--- /dev/null
+(* $Id$
+ * ----------------------------------------------------------------------
+ * 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
+ *
+ * <tag>some XML text
+ * &e; -----> Entity e is bound to "subdir/f2.xml"
+ * </tag> 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
+ * <?xml ... encoding="xyz" ...?>. 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.
+ *
+ *
+ *)
projects / helm.git / blobdiff