mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-05 01:52:46 +00:00
101 lines
2.3 KiB
Go
101 lines
2.3 KiB
Go
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package binary
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import (
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"bytes"
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"fmt"
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"io"
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"math"
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"github.com/tetratelabs/wazero/internal/leb128"
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"github.com/tetratelabs/wazero/internal/wasm"
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)
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func decodeCode(r *bytes.Reader, codeSectionStart uint64, ret *wasm.Code) (err error) {
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ss, _, err := leb128.DecodeUint32(r)
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if err != nil {
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return fmt.Errorf("get the size of code: %w", err)
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}
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remaining := int64(ss)
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// Parse #locals.
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ls, bytesRead, err := leb128.DecodeUint32(r)
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remaining -= int64(bytesRead)
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if err != nil {
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return fmt.Errorf("get the size locals: %v", err)
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} else if remaining < 0 {
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return io.EOF
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}
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// Validate the locals.
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bytesRead = 0
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var sum uint64
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for i := uint32(0); i < ls; i++ {
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num, n, err := leb128.DecodeUint32(r)
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if err != nil {
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return fmt.Errorf("read n of locals: %v", err)
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} else if remaining < 0 {
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return io.EOF
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}
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sum += uint64(num)
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b, err := r.ReadByte()
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if err != nil {
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return fmt.Errorf("read type of local: %v", err)
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}
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bytesRead += n + 1
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switch vt := b; vt {
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case wasm.ValueTypeI32, wasm.ValueTypeF32, wasm.ValueTypeI64, wasm.ValueTypeF64,
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wasm.ValueTypeFuncref, wasm.ValueTypeExternref, wasm.ValueTypeV128:
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default:
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return fmt.Errorf("invalid local type: 0x%x", vt)
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}
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}
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if sum > math.MaxUint32 {
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return fmt.Errorf("too many locals: %d", sum)
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}
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// Rewind the buffer.
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_, err = r.Seek(-int64(bytesRead), io.SeekCurrent)
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if err != nil {
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return err
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}
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localTypes := make([]wasm.ValueType, 0, sum)
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for i := uint32(0); i < ls; i++ {
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num, bytesRead, err := leb128.DecodeUint32(r)
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remaining -= int64(bytesRead) + 1 // +1 for the subsequent ReadByte
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if err != nil {
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return fmt.Errorf("read n of locals: %v", err)
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} else if remaining < 0 {
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return io.EOF
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}
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b, err := r.ReadByte()
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if err != nil {
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return fmt.Errorf("read type of local: %v", err)
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}
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for j := uint32(0); j < num; j++ {
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localTypes = append(localTypes, b)
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}
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}
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bodyOffsetInCodeSection := codeSectionStart - uint64(r.Len())
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body := make([]byte, remaining)
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if _, err = io.ReadFull(r, body); err != nil {
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return fmt.Errorf("read body: %w", err)
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}
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if endIndex := len(body) - 1; endIndex < 0 || body[endIndex] != wasm.OpcodeEnd {
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return fmt.Errorf("expr not end with OpcodeEnd")
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}
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ret.BodyOffsetInCodeSection = bodyOffsetInCodeSection
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ret.LocalTypes = localTypes
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ret.Body = body
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return nil
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}
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