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coding.md 4.3KB

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

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.