NAME

Data::Sah::Compiler - Base class for Sah compilers (Data::Sah::Compiler::*)

VERSION

version 0.06

ATTRIBUTES

main => OBJ

Reference to the main Data::Sah object.

expr_compiler => OBJ

Reference to expression compiler object. In the perl compiler, for example, this will be an instance of Language::Expr::Compiler::Perl object.

METHODS

new() => OBJ

$c->compile(%args) => HASH

Compile schema into target language.

Arguments (* denotes required arguments, subclass may introduce others):

• data_name => STR (default: 'data')

  A unique name. Will be used as default for variable names, etc. Should only be comprised of letters/numbers/underscores.

• schema* => STR|ARRAY

  The schema to use. Will be normalized by compiler, unless schema_is_normalized is set to true.

• schema_is_normalized => BOOL (default: 0)

  If set to true, instruct the compiler not to normalize the input schema and assume it is already normalized.

• allow_expr => BOOL (default: 1)

  Whether to allow expressions. If false, will die when encountering expression during compilation. Usually set to false for security reason, to disallow complex expressions when schemas come from untrusted sources.

• on_unhandled_attr => STR (default: 'die')

  What to do when an attribute can't be handled by compiler (either it is an invalid attribute, or the compiler has not implemented it yet). Valid values include: die, warn, ignore.

• on_unhandled_clause => STR (default: 'die')

  What to do when a clause can't be handled by compiler (either it is an invalid clause, or the compiler has not implemented it yet). Valid values include: die, warn, ignore.

• indent_level => INTT (default: 0)

  Start at a specified indent level. Useful when generated code will be inserted into another code (e.g. inside sub {} where it is nice to be able to indent the inside code).

Compilation data

During compilation, compile() will call various hooks (listed below). The hooks will be passed compilation data ($cd) which is a hashref containing various compilation state and result. Compilation data is written to this hashref instead of on the object's attributes to make it easy to do recursive compilation (compilation of subschemas).

Subclasses may add more data (see their documentation).

Keys which contain input data, compilation state, and others (many of these keys might exist only temporarily during certain phases of compilation and will no longer exist at the end of compilation, for example clause will only exist during processing of a clause and will be seen by hooks like before_clause and after_clause, it will not be seen by before_all_clauses or after_compile):

• args => HASH

  Arguments given to compile().

• compiler => OBJ

  The compiler object.

• outer_cd => HASH

  If compilation is called from within another compile(), this will be set to the outer compilation's $cd. The inner compilation will inherit some values from the outer, like list of types (th_map) and function sets (fsh_map).

• th_map => HASH

  Mapping of fully-qualified type names like int and its Data::Sah::Compiler::*::TH::* type handler object (or array, a normalized schema).

• fsh_map => HASH

  Mapping of function set name like core and its Data::Sah::Compiler::*::FSH::* handler object.

• schema => ARRAY

  The current schema (normalized) being processed. Since schema can contain other schemas, there will be subcompilation and this value will not necessarily equal to $cd->{args}{schema}.

• th => OBJ

  Current type handler.

• type => STR

  Current type name.

• csets => ARRAY

  All the clause sets. Each schema might have more than one clause set, due to processing base type's clause set.

• cset => HASH

  Current clause set being processed. Note that clauses are evaluated not strictly in cset order, but instead based on expression dependencies and priority.

• cset_num => INT

  Set to 0 for the first clause set, 1 for the second, and so on. Due to merging, we might process more than one clause set during compilation.

• ucset => HASH

  Short for "unprocessed clause set", a shallow copy of cset, keys will be removed from here as they are processed by clause handlers, remaining keys after processing the clause set means they are not recognized by hooks and thus constitutes an error.

• ucsets => ARRAY

  All the ucset for each clause set.

• clause => STR

  Current clause name.

• cl_meta => HASH

  Metadata information about the clause, from the clause definition. This include prio (priority), attrs (list of attributes specific for this clause), allow_expr (whether clause allows expression in its value), etc. See Data::Sah::Type::$TYPENAME for more information.

• cl_value => ANY

  Clause value. Note: for putting in generated code, use cl_term.

• cl_term => STR

  Clause value term. If clause value is a literal (.is_expr is false) then it is produced by passing clause value to literal(). Otherwise, it is produced by passing clause value to expr().

• cl_is_expr => STR

  A shortcut for $cd->{cset}{"${clause}.is_expr"}.

• cl_is_multi => STR

  A shortcut for $cd->{cset}{"${clause}.is_multi"}.

• indent_level => INT

  Current level of indent when printing result using $c->line(). 0 means unindented.

• all_expr_vars => ARRAY

  All variables in all expressions in the current schema (and all of its subschemas). Used internally by compiler. For example (XXX syntax not not finalized):

   # schema
   [array => {of=>'str1', min_len=>1, 'max_len=' => '$min_len*3'},
    {def => {
        str1 => [str => {min_len=>6, 'max_len=' => '$min_len*2',
                         check=>'substr($_,0,1) eq "a"'}],
    }}]
  
   all_expr_vars => ['schema:///csets/0/min_len', # or perhaps .../min_len/value
                     'schema://str1/csets/0/min_len']

  This data can be used to order the compilation of clauses based on dependencies. In the above example, min_len needs to be evaluated before max_len (especially if min_len is an expression).

Keys which contain compilation result:

• ccls => [HASH, ...]

  Compiled clauses, collected during processing of schema's clauses. Each element will contain the compiled code in the target language, error message, and other information. At the end of processing, these will be joined together.

• result

  The final result. For most compilers, it will be string/text.

Return value

The compilation data will be returned as return value. Main result will be in the result key. There is also ccls, and subclasses may put additional results in other keys. Final usable result might need to be pieced together from these results, depending on your needs.

Hooks

By default this base compiler does not define any hooks; subclasses can define hooks to implement their compilation process. Each hook will be passed compilation data, and should modify or set the compilation data as needed. The hooks that compile() will call at various points, in calling order, are:

• $c->before_compile($cd)

  Called once at the beginning of compilation.

  If hook sets $cd->{SKIP_COMPILE} to true then the whole compilation process will end (after_compile() will not even be called).

• $c->before_all_clauses($cd)

  Called before calling handler for any clauses.

• $th->before_all_clauses($cd)

  Called before calling handler for any clauses, after compiler's before_all_clauses().

• $c->before_clause($cd)

  Called for each clause, before calling the actual clause handler ($th->clause_NAME() or $th->clause).

  If hook sets $cd->{SKIP_THIS_CLAUSE} to true then compilation for the clause will be skipped (including calling clause_NAME() and after_clause()). If $cd->{SKIP_REMAINING_CLAUSES} is set to true then compilation for the rest of the schema's clauses will be skipped (including current clause's clause_NAME() and after_clause()).

• $th->before_clause($cd)

  After compiler's before_clause() is called, type handler's before_clause() will also be called if available.

  Input and output interpretation is the same as compiler's before_clause().

• $th->clause_NAME($cd)

  Called once for each clause. If hook sets $cd->{SKIP_REMAINING_CLAUSES} to true then compilation for the rest of the clauses to be skipped (including current clause's after_clause()).

• $th->after_clause($cd)

  Called for each clause, after calling the actual clause handler ($th->clause_NAME()).

  If hook sets $cd->{SKIP_REMAINING_CLAUSES} to true then compilation for the rest of the clauses to be skipped.

• $c->after_clause($cd)

  Called for each clause, after calling the actual clause handler ($th->clause_NAME()).

  Output interpretation is the same as $th->after_clause().

• $th->after_all_clauses($cd)

  Called after all clauses have been compiled, before compiler's after_all_clauses().

• $c->after_all_clauses($cd)

  Called after all clauses have been compiled.

• $c->after_compile($cd)

  Called at the very end before compiling process end.

$c->get_th

$c->get_fsh

AUTHOR

Steven Haryanto <stevenharyanto@gmail.com>

COPYRIGHT AND LICENSE

This software is copyright (c) 2012 by Steven Haryanto.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

cpanm Data::Sah

perl -MCPAN -e shell
install Data::Sah