github.com/tetratelabs/wazero@v1.7.3-0.20240513003603-48f702e154b5/internal/wasm/binary/function.go (about)

     1  package binary
     2  
     3  import (
     4  	"bytes"
     5  	"fmt"
     6  
     7  	"github.com/tetratelabs/wazero/api"
     8  	"github.com/tetratelabs/wazero/internal/leb128"
     9  	"github.com/tetratelabs/wazero/internal/wasm"
    10  )
    11  
    12  func decodeFunctionType(enabledFeatures api.CoreFeatures, r *bytes.Reader, ret *wasm.FunctionType) (err error) {
    13  	b, err := r.ReadByte()
    14  	if err != nil {
    15  		return fmt.Errorf("read leading byte: %w", err)
    16  	}
    17  
    18  	if b != 0x60 {
    19  		return fmt.Errorf("%w: %#x != 0x60", ErrInvalidByte, b)
    20  	}
    21  
    22  	paramCount, _, err := leb128.DecodeUint32(r)
    23  	if err != nil {
    24  		return fmt.Errorf("could not read parameter count: %w", err)
    25  	}
    26  
    27  	paramTypes, err := decodeValueTypes(r, paramCount)
    28  	if err != nil {
    29  		return fmt.Errorf("could not read parameter types: %w", err)
    30  	}
    31  
    32  	resultCount, _, err := leb128.DecodeUint32(r)
    33  	if err != nil {
    34  		return fmt.Errorf("could not read result count: %w", err)
    35  	}
    36  
    37  	// Guard >1.0 feature multi-value
    38  	if resultCount > 1 {
    39  		if err = enabledFeatures.RequireEnabled(api.CoreFeatureMultiValue); err != nil {
    40  			return fmt.Errorf("multiple result types invalid as %v", err)
    41  		}
    42  	}
    43  
    44  	resultTypes, err := decodeValueTypes(r, resultCount)
    45  	if err != nil {
    46  		return fmt.Errorf("could not read result types: %w", err)
    47  	}
    48  
    49  	ret.Params = paramTypes
    50  	ret.Results = resultTypes
    51  
    52  	// cache the key for the function type
    53  	_ = ret.String()
    54  
    55  	return nil
    56  }