bitcoin/doc/coding.md

Coding
====================

Please be consistent with the existing coding style.

Block style:
```c++
    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):
```c++
#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:
```c++
class CAlpha;
class CBeta;
```
- When using namespace keyword use the following form:
```c++
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:
```c++
/**
 * ... 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:
```c++
/** 
 * 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:
```c++
int var; //!< Detailed description after the member
```

Also OK:
```c++
///
/// ... text ...
///
bool function2(int arg1, const char *arg2)
```

Not OK (used plenty in the current source, but not picked up):
```c++
//
// ... 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.