1package binary
2
3import (
4 "bytes"
5 "fmt"
6 "io"
7
8 "github.com/tetratelabs/wazero/api"
9 "github.com/tetratelabs/wazero/internal/ieee754"
10 "github.com/tetratelabs/wazero/internal/leb128"
11 "github.com/tetratelabs/wazero/internal/wasm"
12)
13
14func decodeConstantExpression(r *bytes.Reader, enabledFeatures api.CoreFeatures, ret *wasm.ConstantExpression) error {
15 b, err := r.ReadByte()
16 if err != nil {
17 return fmt.Errorf("read opcode: %v", err)
18 }
19
20 remainingBeforeData := int64(r.Len())
21 offsetAtData := r.Size() - remainingBeforeData
22
23 opcode := b
24 switch opcode {
25 case wasm.OpcodeI32Const:
26 // Treat constants as signed as their interpretation is not yet known per /RATIONALE.md
27 _, _, err = leb128.DecodeInt32(r)
28 case wasm.OpcodeI64Const:
29 // Treat constants as signed as their interpretation is not yet known per /RATIONALE.md
30 _, _, err = leb128.DecodeInt64(r)
31 case wasm.OpcodeF32Const:
32 buf := make([]byte, 4)
33 if _, err := io.ReadFull(r, buf); err != nil {
34 return fmt.Errorf("read f32 constant: %v", err)
35 }
36 _, err = ieee754.DecodeFloat32(buf)
37 case wasm.OpcodeF64Const:
38 buf := make([]byte, 8)
39 if _, err := io.ReadFull(r, buf); err != nil {
40 return fmt.Errorf("read f64 constant: %v", err)
41 }
42 _, err = ieee754.DecodeFloat64(buf)
43 case wasm.OpcodeGlobalGet:
44 _, _, err = leb128.DecodeUint32(r)
45 case wasm.OpcodeRefNull:
46 if err := enabledFeatures.RequireEnabled(api.CoreFeatureBulkMemoryOperations); err != nil {
47 return fmt.Errorf("ref.null is not supported as %w", err)
48 }
49 reftype, err := r.ReadByte()
50 if err != nil {
51 return fmt.Errorf("read reference type for ref.null: %w", err)
52 } else if reftype != wasm.RefTypeFuncref && reftype != wasm.RefTypeExternref {
53 return fmt.Errorf("invalid type for ref.null: 0x%x", reftype)
54 }
55 case wasm.OpcodeRefFunc:
56 if err := enabledFeatures.RequireEnabled(api.CoreFeatureBulkMemoryOperations); err != nil {
57 return fmt.Errorf("ref.func is not supported as %w", err)
58 }
59 // Parsing index.
60 _, _, err = leb128.DecodeUint32(r)
61 case wasm.OpcodeVecPrefix:
62 if err := enabledFeatures.RequireEnabled(api.CoreFeatureSIMD); err != nil {
63 return fmt.Errorf("vector instructions are not supported as %w", err)
64 }
65 opcode, err = r.ReadByte()
66 if err != nil {
67 return fmt.Errorf("read vector instruction opcode suffix: %w", err)
68 }
69
70 if opcode != wasm.OpcodeVecV128Const {
71 return fmt.Errorf("invalid vector opcode for const expression: %#x", opcode)
72 }
73
74 remainingBeforeData = int64(r.Len())
75 offsetAtData = r.Size() - remainingBeforeData
76
77 n, err := r.Read(make([]byte, 16))
78 if err != nil {
79 return fmt.Errorf("read vector const instruction immediates: %w", err)
80 } else if n != 16 {
81 return fmt.Errorf("read vector const instruction immediates: needs 16 bytes but was %d bytes", n)
82 }
83 default:
84 return fmt.Errorf("%v for const expression opt code: %#x", ErrInvalidByte, b)
85 }
86
87 if err != nil {
88 return fmt.Errorf("read value: %v", err)
89 }
90
91 if b, err = r.ReadByte(); err != nil {
92 return fmt.Errorf("look for end opcode: %v", err)
93 }
94
95 if b != wasm.OpcodeEnd {
96 return fmt.Errorf("constant expression has been not terminated")
97 }
98
99 ret.Data = make([]byte, remainingBeforeData-int64(r.Len())-1)
100 if _, err = r.ReadAt(ret.Data, offsetAtData); err != nil {
101 return fmt.Errorf("error re-buffering ConstantExpression.Data")
102 }
103 ret.Opcode = opcode
104 return nil
105}