github.com/hack0072008/kafka-go@v1.0.1/protocol/request.go (about)

     1  package protocol
     2  
     3  import (
     4  	"fmt"
     5  	"io"
     6  )
     7  
     8  func ReadRequest(r io.Reader) (apiVersion int16, correlationID int32, clientID string, msg Message, err error) {
     9  	d := &decoder{reader: r, remain: 4}
    10  	size := d.readInt32()
    11  
    12  	if err = d.err; err != nil {
    13  		err = dontExpectEOF(err)
    14  		return
    15  	}
    16  
    17  	d.remain = int(size)
    18  	apiKey := ApiKey(d.readInt16())
    19  	apiVersion = d.readInt16()
    20  	correlationID = d.readInt32()
    21  	clientID = d.readString()
    22  
    23  	if i := int(apiKey); i < 0 || i >= len(apiTypes) {
    24  		err = fmt.Errorf("unsupported api key: %d", i)
    25  		return
    26  	}
    27  
    28  	if err = d.err; err != nil {
    29  		err = dontExpectEOF(err)
    30  		return
    31  	}
    32  
    33  	t := &apiTypes[apiKey]
    34  	if t == nil {
    35  		err = fmt.Errorf("unsupported api: %s", apiNames[apiKey])
    36  		return
    37  	}
    38  
    39  	minVersion := t.minVersion()
    40  	maxVersion := t.maxVersion()
    41  
    42  	if apiVersion < minVersion || apiVersion > maxVersion {
    43  		err = fmt.Errorf("unsupported %s version: v%d not in range v%d-v%d", apiKey, apiVersion, minVersion, maxVersion)
    44  		return
    45  	}
    46  
    47  	req := &t.requests[apiVersion-minVersion]
    48  
    49  	if req.flexible {
    50  		// In the flexible case, there's a tag buffer at the end of the request header
    51  		taggedCount := int(d.readUnsignedVarInt())
    52  		for i := 0; i < taggedCount; i++ {
    53  			d.readUnsignedVarInt() // tagID
    54  			size := d.readUnsignedVarInt()
    55  
    56  			// Just throw away the values for now
    57  			d.read(int(size))
    58  		}
    59  	}
    60  
    61  	msg = req.new()
    62  	req.decode(d, valueOf(msg))
    63  	d.discardAll()
    64  
    65  	if err = d.err; err != nil {
    66  		err = dontExpectEOF(err)
    67  	}
    68  
    69  	return
    70  }
    71  
    72  func WriteRequest(w io.Writer, apiVersion int16, correlationID int32, clientID string, msg Message) error {
    73  	apiKey := msg.ApiKey()
    74  
    75  	if i := int(apiKey); i < 0 || i >= len(apiTypes) {
    76  		return fmt.Errorf("unsupported api key: %d", i)
    77  	}
    78  
    79  	t := &apiTypes[apiKey]
    80  	if t == nil {
    81  		return fmt.Errorf("unsupported api: %s", apiNames[apiKey])
    82  	}
    83  
    84  	minVersion := t.minVersion()
    85  	maxVersion := t.maxVersion()
    86  
    87  	if apiVersion < minVersion || apiVersion > maxVersion {
    88  		return fmt.Errorf("unsupported %s version: v%d not in range v%d-v%d", apiKey, apiVersion, minVersion, maxVersion)
    89  	}
    90  
    91  	r := &t.requests[apiVersion-minVersion]
    92  	v := valueOf(msg)
    93  	b := newPageBuffer()
    94  	defer b.unref()
    95  
    96  	e := &encoder{writer: b}
    97  	e.writeInt32(0) // placeholder for the request size
    98  	e.writeInt16(int16(apiKey))
    99  	e.writeInt16(apiVersion)
   100  	e.writeInt32(correlationID)
   101  
   102  	if r.flexible {
   103  		// Flexible messages use a nullable string for the client ID, then extra space for a
   104  		// tag buffer, which begins with a size value. Since we're not writing any fields into the
   105  		// latter, we can just write zero for now.
   106  		//
   107  		// See
   108  		// https://cwiki.apache.org/confluence/display/KAFKA/KIP-482%3A+The+Kafka+Protocol+should+Support+Optional+Tagged+Fields
   109  		// for details.
   110  		e.writeNullString(clientID)
   111  		e.writeUnsignedVarInt(0)
   112  	} else {
   113  		// Technically, recent versions of kafka interpret this field as a nullable
   114  		// string, however kafka 0.10 expected a non-nullable string and fails with
   115  		// a NullPointerException when it receives a null client id.
   116  		e.writeString(clientID)
   117  	}
   118  	r.encode(e, v)
   119  	err := e.err
   120  
   121  	if err == nil {
   122  		size := packUint32(uint32(b.Size()) - 4)
   123  		b.WriteAt(size[:], 0)
   124  		_, err = b.WriteTo(w)
   125  	}
   126  
   127  	return err
   128  }