1 Commits

Author	SHA1	Message	Date
David Teigland	1e2420bca8	commands: new method for defining commands ... . Define a prototype for every lvm command. . Match every user command with one definition. . Generate help text and man pages from them. The new file command-lines.in defines a prototype for every unique lvm command. A unique lvm command is a unique combination of: command name + required option args + required positional args. Each of these prototypes also includes the optional option args and optional positional args that the command will accept, a description, and a unique string ID for the definition. Any valid command will match one of the prototypes. Here's an example of the lvresize command definitions from command-lines.in, there are three unique lvresize commands: lvresize --size SizeMB LV OO: --alloc Alloc, --autobackup Bool, --force, --nofsck, --nosync, --noudevsync, --reportformat String, --resizefs, --stripes Number, --stripesize SizeKB, --poolmetadatasize SizeMB OP: PV ... ID: lvresize_by_size DESC: Resize an LV by a specified size. lvresize LV PV ... OO: --alloc Alloc, --autobackup Bool, --force, --nofsck, --nosync, --noudevsync, --reportformat String, --resizefs, --stripes Number, --stripesize SizeKB ID: lvresize_by_pv DESC: Resize an LV by specified PV extents. FLAGS: SECONDARY_SYNTAX lvresize --poolmetadatasize SizeMB LV_thinpool OO: --alloc Alloc, --autobackup Bool, --force, --nofsck, --nosync, --noudevsync, --reportformat String, --stripes Number, --stripesize SizeKB OP: PV ... ID: lvresize_pool_metadata_by_size DESC: Resize a pool metadata SubLV by a specified size. The three commands have separate definitions because they have different required parameters. Required parameters are specified on the first line of the definition. Optional options are listed after OO, and optional positional args are listed after OP. This data is used to generate corresponding command definition structures for lvm in command-lines.h. usage/help output is also auto generated, so it is always in sync with the definitions. Every user-entered command is compared against the set of command structures, and matched with one. An error is reported if an entered command does not have the required parameters for any definition. The closest match is printed as a suggestion, and running lvresize --help will display the usage for each possible lvresize command. The prototype syntax used for help/man output includes required --option and positional args on the first line, and optional --option and positional args enclosed in [ ] on subsequent lines. command_name <required_opt_args> <required_pos_args> [ <optional_opt_args> ] [ <optional_pos_args> ] Command definitions that are not to be advertised/suggested have the flag SECONDARY_SYNTAX. These commands will not be printed in the normal help output. Man page prototypes are also generated from the same original command definitions, and are always in sync with the code and help text. Very early in command execution, a matching command definition is found. lvm then knows the operation being done, and that the provided args conform to the definition. This will allow lots of ad hoc checking/validation to be removed throughout the code. Each command definition can also be routed to a specific function to implement it. The function is associated with an enum value for the command definition (generated from the ID string.) These per-command-definition implementation functions have not yet been created, so all commands currently fall back to the existing per-command-name implementation functions. Using per-command-definition functions will allow lots of code to be removed which tries to figure out what the command is meant to do. This is currently based on ad hoc and complicated option analysis. When using the new functions, what the command is doing is already known from the associated command definition.	2017-02-13 08:20:10 -06:00