Source file src/github.com/tetratelabs/wazero/internal/testing/binaryencoding/value.go

Documentation: github.com/tetratelabs/wazero/internal/testing/binaryencoding

     1  package binaryencoding
     2  
     3  import (
     4  	"github.com/tetratelabs/wazero/internal/leb128"
     5  	"github.com/tetratelabs/wazero/internal/wasm"
     6  )
     7  
     8  var noValType = []byte{0}
     9  
    10  // encodedValTypes is a cache of size prefixed binary encoding of known val types.
    11  var encodedValTypes = map[wasm.ValueType][]byte{
    12  	wasm.ValueTypeI32:       {1, wasm.ValueTypeI32},
    13  	wasm.ValueTypeI64:       {1, wasm.ValueTypeI64},
    14  	wasm.ValueTypeF32:       {1, wasm.ValueTypeF32},
    15  	wasm.ValueTypeF64:       {1, wasm.ValueTypeF64},
    16  	wasm.ValueTypeExternref: {1, wasm.ValueTypeExternref},
    17  	wasm.ValueTypeFuncref:   {1, wasm.ValueTypeFuncref},
    18  	wasm.ValueTypeV128:      {1, wasm.ValueTypeV128},
    19  }
    20  
    21  // EncodeValTypes fast paths binary encoding of common value type lengths
    22  func EncodeValTypes(vt []wasm.ValueType) []byte {
    23  	// Special case nullary and parameter lengths of wasi_snapshot_preview1 to avoid excess allocations
    24  	switch uint32(len(vt)) {
    25  	case 0: // nullary
    26  		return noValType
    27  	case 1: // ex $wasi.fd_close or any result
    28  		if encoded, ok := encodedValTypes[vt[0]]; ok {
    29  			return encoded
    30  		}
    31  	case 2: // ex $wasi.environ_sizes_get
    32  		return []byte{2, vt[0], vt[1]}
    33  	case 4: // ex $wasi.fd_write
    34  		return []byte{4, vt[0], vt[1], vt[2], vt[3]}
    35  	case 9: // ex $wasi.fd_write
    36  		return []byte{9, vt[0], vt[1], vt[2], vt[3], vt[4], vt[5], vt[6], vt[7], vt[8]}
    37  	}
    38  	// Slow path others until someone complains with a valid signature
    39  	count := leb128.EncodeUint32(uint32(len(vt)))
    40  	return append(count, vt...)
    41  }
    42  

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