--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/curl/packages/OS400/README.OS400	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,341 @@
+
+Implementation notes:
+
+  This is a true OS/400 implementation, not a PASE implementation (for PASE,
+use AIX implementation).
+
+  The biggest problem with OS/400 is EBCDIC. Libcurl implements an internal
+conversion mechanism, but it has been designed for computers that have a
+single native character set. OS/400 default native character set varies
+depending on the country for which it has been localized. And more, a job
+may dynamically alter its "native" character set.
+  Several characters that do not have fixed code in EBCDIC variants are
+used in libcurl strings. As a consequence, using the existing conversion
+mechanism would have lead in a localized binary library - not portable across
+countries.
+  For this reason, and because libcurl was originally designed for ASCII based
+operating systems, the current OS/400 implementation uses ASCII as internal
+character set. This has been accomplished using the QADRT library and
+include files, a C and system procedures ASCII wrapper library. See IBM QADRT
+description for more information.
+  This then results in libcurl being an ASCII library: any function string
+argument is taken/returned in ASCII and a C/C++ calling program built around
+QADRT may use libcurl functions as on any other platform.
+  QADRT does not define ASCII wrappers for all C/system procedures: the
+OS/400 configuration header file and an additional module (os400sys.c) define
+some more of them, that are used by libcurl and that QADRT left out.
+  To support all the different variants of EBCDIC, non-standard wrapper
+procedures have been added to libcurl on OS/400: they provide an additional
+CCSID (numeric Coded Character Set ID specific to OS/400) parameter for each
+string argument. String values passed to callback procedures are NOT converted,
+so text gathered this way is (probably !) ASCII.
+
+  Another OS/400 problem comes from the fact that the last fixed argument of a
+vararg procedure may not be of type char, unsigned char, short or unsigned
+short. Enums that are internally implemented by the C compiler as one of these
+types are also forbidden. Libcurl uses enums as vararg procedure tagfields...
+Happily, there is a pragma forcing enums to type "int". The original libcurl
+header files are thus altered during build process to use this pragma, in
+order to force libcurl enums of being type int (the pragma disposition in use
+before inclusion is restored before resuming the including unit compilation).
+
+  Secure socket layer is provided by the IBM GSKit API: unlike other SSL
+implementations, GSKit is based on "certificate stores" or keyrings
+rather than individual certificate/key files. Certificate stores, as well as
+"certificate labels" are managed by external IBM-defined applications.
+  There are two ways to specify an SSL context:
+- By an application identifier.
+- By a keyring file pathname and (optionally) certificate label.
+  To identify an SSL context by application identifier, use option
+SETOPT_SSLCERT to specify the application identifier.
+  To address an SSL context by keyring and certificate label, use CURLOPT_CAINFO
+to set-up the keyring pathname, CURLOPT_SSLCERT to define the certificate label
+(omitting it will cause the default certificate in keyring to be used) and
+CURLOPT_KEYPASSWD to give the keyring password. If SSL is used without
+defining any of these options, the default (i.e.: system) keyring is used for
+server certificate validation.
+
+  Non-standard EBCDIC wrapper prototypes are defined in an additional header
+file: ccsidcurl.h. These should be self-explanatory to an OS/400-aware
+designer. CCSID 0 can be used to select the current job's CCSID.
+  Wrapper procedures with variable arguments are described below:
+
+_ curl_easy_setopt_ccsid()
+  Variable arguments are a string pointer and a CCSID (unsigned int) for
+options:
+        CURLOPT_ABSTRACT_UNIX_SOCKET
+        CURLOPT_ALTSVC
+        CURLOPT_CAINFO
+        CURLOPT_CAPATH
+        CURLOPT_COOKIE
+        CURLOPT_COOKIEFILE
+        CURLOPT_COOKIEJAR
+        CURLOPT_COOKIELIST
+        CURLOPT_COPYPOSTFIELDS
+        CURLOPT_CRLFILE
+        CURLOPT_CUSTOMREQUEST
+        CURLOPT_DEFAULT_PROTOCOL
+        CURLOPT_DNS_SERVERS
+        CURLOPT_DOH_URL
+        CURLOPT_EGDSOCKET
+        CURLOPT_ENCODING
+        CURLOPT_FTPPORT
+        CURLOPT_FTP_ACCOUNT
+        CURLOPT_FTP_ALTERNATIVE_TO_USER
+        CURLOPT_INTERFACE
+        CURLOPT_ISSUERCERT
+        CURLOPT_KEYPASSWD
+        CURLOPT_KRBLEVEL
+        CURLOPT_LOGIN_OPTIONS
+        CURLOPT_MAIL_AUTH
+        CURLOPT_MAIL_FROM
+        CURLOPT_NETRC_FILE
+        CURLOPT_NOPROXY
+        CURLOPT_PASSWORD
+        CURLOPT_PINNEDPUBLICKEY
+        CURLOPT_PRE_PROXY
+        CURLOPT_PROXY
+        CURLOPT_PROXYPASSWORD
+        CURLOPT_PROXYUSERNAME
+        CURLOPT_PROXYUSERPWD
+        CURLOPT_PROXY_CAINFO
+        CURLOPT_PROXY_CAPATH
+        CURLOPT_PROXY_CRLFILE
+        CURLOPT_PROXY_KEYPASSWD
+        CURLOPT_PROXY_PINNEDPUBLICKEY
+        CURLOPT_PROXY_SERVICE_NAME
+        CURLOPT_PROXY_SSLCERT
+        CURLOPT_PROXY_SSLCERTTYPE
+        CURLOPT_PROXY_SSLKEY
+        CURLOPT_PROXY_SSLKEYTYPE
+        CURLOPT_PROXY_SSL_CIPHER_LIST
+        CURLOPT_PROXY_TLS13_CIPHERS
+        CURLOPT_PROXY_TLSAUTH_PASSWORD
+        CURLOPT_PROXY_TLSAUTH_TYPE
+        CURLOPT_PROXY_TLSAUTH_USERNAME
+        CURLOPT_RANDOM_FILE
+        CURLOPT_RANGE
+        CURLOPT_REFERER
+        CURLOPT_REQUEST_TARGET
+        CURLOPT_RTSP_SESSION_UID
+        CURLOPT_RTSP_STREAM_URI
+        CURLOPT_RTSP_TRANSPORT
+        CURLOPT_SASL_AUTHZID
+        CURLOPT_SERVICE_NAME
+        CURLOPT_SOCKS5_GSSAPI_SERVICE
+        CURLOPT_SSH_HOST_PUBLIC_KEY_MD5
+        CURLOPT_SSH_KNOWNHOSTS
+        CURLOPT_SSH_PRIVATE_KEYFILE
+        CURLOPT_SSH_PUBLIC_KEYFILE
+        CURLOPT_SSLCERT
+        CURLOPT_SSLCERTTYPE
+        CURLOPT_SSLENGINE
+        CURLOPT_SSLKEY
+        CURLOPT_SSLKEYTYPE
+        CURLOPT_SSL_CIPHER_LIST
+        CURLOPT_TLS13_CIPHERS
+        CURLOPT_TLSAUTH_PASSWORD
+        CURLOPT_TLSAUTH_TYPE
+        CURLOPT_TLSAUTH_USERNAME
+        CURLOPT_UNIX_SOCKET_PATH
+        CURLOPT_URL
+        CURLOPT_USERAGENT
+        CURLOPT_USERNAME
+        CURLOPT_USERPWD
+        CURLOPT_XOAUTH2_BEARER
+  Else it is the same as for curl_easy_setopt().
+  Note that CURLOPT_ERRORBUFFER is not in the list above, since it gives the
+address of an (empty) character buffer, not the address of a string.
+CURLOPT_POSTFIELDS stores the address of static binary data (of type void *) and
+thus is not converted. If CURLOPT_COPYPOSTFIELDS is issued after
+CURLOPT_POSTFIELDSIZE != -1, the data size is adjusted according to the
+CCSID conversion result length.
+
+_ curl_formadd_ccsid()
+  In the variable argument list, string pointers should be followed by a (long)
+CCSID for the following options:
+        CURLFORM_FILENAME
+        CURLFORM_CONTENTTYPE
+        CURLFORM_BUFFER
+        CURLFORM_FILE
+        CURLFORM_FILECONTENT
+        CURLFORM_COPYCONTENTS
+        CURLFORM_COPYNAME
+        CURLFORM_PTRNAME
+  If taken from an argument array, an additional array entry must follow each
+entry containing one of the above option. This additional entry holds the CCSID
+in its value field, and the option field is meaningless.
+  It is not possible to have a string pointer and its CCSID across a function
+parameter/array boundary.
+  Please note that CURLFORM_PTRCONTENTS and CURLFORM_BUFFERPTR are considered
+unconvertible strings and thus are NOT followed by a CCSID.
+
+_ curl_easy_getinfo_ccsid()
+  The following options are followed by a 'char * *' and a CCSID. Unlike
+curl_easy_getinfo(), the value returned in the pointer should be freed after
+use:
+        CURLINFO_EFFECTIVE_URL
+        CURLINFO_CONTENT_TYPE
+        CURLINFO_FTP_ENTRY_PATH
+        CURLINFO_REDIRECT_URL
+        CURLINFO_PRIMARY_IP
+        CURLINFO_RTSP_SESSION_ID
+        CURLINFO_LOCAL_IP
+        CURLINFO_SCHEME
+  Likewise, the following options are followed by a struct curl_slist * * and a
+CCSID.
+        CURLINFO_SSL_ENGINES
+        CURLINFO_COOKIELIST
+Lists returned should be released with curl_slist_free_all() after use.
+  Option CURLINFO_CERTINFO is followed by a struct curl_certinfo * * and a
+CCSID. Returned structures should be free'ed using curl_certinfo_free_all()
+after use.
+  Other options are processed like in curl_easy_getinfo().
+
+_ curl_pushheader_bynum_cssid() and curl_pushheader_byname_ccsid()
+  Although the prototypes are self-explanatory, the returned string pointer
+should be freed after use, as opposite to the non-ccsid versions of these
+procedures.
+  Please note that HTTP2 is not (yet) implemented on OS/400, thus these
+functions will always return NULL.
+
+
+  Standard compilation environment does support neither autotools nor make;
+in fact, very few common utilities are available. As a consequence, the
+config-os400.h has been coded manually and the compilation scripts are
+a set of shell scripts stored in subdirectory packages/OS400.
+
+  The "curl" command and the test environment are currently not supported on
+OS/400.
+
+
+Protocols currently implemented on OS/400:
+_ DICT
+_ FILE
+_ FTP
+_ FTPS
+_ FTP with secure transmission
+_ GOPHER
+_ HTTP
+_ HTTPS
+_ IMAP
+_ IMAPS
+_ IMAP with secure transmission
+_ LDAP
+_ POP3
+_ POP3S
+_ POP3 with secure transmission
+_ RTSP
+_ SCP if libssh2 is enabled
+_ SFTP if libssh2 is enabled
+_ SMTP
+_ SMTPS
+_ SMTP with secure transmission
+_ TELNET
+_ TFTP
+
+
+
+Compiling on OS/400:
+
+  These instructions targets people who knows about OS/400, compiling, IFS and
+archive extraction. Do not ask questions about these subjects if you're not
+familiar with.
+
+_ As a prerequisite, QADRT development environment must be installed.
+_ If data compression has to be supported, ZLIB development environment must
+  be installed.
+_ Likewise, if SCP and SFTP protocols have to be compiled in, LIBSSH2
+  developent environment must be installed.
+_ Install the curl source directory in IFS. Do NOT install it in the
+  installation target directory (which defaults to /curl).
+_ Enter shell (QSH)
+_ Change current directory to the curl installation directory
+_ Change current directory to ./packages/OS400
+_ Edit file iniscript.sh. You may want to change tunable configuration
+  parameters, like debug info generation, optimisation level, listing option,
+  target library, ZLIB/LIBSSH2 availability and location, etc.
+_ Copy any file in the current directory to makelog (i.e.:
+  cp initscript.sh makelog): this is intended to create the makelog file with
+  an ASCII CCSID!
+_ Enter the command "sh makefile.sh > makelog 2>&1'
+_ Examine the makelog file to check for compilation errors.
+
+  Leaving file initscript.sh unchanged, this will produce the following OS/400
+objects:
+_ Library CURL. All other objects will be stored in this library.
+_ Modules for all libcurl units.
+_ Binding directory CURL_A, to be used at calling program link time for
+  statically binding the modules (specify BNDSRVPGM(QADRTTS QGLDCLNT QGLDBRDR)
+  when creating a program using CURL_A).
+_ Service program CURL.<soname>, where <soname> is extracted from the
+  lib/Makefile.am VERSION variable. To be used at calling program run-time
+  when this program has dynamically bound curl at link time.
+_ Binding directory CURL. To be used to dynamically bind libcurl when linking a
+  calling program.
+_ Source file H. It contains all the include members needed to compile a C/C++
+  module using libcurl, and an ILE/RPG /copy member for support in this
+  language.
+_ Standard C/C++ libcurl include members in file H.
+_ CCSIDCURL member in file H. This defines the non-standard EBCDIC wrappers for
+  C and C++.
+_ CURL.INC member in file H. This defines everything needed by an ILE/RPG
+  program using libcurl.
+_ LIBxxx modules and programs. Although the test environment is not supported
+  on OS/400, the libcurl test programs are compiled for manual tests.
+_ IFS directory /curl/include/curl containing the C header files for IFS source
+  C/C++ compilation and curl.inc.rpgle for IFS source ILE/RPG compilation.
+
+
+
+Special programming consideration:
+
+QADRT being used, the following points must be considered:
+_ If static binding is used, service program QADRTTS must be linked too.
+_ The EBCDIC CCSID used by QADRT is 37 by default, NOT THE JOB'S CCSID. If
+  another EBCDIC CCSID is required, it must be set via a locale through a call
+  to setlocale_a (QADRT's setlocale() ASCII wrapper) with category LC_ALL or
+  LC_CTYPE, or by setting environment variable QADRT_ENV_LOCALE to the locale
+  object path before executing the program.
+_ Do not use original source include files unless you know what you are doing.
+  Use the installed members instead (in /QSYS.LIB/CURL.LIB/H.FILE and
+  /curl/include/curl).
+
+
+
+ILE/RPG support:
+
+  Since 95% of the OS/400 programmers use ILE/RPG exclusively, a definition
+  /INCLUDE member is provided for this language. To include all libcurl
+  definitions in an ILE/RPG module, line
+
+     h bnddir('CURL/CURL')
+
+must figure in the program header, and line
+
+     d/include curl/h,curl.inc
+
+in the global data section of the module's source code.
+
+  No vararg procedure support exists in ILE/RPG: for this reason, the following
+considerations apply:
+_ Procedures curl_easy_setopt_long(), curl_easy_setopt_object(),
+  curl_easy_setopt_function() and curl_easy_setopt_offset() are all alias
+  prototypes to curl_easy_setopt(), but with different parameter lists.
+_ Procedures curl_easy_getinfo_string(), curl_easy_getinfo_long(),
+  curl_easy_getinfo_double(), curl_easy_getinfo_slist(),
+  curl_easy_getinfo_ptr(), curl_easy_getinfo_socket() and
+  curl_easy_getinfo_off_t() are all alias prototypes to curl_easy_getinfo(),
+  but with different parameter lists.
+_ Procedures curl_multi_setopt_long(), curl_multi_setopt_object(),
+  curl_multi_setopt_function() and curl_multi_setopt_offset() are all alias
+  prototypes to curl_multi_setopt(), but with different parameter lists.
+_ The prototype of procedure curl_formadd() allows specifying a pointer option
+  and the CURLFORM_END option. This makes possible to use an option array
+  without any additional definition. If some specific incompatible argument
+  list is used in the ILE/RPG program, the latter must define a specialised
+  alias. The same applies to curl_formadd_ccsid() too.
+
+  Since RPG cannot cast a long to a pointer, procedure curl_form_long_value()
+is provided for that purpose: this allows storing a long value in the curl_forms
+array.