9 Libucl is a parser and `C` API to parse and generate `ucl` objects. Libucl consist of several groups of functions:
12 Used to parse `ucl` files and provide interface to extract `ucl` object
14 ### Emitting functions
15 Convert `ucl` objects to some textual or binary representation.
17 ### Conversion functions
18 Help to convert `ucl` objects to C types
20 ### Generation functions
21 Allow creating of `ucl` objects from C types
23 ### Iteration functions
24 Iterate over `ucl` objects
27 Provide basic utilities to manage `ucl` objects
31 Parser functions operates with `struct ucl_parser`.
36 struct ucl_parser* ucl_parser_new (int flags);
39 Creates new parser with the specified flags:
41 - `UCL_PARSER_KEY_LOWERCASE` - lowercase keys parsed
42 - `UCL_PARSER_ZEROCOPY` - try to use zero-copy mode when reading files (in zero-copy mode text chunk being parsed without copying strings so it should exist till any object parsed is used)
44 ### ucl_parser_register_macro
47 void ucl_parser_register_macro (struct ucl_parser *parser,
48 const char *macro, ucl_macro_handler handler, void* ud);
51 Register new macro with name .`macro` parsed by handler `handler` that accepts opaque data pointer `ud`. Macro handler should be of the following type:
54 bool (*ucl_macro_handler) (const unsigned char *data,
55 size_t len, void* ud);`
58 Handler function accepts macro text `data` of length `len` and the opaque pointer `ud`. If macro is parsed successfully the handler should return `true`. `false` indicates parsing failure and the parser can be terminated.
60 ### ucl_parser_register_variable
63 void ucl_parser_register_variable (struct ucl_parser *parser,
64 const char *var, const char *value);
67 Register new variable $`var` that should be replaced by the parser to the `value` string.
69 ### ucl_parser_add_chunk
72 bool ucl_parser_add_chunk (struct ucl_parser *parser,
73 const unsigned char *data, size_t len);
76 Add new text chunk with `data` of length `len` to the parser. At the moment, `libucl` parser is not a streamlined parser and chunk *must* contain the *valid* ucl object. For example, this object should be valid:
82 while this one won't be parsed correctly:
88 This limitation may possible be removed in future.
90 ### ucl_parser_add_file
93 bool ucl_parser_add_file (struct ucl_parser *parser,
94 const char *filename);
97 Load file `filename` and parse it with the specified `parser`. This function uses `mmap` call to load file, therefore, it should not be `shrinked` during parsing. Otherwise, `libucl` can cause memory corruption and terminate the calling application. This function is also used by the internal handler of `include` macro, hence, this macro has the same limitation.
99 ### ucl_parser_get_object
102 ucl_object_t* ucl_parser_get_object (struct ucl_parser *parser);
105 If the `ucl` data has been parsed correctly this function returns the top object for the parser. Otherwise, this function returns the `NULL` pointer. The reference count for `ucl` object returned is increased by one, therefore, a caller should decrease reference by using `ucl_object_unref` to free object after usage.
107 ### ucl_parser_get_error
110 const char *ucl_parser_get_error(struct ucl_parser *parser);
113 Returns the constant error string for the parser object. If no error occurred during parsing a `NULL` object is returned. A caller should not try to free or modify this string.
118 void ucl_parser_free (struct ucl_parser *parser);
121 Frees memory occupied by the parser object. The reference count for top object is decreased as well, however if the function `ucl_parser_get_object` was called previously then the top object won't be freed.
126 bool ucl_pubkey_add (struct ucl_parser *parser,
127 const unsigned char *key, size_t len);
130 This function adds a public key from text blob `key` of length `len` to the `parser` object. This public key should be in the `PEM` format and can be used by `.includes` macro for checking signatures of files included. `Openssl` support should be enabled to make this function working. If a key cannot be added (e.g. due to format error) or `openssl` was not linked to `libucl` then this function returns `false`.
132 ### ucl_parser_set_filevars
135 bool ucl_parser_set_filevars (struct ucl_parser *parser,
136 const char *filename, bool need_expand);
139 Add the standard file variables to the `parser` based on the `filename` specified:
141 - `$FILENAME` - a filename of `ucl` input
142 - `$CURDIR` - a current directory of the input
144 For example, if a `filename` param is `../something.conf` then the variables will have the following values:
146 - `$FILENAME` - "../something.conf"
149 if `need_expand` parameter is `true` then all relative paths are expanded using `realpath` call. In this example if `..` is `/etc/dir` then variables will have these values:
151 - `$FILENAME` - "/etc/something.conf"
154 ## Parser usage example
156 The following example loads, parses and extracts `ucl` object from stdin using `libucl` parser functions (the length of input is limited to 8K):
160 struct ucl_parser *parser = NULL;
162 ucl_object_t *obj = NULL;
166 parser = ucl_parser_new (0);
167 while (!feof (in) && r < (int)sizeof (inbuf)) {
168 r += fread (inbuf + r, 1, sizeof (inbuf) - r, in);
170 ucl_parser_add_chunk (parser, inbuf, r);
173 if (ucl_parser_get_error (parser)) {
174 printf ("Error occured: %s\n", ucl_parser_get_error (parser));
178 obj = ucl_parser_get_object (parser);
181 if (parser != NULL) {
182 ucl_parser_free (parser);
185 ucl_object_unref (obj);
192 Libucl can transform UCL objects to a number of tectual formats:
194 - configuration (`UCL_EMIT_CONFIG`) - nginx like human readable configuration file where implicit arrays are transformed to the duplicate keys
195 - compact json: `UCL_EMIT_JSON_COMPACT` - single line valid json without spaces
196 - formatted json: `UCL_EMIT_JSON` - pretty formatted JSON with newlines and spaces
197 - compact yaml: `UCL_EMIT_YAML` - compact YAML output
199 Moreover, libucl API allows to select a custom set of emitting functions allowing
200 efficent and zero-copy output of libucl objects. Libucl uses the following structure to support this feature:
203 struct ucl_emitter_functions {
204 /** Append a single character */
205 int (*ucl_emitter_append_character) (unsigned char c, size_t nchars, void *ud);
206 /** Append a string of a specified length */
207 int (*ucl_emitter_append_len) (unsigned const char *str, size_t len, void *ud);
208 /** Append a 64 bit integer */
209 int (*ucl_emitter_append_int) (int64_t elt, void *ud);
210 /** Append floating point element */
211 int (*ucl_emitter_append_double) (double elt, void *ud);
212 /** Opaque userdata pointer */
217 This structure defines the following callbacks:
219 - `ucl_emitter_append_character` - a function that is called to append `nchars` characters equal to `c`
220 - `ucl_emitter_append_len` - used to append a string of length `len` starting from pointer `str`
221 - `ucl_emitter_append_int` - this function applies to integer numbers
222 - `ucl_emitter_append_double` - this function is intended to output floating point variable
224 The set of these functions could be used to output text formats of `UCL` objects to different structures or streams.
226 Libucl provides the following functions for emitting UCL objects:
231 unsigned char *ucl_object_emit (ucl_object_t *obj, enum ucl_emitter emit_type);
234 Allocate a string that is suitable to fit the underlying UCL object `obj` and fill it with the textual representation of the object `obj` according to style `emit_type`. The caller should free the returned string after using.
236 ### ucl_object_emit_full
239 bool ucl_object_emit_full (ucl_object_t *obj, enum ucl_emitter emit_type,
240 struct ucl_emitter_functions *emitter);
243 This function is similar to the previous with the exception that it accepts the additional argument `emitter` that defines the concrete set of output functions. This emit function could be useful for custom structures or streams emitters (including C++ ones, for example).
245 # Conversion functions
247 Conversion functions are used to convert UCL objects to primitive types, such as strings, numbers or boolean values. There are two types of conversion functions:
249 - safe: try to convert an ucl object to a primitive type and fail if such a conversion is not possible
250 - unsafe: return primitive type without additional checks, if the object cannot be converted then some reasonable default is returned (NULL for strings and 0 for numbers)
252 Also there is a single `ucl_object_tostring_forced` function that converts any UCL object (including compound types - arrays and objects) to a string representation. For compound and numeric types this function performs emitting to a compact json format actually.
254 Here is a list of all conversion functions:
256 - `ucl_object_toint` - returns `int64_t` of UCL object
257 - `ucl_object_todouble` - returns `double` of UCL object
258 - `ucl_object_toboolean` - returns `bool` of UCL object
259 - `ucl_object_tostring` - returns `const char *` of UCL object (this string is NULL terminated)
260 - `ucl_object_tolstring` - returns `const char *` and `size_t` len of UCL object (string can be not NULL terminated)
261 - `ucl_object_tostring_forced` - returns string representation of any UCL object
263 Strings returned by these pointers are associated with the UCL object and exist over its lifetime. A caller should not free this memory.
265 # Generation functions
267 It is possible to generate UCL objects from C primitive types. Moreover, libucl permits to create and modify complex UCL objects, such as arrays or associative objects.
271 ucl_object_t * ucl_object_new (void)
274 Creates new object of type `UCL_NULL`. This object should be released by caller.
276 ## ucl_object_typed_new
278 ucl_object_t * ucl_object_typed_new (unsigned int type)
281 Create an object of a specified type:
282 - `UCL_OBJECT` - UCL object - key/value pairs
283 - `UCL_ARRAY` - UCL array
284 - `UCL_INT` - integer number
285 - `UCL_FLOAT` - floating point number
286 - `UCL_STRING` - NULL terminated string
287 - `UCL_BOOLEAN` - boolean value
288 - `UCL_TIME` - time value (floating point number of seconds)
289 - `UCL_USERDATA` - opaque userdata pointer (may be used in macros)
290 - `UCL_NULL` - null value
292 This object should be released by caller.
294 ## Primitive objects generation
295 Libucl provides the functions similar to inverse conversion functions called with the specific C type:
296 - `ucl_object_fromint` - converts `int64_t` to UCL object
297 - `ucl_object_fromdouble` - converts `double` to UCL object
298 - `ucl_object_fromboolean` - converts `bool` to UCL object
299 - `ucl_object_fromstring` - converts `const char *` to UCL object (this string is NULL terminated)
300 - `ucl_object_fromlstring` - converts `const char *` and `size_t` len to UCL object (string can be not NULL terminated)
302 Also there is a function to generate UCL object from a string performing various parsing or conversion operations called `ucl_object_fromstring_common`.
304 ## ucl_object_fromstring_common
306 ucl_object_t * ucl_object_fromstring_common (const char *str,
307 size_t len, enum ucl_string_flags flags)
310 This function is used to convert a string `str` of size `len` to an UCL objects applying `flags` conversions. If `len` is equal to zero then a `str` is assumed as NULL-terminated. This function supports the following flags (a set of flags can be specified using logical `OR` operation):
312 - `UCL_STRING_ESCAPE` - perform JSON escape
313 - `UCL_STRING_TRIM` - trim leading and trailing whitespaces
314 - `UCL_STRING_PARSE_BOOLEAN` - parse passed string and detect boolean
315 - `UCL_STRING_PARSE_INT` - parse passed string and detect integer number
316 - `UCL_STRING_PARSE_DOUBLE` - parse passed string and detect integer or float number
317 - `UCL_STRING_PARSE_NUMBER` - parse passed string and detect number (both float or integer types)
318 - `UCL_STRING_PARSE` - parse passed string (and detect booleans and numbers)
319 - `UCL_STRING_PARSE_BYTES` - assume that numeric multipliers are in bytes notation, for example `10k` means `10*1024` and not `10*1000` as assumed without this flag
321 If parsing operations fail then the resulting UCL object will be a `UCL_STRING`. A caller should always check the type of the returned object and release it after using.
325 Iteration are used to iterate over UCL compound types: arrays and objects. Moreover, iterations could be performed over the keys with multiple values (implicit arrays). To iterate over an object, an array or a key with multiple values there is a function `ucl_iterate_object`.
327 ## ucl_iterate_object
329 ucl_object_t* ucl_iterate_object (ucl_object_t *obj,
330 ucl_object_iter_t *iter, bool expand_values);
333 This function accept opaque iterator pointer `iter`. In the first call this iterator *must* be initialized to `NULL`. Iterator is changed by this function call. `ucl_iterate_object` returns the next UCL object in the compound object `obj` or `NULL` if all objects have been iterated. The reference count of the object returned is not increased, so a caller should not unref the object or modify its content (e.g. by inserting to another compound object). The object `obj` should not be changed during the iteration process as well. `expand_values` flag speicifies whether `ucl_iterate_object` should expand keys with multiple values. The general rule is that if you need to iterate throught the *object* or *explicit array*, then you always need to set this flag to `true`. However, if you get some key in the object and want to extract all its values then you should set `expand_values` to `false`. Mixing of iteration types are not permitted since the iterator is set according to the iteration type and cannot be reused. Here is an example of iteration over the objects using libucl API (assuming that `top` is `UCL_OBJECT` in this example):
336 ucl_object_iter_t it = NULL, it_obj = NULL;
337 ucl_object_t *cur, *tmp;
339 /* Iterate over the object */
340 while ((obj = ucl_iterate_object (top, &it, true))) {
341 printf ("key: \"%s\"\n", ucl_object_key (obj));
342 /* Iterate over the values of a key */
343 while ((cur = ucl_iterate_object (obj, &it_obj, false))) {
344 printf ("value: \"%s\"\n",
345 ucl_object_tostring_forced (cur));