Function newASTDecoder

internal/api/encoder/decoder.go:53–96

(data []byte)

}

func newASTDecoder(data []byte) (*astDecoder, error) {
	if len(data) < HeaderSize {
		return nil, fmt.Errorf("data too short for header: %d bytes", len(data))
	}
	version := data[HeaderOffsetMetadata+3]
	if version != ProtocolVersion {
		return nil, fmt.Errorf("unsupported protocol version %d (expected %d)", version, ProtocolVersion)
	}

	strTable := readLE32(data, HeaderOffsetStringOffsets)
	strData := readLE32(data, HeaderOffsetStringData)
	extData := readLE32(data, HeaderOffsetExtendedData)
	nodeOff := readLE32(data, HeaderOffsetNodes)

	dataLen := uint32(len(data))

	// Validate that all offsets are within the buffer.
	if strTable > dataLen || strData > dataLen || extData > dataLen || nodeOff > dataLen {
		return nil, fmt.Errorf("invalid AST header offsets: offsets exceed data length (%d)", dataLen)
	}

	// Validate monotonic non-decreasing order of regions.
	if !(strTable <= strData && strData <= extData && extData <= nodeOff) {
		return nil, fmt.Errorf("invalid AST header offsets: expected strTable <= strData <= extData <= nodeOff (got %d, %d, %d, %d)", strTable, strData, extData, nodeOff)
	}

	d := &astDecoder{
		raw:      data,
		strTable: strTable,
		strData:  strData,
		extData:  extData,
		nodeOff:  nodeOff,
		factory:  ast.NewNodeFactory(ast.NodeFactoryHooks{}),
	}

	d.nodeCount = (len(data) - int(d.nodeOff)) / NodeSize

	// Convert entire string data region to a single Go string upfront.
	// Substringing a Go string shares the backing array, so subsequent
	// getString calls produce substrings with zero allocations.
	d.allStringData = string(data[d.strData:])

	return d, nil
}

// allocNodeSlice returns a zero-length slice with the given capacity, backed by
// the pre-allocated nodeArena. This avoids a heap allocation per NodeList.