a value from an array or matrix, as in 'm[2]'.
43 */
44struct IndexExpression : public Expression {
45    IndexExpression(std::unique_ptr<Expression> base, std::unique_ptr<Expression> index)
46    : INHERITED(base->fPosition, kIndex_Kind, index_type(*base->fType))
47    , fBase(std::move(base))
48    , fIndex(std::move(index)) {
49        ASSERT(fIndex->fType == kInt_Type);
50    }
51
52    std::string description() const override {
53        return fBase->description() + "[" + fIndex->description() + "]";
54    }
55
56    const std::unique_ptr<Expression> fBase;
57    const std::unique_ptr<Expression> fIndex;
58
59    typedef Expression INHERITED;
60};
61
62} // namespace
63
64#endif
65