Re: [PATCH] Block parameter support for GRUB script

[BVK Chaitanya]

Attached is an updated patch for block-arguments support.  It
restricts the syntax to only one block-argument per command, that too,
only as the last parameter.  This is a requirement to make menuentry
as a regular command.

Since this is a BASH incompatible feature, some notes are necessary:

1.  Block arguments feature makes use of '{' and '}' characters for
its syntax.  So we need to escape these characters, if we want to pass
them to commands as regular parameters.

2.  Text between '{' and '}' must be in a valid GRUB script commands
syntax.  Since functions are not commands in GRUB script, one cannot
define new functions with in a block argument.

3.  Block arguments can be nested to arbitrary depths, that is,
commands with-in a block argument may themselves use block arguments,
etc.

4.  A block argument parameter is passed to commands' implementation
as a single parameter (whitespaces and all within { and } are part of
the same parameter).  Enclosing characters, { and } are also passed as
part of the parameter.

5.  Block argument parameter is also passed as a pre-parsed
grub_script object, to all extended commands (grub_extcmd_t).
Commands that want to save this object needs to take a reference using
grub_script_get/grub_script_put methods.


This feature is currently being used by new menuentry-as-a-command
implementation.  I will send the patch for it shortly.



regards,
bvk.chaitanya

block-arg.patch
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