lbcd/msgheaders.go

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// Copyright (c) 2013-2014 Conformal Systems LLC.
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// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package btcwire
import (
"fmt"
"io"
)
// MaxBlockHeadersPerMsg is the maximum number of block headers that can be in
// a single bitcoin headers message.
const MaxBlockHeadersPerMsg = 2000
// MsgHeaders implements the Message interface and represents a bitcoin headers
// message. It is used to deliver block header information in response
// to a getheaders message (MsgGetHeaders). The maximum number of block headers
// per message is currently 2000. See MsgGetHeaders for details on requesting
// the headers.
type MsgHeaders struct {
Headers []*BlockHeader
}
// AddBlockHeader adds a new block header to the message.
func (msg *MsgHeaders) AddBlockHeader(bh *BlockHeader) error {
if len(msg.Headers)+1 > MaxBlockHeadersPerMsg {
str := fmt.Sprintf("too many block headers in message [max %v]",
MaxBlockHeadersPerMsg)
return messageError("MsgHeaders.AddBlockHeader", str)
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}
msg.Headers = append(msg.Headers, bh)
return nil
}
// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
// This is part of the Message interface implementation.
func (msg *MsgHeaders) BtcDecode(r io.Reader, pver uint32) error {
count, err := readVarInt(r, pver)
if err != nil {
return err
}
// Limit to max block headers per message.
if count > MaxBlockHeadersPerMsg {
str := fmt.Sprintf("too many block headers for message "+
"[count %v, max %v]", count, MaxBlockHeadersPerMsg)
return messageError("MsgHeaders.BtcDecode", str)
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}
msg.Headers = make([]*BlockHeader, 0, count)
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for i := uint64(0); i < count; i++ {
bh := BlockHeader{}
err := readBlockHeader(r, pver, &bh)
if err != nil {
return err
}
Remove BlockHeader.TxnCount field. This commit removes the TxnCount field from the BlockHeader type and updates the tests accordingly. Note that this change does not affect the actual wire protocol encoding in any way. The reason the field has been removed is it really doesn't belong there even though the wire protocol wiki entry on the official bitcoin wiki implies it does. The implication is an artifact from the way the reference implementation serializes headers (MsgHeaders) messages. It includes the transaction count, which is naturally always 0 for headers, along with every header. However, in reality, a block header does not include the transaction count. This can be evidenced by looking at how a block hash is calculated. It is only up to and including the Nonce field (a total of 80 bytes). From an API standpoint, having the field as part of the BlockHeader type results in several odd cases. For example, the transaction count for MsgBlocks (the only place that actually has a real transaction count since MsgHeaders does not) is available by taking the len of the Transactions slice. As such, having the extra field in the BlockHeader is really a useless field that could potentially get out of sync and cause the encode to fail. Another example is related to deserializing a block header from the database in order to serve it in response to a getheaders (MsgGetheaders) request. If a block header is assumed to have the transaction count as a part of it, then derserializing a block header not only consumes more than the 80 bytes that actually comprise the header as stated above, but you then need to change the transaction count to 0 before sending the headers (MsgHeaders) message. So, not only are you reading and deserializing more bytes than needed, but worse, you generally have to make a copy of it so you can change the transaction count without busting cached headers. This is part 1 of #13.
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txCount, err := readVarInt(r, pver)
if err != nil {
return err
}
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// Ensure the transaction count is zero for headers.
Remove BlockHeader.TxnCount field. This commit removes the TxnCount field from the BlockHeader type and updates the tests accordingly. Note that this change does not affect the actual wire protocol encoding in any way. The reason the field has been removed is it really doesn't belong there even though the wire protocol wiki entry on the official bitcoin wiki implies it does. The implication is an artifact from the way the reference implementation serializes headers (MsgHeaders) messages. It includes the transaction count, which is naturally always 0 for headers, along with every header. However, in reality, a block header does not include the transaction count. This can be evidenced by looking at how a block hash is calculated. It is only up to and including the Nonce field (a total of 80 bytes). From an API standpoint, having the field as part of the BlockHeader type results in several odd cases. For example, the transaction count for MsgBlocks (the only place that actually has a real transaction count since MsgHeaders does not) is available by taking the len of the Transactions slice. As such, having the extra field in the BlockHeader is really a useless field that could potentially get out of sync and cause the encode to fail. Another example is related to deserializing a block header from the database in order to serve it in response to a getheaders (MsgGetheaders) request. If a block header is assumed to have the transaction count as a part of it, then derserializing a block header not only consumes more than the 80 bytes that actually comprise the header as stated above, but you then need to change the transaction count to 0 before sending the headers (MsgHeaders) message. So, not only are you reading and deserializing more bytes than needed, but worse, you generally have to make a copy of it so you can change the transaction count without busting cached headers. This is part 1 of #13.
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if txCount > 0 {
str := fmt.Sprintf("block headers may not contain "+
Remove BlockHeader.TxnCount field. This commit removes the TxnCount field from the BlockHeader type and updates the tests accordingly. Note that this change does not affect the actual wire protocol encoding in any way. The reason the field has been removed is it really doesn't belong there even though the wire protocol wiki entry on the official bitcoin wiki implies it does. The implication is an artifact from the way the reference implementation serializes headers (MsgHeaders) messages. It includes the transaction count, which is naturally always 0 for headers, along with every header. However, in reality, a block header does not include the transaction count. This can be evidenced by looking at how a block hash is calculated. It is only up to and including the Nonce field (a total of 80 bytes). From an API standpoint, having the field as part of the BlockHeader type results in several odd cases. For example, the transaction count for MsgBlocks (the only place that actually has a real transaction count since MsgHeaders does not) is available by taking the len of the Transactions slice. As such, having the extra field in the BlockHeader is really a useless field that could potentially get out of sync and cause the encode to fail. Another example is related to deserializing a block header from the database in order to serve it in response to a getheaders (MsgGetheaders) request. If a block header is assumed to have the transaction count as a part of it, then derserializing a block header not only consumes more than the 80 bytes that actually comprise the header as stated above, but you then need to change the transaction count to 0 before sending the headers (MsgHeaders) message. So, not only are you reading and deserializing more bytes than needed, but worse, you generally have to make a copy of it so you can change the transaction count without busting cached headers. This is part 1 of #13.
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"transactions [count %v]", txCount)
return messageError("MsgHeaders.BtcDecode", str)
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}
msg.AddBlockHeader(&bh)
}
return nil
}
// BtcEncode encodes the receiver to w using the bitcoin protocol encoding.
// This is part of the Message interface implementation.
func (msg *MsgHeaders) BtcEncode(w io.Writer, pver uint32) error {
// Limit to max block headers per message.
count := len(msg.Headers)
if count > MaxBlockHeadersPerMsg {
str := fmt.Sprintf("too many block headers for message "+
"[count %v, max %v]", count, MaxBlockHeadersPerMsg)
return messageError("MsgHeaders.BtcEncode", str)
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}
err := writeVarInt(w, pver, uint64(count))
if err != nil {
return err
}
for _, bh := range msg.Headers {
Remove BlockHeader.TxnCount field. This commit removes the TxnCount field from the BlockHeader type and updates the tests accordingly. Note that this change does not affect the actual wire protocol encoding in any way. The reason the field has been removed is it really doesn't belong there even though the wire protocol wiki entry on the official bitcoin wiki implies it does. The implication is an artifact from the way the reference implementation serializes headers (MsgHeaders) messages. It includes the transaction count, which is naturally always 0 for headers, along with every header. However, in reality, a block header does not include the transaction count. This can be evidenced by looking at how a block hash is calculated. It is only up to and including the Nonce field (a total of 80 bytes). From an API standpoint, having the field as part of the BlockHeader type results in several odd cases. For example, the transaction count for MsgBlocks (the only place that actually has a real transaction count since MsgHeaders does not) is available by taking the len of the Transactions slice. As such, having the extra field in the BlockHeader is really a useless field that could potentially get out of sync and cause the encode to fail. Another example is related to deserializing a block header from the database in order to serve it in response to a getheaders (MsgGetheaders) request. If a block header is assumed to have the transaction count as a part of it, then derserializing a block header not only consumes more than the 80 bytes that actually comprise the header as stated above, but you then need to change the transaction count to 0 before sending the headers (MsgHeaders) message. So, not only are you reading and deserializing more bytes than needed, but worse, you generally have to make a copy of it so you can change the transaction count without busting cached headers. This is part 1 of #13.
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err := writeBlockHeader(w, pver, bh)
if err != nil {
return err
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}
Remove BlockHeader.TxnCount field. This commit removes the TxnCount field from the BlockHeader type and updates the tests accordingly. Note that this change does not affect the actual wire protocol encoding in any way. The reason the field has been removed is it really doesn't belong there even though the wire protocol wiki entry on the official bitcoin wiki implies it does. The implication is an artifact from the way the reference implementation serializes headers (MsgHeaders) messages. It includes the transaction count, which is naturally always 0 for headers, along with every header. However, in reality, a block header does not include the transaction count. This can be evidenced by looking at how a block hash is calculated. It is only up to and including the Nonce field (a total of 80 bytes). From an API standpoint, having the field as part of the BlockHeader type results in several odd cases. For example, the transaction count for MsgBlocks (the only place that actually has a real transaction count since MsgHeaders does not) is available by taking the len of the Transactions slice. As such, having the extra field in the BlockHeader is really a useless field that could potentially get out of sync and cause the encode to fail. Another example is related to deserializing a block header from the database in order to serve it in response to a getheaders (MsgGetheaders) request. If a block header is assumed to have the transaction count as a part of it, then derserializing a block header not only consumes more than the 80 bytes that actually comprise the header as stated above, but you then need to change the transaction count to 0 before sending the headers (MsgHeaders) message. So, not only are you reading and deserializing more bytes than needed, but worse, you generally have to make a copy of it so you can change the transaction count without busting cached headers. This is part 1 of #13.
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// The wire protocol encoding always includes a 0 for the number
// of transactions on header messages. This is really just an
// artifact of the way the original implementation serializes
// block headers, but it is required.
err = writeVarInt(w, pver, 0)
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if err != nil {
return err
}
Remove BlockHeader.TxnCount field. This commit removes the TxnCount field from the BlockHeader type and updates the tests accordingly. Note that this change does not affect the actual wire protocol encoding in any way. The reason the field has been removed is it really doesn't belong there even though the wire protocol wiki entry on the official bitcoin wiki implies it does. The implication is an artifact from the way the reference implementation serializes headers (MsgHeaders) messages. It includes the transaction count, which is naturally always 0 for headers, along with every header. However, in reality, a block header does not include the transaction count. This can be evidenced by looking at how a block hash is calculated. It is only up to and including the Nonce field (a total of 80 bytes). From an API standpoint, having the field as part of the BlockHeader type results in several odd cases. For example, the transaction count for MsgBlocks (the only place that actually has a real transaction count since MsgHeaders does not) is available by taking the len of the Transactions slice. As such, having the extra field in the BlockHeader is really a useless field that could potentially get out of sync and cause the encode to fail. Another example is related to deserializing a block header from the database in order to serve it in response to a getheaders (MsgGetheaders) request. If a block header is assumed to have the transaction count as a part of it, then derserializing a block header not only consumes more than the 80 bytes that actually comprise the header as stated above, but you then need to change the transaction count to 0 before sending the headers (MsgHeaders) message. So, not only are you reading and deserializing more bytes than needed, but worse, you generally have to make a copy of it so you can change the transaction count without busting cached headers. This is part 1 of #13.
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}
return nil
}
// Command returns the protocol command string for the message. This is part
// of the Message interface implementation.
func (msg *MsgHeaders) Command() string {
return cmdHeaders
}
// MaxPayloadLength returns the maximum length the payload can be for the
// receiver. This is part of the Message interface implementation.
func (msg *MsgHeaders) MaxPayloadLength(pver uint32) uint32 {
Remove BlockHeader.TxnCount field. This commit removes the TxnCount field from the BlockHeader type and updates the tests accordingly. Note that this change does not affect the actual wire protocol encoding in any way. The reason the field has been removed is it really doesn't belong there even though the wire protocol wiki entry on the official bitcoin wiki implies it does. The implication is an artifact from the way the reference implementation serializes headers (MsgHeaders) messages. It includes the transaction count, which is naturally always 0 for headers, along with every header. However, in reality, a block header does not include the transaction count. This can be evidenced by looking at how a block hash is calculated. It is only up to and including the Nonce field (a total of 80 bytes). From an API standpoint, having the field as part of the BlockHeader type results in several odd cases. For example, the transaction count for MsgBlocks (the only place that actually has a real transaction count since MsgHeaders does not) is available by taking the len of the Transactions slice. As such, having the extra field in the BlockHeader is really a useless field that could potentially get out of sync and cause the encode to fail. Another example is related to deserializing a block header from the database in order to serve it in response to a getheaders (MsgGetheaders) request. If a block header is assumed to have the transaction count as a part of it, then derserializing a block header not only consumes more than the 80 bytes that actually comprise the header as stated above, but you then need to change the transaction count to 0 before sending the headers (MsgHeaders) message. So, not only are you reading and deserializing more bytes than needed, but worse, you generally have to make a copy of it so you can change the transaction count without busting cached headers. This is part 1 of #13.
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// Num headers (varInt) + max allowed headers (header length + 1 byte
// for the number of transactions which is always 0).
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return MaxVarIntPayload + ((MaxBlockHeaderPayload + 1) *
Remove BlockHeader.TxnCount field. This commit removes the TxnCount field from the BlockHeader type and updates the tests accordingly. Note that this change does not affect the actual wire protocol encoding in any way. The reason the field has been removed is it really doesn't belong there even though the wire protocol wiki entry on the official bitcoin wiki implies it does. The implication is an artifact from the way the reference implementation serializes headers (MsgHeaders) messages. It includes the transaction count, which is naturally always 0 for headers, along with every header. However, in reality, a block header does not include the transaction count. This can be evidenced by looking at how a block hash is calculated. It is only up to and including the Nonce field (a total of 80 bytes). From an API standpoint, having the field as part of the BlockHeader type results in several odd cases. For example, the transaction count for MsgBlocks (the only place that actually has a real transaction count since MsgHeaders does not) is available by taking the len of the Transactions slice. As such, having the extra field in the BlockHeader is really a useless field that could potentially get out of sync and cause the encode to fail. Another example is related to deserializing a block header from the database in order to serve it in response to a getheaders (MsgGetheaders) request. If a block header is assumed to have the transaction count as a part of it, then derserializing a block header not only consumes more than the 80 bytes that actually comprise the header as stated above, but you then need to change the transaction count to 0 before sending the headers (MsgHeaders) message. So, not only are you reading and deserializing more bytes than needed, but worse, you generally have to make a copy of it so you can change the transaction count without busting cached headers. This is part 1 of #13.
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MaxBlockHeadersPerMsg)
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}
// NewMsgHeaders returns a new bitcoin headers message that conforms to the
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// Message interface. See MsgHeaders for details.
func NewMsgHeaders() *MsgHeaders {
return &MsgHeaders{
Headers: make([]*BlockHeader, 0, MaxBlockHeadersPerMsg),
}
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}