48 lines
1.2 KiB
Go
48 lines
1.2 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/wazero/internal/leb128"
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)
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// decodeLimitsType returns the `limitsType` (min, max) decoded with the WebAssembly 1.0 (20191205) Binary Format.
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//
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// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#limits%E2%91%A6
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//
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// Extended in threads proposal: https://webassembly.github.io/threads/core/binary/types.html#limits
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func decodeLimitsType(r *bytes.Reader) (min uint32, max *uint32, shared bool, err error) {
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var flag byte
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if flag, err = r.ReadByte(); err != nil {
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err = fmt.Errorf("read leading byte: %v", err)
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return
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}
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switch flag {
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case 0x00, 0x02:
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min, _, err = leb128.DecodeUint32(r)
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if err != nil {
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err = fmt.Errorf("read min of limit: %v", err)
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}
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case 0x01, 0x03:
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min, _, err = leb128.DecodeUint32(r)
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if err != nil {
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err = fmt.Errorf("read min of limit: %v", err)
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return
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}
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var m uint32
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if m, _, err = leb128.DecodeUint32(r); err != nil {
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err = fmt.Errorf("read max of limit: %v", err)
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} else {
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max = &m
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}
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default:
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err = fmt.Errorf("%v for limits: %#x not in (0x00, 0x01, 0x02, 0x03)", ErrInvalidByte, flag)
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}
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shared = flag == 0x02 || flag == 0x03
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return
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}
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