wa-lang.org/wazero@v1.0.2/internal/wasm/binary/limits.go (about)

     1  package binary
     2  
     3  import (
     4  	"bytes"
     5  	"fmt"
     6  
     7  	"wa-lang.org/wazero/internal/leb128"
     8  )
     9  
    10  // decodeLimitsType returns the `limitsType` (min, max) decoded with the WebAssembly 1.0 (20191205) Binary Format.
    11  //
    12  // See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#limits%E2%91%A6
    13  func decodeLimitsType(r *bytes.Reader) (min uint32, max *uint32, err error) {
    14  	var flag byte
    15  	if flag, err = r.ReadByte(); err != nil {
    16  		err = fmt.Errorf("read leading byte: %v", err)
    17  		return
    18  	}
    19  
    20  	switch flag {
    21  	case 0x00:
    22  		min, _, err = leb128.DecodeUint32(r)
    23  		if err != nil {
    24  			err = fmt.Errorf("read min of limit: %v", err)
    25  		}
    26  	case 0x01:
    27  		min, _, err = leb128.DecodeUint32(r)
    28  		if err != nil {
    29  			err = fmt.Errorf("read min of limit: %v", err)
    30  			return
    31  		}
    32  		var m uint32
    33  		if m, _, err = leb128.DecodeUint32(r); err != nil {
    34  			err = fmt.Errorf("read max of limit: %v", err)
    35  		} else {
    36  			max = &m
    37  		}
    38  	default:
    39  		err = fmt.Errorf("%v for limits: %#x != 0x00 or 0x01", ErrInvalidByte, flag)
    40  	}
    41  	return
    42  }
    43  
    44  // encodeLimitsType returns the `limitsType` (min, max) encoded in WebAssembly 1.0 (20191205) Binary Format.
    45  //
    46  // See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#limits%E2%91%A6
    47  func encodeLimitsType(min uint32, max *uint32) []byte {
    48  	if max == nil {
    49  		return append(leb128.EncodeUint32(0x00), leb128.EncodeUint32(min)...)
    50  	}
    51  	return append(leb128.EncodeUint32(0x01), append(leb128.EncodeUint32(min), leb128.EncodeUint32(*max)...)...)
    52  }