[libvirt] [PATCH v3] Document preferred naming conventions

[Laine Stump]

On 03/06/2017 06:09 AM, Daniel P. Berrange wrote:
> This documents the preferred conventions for naming files,
> structs, enums, typedefs and functions.
>
> Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
> ---
>
> Changed in v3:
>   - Clarify function naming wrt verb & subject
>   - Simplify macro naming, since in practice libvirt code doesn't follow any
>     rules consistently aside from having a VIR_ prefix.
>
>   HACKING              | 80 ++++++++++++++++++++++++++++++++++++++++++++
>   docs/hacking.html.in | 93 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>   docs/hacking2.xsl    |  4 +++
>   3 files changed, 177 insertions(+)
>
> diff --git a/HACKING b/HACKING
> index fff003b..2c65985 100644
> --- a/HACKING
> +++ b/HACKING
> @@ -239,6 +239,86 @@ on the subject, on Richard Jones' guide to working with open source projects
>   <http://people.redhat.com/rjones/how-to-supply-code-to-open-source-projects/>.
>   
>   
> +Naming conventions
> +==================
> +When reading libvirt code, a number of different naming conventions will be
> +evident due to various changes in thinking over the course of the project's
> +lifetime. The conventions documented below should be followed when creating
> +any entirely new files in libvirt. When working on existing files, while it is
> +desirable to apply these conventions, keeping a consistent style with existing
> +code in that particular file is generally more important. The overall guiding
> +principal is that every file, enum, struct, function, macro and typedef name
> +must have a 'vir' or 'VIR' prefix. All local scope variable names are exempt,
> +and global variables are exempt, unless exported in a header file.
> +
> +*File names*
> +
> +File naming varies depending on the subdirectory. The preferred style is to
> +have a 'vir' prefix, followed by a name which matches the name of the
> +functions / objects inside the file. For example, a file containing an object
> +'virHashtable' is stored in files 'virhashtable.c' and 'virhashtable.h'.
> +Sometimes, methods which would otherwise be declared 'static' need to be
> +exported for use by a test suite. For this purpose a second header file should
> +be added with a suffix of 'priv'. e.g. 'virhashtablepriv.h'. Use of
> +underscores in file names is discouraged when using the 'vir' prefix style.
> +The 'vir' prefix naming applies to src/util, src/rpc and tests/ directories.
> +Most other directories do not follow this convention.
> +
> +
> +
> +*Enum type & field names*
> +
> +All enums should have a 'vir' prefix in their typedef name, and each following
> +word should have its first letter in uppercase. The enum name should match the
> +typedef name with a leading underscore. The enum member names should be in all
> +uppercase, and use an underscore to separate each word. The enum member name
> +prefix should match the enum typedef name.
> +
> +    typedef enum _virSocketType virSocketType;
> +    enum _virSocketType {
> +        VIR_SOCKET_TYPE_IPV4,
> +        VIR_SOCKET_TYPE_IPV6,
> +    };
> +
> +
> +*Struct type names*
> +
> +All structs should have a 'vir' prefix in their typedef name, and each
> +following word should have its first letter in uppercase. The struct name
> +should be the same as the typedef name with a leading underscore. A second
> +typedef should be given for a pointer to the struct with a 'Ptr' suffix.
> +
> +    typedef struct _virHashTable virHashTable;
> +    typedef virHashTable *virHashTablePtr;
> +    struct _virHashTable {
> +       ...
> +    };
> +
> +
> +*Function names*
> +
> +All functions should have a 'vir' prefix in their name, followed by one or
> +more words with first letter of each word capitalized. Underscores should not
> +be used in function names. If the function is operating on an object, then the
> +function name prefix should match the object typedef name, otherwise it should
> +match the filename. Following this comes the verb / action name, and finally
> +an optional subject name. For example, given an object 'virHashTable', all
> +functions should have a name 'virHashTable$VERB' or
> +'virHashTable$VERB$SUBJECT". e.g. 'virHashTableLookup' or
> +'virHashTableGetValue'.
> +
> +
> +
> +*Macro names*
> +
> +All macros should have a "VIR" prefix in their name, followed by one or more
> +uppercase words separated by underscores. The macro argument names should be
> +in lowercase. Aside from having a "VIR" prefix there are no common practices
> +for the rest of the macro name.
> +
> +
> +
> +
>   Code indentation
>   ================
>   Libvirt's C source code generally adheres to some basic code-formatting
> diff --git a/docs/hacking.html.in b/docs/hacking.html.in
> index b1bb149..d904c3a 100644
> --- a/docs/hacking.html.in
> +++ b/docs/hacking.html.in
> @@ -314,6 +314,99 @@
>           Richard Jones' guide to working with open source projects</a>.
>       </p>
>   
> +    <h2><a name="naming">Naming conventions</a></h2>
> +
> +    <p>
> +      When reading libvirt code, a number of different naming conventions will
> +      be evident due to various changes in thinking over the course of the
> +      project's lifetime. The conventions documented below should be followed
> +      when creating any entirely new files in libvirt. When working on existing
> +      files, while it is desirable to apply these conventions, keeping a
> +      consistent style with existing code in that particular file is generally
> +      more important. The overall guiding principal is that every file, enum,
> +      struct, function, macro and typedef name must have a 'vir' or 'VIR' prefix.
> +      All local scope variable names are exempt, and global variables are exempt,
> +      unless exported in a header file.
> +    </p>
> +
> +    <dl>
> +      <dt>File names</dt>
> +      <dd>
> +        <p>
> +          File naming varies depending on the subdirectory. The preferred
> +          style is to have a 'vir' prefix, followed by a name which matches
> +          the name of the functions / objects inside the file. For example,
> +          a file containing an object  'virHashtable' is stored in files
> +          'virhashtable.c' and 'virhashtable.h'. Sometimes, methods which
> +          would otherwise be declared 'static' need to be exported for use
> +          by a test suite. For this purpose a second header file should be
> +          added with a suffix of 'priv'. e.g. 'virhashtablepriv.h'. Use of
> +          underscores in file names is discouraged when using the 'vir'
> +          prefix style. The 'vir' prefix naming applies to src/util,
> +          src/rpc and tests/ directories. Most other directories do not
> +          follow this convention.
> +        </p>
> +      </dd>
> +      <dt>Enum type & field names</dt>
> +      <dd>
> +        <p>
> +          All enums should have a 'vir' prefix in their typedef name,
> +          and each following word should have its first letter in
> +          uppercase. The enum name should match the typedef name with
> +          a leading underscore. The enum member names should be in all
> +          uppercase, and use an underscore to separate each word. The
> +          enum member name prefix should match the enum typedef name.
> +        </p>
> +        <pre>
> +    typedef enum _virSocketType virSocketType;
> +    enum _virSocketType {
> +        VIR_SOCKET_TYPE_IPV4,
> +        VIR_SOCKET_TYPE_IPV6,
> +    };</pre>
> +      </dd>
> +      <dt>Struct type names</dt>
> +      <dd>
> +        <p>
> +          All structs should have a 'vir' prefix in their typedef name,
> +          and each following word should have its first letter in
> +          uppercase. The struct name should be the same as the typedef
> +          name with a leading underscore. A second typedef should be
> +          given for a pointer to the struct with a 'Ptr' suffix.
> +        </p>
> +        <pre>
> +    typedef struct _virHashTable virHashTable;
> +    typedef virHashTable *virHashTablePtr;
> +    struct _virHashTable {
> +       ...
> +    };</pre>
> +      </dd>
> +      <dt>Function names</dt>
> +      <dd>
> +        <p>
> +          All functions should have a 'vir' prefix in their name,

What about the hypervisor-specific functions that are "semi-public" 
(used in other files within the same directory, but not exported outside 
of that directory)? I like that qemu-specific functions are prefixed 
with "qemu", lxc functions with "lxc", etc. and I'm guessing you aren't 
suggesting that we want those to all be "virQEMU", "virLXC", etc (or are 
you?)

Regardless of that,  this is useful to have as it is, and I think it's 
safe to push this now and tweak it as it's discussed more, so ACK. 
(unless you *want* to talk about it more :-)

> +          followed by one or more words with first letter of each
> +          word capitalized. Underscores should not be used in function
> +          names. If the function is operating on an object, then the
> +          function name prefix should match the object typedef name,
> +          otherwise it should match the filename. Following this
> +          comes the verb / action name, and finally an optional
> +          subject name. For example, given an object 'virHashTable',
> +          all functions should have a name 'virHashTable$VERB' or
> +          'virHashTable$VERB$SUBJECT". e.g. 'virHashTableLookup'
> +          or 'virHashTableGetValue'.
> +        </p>
> +      </dd>
> +      <dt>Macro names</dt>
> +      <dd>
> +        <p>
> +          All macros should have a "VIR" prefix in their name, followed
> +          by one or more uppercase words separated by underscores. The
> +          macro argument names should be in lowercase. Aside from having
> +          a "VIR" prefix there are no common practices for the rest of
> +          the macro name.
> +        </p>
> +      </dd>
> +    </dl>
>   
>       <h2><a name="indent">Code indentation</a></h2>
>       <p>
> diff --git a/docs/hacking2.xsl b/docs/hacking2.xsl
> index 3595b7e..7e5ac82 100644
> --- a/docs/hacking2.xsl
> +++ b/docs/hacking2.xsl
> @@ -114,6 +114,10 @@ from docs/hacking.html.in!
>   <xsl:template match="html:li/html:ul/html:li">-- <xsl:apply-templates/><xsl:value-of select="$newline"/><xsl:value-of select="$newline"/>
>   </xsl:template>
>   
> +<xsl:template match="html:dl/html:dt">*<xsl:apply-templates/>*<xsl:value-of select="$newline"/><xsl:value-of select="$newline"/>
> +</xsl:template>
> +<xsl:template match="html:dl/html:dd"><xsl:apply-templates/><xsl:value-of select="$newline"/><xsl:value-of select="$newline"/>
> +</xsl:template>
>   
>   
>   <!-- add newline before nested <ul> -->