libdatovka - Man Page

ISDS client library

Synopsis

#include <libdatovka/isds.h>
#include <stdio.h>

isds_error err;
struct isds_ctx *ctx;

err = isds_init();
ctx = isds_ctx_create();

err = isds_login(ctx, NULL, "username", "password", NULL, NULL);
if (err) {
    printf("isds_login() failed: %s: %s\n",
        isds_strerror(err), isds_long_message(ctx));
} else {
    printf("Logged in.\n");
}

err = isds_ctx_free(&ctx);
err = isds_cleanup();

This is a client library for accessing SOAP services of ISDS (Informační systém datových schránek / Data Box Information System) as defined in Czech ISDS Act (300/2008 Coll.)^[1] and implied documents. Current implementation details are described in Provozní řád that can be downloaded from Dokumenty ke stažení section of ISDS Information Portal^[2].

The library provides a C language interface with synchronous non-reentrant blocking calls. Network communication progress reporting and operation logging and library debugging are implemented by calling back application-provided functions. Network operations can be cancelled from network reporting call-back.

Library Initialization and Deinitialization

A libdatovka application must include the libdatovka/isds.h header file. The application must call isds_init function to initialize the library before calling any other library functions. After last libdatovka call, isds_cleanup function should be called to clean up some global resources and to deinitialize dependent libraries.

Contexts

Most of the functions operate on an established connection to the ISDS server. This is called a context and it's represented by a pointer to an opaque isds_ctx structure. The structure maintains state about network connection, authorization or error from last call on the context.

The context is allocated by isds_ctx_create function and deallocated by isds_ctx_free function.

There are more context subtypes. A specific subtype is assigned to the context when a fresh new context is passed to one of the few stratifying functions (isds_login, czp_convert_document, isds_request_new_testing_box). Once the context is specialized, you can use it only with functions understanding the subtype. This is not enforced by the library now, but it does not matter much because all the other functions assume the isds_login was called on the context. In other words, do not share the context among the three stratifying functions.

For example create a context with isds_ctx_create, then call isds_login, then work with box, then call isds_logout. Here you can reuse the context and log in as another user by calling isds_login again or destroy the context with isds_ctx_free if you don't need it anymore.

Or create a context with isds_ctx_create, send a document to authorized conversion using czp_convert_document, then you can send more documents to the authorized conversion by calling czp_convert_document again on the same context and finally destroy the context with isds_ctx_free.

Errors

Most of the functions return an error code of isds_error type. IE_SUCCESS value denotes a successful call. Other values represent some kind of failure.

You can use isds_strerror function to obtain a human readable string representation of the error code.

If a function with context argument failed, you can use isds_long_message function to obtain a detailed error message. Please note that returned value lasts only to the next call on the context.

Character Encoding

All strings exchanged between the library and the application are encoded in UTF-8. Although there are a few exceptions:

isds_strerror and isds_long_message functions return locale encoded string.
isds_version returns locale encoded string.
Log call-back function set by isds_set_log_callback function is called with raw byte stream.
isds_pki_credentials structure string members have encoding specific to cryptographic library linked to cURL library.

Global Settings

Some functions influence library behaviour globally. These are:

isds_init and isds_cleanup used to initialize and deinitialize the library.
isds_set_logging and isds_set_log_callback to set logging.

Logging and Debugging

Logging is global for all libdatovka calls. Log level and facility can be set with isds_set_logging function.

The log is printed on standard error output by default. Application can redirect the messages to a call-back function by registering the call-back function with isds_set_log_callback.

Network Input/Output

Some functions operating on a context create network sockets and do network input and output.

Network timeout can be set with isds_set_timeout function. Function calls aborted owing to the timeout will return IE_TIMED_OUT.

Network operation progress can be monitored by a call-back function. The call-back function can be registered using isds_set_xferinfo_callback function. Registered call-back function will be called periodically with arguments declaring amount of transferred data. The call-back return value determines whether to continue in the network operation or to cancel the operation. Functions failed owing to cancelling network operation will return IE_ABORTED. The now deprecated call-back function isds_set_progress_callback behaves similarly but uses floating-point values to pass amounts of transferred data. Is is discouraged to use isds_set_progress_callback in new code.

Memory Management

The library provides destructors for all libdatovka data structures. For example isds_ctx_free function accepts a pointer to a pointer to the isds_ctx structure, frees the double referenced structure (recursively), writes NULL to the pointed pointer (which invalidates the pointer effectively) and returns nothing.

Upon a function call, all output arguments are automatically reallocated to desired size. On a function failure, all output arguments are automatically deallocated and their pointers set to NULL. Exceptions are documented at respective functions.

Output strings are allocated using standard malloc call. Application is responsible for their deallocation (in case of no failure and if not specified otherwise.) Use standard free call for strings, use libdatovka destructors for libdatovka structures.