(* $Id$ * ---------------------------------------------------------------------- * PXP: The polymorphic XML parser for Objective Caml. * Copyright by Gerd Stolpmann. See LICENSE for details. *) open Pxp_types;; exception Not_competent;; (* Raised by the 'open_in' method if the object does not know how to * handle the passed external ID. *) exception Not_resolvable of exn;; (* Indicates that one resolver was competent, but there was an error * while resolving the external ID. The passed exception explains the * reason. * Not_resolvable(Not_found) serves as indicator for an unknown reason. *) (* 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 the latter: * * Resolver r reads from file:/dir/f1.xml * * some XML text * &e; -----> Entity e is bound to "subdir/f2.xml" * Step (1): let r' = "clone of r" * Step (2): open 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" = "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 (* A resolver can open an input source, and returns this source as * Lexing.lexbuf. * * After creating a resolver, one must invoke the two methods * init_rep_encoding and init_warner to set the internal encoding of * strings and the warner object, respectively. This is normally * done by the parsing functions in Pxp_yacc. * It is not necessary to invoke these two methods for a fresh * clone. * * It is possible that the character encoding of the source and the * internal encoding of the parser are different. To cope with this, * one of the tasks of the resolver is to recode the characters of * the input source into the internal character encoding. * * Note that there are several ways of determining the encoding of the * input: (1) It is possible that the transport protocol (e.g. HTTP) * transmits the encoding, and (2) it is possible to inspect the beginning * of the file, and to analyze: * (2.1) The first two bytes indicate whether UTF-16 is used * (2.2) Otherwise, one can assume that an ASCII-compatible character * set is used. It is now possible to read the XML declaration * . The encoding found here is * to be used. * (2.3) If the XML declaration is missing, the encoding is UTF-8. * The resolver needs only to distinguish between cases (1), (2.1), * and the rest. * The details of analyzing whether (2.2) or (2.3) applies are programmed * elsewhere, and the resolver will be told the result (see below). * * A resolver is like a file: it must be opened before one can work * with it, and it should be closed after all operations on it have been * done. The method 'open_in' is called with the external ID as argument * and it must return the lexbuf reading from the external resource. * The method 'close_in' does not require an argument. * * It is allowed to re-open a resolver after it has been closed. It is * forbidden to open a resolver again while it is open. * It is allowed to close a resolver several times: If 'close_in' is * invoked while the resolver is already closed, nothing happens. * * The method 'open_in' may raise Not_competent to indicate that this * resolver is not able to open this type of IDs. * * The method 'change_encoding' is called from the parser after the * analysis of case (2) has been done; the argument is either the * string name of the encoding, or the empty string to indicate * that no XML declaration was found. It is guaranteed that * 'change_encoding' is invoked after only a few tokens of the * file. The resolver should react as follows: * - If case (1) applies: Ignore the encoding passed to 'change_encoding'. * - If case (2.1) applies: The encoding passed to 'change_encoding' must * be compatible with UTF-16. This should be * checked, and violations should be reported. * - Else: If the passed encoding is "", assume UTF-8. * Otherwise, assume the passed encoding. * * The following rule helps synchronizing the lexbuf with the encoding: * If the resolver has been opened, but 'change_encoding' has not yet * been invoked, the lexbuf contains at most one character (which may * be represented by multiple bytes); i.e. the lexbuf is created by * Lexing.from_function, and the function puts only one character into * the buffer at once. * After 'change_encoding' has been invoked, there is no longer a limit * on the lexbuf size. * * The reason for this rule is that you know exactly the character where * the encoding changes to the encoding passed by 'change_encoding'. * * The method 'clone' may be invoked for open or closed resolvers. * Basically, 'clone' returns a new resolver which is always closed. * If the original resolver is closed, the clone is simply a clone. * If the original resolver is open at the moment of cloning: * If the clone is later opened for a relative system ID (i.e. relative * URL), the clone must interpret this ID relative to the ID of the * original resolver. *) method init_rep_encoding : rep_encoding -> unit method init_warner : collect_warnings -> unit method rep_encoding : rep_encoding method open_in : ext_id -> Lexing.lexbuf (* May raise Not_competent if the object does not know how to handle * this ext_id. *) method close_in : unit method change_encoding : string -> unit (* Every resolver can be cloned. The clone does not inherit the connection * with the external object, i.e. it is initially closed. *) method clone : resolver method close_all : unit (* Closes this resolver and every clone *) end ;; (* Note: resolve_general is no longer exported. In most cases, the classes * resolve_read_any_channel or resolve_read_any_string are applicable, too, * and much easier to configure. *) (* The next classes are resolvers for concrete input sources. *) class resolve_read_this_channel : ?id:ext_id -> ?fixenc:encoding -> ?auto_close:bool -> in_channel -> resolver;; (* Reads from the passed channel (it may be even a pipe). If the ~id * argument is passed to the object, the created resolver accepts only * this ID. Otherwise all IDs are accepted. * Once the resolver has been cloned, it does not accept any ID. This * means that this resolver cannot handle inner references to external * entities. Note that you can combine this resolver with another resolver * that can handle inner references (such as resolve_as_file); see * class 'combine' below. * If you pass the ~fixenc argument, the encoding of the channel is * set to the passed value, regardless of any auto-recognition or * any XML declaration. * If ?auto_close = true (which is the default), the channel is * closed after use. If ?auto_close = false, the channel is left open. *) class resolve_read_any_channel : ?auto_close:bool -> channel_of_id:(ext_id -> (in_channel * encoding option)) -> resolver;; (* resolve_read_any_channel f_open: * This resolver calls the function f_open to open a new channel for * the passed ext_id. This function must either return the channel and * the encoding, or it must fail with Not_competent. * The function must return None as encoding if the default mechanism to * recognize the encoding should be used. It must return Some e if it is * already known that the encoding of the channel is e. * If ?auto_close = true (which is the default), the channel is * closed after use. If ?auto_close = false, the channel is left open. *) class resolve_read_url_channel : ?base_url:Neturl.url -> ?auto_close:bool -> url_of_id:(ext_id -> Neturl.url) -> channel_of_url:(Neturl.url -> (in_channel * encoding option)) -> resolver;; (* resolve_read_url_channel url_of_id channel_of_url: * * When this resolver gets an ID to read from, it calls the function * ~url_of_id to get the corresponding URL. This URL may be a relative * URL; however, a URL scheme must be used which contains a path. * The resolver converts the URL to an absolute URL if necessary. * The second function, ~channel_of_url, is fed with the absolute URL * as input. This function opens the resource to read from, and returns * the channel and the encoding of the resource. * * Both functions, ~url_of_id and ~channel_of_url, can raise * Not_competent to indicate that the object is not able to read from * the specified resource. However, there is a difference: A Not_competent * from ~url_of_id is left as it is, but a Not_competent from ~channel_of_url * is converted to Not_resolvable. So only ~url_of_id decides which URLs * are accepted by the resolver and which not. * * The function ~channel_of_url must return None as encoding if the default * mechanism to recognize the encoding should be used. It must return * Some e if it is already known that the encoding of the channel is e. * * If ?auto_close = true (which is the default), the channel is * closed after use. If ?auto_close = false, the channel is left open. * * Objects of this class contain a base URL relative to which relative * URLs are interpreted. When creating a new object, you can specify * the base URL by passing it as ~base_url argument. When an existing * object is cloned, the base URL of the clone is the URL of the original * object. * * Note that the term "base URL" has a strict definition in RFC 1808. *) class resolve_read_this_string : ?id:ext_id -> ?fixenc:encoding -> string -> resolver;; (* Reads from the passed string. If the ~id * argument is passed to the object, the created resolver accepts only * this ID. Otherwise all IDs are accepted. * Once the resolver has been cloned, it does not accept any ID. This * means that this resolver cannot handle inner references to external * entities. Note that you can combine this resolver with another resolver * that can handle inner references (such as resolve_as_file); see * class 'combine' below. * If you pass the ~fixenc argument, the encoding of the string is * set to the passed value, regardless of any auto-recognition or * any XML declaration. *) class resolve_read_any_string : string_of_id:(ext_id -> (string * encoding option)) -> resolver;; (* resolver_read_any_string f_open: * This resolver calls the function f_open to get the string for * the passed ext_id. This function must either return the string and * the encoding, or it must fail with Not_competent. * The function must return None as encoding if the default mechanism to * recognize the encoding should be used. It must return Some e if it is * already known that the encoding of the string is e. *) class resolve_as_file : ?file_prefix:[ `Not_recognized | `Allowed | `Required ] -> ?host_prefix:[ `Not_recognized | `Allowed | `Required ] -> ?system_encoding:encoding -> ?url_of_id:(ext_id -> Neturl.url) -> ?channel_of_url: (Neturl.url -> (in_channel * encoding option)) -> unit -> resolver;; (* Reads from the local file system. Every file name is interpreted as * file name of the local file system, and the referred file is read. * * The full form of a file URL is: file://host/path, where * 'host' specifies the host system where the file identified 'path' * resides. host = "" or host = "localhost" are accepted; other values * will raise Not_competent. The standard for file URLs is * defined in RFC 1738. * * Option ~file_prefix: Specifies how the "file:" prefix of file names * is handled: * `Not_recognized: The prefix is not recognized. * `Allowed: The prefix is allowed but not required (the default). * `Required: The prefix is required. * * Option ~host_prefix: Specifies how the "//host" phrase of file names * is handled: * `Not_recognized: The phrase is not recognized. * `Allowed: The phrase is allowed but not required (the default). * `Required: The phrase is required. * * Option ~system_encoding: Specifies the encoding of file names of * the local file system. Default: UTF-8. * * Options ~url_of_id, ~channel_of_url: Not for the end user! *) class combine : ?prefer:resolver -> resolver list -> resolver;; (* Combines several resolver objects. If a concrete entity with an * ext_id is to be opened, the combined resolver tries the contained * resolvers in turn until a resolver accepts opening the entity * (i.e. it does not raise Not_competent on open_in). * * Clones: If the 'clone' method is invoked before 'open_in', all contained * resolvers are cloned and again combined. If the 'clone' method is * invoked after 'open_in' (i.e. while the resolver is open), only the * active resolver is cloned. *) (* EXAMPLES OF RESOLVERS: * * let r1 = new resolve_as_file * - r1 can open all local files * * let r2 = new resolve_read_this_channel * ~id:"file:/dir/f.xml" * (open_in "/dir/f.xml") * - r2 can only read /dir/f.xml of the local file system. If this file * contains references to other files, r2 will fail * * let r3 = new combine [ r2; r1 ] * - r3 reads /dir/f.xml of the local file system by calling r2, and all * other files by calling r1 *) (* ====================================================================== * History: * * $Log$ * Revision 1.1 2000/11/17 09:57:29 lpadovan * Initial revision * * Revision 1.5 2000/07/09 01:05:33 gerd * New methode 'close_all' that closes the clones, too. * * Revision 1.4 2000/07/08 16:24:56 gerd * Introduced the exception 'Not_resolvable' to indicate that * 'combine' should not try the next resolver of the list. * * Revision 1.3 2000/07/06 23:04:46 gerd * Quick fix for 'combine': The active resolver is "prefered", * but the other resolvers are also used. * * Revision 1.2 2000/07/04 22:06:49 gerd * MAJOR CHANGE: Complete redesign of the reader classes. * * Revision 1.1 2000/05/29 23:48:38 gerd * Changed module names: * Markup_aux into Pxp_aux * Markup_codewriter into Pxp_codewriter * Markup_document into Pxp_document * Markup_dtd into Pxp_dtd * Markup_entity into Pxp_entity * Markup_lexer_types into Pxp_lexer_types * Markup_reader into Pxp_reader * Markup_types into Pxp_types * Markup_yacc into Pxp_yacc * See directory "compatibility" for (almost) compatible wrappers emulating * Markup_document, Markup_dtd, Markup_reader, Markup_types, and Markup_yacc. * * ====================================================================== * Old logs from markup_reader.mli: * * Revision 1.3 2000/05/29 21:14:57 gerd * Changed the type 'encoding' into a polymorphic variant. * * Revision 1.2 2000/05/20 20:31:40 gerd * Big change: Added support for various encodings of the * internal representation. * * Revision 1.1 2000/03/13 23:41:54 gerd * Initial revision. * * *)