X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2FDEVEL%2Fpxp%2Fpxp%2Fpxp_reader.mli;fp=helm%2FDEVEL%2Fpxp%2Fpxp%2Fpxp_reader.mli;h=27a3680ecdbbda1e4253134770710906caa7d6d9;hb=c03d2c1fdab8d228cb88aaba5ca0f556318bebc5;hp=0000000000000000000000000000000000000000;hpb=758057e85325f94cd88583feb1fdf6b038e35055;p=helm.git diff --git a/helm/DEVEL/pxp/pxp/pxp_reader.mli b/helm/DEVEL/pxp/pxp/pxp_reader.mli new file mode 100644 index 000000000..27a3680ec --- /dev/null +++ b/helm/DEVEL/pxp/pxp/pxp_reader.mli @@ -0,0 +1,388 @@ +(* $Id$ + * ---------------------------------------------------------------------- + * 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. + * + * + *)