github.com/wasilibs/wazerox@v0.0.0-20240124024944-4923be63ab5f/internal/testing/binaryencoding/names.go (about)

     1  package binaryencoding
     2  
     3  import (
     4  	"github.com/wasilibs/wazerox/internal/leb128"
     5  	"github.com/wasilibs/wazerox/internal/wasm"
     6  )
     7  
     8  const (
     9  	// subsectionIDModuleName contains only the module name.
    10  	subsectionIDModuleName = uint8(0)
    11  	// subsectionIDFunctionNames is a map of indices to function names, in ascending order by function index
    12  	subsectionIDFunctionNames = uint8(1)
    13  	// subsectionIDLocalNames contain a map of function indices to a map of local indices to their names, in ascending
    14  	// order by function and local index
    15  	subsectionIDLocalNames = uint8(2)
    16  )
    17  
    18  // EncodeNameSectionData serializes the data for the "name" key in wasm.SectionIDCustom according to the
    19  // standard:
    20  //
    21  // Note: The result can be nil because this does not encode empty subsections
    22  //
    23  // See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-namesec
    24  func EncodeNameSectionData(n *wasm.NameSection) (data []byte) {
    25  	if n.ModuleName != "" {
    26  		data = append(data, encodeNameSubsection(subsectionIDModuleName, encodeSizePrefixed([]byte(n.ModuleName)))...)
    27  	}
    28  	if fd := encodeFunctionNameData(n); len(fd) > 0 {
    29  		data = append(data, encodeNameSubsection(subsectionIDFunctionNames, fd)...)
    30  	}
    31  	if ld := encodeLocalNameData(n); len(ld) > 0 {
    32  		data = append(data, encodeNameSubsection(subsectionIDLocalNames, ld)...)
    33  	}
    34  	return
    35  }
    36  
    37  // encodeFunctionNameData encodes the data for the function name subsection.
    38  // See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-funcnamesec
    39  func encodeFunctionNameData(n *wasm.NameSection) []byte {
    40  	if len(n.FunctionNames) == 0 {
    41  		return nil
    42  	}
    43  
    44  	return encodeNameMap(n.FunctionNames)
    45  }
    46  
    47  func encodeNameMap(m wasm.NameMap) []byte {
    48  	count := uint32(len(m))
    49  	data := leb128.EncodeUint32(count)
    50  	for _, na := range m {
    51  		data = append(data, encodeNameAssoc(na)...)
    52  	}
    53  	return data
    54  }
    55  
    56  // encodeLocalNameData encodes the data for the local name subsection.
    57  // See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-localnamesec
    58  func encodeLocalNameData(n *wasm.NameSection) []byte {
    59  	if len(n.LocalNames) == 0 {
    60  		return nil
    61  	}
    62  
    63  	funcNameCount := uint32(len(n.LocalNames))
    64  	subsection := leb128.EncodeUint32(funcNameCount)
    65  
    66  	for _, na := range n.LocalNames {
    67  		locals := encodeNameMap(na.NameMap)
    68  		subsection = append(subsection, append(leb128.EncodeUint32(na.Index), locals...)...)
    69  	}
    70  	return subsection
    71  }
    72  
    73  // encodeNameSubsection returns a buffer encoding the given subsection
    74  // See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#subsections%E2%91%A0
    75  func encodeNameSubsection(subsectionID uint8, content []byte) []byte {
    76  	contentSizeInBytes := leb128.EncodeUint32(uint32(len(content)))
    77  	result := []byte{subsectionID}
    78  	result = append(result, contentSizeInBytes...)
    79  	result = append(result, content...)
    80  	return result
    81  }
    82  
    83  // encodeNameAssoc encodes the index and data prefixed by their size.
    84  // See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-namemap
    85  func encodeNameAssoc(na wasm.NameAssoc) []byte {
    86  	return append(leb128.EncodeUint32(na.Index), encodeSizePrefixed([]byte(na.Name))...)
    87  }
    88  
    89  // encodeSizePrefixed encodes the data prefixed by their size.
    90  func encodeSizePrefixed(data []byte) []byte {
    91  	size := leb128.EncodeUint32(uint32(len(data)))
    92  	return append(size, data...)
    93  }