ACL file format for brokers.

The C++ Broker M4 or later supports the following:

 Notes on file formats

• A line starting with the character '#' will be considered a comment, and are ignored.
• Since the '#' char (and others that are commonly used for comments) are commonly found in routing keys and other AMQP literals, it is simpler (for now) to hold off on allowing trailing comments (ie comments in which everything following a '#' is considered a comment). This could be reviewed later once the rest of the format is finalized.
• Empty lines ("") and lines that contain only whitespace (any combination of ' ', '\f', '\n', '\r', '\t', '\v') are ignored.
• All tokens are case sensitive. "name1" != "Name1" and "create" != "CREATE".
• Group lists may be extended to the following line by terminating the line with the '\' character. However, this may only occur after the group name or any of the names following the group name. Empty extension lines (ie just a '\' character) are not permitted.

  Code Block
  # Examples of extending group lists using a trailing '\' character group group1 name1 name2 \ name3 name4 \ name5 group group2 \ group1 \ name6 # The following are illegal: # '\' must be after group name group \ group3 name7 name8 # No empty extension lines group group4 name9 \ \ name10

• Additional whitespace (ie more than one whitespace char) between and after tokens is ignored. However group and acl definitions must start with "group" or "acl" respectively and with no preceding whitespace.
• All acl rules are limited to a single line.
• Rules are interpreted from the top of the file down until the name match is obtained; at which point processing stops.
• The keyword "all" is reserved, and matches all individuals, groups and actions. It may be used in place of a group or individual name and/or an action - eg "acl allow all all", "acl deny all all" or "acl deny user1 all".
• The last line of the file (whether present or not) will be assumed to be "acl deny all all". If present in the file, any lines below this one are ignored.
• Names and group names may contain only a-z, A-Z, 0-9, '-','_'.
• Rules must be preceded by any group definitions they may use; any name not previously defined as a group will be assumed to be that of an individual.
• ACL rules must have the following tokens in order on a single line:
  • The string literal "acl";
  • The permission;
  • The name of a single group or individual or the keyword "all";
  • The name of an action or the keyword "all";
  • Optionally, a single object name or the keyword "all";
  • If the object is present, then optionally one or more property name-value pair(s) (in the form property=value).

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