neobytes/doc/coding.md

Coding

Please be consistent with the existing coding style.

Block style:

    bool Function(char* psz, int n)
    {
        // Comment summarising what this section of code does
        for (int i = 0; i < n; i++)
        {
            // When something fails, return early
            if (!Something())
                return false;
            ...
        }

        // Success return is usually at the end
        return true;
    }

• ANSI/Allman block style
• 4 space indenting, no tabs
• No extra spaces inside parenthesis; please don't do ( this )
• No space after function names, one space after if, for and while
• Includes need to be ordered alphabetically, separate own and foreign headers with a new-line (example key.cpp):

#include "key.h"

#include "crypto/sha2.h"
#include "util.h"

#include <openssl/foo.h>

• Class or struct keywords in header files need to be ordered alphabetically:

class CAlpha;
class CBeta;

• When using namespace keyword use the following form:

namespace Foo {

...

} // Foo

Variable names begin with the type in lowercase, like nSomeVariable. Please don't put the first word of the variable name in lowercase like someVariable.

Common types:

n       integer number: short, unsigned short, int, unsigned int, int64, uint64, sometimes char if used as a number
d       double, float
f       flag
hash    uint256
p       pointer or array, one p for each level of indirection
psz     pointer to null terminated string
str     string object
v       vector or similar list objects
map     map or multimap
set     set or multiset
bn      CBigNum

Doxygen comments

To facilitate the generation of documentation, use doxygen-compatible comment blocks for functions, methods and fields.

For example, to describe a function use:

/**
 * ... text ...
 * @param[in] arg1    A description
 * @param[in] arg2    Another argument description
 * @pre Precondition for function...
 */
bool function(int arg1, const char *arg2)

A complete list of @xxx commands can be found at http://www.stack.nl/~dimitri/doxygen/manual/commands.html. As Doxygen recognizes the comments by the delimiters (/** and */ in this case), you don't need to provide any commands for a comment to be valid, just a description text is fine.

To describe a class use the same construct above the class definition:

/** 
 * Alerts are for notifying old versions if they become too obsolete and
 * need to upgrade. The message is displayed in the status bar.
 * @see GetWarnings()
 */
class CAlert
{

To describe a member or variable use:

int var; //!< Detailed description after the member

Also OK:

///
/// ... text ...
///
bool function2(int arg1, const char *arg2)

Not OK (used plenty in the current source, but not picked up):

//
// ... text ...
//

A full list of comment syntaxes picked up by doxygen can be found at http://www.stack.nl/~dimitri/doxygen/manual/docblocks.html, but if possible use one of the above styles.

Locking/mutex usage notes

The code is multi-threaded, and uses mutexes and the LOCK/TRY_LOCK macros to protect data structures.

Deadlocks due to inconsistent lock ordering (thread 1 locks cs_main and then cs_wallet, while thread 2 locks them in the opposite order: result, deadlock as each waits for the other to release its lock) are a problem. Compile with -DDEBUG_LOCKORDER to get lock order inconsistencies reported in the debug.log file.

Re-architecting the core code so there are better-defined interfaces between the various components is a goal, with any necessary locking done by the components (e.g. see the self-contained CKeyStore class and its cs_KeyStore lock for example).

Threads

• ThreadScriptCheck : Verifies block scripts.

• ThreadImport : Loads blocks from blk*.dat files or bootstrap.dat.

• StartNode : Starts other threads.

• ThreadGetMyExternalIP : Determines outside-the-firewall IP address, sends addr message to connected peers when it determines it.

• ThreadDNSAddressSeed : Loads addresses of peers from the DNS.

• ThreadMapPort : Universal plug-and-play startup/shutdown

• ThreadSocketHandler : Sends/Receives data from peers on port 8333.

• ThreadOpenAddedConnections : Opens network connections to added nodes.

• ThreadOpenConnections : Initiates new connections to peers.

• ThreadMessageHandler : Higher-level message handling (sending and receiving).

• DumpAddresses : Dumps IP addresses of nodes to peers.dat.

• ThreadFlushWalletDB : Close the wallet.dat file if it hasn't been used in 500ms.

• ThreadRPCServer : Remote procedure call handler, listens on port 8332 for connections and services them.

• BitcoinMiner : Generates bitcoins (if wallet is enabled).

• Shutdown : Does an orderly shutdown of everything.