libconfini
Yet another INI parser
Library Functions Manual

User Guide for libconfini

DESCRIPTION

libconfini is a simple INI parsing library with the ability to read disabled entries (i.e. valid entries nested in comments). libconfini does not store the data read from an INI file, but rather dispatches it, formatted, to a custom listener.

The code is written in C (C99) and does not depend on any particular library, except for the C standard headers stdio.h, stdlib.h and stdint.h.

If you want to start to learn directly from the code, you can find partially self-documented sample usages of libconfini under /usr/share/doc/libconfini/examples/.

WHAT IS AN INI FILE?

INI files were introduced with the early versions of Microsoft Windows, where the .ini file name extension stood for INItialization. An INI file may be considered as a string representation of a tree object, with new lines used as delimiters between nodes. A typical INI file is a plain text file looking like the following example:

# delivery.conf
; general options
location = Colosseum
place = Rome
[sender]
name = John Smith
email = john.smith@example.com
[receiver]
name = Mario Rossi # He's a big guy
email = mario.rossi@example.com

SUPPORTED SYNTAXES

During the years several interpretations of INI files appeared. In some implementations the colon character (:) has been adopted as delimiter between keys and values instead of the classic equals sign (a typical example under GNU/Linux is /etc/nsswitch.conf); in other implementations, under the influence of Unix standard configuration files, a sequence of one or more spaces (/[ \t\v\f]+/ or /(?:\\(?:\n\r?|\r\n?)|[\t \v\f])+/) has been used instead (see for example /etc/host.conf).

Equals sign used as delimiter between keys and values:

# example1.ini
home = Champ de Mars, 5 Avenue Anatole
city = Paris

Colon sign used as delimiter between keys and values:

# example2.ini
home: Champ de Mars, 5 Avenue Anatole
city: Paris

Space sequence used as delimiter between keys and values:

# example3.ini
home Champ de Mars, 5 Avenue Anatole
city Paris

This library has been born as a general INI parser for GNU, so the support of most part of INI dialects has been implemented within it.

Especially in Microsoft Windows a more radical syntax variation has been implemented: the use of semicolon, instead of new lines, as delimiter between nodes, as in the following example:

# delivery.conf
; general options
location=Colosseum;place=Rome;[sender] name=John Smith;
email=john.smith@example.com;
[receiver] name=Mario Rossi; # He's a big guy
email=mario.rossi@example.com

For several reasons the use of semicolon as node delimiter is not (and will never be) supported by libconfini.

KEYS

A key element is identified as a string placed after a new line and followed by a delimiter – typically the equals sign (=) or the colon sign (:) or a space sequence (/\s+/) – which is followed by a value, which is followed by a new line or an inline comment.

Both the key part and the value part may be enclosed within quotes (' or "):

foo = 'bar'
"hello" = world
"artist" = "Pablo Picasso"

The key part can contain any character, except the delimiter (which may be enclosed within quotes for not beeing considered as such). In multi-line formats internal new line sequences must be escaped (/\\(?:\n\r?|\r\n?)/).

If the key part part is missing libconfini considers the element of unknown type (example: = foo). If the value part is missing the key element is considered empty (example: foo =). If the delimiter is missing (and therefore the value part as well), according to some formats the key element is considered to be an implicit key – typically representing the boolean true (example: foo). For instance, in the following example from /etc/pacman.conf, IgnorePkg is an empty key, while Color is an implicit key (representing a true boolean – i.e. Color = YES):

HoldPkg = pacman glibc
Architecture = auto
IgnorePkg =
Color
SigLevel = Required DatabaseOptional
LocalFileSigLevel = Optional

The value part can contain typed data, usually: a boolean (booleans supported by libconfini are: FALSE/TRUE, NO/YES, OFF/ON – case insensitive), a string, a number, or an array (typically with commas or spaces as delimiters between members – examples: paths = /etc, /usr, "/home/john/Personal Data" or paths = /etc /usr "/home/john/Personal Data"). In multi-line formats internal new line sequences must be escaped (/\\(?:\n\r?|\r\n?)/).

[my_section]
my_string = "Hello world"
'my_number' = 42
my_boolean = NO
my_implicit_boolean
my_array = Asia, Africa, 'North America', South America,\
Antarctica, Europe, Australia

SECTIONS

A section might be imagined like a directory. A section path is identified as the string "$1" in the regular expression /(?:^|\n|\r)[ \t\v\f]*\[[ \t\v\f]*([^\]]*)[ \t\v\f]*\][ \t\v\f]*(?:\n|\r|$)/ globally applied to an INI file. A section path expresses nesting using the “dot” character, as in the following example:

[section]
foo = bar
[section.subsection]
foo = bar

A section path starting with a dot expresses nesting to the previous section. Hence the last example is equivalent to:

[section]
foo = bar
[.subsection]
foo = bar

Keys appearing before any section path belong to a virtual root node (with an empty string as path), as the key foo in the following example:

foo = bar
[options]
interval = 3600
[host]
address = 127.0.0.1
port = 80

Section parts may be enclosed within quotes:

["world".europe.'germany'.berlin]
foo = bar

COMMENTS

Comments are string segments enclosed within the sequence /(?:^|\s)[;#]/ and a new line sequence, as in the following example:

# this is a comment
foo = bar # this is an inline comment
; this is another comment

Comments may in theory be multi-line, following the same syntax of multi-line disabled entries (see below). This is usually of little utility, except for inline comments you want to make sure will refer to the previous entry:

play1 = The Tempest
play2 = Twelfth Night # If music be the food of love, play on; \
# Give me excess of it; that, surfeiting, \
# The appetite may sicken, and so die. \
# That strain again; it had a dying fall: \
# O, it came oer my ear, like the sweet sound \
# That breathes upon a bank of violets, \
# Stealing, and giving odour! Enough! No more.\
# 'Tis not so sweet now as it was before. \
# \
# Orsino, scene I
# This is also a masterpiece!
comedy3 = The Merchant of Venice

DISABLED ENTRIES

A disabled entry is either a section or a key that has been nested inside a comment as its only child. Inline comments cannot represent disabled entries. According to some formats disabled entries can be multi-line, using /\\(?:\n\r?|\r\n?)[\t \v\f]*[;#]/ as multi-line escape sequence. For example:

#this = is\
#a\
#multi-line\
#disabled\
#entry

ESCAPE SEQUENCES

In order to maximize the flexibility of the data, only four escape sequences are supported by libconfini: \', \", \\ and the multi-line escape sequence (/\\(?:\n\r?|\r\n?)/).

The first three escape sequences are left untouched by all functions except ini_string_parse() and ini_unquote() (see below). Nevertheless, the characters ', " and \ can determine different behaviors during the parsing depending on whether they are escaped or unescaped. For instance, the string johnsmith !" in the following example will not be parsed as a comment:

[users.jsmith]
comment = "hey! have a look at my hashtag #johnsmith !"

A particular case of escape sequence is the multi-line escape sequence (/\\(?:\n\r?|\r\n?)/), which in multi-line INI files gets immediately unescaped by libconfini.

foo = this\
is\
a\
multi-line\
value

READ AN INI FILE

The syntax of libconfini's parsing functions is:

#1 Using a pointer to a FILE handle:

FILE * ini_file,
IniFormat format,
IniDispHandler f_foreach,
void * user_data
)

#2 Using a path:

const char * path,
IniFormat format,
IniDispHandler f_foreach,
void * user_data
)

where

  • ini_file in load_ini_file() is the FILE handle pointing to the INI file
  • path in load_ini_path() is the path where the INI file is located (pointer to a char array, a.k.a. a "C string")
  • format is a bitfield that defines the syntax of the INI file (see the IniFormat struct)
  • f_init is the function that will be invoked before any dispatching begins – it can be NULL
  • f_foreach is the callback function that will be repeatedly invoked for each member of the INI file - it can be NULL
  • user_data is a pointer to a custom argument – it can be NULL

The user given function f_init (see IniStatsHandler data type) will be invoked with two arguments:

  • statistics – a pointer to an IniStatistics object containing some properties about the file read (like its size in bytes and the number of its members)
  • user_data – a pointer to the custom argument previously passed to the load_ini_file() / load_ini_path() functions

The user given function f_foreach (see IniDispHandler data type) will be invoked with two arguments:

  • dispatch – a pointer to an IniDispatch object containing the parsed member of the INI file
  • user_data – a pointer to the custom argument previously passed to the load_ini_file() / load_ini_path() functions

Both functions load_ini_file() and load_ini_path() will return zero if the INI file has been completely dispatched, non-zero otherwise.

BASIC EXAMPLES

#1:

/* examples/topics/load_ini_file.c */
#include <stdio.h>
#include <confini.h>
static int my_callback (IniDispatch * dispatch, void * v_null) {
printf(
"DATA: %s\nVALUE: %s\nNODE TYPE: %u\n\n",
dispatch->data, dispatch->value, dispatch->type
);
return 0;
}
int main () {
FILE * const ini_file = fopen("ini_files/delivery.conf", "rb");
if (ini_file == NULL) {
fprintf(stderr, "File doesn't exist :-(\n");
return 1;
}
ini_file,
NULL,
my_callback,
NULL
)) {
fprintf(stderr, "Sorry, something went wrong :-(\n");
return 1;
}
fclose(ini_file);
return 0;
}

#2:

/* examples/topics/load_ini_path.c */
#include <stdio.h>
#include <confini.h>
static int my_callback (IniDispatch * dispatch, void * v_null) {
printf(
"DATA: %s\nVALUE: %s\nNODE TYPE: %u\n\n",
dispatch->data, dispatch->value, dispatch->type
);
return 0;
}
int main () {
"ini_files/delivery.conf",
NULL,
my_callback,
NULL
)) {
fprintf(stderr, "Sorry, something went wrong :-(\n");
return 1;
}
return 0;
}

HOW IT WORKS

The function load_ini_path() is a shortcut to the function load_ini_file() that requires a path instead of a FILE handle.

The function load_ini_file() dynamically allocates at once the whole INI file into the heap, and the two structures IniStatistics and IniDispatch into the stack. All members of the INI file are then dispatched to the custom listener f_foreach(). Finally the allocated memory gets automatically freed.

Because of this mechanism it is very important that all the dispatched data be immediately copied by the user (when needed), and no pointers to the passed data be saved: after the end of the functions load_ini_file() / load_ini_path() all the allocated data will be destroyed indeed.

Within a dispatching cycle, the structure containing each dispatch (IniDispatch * dispatch) is always the same struct that gets constantly updated with new information.

THE IniFormat DATA TYPE

For a correct use of this library it is fundamental to understand the IniFormat data type. libconfini has been born as a general INI parser, with the main purpose of being able to understand INI files written by other programs (see Rationale), therefore some flexibility was required. When an INI file is parsed it is parsed according to a particular format. The IniFormat data type is a univocal description of such format. It is implemented as a 24-bit bitfield. Its small size (3 bytes) allows it to be passed by value to the functions that require it.

THE MODEL FORMATS

A default format named INI_DEFAULT_FORMAT is available.

IniFormat my_format;
my_format = INI_DEFAULT_FORMAT;

The code above corresponds to:

#define NO 0
#define YES 1
IniFormat my_format;
my_format.delimiter_symbol = INI_EQUALS; // or '='
my_format.case_sensitive = NO;
my_format.no_single_quotes = NO;
my_format.no_double_quotes = NO;
my_format.no_spaces_in_names = NO;
my_format.implicit_is_not_empty = NO;
my_format.do_not_collapse_values = NO;
my_format.preserve_empty_quotes = NO;
my_format.disabled_after_space = NO;
my_format.disabled_can_be_implicit = NO;

Since version 1.7.0 a format named INI_UNIXLIKE_FORMAT is available as well.

This format is a clone of INI_DEFAULT_FORMAT with the only exception of the IniFormat::delimiter_symbol field, whose value is set to INI_ANY_SPACE instead of INI_EQUALS.

The semantics of the IniFormat bitfield has been designed in order to ensure that when all its fields are set to zero it equals INI_UNIXLIKE_FORMAT.

IniFormat format_zero = (IniFormat) { 0 };
printf(
"`format_zero` and `INI_UNIXLIKE_FORMAT` are %s.\n",
memcmp(&format_zero, &INI_UNIXLIKE_FORMAT, sizeof(IniFormat)) ?
"not equal"
:
"equal"
); // "`format_zero` and `INI_UNIXLIKE_FORMAT` are equal."

THE IniFormatNum DATA TYPE

Each format can be represented also as a univocal 24-bit unsigned integer. In order to convert an IniFormat to an unsigned integer and vice versa the functions ini_fton() and ini_ntof() are available.

For instance, imagine we want to create a format as close as possible to the typical Windows INI files. Probably we would define our format as follows:

#define NO 0
#define YES 1
IniFormat my_format = {
.case_sensitive = NO,
.semicolon_marker = INI_IGNORE,
.hash_marker = INI_IS_NOT_A_MARKER,
.section_paths = INI_ABSOLUTE_ONLY,
.multiline_nodes = INI_NO_MULTILINE,
.no_single_quotes = NO,
.no_double_quotes = NO,
.no_spaces_in_names = NO,
.implicit_is_not_empty = NO,
.do_not_collapse_values = NO,
.preserve_empty_quotes = NO,
.disabled_after_space = NO,
.disabled_can_be_implicit = NO
};
IniFormatNum my_format_num = ini_fton(my_format);
printf("Format No. %u\n", my_format_num); // "Format No. 56893"

The function ini_fton() tells us that this format is univocally the format No. 56893. The function ini_ntof() gives us then a shortcut to construct the very same format using its format number. Hence, the code above corresponds to:

IniFormat my_format = ini_ntof(56893);

Please be aware that the same INI format might have different format numbers in different versions of this library.

THE IniStatistics AND IniDispatch STRUCTURES

When the functions load_ini_file() and load_ini_path() read an INI file, they dispatch the file content to the f_foreach() listener. Before the dispatching begins some statistics about the parsed file can be dispatched to the f_init() listener (if this is non-NULL).

The information passed to f_init() is passed through an IniStatistics structure, while the information passed to f_foreach() is passed through an IniDispatch structure.

RENDERING

The output strings dispatched by libconfini will follow some formatting rules depending on their role within the INI file. First, multi-line escape sequences will be unescaped, then

  • Key names will be rendered according to ECMAScript key_name.replace(/^[\n\r]\s*|\s+/g, " ") – within single or double quotes, if active, the text will be rendered verbatim.
  • Section paths, if format supports nesting, will be rendered according to ECMAScript section_name.replace(/\.*\s*$|(?:\s*(\.))+\s*|^\s+/g, "$1").replace(/\s+/g, " ") – within single or double quotes, if active, the text will be rendered verbatim – otherwise, will be rendered according to the same algorithm used for key names.
  • Values, if format.do_not_collapse_values is active, will only be cleaned of spaces at the beginning and at the end; otherwise will be rendered according to the same algorithm used for key names (with the difference that, if format.preserve_empty_quotes is set to true, empty quotes surrounded by spaces will be preserved).
  • Comments, in multi-line formats, will be rendered according to ECMAScript comment_string.replace(/(^|\n\r?|\r\n?)[ \t\v\f]*[#;]+/g, "$1"); elsewhere, according to ECMAScript comment_string.replace(/^[ \t\v\f]*[#;]+/, "").
  • Unknown nodes will be rendered verbatim.

The strings dispatched, as already said, must not be freed. Nevertheless, before being copied or analyzed they can be edited, with some precautions:

  1. Be sure that your edit remains within the buffer lengths given (see IniDispatch::d_len and IniDispatch::v_len).
  2. If you want to edit the content of IniDispatch::data and this contains a section path, the IniDispatch::append_to properties of its children may share this buffer. In this case, if you edit its content, you can no more rely on the IniDispatch::append_to properties of this node's children (you will not make any damage, the loop will continue just fine: so if you think you are going to never use the property IniDispatch::append_to just do it); alternatively, use strdup(). If, instead, IniDispatch::data contains a key name or a comment, it is granted that no other dispatch will share this buffer, so feel free to edit it before it gets lost.
  3. Regarding IniDispatch::value, if it does not represent an implicit value (see below), this buffer is never shared between dispatches, so feel free to edit it.
  4. Regarding IniDispatch::append_to, this buffer is likely to be shared with other dispatches. Again, you would not destroy the world nor generate errors, but you would make the next IniDispatch::append_tos useless. For this reason the buffer pointed by IniDispatch::append_to is passed as constant. To unquote the path parts listed in this field please use strdup().

Typical peaceful edits are the ones obtained by calling the functions ini_array_collapse() and ini_string_parse() directly on the buffer IniDispatch::value – but make sure that you are not going to edit the global string INI_GLOBAL_IMPLICIT_VALUE, if used (see below):

/* examples/topics/ini_string_parse.c */
#include <stdio.h>
#include <confini.h>
static int ini_listener (IniDispatch * dispatch, void * v_null) {
if (
dispatch->type == INI_KEY || dispatch->type == INI_DISABLED_KEY
) {
ini_unquote(dispatch->data, dispatch->format);
ini_string_parse(dispatch->value, dispatch->format);
}
printf(
"DATA: %s\nVALUE: %s\nNODE TYPE: %u\n\n",
dispatch->data,
dispatch->value,
dispatch->type
);
return 0;
}
int main () {
"ini_files/self_explaining.conf",
NULL,
ini_listener,
NULL
)) {
fprintf(stderr, "Sorry, something went wrong :-(\n");
return 1;
}
return 0;
}

STRING COMPARISONS

In order to perform comparisons between strings the functions ini_string_match_ss(), ini_string_match_si(), ini_string_match_ii() and ini_array_match() are available. The function ini_string_match_ss() compares two simple strings, the function ini_string_match_si() compares a simple string with an unparsed INI string, the function ini_string_match_ii() compares two unparsed INI strings, and the function ini_array_match() compares two INI arrays. INI strings are the strings typically dispatched by load_ini_file() and load_ini_path(), which may contain quotes and the three escape sequences \\, \', \". Simple strings are user-given strings or the result of ini_string_parse().

As a consequence, the functions ini_string_match_si(), ini_string_match_ii() and ini_array_match() do not perform literal comparisons of equality between strings. For example, in the following (absurd) INI file the two keys foo and hello belong to the same section named this is a double quotation mark: "! (after being parsed by ini_string_parse()).

[this is a double quotation mark: \"!]
foo = bar
[this is a double quotation mark: '"'!]
hello = world

Therefore...

char
string1[] = "This is a double quotation mark: \\\"!",
string2[] = "This is a double quotation mark: '\"'!";
printf(
"%s\n",
"They match"
:
"They don't match"
); // "They match"

Or, for instance, in the following example the first two arrays are considered equal, while the third one is considered different.

#include <stdio.h>
#include <confini.h>
int main () {
char
list_1[] = "foo:bar : apple : 'I said: wait!' : bye bye ",
list_2[] = "'foo':'bar':'apple':'I said: wait!':'bye' bye",
list_3[] = "foo:bar:tomorrow:apple:I said: wait!:bye bye";
printf(
"%s\n",
ini_array_match(list_1, list_2, ':', INI_DEFAULT_FORMAT) ?
"They match"
:
"They don't match"
); // "They match"
printf(
"%s\n",
ini_array_match(list_1, list_3, ':', INI_DEFAULT_FORMAT) ?
"They match"
:
"They don't match"
); // "They don't match"
return 0;
}

In formats that support quotes, the function ini_array_match() is also the function that should be used, with '.' or INI_DOT as delimiter (see enum IniDelimiters), to properly compare section paths containing more than one level of nesting.

if (
ini_array_match("foo.bar", this->append_to, INI_DOT, this->format) &&
ini_string_match_si("username", this->data, this->format)
) {
// Do something
}

In case of multiple comparisons you might want to use a macro:

if (disp->type == INI_KEY) {
#define IS_KEY(SECTION,KEY)\
(ini_array_match(SECTION, disp->append_to, '.', disp->format) &&\
ini_string_match_ii(KEY, disp->data, disp->format))
if (IS_KEY("europe.madrid", "have_visited")) {
// Do something
} else if (IS_KEY("europe.london", "date")) {
// Do something
} else if (...) {
// etc.
}
}

The four functions ini_string_match_ss(), ini_string_match_si(), ini_string_match_ii(), ini_array_match() perform case-sensitive or case-insensitive comparisons depending on the format given. UTF-8 codepoints out of the ASCII range are always compared case-sensitive.

Note that, within INI strings, empty quotes and spaces out of quotes are always collapsed during comparisons. Furthermore, remember that the multi-line escape sequence /\\(?:\n\r?|\r\n?)/ is not considered as such in INI strings, since this is the only escape sequence automatically unescaped by libconfini before each dispatch.

FORMATTING THE VALUES

Once your listener starts to receive the parsed data you may want to format and better parse the value part of key elements. The following functions might be useful for this purpose:

Together with the functions listed above the following links are available, in case you don't have #include <stdlib.h> in your source:

FORMATTING THE KEY NAMES

The function ini_unquote() might be useful for key names enclosed within quotes. This function is very similar to ini_string_parse(), except that does not bother collapsing the sequences of more than one space that might result from removing empty quotes – this is never necessary, since empty quotes surrounded by spaces in key and section names are always collapsed before being dispatched.

You could use ini_string_parse() as well to parse key and section names, but you would obtain the same result with a slightly bigger effort from the CPU.

FORMATTING THE SECTION PATHS

In order to retrieve the parts of a section path, the functions ini_array_get_length(), ini_array_foreach(), ini_array_break(), ini_array_release(), ini_array_shift() and ini_array_split() can be used with '.' as delimiter. Note that section paths dispatched by libconfini are always collapsed arrays, therefore calling the function ini_array_collapse() on them will have no effects.

It might be required that the function ini_unquote() be applied to each part of a section path, depending on the content and the format of the INI file.

IMPLICIT KEYS

In order to set the value to be assigned to implicit keys (i.e. keys without a delimiter and a value), please use the ini_global_set_implicit_value() function. A zero-length TRUE-boolean is usually a good choice:

Alternatively, instead of ini_global_set_implicit_value() you can manually declare at the beginning of your code the two global variables INI_GLOBAL_IMPLICIT_VALUE and INI_GLOBAL_IMPLICIT_V_LEN, which will be retrieved by libconfini:

Or you can assign a value to them at the beginning of the main() function of your program:

#include <confini.h>
int main () {
/* ... */
}

If not defined elsewhere, these variables are initialized respectively to NULL and 0 by default.

The two variables INI_GLOBAL_IMPLICIT_VALUE and INI_GLOBAL_IMPLICIT_V_LEN may be set to any arbitrary values. In fact these will not be parsed or analyzed anywhere by libconfini, they are only used as placeholders for custom information accessible solely by the user.

After having set the value to be assigned to implicit key elements, and having enabled IniFormat::implicit_is_not_empty in the format, it is possible to test whether a dispatched key is implicit or not by comparing the address of its value property with the global variable INI_GLOBAL_IMPLICIT_VALUE:

/* examples/topics/ini_global_set_implicit_value.c */
#include <stdio.h>
#include <confini.h>
#define NO 0
#define YES 1
static int ini_listener (IniDispatch * dispatch, void * v_null) {
if (dispatch->value == INI_GLOBAL_IMPLICIT_VALUE) {
printf(
"\nDATA: %s\nVALUE: %s\nNODE TYPE: %u\n"
"(This is an implicit key element)\n",
dispatch->data,
dispatch->value,
dispatch->type
);
} else {
printf(
"\nDATA: %s\nVALUE: %s\nNODE TYPE: %u\n",
dispatch->data,
dispatch->value,
dispatch->type
);
}
return 0;
}
int main () {
ini_global_set_implicit_value("[implicit default value]", 0);
/* Without setting this implicit keys will be considered empty */
my_format.implicit_is_not_empty = YES;
"ini_files/unix-like.conf",
my_format,
NULL,
ini_listener,
NULL
)) {
fprintf(stderr, "Sorry, something went wrong :-(\n");
return 1;
}
}

CODE CONSIDERATIONS

RETURN VALUES

The functions load_ini_file(), load_ini_path(), ini_array_foreach() and ini_array_split() require some listeners defined by the user. Such listeners must return an int value. When this is non-zero the caller function is interrupted, its loop stopped, and a non-zero value is returned by the caller as well.

The functions load_ini_file() and load_ini_path() return a non-zero value also if the INI file, for any reason, has not been completely parsed (see enum ConfiniInterruptNo). Therefore, in order to be able to distinguish between internal errors and user-generated interruptions the mask CONFINI_ERROR can be used.

For instance, in the following example the f_foreach() listener returns a non-zero value if a key named password with a value that equals Hello world is found. Hence, by using the mask CONFINI_ERROR, the code below distinguishes a non-zero value generated by the listener from a non-zero value due to a parsing error.

/* examples/topics/ini_string_match_si.c */
#include <stdio.h>
#include <confini.h>
static int passfinder (IniDispatch * disp, void * v_membid) {
/* Search for `password = "hello world"` in the INI file */
if (
ini_string_match_si("password", disp->data, disp->format) &&
ini_string_match_si("hello world", disp->value, disp->format)
) {
*((size_t *) v_membid) = disp->dispatch_id;
return 1;
}
return 0;
}
int main () {
size_t membid;
/* Load INI file */
int retval = load_ini_path(
"ini_files/self_explaining.conf",
NULL,
passfinder,
&membid
);
/* Check for errors */
if (retval & CONFINI_ERROR) {
fprintf(stderr, "Sorry, something went wrong :-(\n");
return 1;
}
/* Check if parsing has been interrupted by `passfinder()` */
retval == CONFINI_FEINTR ?
printf(
"We found it! It's the INI element number #%zu!\n",
membid
)
:
printf("We didn't find it :-(\n");
return 0;
}

THE FORMATTING FUNCTIONS

The functions ini_unquote(), ini_string_parse(), ini_array_collapse(), ini_array_break(), ini_array_release() and ini_array_split() change the content of the given strings. It is important to point out that the edit is always performed within the lengths of the strings given.

The behavior of these functions depends on the format used. In particular, using ini_string_parse() as model one obtains the following scheme:

  1. Condition: !format.no_single_quotes && !format.no_double_quotes && format.multiline_nodes != INI_NO_MULTILINE
    ⇒ Escape sequences: \\, \", \'
    ⇒ Behavior of ini_string_parse(): \\, \' and \" will be unescaped, all unescaped single and double quotes will be removed, then the new length of the string will be returned.
  2. Condition: !format.no_single_quotes && format.no_double_quotes && format.multiline_nodes != INI_NO_MULTILINE
    ⇒ Escape sequences: \\, \'
    ⇒ Behavior of ini_string_parse(): \\ and \' will be unescaped, all unescaped single quotes will be removed, then the new length of the string will be returned.
  3. Condition: format.no_single_quotes && !format.no_double_quotes && format.multiline_nodes != INI_NO_MULTILINE
    ⇒ Escape sequences: \\, \"
    ⇒ Behavior of ini_string_parse(): \\ and \" will be unescaped, all unescaped double quotes will be removed, then the new length of the string will be returned.
  4. Condition: format.no_single_quotes && format.no_double_quotes && format.multiline_nodes != INI_NO_MULTILINE
    ⇒ Escape sequences: \\
    ⇒ Behavior of ini_string_parse(): only \\ will be unescaped, spaces at the beginning and at the end of the string will be removed, then the new length of the string will be returned.
  5. Condition: format.no_single_quotes && format.no_double_quotes && format.multiline_nodes == INI_NO_MULTILINE
    ⇒ Escape sequences: No escape sequences
    ⇒ Behavior of ini_string_parse(): Spaces at the beginning and at the end of the string will be removed, then the new length of the string will be returned.

A function-like macro named INIFORMAT_HAS_NO_ESC() is available in order to check whether a format supports escape sequences or not.

STORING THE DISPATCHED DATA

In order to be as flexible as possible, libconfini does not store the dispatched data, nor indicizes it. This gives the developer the power to deal with it in many different ways.

For small INI files a normal if/else chain, using ini_array_match() for comparing section paths and ini_string_match_si()/ini_string_match_ii() for comparing key names, usually represents the most practical way to obtain the information required from an INI file.

Sometimes however, especially in case of sizeable INI files, the most efficient solution would be to store the parsed data in a hash table before trying to access it.

Some INI parsers are released with a hash table API included by default. This is often an unpractical solution, since fantastic free software libraries that focus solely on hash tables already exist, and providing a further API for managing a hash function together with an INI parser only complicates the code, makes it harder to maintain, and does not give the user the real freedom to choose what suits best to each single case.

When a user needs it, the data parsed by libconfini can still be stored in a third-party hash table while it is being dispatched. By doing so the resulting performance will equal that of an INI parser with a hash table included by default, since the only job of libconfini is that of scrolling the content of an INI file linearly from the beginning to the end – and there are not more efficient ways to parse and indicize the content of a serialized tree.

If you are interested in combining libconfini with a hash table, I have left a general example of how to use GLib's GHashTable together with libconfini under examples/miscellanea/glib_hash_table.c. By keeping this example as a model other solutions can be easily explored as well.

SIZE OF THE DISPATCHED DATA

Within an INI file it is granted that if one sums together all the (disp->d_len + 1) and all the (disp->v_len > 0 ? disp->v_len + 1 : 0) received, the result will always be less-than or equal-to (stats->bytes + 1) – where + 1 represents the NUL terminators and disp and stats are respectively the IniDispatch and IniStatistics structures passed as arguments to the callback functions. If one adds to this also all the disp->at_len properties, or if the disp->v_len properties of implicit keys are non-zero, the sum may exceed it. This might be relevant or irrelevant depending on your code.

#include <stdio.h>
#include <confini.h>
struct size_check {
size_t bytes, buff_lengths;
};
static int ini_init (IniStatistics * stats, void * v_check_struct) {
((struct size_check *) v_check_struct)->bytes = stats->bytes;
((struct size_check *) v_check_struct)->buff_lengths = 0;
return 0;
}
static int ini_listener (IniDispatch * this, void * v_check) {
((struct size_check *) v_check)->buff_lengths += this->d_len + 1 +
(this->v_len ? this->v_len + 1 : 0);
return 0;
}
int main () {
struct size_check check;
"ini_files/example.conf",
ini_init,
ini_listener,
&check
)) {
fprintf(stderr, "Sorry, something went wrong :-(\n");
return 1;
}
printf(
"The file is %zu bytes large.\n\n"
"The sum of the lengths of all `disp->data` "
"plus the lengths of all non-empty\n"
"`disp->value`s is %zu.\n",
check.bytes, check.buff_lengths
);
/* `INI_GLOBAL_IMPLICIT_V_LEN` is 0 and not even used, so this
cannot happen: */
if (check.buff_lengths > check.bytes) {
fprintf(stderr, "The end is near!");
return 1;
}
return 0;
}

OTHER GLOBAL SETTINGS

Besides the two global variables INI_GLOBAL_IMPLICIT_VALUE and INI_GLOBAL_IMPLICIT_V_LEN, a third variable named INI_GLOBAL_LOWERCASE_MODE tells libconfini whether to dispatch in lower case all key names and section paths of case-insensitive INI files.

As with the other global variables, you can declare the variable INI_GLOBAL_LOWERCASE_MODE at the beginning of your code:

#include <stdbool.h>
#include <confini.h>

or assign a value to it at the beginning of the main() function:

#include <stdbool.h>
#include <confini.h>
int main () {
/* ... */
}

Alternatively, this variable can be set by using its setter function ini_global_set_lowercase_mode().

When the variable INI_GLOBAL_LOWERCASE_MODE is set to true, libconfini always dispatches in lower case all ASCII letters of key and section names in case-insensitive formats – even when these are enclosed within quotes – but does not dispatch in lower case UTF-8 code points out of the ASCII range (for instance, Ā will not be rendered as ā, but will be rather rendered verbatim). In general it is a good practice to use UTF-8 within values, but to use ASCII only within key and section names, at least in case insensitive INI files (see below). As for the dispatched values instead, their case is always preserved.

Normally INI_GLOBAL_LOWERCASE_MODE does not need to be set to true, since string comparisons made by libconfini are always either case-sensitive or case-insensitive depending on the format given.

THE UNICODE PROBLEM

Comparing an ASCII upper case letter to an ASCII lower case letter is an invariant process. But comparing two Unicode letter cases is a process that depends on the locale of the machine. Consider for example the lower case letter i: in most European languages its upper case is I, while this is not the case in Turkish, where the upper case of i is İ (and the lower case of I is ı). Therefore for a person living in Italy or France, i and I will represent the same letter, while for a person living in Turkey they will not.

Key and section names of an INI file however cannot depend on the locale of the machine, since they must be reliably searched for independently of where a machine is located. Imagine for example a key named “INI” and imagine that Unicode case folding were performed on key names during string comparisons. If you lived in Europe you could look up for such key using its lower case “ini”, while if you lived in Turkey you would have to use the lower case “ını” to find it. So the only solution in this context is to consider Unicode characters out of the ASCII range always as case sensitive. For this reason, libconfini (and probably any senseful INI parser) will never perform a case folding of Unicode characters out of the ASCII range within key and section names.

It must be said however that most Unicode characters do not possess a lower and upper case, and most characters outside of the ASCII range could theoretically appear without problems in key and section names also in case insensitive INI files (think of the character § for example). And, as for case sensitive INI files, no Unicode character would ever represent a problem. Nonetheless, it is still generally more acceptable to use ASCII only within key and section names – and possibly, if needed, non-ASCII Unicode characters within values and comments.

That said, libconfini deals perfectly fine with UTF-8 (but is always case sensitive outside of the ASCII range), so use the latter as you feel appropriate.

THREAD SAFETY

Depending on the format of the INI file, libconfini may use up to three global variables (INI_GLOBAL_IMPLICIT_VALUE, INI_GLOBAL_IMPLICIT_V_LEN and INI_GLOBAL_LOWERCASE_MODE). In order to be thread-safe these three variables (if needed) must be defined only once (either directly, or by using their setter functions ini_global_set_implicit_value() and ini_global_set_lowercase_mode()), or otherwise a mutex logic must be introduced.

Apart from the three variables above, each parsing allocates and frees its own memory and every function is fully reentrant, therefore the library can be considered thread-safe.

ERROR EXCEPTIONS

The philosophy of libconfini is to parse as much as possible without generating error exceptions. No parsing errors are returned once an INI file has been correctly allocated into the stack, with the exception of the out-of-range error CONFINI_EOOR (see enum ConfiniInterruptNo), whose meaning is that the dispatches are for unknown reasons more than expected – this error is possibly generated by the presence of bugs in the library's code and should never be returned (please contact me if this happens).

When an INI node is wrongly written in respect to the format given, it is dispatched verbatim as an INI_UNKNOWN node – see enum IniNodeType. Empty lines, or lines containing only spaces and empty quotes (if the latter are supported) will be skipped.

In order to avoid error exceptions, strings containing an unterminated quote will always be treated as if they had a virtual quote as their last + 1 character. For example,

foo = "bar

will always determine the same behavior as if it were

foo = "bar"

PERFORMANCE

The algorithms used by libconfini stand in a delicate equilibrium between flexibility, speed and code readability, with flexibility as primary target. Performance can vary with the format used to parse an INI file, but in most cases is not a concern.

One can measure the performance of the library by doing something like:

/* Please create an INI file large enough */
#include <stdio.h>
#include <confini.h>
#include <time.h>
static int get_ini_size (IniStatistics * stats, void * v_bytes) {
*((size_t *) v_bytes) = stats->bytes;
return 0;
}
static int empty_listener (IniDispatch * dispatch, void * v_bytes) {
return 0;
}
int main () {
size_t bytes;
double seconds;
clock_t start, end;
start = clock();
"big_file.ini",
get_ini_size,
empty_listener,
&bytes
)) {
return 1;
}
end = clock();
seconds = (double) (end - start) / CLOCKS_PER_SEC;
printf(
"%zu bytes parsed in %f seconds.\n"
"Number of bytes parsed per second: %f\n",
bytes, seconds, bytes / seconds
);
return 0;
}

By changing the properties of the variable my_format on the code above you may obtain different results.

On my old laptop libconfini seems to parse around 23 MiB per second using the model format INI_DEFAULT_FORMAT. Whether this is enough for you or not, that depends on your needs.

54692353 bytes parsed in 2.221189 seconds.
Number of bytes parsed per second: 24623007.317252

INI SYNTAX CONSIDERATIONS

COMMENT OR DISABLED ENTRY?

I can hardly imagine a reason to be interested in disabled entries if not for writing a GUI editor for INI files. However, if this is the case and you are not using libconfini like normal people do, you might wonder how to ensure that disabled entries and comments be always parsed without ambiguity.

In most of the cases libconfini is smart enough to distinguish a disabled entry from a comment. However some INI files can be tricky and might require some workarounds. For instance, imagine to have the following INI file:

# INI key/value delimiter: `=`
[some_section]
hello = world
;foo = bar
##now=Sunday April 3rd, 2016

And imagine that for unknown reasons the author of the INI file wanted only ;foo = bar to be considered as a disabled entry, and the first and last line as normal comments.

If we tried to parse it according to the format used below

#include <stdio.h>
#include <confini.h>
static int ini_listener (IniDispatch * disp, void * v_null) {
printf(
"#%zu - TYPE: %u, DATA: '%s', VALUE: '%s'\n",
disp->dispatch_id, disp->type, disp->data, disp->value
);
return 0;
}
int main () {
#define NO 0
#define YES 1
IniFormat my_format = {
.case_sensitive = NO,
.semicolon_marker = INI_IGNORE,
.hash_marker = INI_IS_NOT_A_MARKER,
.multiline_nodes = INI_NO_MULTILINE,
.section_paths = INI_ABSOLUTE_ONLY,
.no_single_quotes = NO,
.no_double_quotes = NO,
.no_spaces_in_names = NO,
.implicit_is_not_empty = YES,
.do_not_collapse_values = NO,
.preserve_empty_quotes = NO,
.disabled_after_space = YES,
.disabled_can_be_implicit = YES
};
printf(":: Content of 'ambiguous.conf' ::\n\n");
"ini_files/ambiguous.conf",
my_format,
NULL,
ini_listener,
NULL
)) {
fprintf(stderr, "Sorry, something went wrong :-(\n");
return 1;
}
return 0;
}

we would obtain the following result:

:: Content of 'ambiguous.conf' ::
#0 - TYPE: 6, DATA: 'INI key/value delimiter: `', VALUE: '`'
#1 - TYPE: 3, DATA: 'some_section', VALUE: ''
#2 - TYPE: 2, DATA: 'hello', VALUE: 'world'
#3 - TYPE: 6, DATA: 'foo', VALUE: 'bar'
#4 - TYPE: 4, DATA: 'now=Sunday April 3rd, 2016', VALUE: ''

As we can see, all comments but now=Sunday April 3rd, 2016 would be parsed as disabled entries – which is not what the author intended. Therefore, to ensure that such INI file is parsed properly, we can follow two possible approaches.

1. Intervene on the INI file. The reason why now=Sunday April 3rd, 2016 has been properly parsed as a comment – despite it really looks like a disabled entry – is because it has been nested within a comment block opened by more than one leading comment marker (in this case the two ##). As a general rule, libconfini never parses a comment beginning with more than one leading marker as a disabled entry, therefore this is the surest way to ensure that proper comments are always considered as such.

Hence, by adding one more number sign to the first comment

## INI key/value delimiter: `=`
[some_section]
hello = world
;foo = bar
##now=Sunday April 3rd, 2016

we obtain the wanted result:

:: Content of 'ambiguous.conf' ::
#0 - TYPE: 4, DATA: ' INI key/value delimiter: `=`', VALUE: ''
#1 - TYPE: 3, DATA: 'some_section', VALUE: ''
#2 - TYPE: 2, DATA: 'hello', VALUE: 'world'
#3 - TYPE: 6, DATA: 'foo', VALUE: 'bar'
#4 - TYPE: 4, DATA: 'now=Sunday April 3rd, 2016', VALUE: ''

2. Intervene on the format. There are cases where the INI file is automatically generated by machines (comments included), or distributed as such, and human intervention would be required on each machine-generated realease of the INI file. In these cases – and if we are sure about the expected content of the INI file – we can restrict the format chosen in order to parse comments and disabled entries properly. In particular, the following fields of the IniFormat bitfield can have an impact on the disambiguation between comments and disabled entries.

Reliable general patterns:

  • IniFormat::semicolon_marker and IniFormat::hash_marker – The imaginary author of our INI file, if we observe the latter closer, chose the semicolon symbol as the marker of disabled entries and the hash symbol as the marker of comments. We may exploit this difference and set our my_format.semicolon_marker to INI_DISABLED_OR_COMMENT and our my_format.hash_marker to INI_ONLY_COMMENT to obtain the correct disambiguation. If you believe that this solution is too artificial, think that /etc/samba/smb.conf and /etc/pulse/daemon.conf are systematically distributed using this pattern.
  • IniFormat::disabled_after_space – Setting this property to false, due to the initial space that follows the comment marker (# INI...), forces # INI key/value delimiter: = (everywhere) to be considered as a comment. Some authors use this syntax to distinguish between comments and disabled entries (examples are /etc/pacman.conf and /etc/bluetooth/main.conf)

Temporary workarounds:

  • IniFormat::no_spaces_in_names – If our INI file has only comments containing more than one word and we are sure that key and section names cannot contain internal white spaces, we can set this property to true to enhance disambiguation.
  • IniFormat::disabled_can_be_implicit – This property, if set to false, forces all comments that do not contain a key-value delimiter to be never considered as disabled entries. Despite not having an impact on our example, it has a big impact on the disambiguation algorithms used by libconfini. Its value in INI_DEFAULT_FORMAT is set to false.

As a general rule, libconfini will always try to parse as a disabled entry whatever comment is allowed (by the format) to contain one. Only if this attempt fails, the block will be dispatched as a normal comment.