67 lines
1.6 KiB
Go
67 lines
1.6 KiB
Go
package binary
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import (
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"bytes"
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"fmt"
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"github.com/tetratelabs/wabin/wasm"
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)
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// decodeGlobal returns the wasm.Global decoded with the WebAssembly Binary Format.
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//
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// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-global
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func decodeGlobal(r *bytes.Reader, features wasm.CoreFeatures) (*wasm.Global, error) {
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gt, err := decodeGlobalType(r)
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if err != nil {
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return nil, err
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}
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init, err := decodeConstantExpression(r, features)
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if err != nil {
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return nil, err
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}
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return &wasm.Global{Type: gt, Init: init}, nil
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}
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// decodeGlobalType returns the wasm.GlobalType decoded with the WebAssembly Binary Format.
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//
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// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-globaltype
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func decodeGlobalType(r *bytes.Reader) (*wasm.GlobalType, error) {
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vt, err := decodeValueTypes(r, 1)
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if err != nil {
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return nil, fmt.Errorf("read value type: %w", err)
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}
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ret := &wasm.GlobalType{
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ValType: vt[0],
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}
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b, err := r.ReadByte()
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if err != nil {
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return nil, fmt.Errorf("read mutablity: %w", err)
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}
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switch mut := b; mut {
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case 0x00: // not mutable
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case 0x01: // mutable
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ret.Mutable = true
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default:
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return nil, fmt.Errorf("%w for mutability: %#x != 0x00 or 0x01", ErrInvalidByte, mut)
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}
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return ret, nil
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}
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// encodeGlobal returns the wasm.Global encoded in WebAssembly Binary Format.
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//
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// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#global-section%E2%91%A0
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func encodeGlobal(g *wasm.Global) (data []byte) {
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var mutable byte
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if g.Type.Mutable {
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mutable = 1
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}
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data = []byte{g.Type.ValType, mutable}
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data = append(data, encodeConstantExpression(g.Init)...)
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return
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}
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