value.go

Documentation: github.com/tetratelabs/wazero/internal/wasm/binary

     1  package binary
     2  
     3  import (
     4  	"bytes"
     5  	"fmt"
     6  	"io"
     7  	"unicode/utf8"
     8  	"unsafe"
     9  
    10  	"github.com/tetratelabs/wazero/internal/leb128"
    11  	"github.com/tetratelabs/wazero/internal/wasm"
    12  )
    13  
    14  func decodeValueTypes(r *bytes.Reader, num uint32) ([]wasm.ValueType, error) {
    15  	if num == 0 {
    16  		return nil, nil
    17  	}
    18  
    19  	ret := make([]wasm.ValueType, num)
    20  	_, err := io.ReadFull(r, ret)
    21  	if err != nil {
    22  		return nil, err
    23  	}
    24  
    25  	for _, v := range ret {
    26  		switch v {
    27  		case wasm.ValueTypeI32, wasm.ValueTypeF32, wasm.ValueTypeI64, wasm.ValueTypeF64,
    28  			wasm.ValueTypeExternref, wasm.ValueTypeFuncref, wasm.ValueTypeV128:
    29  		default:
    30  			return nil, fmt.Errorf("invalid value type: %d", v)
    31  		}
    32  	}
    33  	return ret, nil
    34  }
    35  
    36  // decodeUTF8 decodes a size prefixed string from the reader, returning it and the count of bytes read.
    37  // contextFormat and contextArgs apply an error format when present
    38  func decodeUTF8(r *bytes.Reader, contextFormat string, contextArgs ...interface{}) (string, uint32, error) {
    39  	size, sizeOfSize, err := leb128.DecodeUint32(r)
    40  	if err != nil {
    41  		return "", 0, fmt.Errorf("failed to read %s size: %w", fmt.Sprintf(contextFormat, contextArgs...), err)
    42  	}
    43  
    44  	if size == 0 {
    45  		return "", uint32(sizeOfSize), nil
    46  	}
    47  
    48  	buf := make([]byte, size)
    49  	if _, err = io.ReadFull(r, buf); err != nil {
    50  		return "", 0, fmt.Errorf("failed to read %s: %w", fmt.Sprintf(contextFormat, contextArgs...), err)
    51  	}
    52  
    53  	if !utf8.Valid(buf) {
    54  		return "", 0, fmt.Errorf("%s is not valid UTF-8", fmt.Sprintf(contextFormat, contextArgs...))
    55  	}
    56  
    57  	// TODO: use unsafe.String after flooring Go 1.20.
    58  	ret := *(*string)(unsafe.Pointer(&buf))
    59  	return ret, size + uint32(sizeOfSize), nil
    60  }
    61
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