Skip to content

G
git2
Commit 24aec6db by Ben Straub
Options

Rewrite conventions to be more complete

parent ee72ffd0
Showing with 115 additions and 59 deletions
CONVENTIONS.md
libgit2 conventions # Libgit2 Conventions
===================
Namespace Prefixes We like to keep the source consistent and readable. Herein are some guidelines
------------------ that should help with that.
All types and functions start with 'git_'.
All #define macros start with 'GIT_'. ## Naming Things
All types and functions start with `git_`, and all #define macros start with `GIT_`.
Type Definitions Functions with a single output parameter should name that parameter `out`.
---------------- Multiple outputs should be named `foo_out`, `bar_out`, etc.
Most types should be opaque, e.g.: Parameters of type `git_oid` should be named `id`, or `foo_id`. Calls that
return an OID should be named `git_foo_id`.
```C Where there is a callback passed in, the `void *` that is passed into it should
typedef struct git_odb git_odb; be named "payload".
```
with allocation functions returning an "instance" created within ## Typedef
the library, and not within the application. This allows the type
to grow (or shrink) in size without rebuilding client code.
Wherever possible, use `typedef`. If a structure is just a collection of
function pointers, the pointer types don't need to be separately typedef'd, but
loose function pointer types should be.
Public Exported Function Definitions ## Exports
------------------------------------
All exported functions must be declared as: All exported functions must be declared as:
```C ```C
GIT_EXTERN(result_type) git_modulename_functionname(arg_list); GIT_EXTERN(result_type) git_modulename_functionname(arg_list);
``` ```
## Internals
Semi-Private Exported Functions
-------------------------------
Functions whose modulename is followed by two underscores, Functions whose modulename is followed by two underscores,
for example 'git_odb__read_packed', are semi-private functions. for example `git_odb__read_packed`, are semi-private functions.
They are primarily intended for use within the library itself, They are primarily intended for use within the library itself,
and may disappear or change their signature in a future release. and may disappear or change their signature in a future release.
## Parameters
Out parameters come first.
Whenever possible, pass argument pointers as `const`. Some structures (such
as `git_repository` and `git_index`) have internal structure that prevents
this.
Callbacks should always take a `void *` payload as their last parameter.
Callback pointers are grouped with their payloads, and come last when passed as
arguments:
```C
int foo(git_repository *repo, git_foo_cb callback, void *payload);
```
## Memory Ownership
Some APIs allocate memory which the caller is responsible for freeing; others
return a pointer into a buffer that's owned by some other object. Make this
explicit in the documentation.
## Return codes
Return an `int` when a public API can fail in multiple ways. These may be
transformed into exception types in some bindings, so returning a semantically
appropriate error code is important. Check
[`errors.h`](https://github.com/libgit2/libgit2/blob/development/include/git2/errors.h)
for the return codes already defined.
Use `giterr_set` to provide extended error information to callers.
Calling Conventions If an error is not to be propagated, use `giterr_clear` to prevent callers from
------------------- getting the wrong error message later on.
Functions should prefer to return a 'int' to indicate success or
failure and supply any output through the first argument (or first
few arguments if multiple outputs are supplied).
int status codes are 0 for GIT_OK and < 0 for an error. ## Opaque Structs
This permits common POSIX result testing:
Most types should be opaque, e.g.:
```C ```C
if (git_odb_open(&odb, path)) typedef struct git_odb git_odb;
abort("odb open failed");
``` ```
Functions returning a pointer may return NULL instead of an int ...with allocation functions returning an "instance" created within
if there is only one type of failure (GIT_ENOMEM). the library, and not within the application. This allows the type
to grow (or shrink) in size without rebuilding client code.
To preserve ABI compatibility, include an `int version` field in all opaque
structures, and initialize to the latest version in the construction call.
Increment the "latest" version whenever the structure changes, and try to only
append to the end of the structure.
Functions returning a pointer may also return NULL if the common ## Option Structures
case needed by the application is strictly success/failure and a
(possibly slower) function exists that the caller can use to get
more detailed information. Parsing common data structures from
on-disk formats is a good example of this pattern; in general a
"corrupt" entity can be treated as though it does not exist but
a more sophisticated "fsck" support function can report how the
entity is malformed.
If a function's parameter count is too high, it may be desirable to package up
the options in a structure. Make them transparent, include a version field,
and provide an initializer constant or constructor. Using these structures
should be this easy:
Documentation Fomatting ```C
----------------------- git_foo_options opts = GIT_FOO_OPTIONS_INIT;
opts.baz = BAZ_OPTION_ONE;
git_foo(&opts);
```
All comments should conform to Doxygen "javadoc" style conventions ## Enumerations
for formatting the public API documentation.
Typedef all enumerated types. If each option stands alone, use the enum type
for passing them as parameters; if they are flags, pass them as `unsigned int`.
Public Header Format ## Code Layout
--------------------
All public headers defining types, functions or macros must use Try to keep lines less than 80 characters long. Use common sense to wrap most
the following form, where ${filename} is the name of the file, code lines; public function declarations should use this convention:
after replacing non-identifier characters with '_'.
```C ```C
#ifndef INCLUDE_git_${filename}_h__ GIT_EXTERN(int) git_foo_id(
#define INCLUDE_git_${filename}_h__ git_oid **out,
int a,
int b);
```
Public headers are indented with spaces, three to a tab. Internal code is
indented with tabs; set your editor's tab width to 3 for best effect.
#include "git/common.h" ## Documentation
/** All comments should conform to Doxygen "javadoc" style conventions for
formatting the public API documentation. Try to document every parameter, and
keep the comments up to date if you change the parameter list.
## Public Header Template
Use this template when creating a new public header.
```C
#ifndef INCLUDE_git_${filename}_h__
#define INCLUDE_git_${filename}_h__
#include "git/common.h"
/**
* @file git/${filename}.h * @file git/${filename}.h
* @brief Git some description * @brief Git some description
* @defgroup git_${filename} some description routines * @defgroup git_${filename} some description routines
* @ingroup Git * @ingroup Git
* @{ * @{
*/ */
GIT_BEGIN_DECL GIT_BEGIN_DECL
... definitions ... /* ... definitions ... */
/** @} */ /** @} */
GIT_END_DECL GIT_END_DECL
#endif #endif
``` ```
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment