Module Pxp_reader

module Pxp_reader: sig .. end

Resolving identifiers and associating resources

---

Purpose of this module: The Pxp_reader module allows you to exactly specify how external identifiers (SYSTEM or PUBLIC) are mapped to files or channels. This is normally only necessary for advanced configurations, as the built-in functions Pxp_types.from_file, Pxp_types.from_channel, and Pxp_types.from_string often suffice.

There are two ways to use this module. First, you can compose the desired behaviour by combining several predefined resolver objects or functions. See the example section at the end of the file. Second, you can inherit from the classes (or define a resolver class from scratch). I hope this is seldom necessary as this way is much more complicated; however it allows you to implement any required magic.

Types and exceptions

exception Not_competent

exception Not_resolvable of exn

type lexer_source = {

	lsrc_lexbuf : Lexing.lexbuf Lazy.t;
	lsrc_unicode_lexbuf : Netulex.ULB.unicode_lexbuf Lazy.t;

}

The resolver class type

The class type resolver is the official type of all "resolvers". Resolvers take file names (or better, external identifiers) and return lexbufs, scanning the file for tokens. Resolvers may be cloned, and clones can interpret relative file names relative to their creator.

Example of cloning:

Given resolver r reads from file:/dir/f1.xml this text:

 <tag>some XML text &e; </tag> 

The task is to switch to a resolver for reading from the entity e (which is referenced by &e;), and to switch back to the original resolver when the parser is done with e. Let us assume that e has the SYSTEM ID subdir/f2.xml. Our approach is to first create a clone of the original resolver so that we can do the switch to e in a copy. That means switching back is easy: We give up the cloned resolver, and continue with the original, unmodified resolver. This gives us the freedom to modify the clone in order to switch to e. We do this by changing the input file:

• Step 1: let r' = <create clone of r>
• Step 2: <direct r' to open the file subdir/f2.xml>

r' must still know the directory of the file r is reading, otherwise it would not be able to resolve subdir/f2.xml, which expands to file:/dir/subdir/f2.xml.

Actually, this example can be coded as:

 let r = new resolve_as_file in
 let lbuf = r # open_in "file:/dir/f1.xml" in
 ... read from lbuf ...
 let r' = r # clone in
 let lbuf' = r' # open_in "subdir/f2.xml" in
 ... read from lbuf' ...
 r' # close_in;
 ... read from lbuf ...
 r # close_in;
 

class type resolver = object .. end

type accepted_id = Netchannels.in_obj_channel * Pxp_core_types.I.encoding option *
       Pxp_core_types.I.resolver_id option 

Base resolvers

class resolve_to_this_obj_channel : ?id:Pxp_core_types.I.ext_id -> ?rid:Pxp_core_types.I.resolver_id -> ?fixenc:Pxp_core_types.I.encoding -> ?close:Netchannels.in_obj_channel -> unit -> Netchannels.in_obj_channel -> resolver

class resolve_to_any_obj_channel : ?close:Netchannels.in_obj_channel -> unit -> channel_of_id:(Pxp_core_types.I.resolver_id -> accepted_id) -> unit -> resolver

class resolve_to_url_obj_channel : ?close:Netchannels.in_obj_channel -> unit -> url_of_id:(Pxp_core_types.I.resolver_id -> Neturl.url) -> base_url_of_id:(Pxp_core_types.I.resolver_id -> Neturl.url) -> channel_of_url:(Pxp_core_types.I.resolver_id -> Neturl.url -> accepted_id) -> unit -> resolver

class resolve_as_file : ?file_prefix:[ `Allowed | `Not_recognized | `Required ] -> ?host_prefix:[ `Allowed | `Not_recognized | `Required ] -> ?system_encoding:Pxp_core_types.I.encoding -> ?map_private_id:Pxp_core_types.I.private_id -> Neturl.url -> ?open_private_id:Pxp_core_types.I.private_id ->
       Pervasives.in_channel * Pxp_core_types.I.encoding option -> ?base_url_defaults_to_cwd:bool -> ?not_resolvable_if_not_found:bool -> unit -> resolver

val make_file_url : ?system_encoding:Pxp_core_types.I.encoding ->
       ?enc:Pxp_core_types.I.encoding -> string -> Neturl.url

Catalog resolvers

class lookup_id : (Pxp_core_types.I.ext_id * resolver) list -> resolver

class lookup_id_as_file : ?fixenc:Pxp_core_types.I.encoding -> (Pxp_core_types.I.ext_id * string) list -> resolver

class lookup_id_as_string : ?fixenc:Pxp_core_types.I.encoding -> (Pxp_core_types.I.ext_id * string) list -> resolver

class lookup_public_id : (string * resolver) list -> resolver

class lookup_public_id_as_file : ?fixenc:Pxp_core_types.I.encoding -> (string * string) list -> resolver

class lookup_public_id_as_string : ?fixenc:Pxp_core_types.I.encoding -> (string * string) list -> resolver

class lookup_system_id : (string * resolver) list -> resolver

class lookup_system_id_as_file : ?fixenc:Pxp_core_types.I.encoding -> (string * string) list -> resolver

class lookup_system_id_as_string : ?fixenc:Pxp_core_types.I.encoding -> (string * string) list -> resolver

System ID normalization

class norm_system_id : resolver -> resolver

ID rewriting

class rewrite_system_id : ?forward_unmatching_urls:bool -> (string * string) list -> resolver -> resolver

Resolver construction

type combination_mode =

|	Public_before_system
|	System_before_public

class combine : ?mode:combination_mode -> resolver list -> resolver

val set_debug_mode : bool -> unit

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