azahac / tomlc99

TOML C library

tomlc99

TOML in c99; v1.0 compliant.

If you are looking for a C++ library, you might try this wrapper: https://github.com/cktan/tomlcpp.

• Compatible with TOML v1.0.0.
• Tested with multiple test suites, including BurntSushi/toml-test and iarna/toml-spec-tests.
• Provides very simple and intuitive interface.

Usage

Please see the toml.h file for details. What follows is a simple example that parses this config file:

[server]
	host = "www.example.com"
	port = [ 8080, 8181, 8282 ]

The steps for getting values from our file is usually :

1. Parse the TOML file.
2. Traverse and locate a table in TOML.
3. Extract values from the table.
4. Free up allocated memory.

Below is an example of parsing the values from the example table.

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include "toml.h"

static void error(const char* msg, const char* msg1)
{
    fprintf(stderr, "ERROR: %s%s\n", msg, msg1?msg1:"");
    exit(1);
}


int main()
{
    FILE* fp;
    char errbuf[200];

    // 1. Read and parse toml file
    fp = fopen("sample.toml", "r");
    if (!fp) {
        error("cannot open sample.toml - ", strerror(errno));
    }

    toml_table_t* conf = toml_parse_file(fp, errbuf, sizeof(errbuf));
    fclose(fp);

    if (!conf) {
        error("cannot parse - ", errbuf);
    }

    // 2. Traverse to a table.
    toml_table_t* server = toml_table_in(conf, "server");
    if (!server) {
        error("missing [server]", "");
    }

    // 3. Extract values
    toml_datum_t host = toml_string_in(server, "host");
    if (!host.ok) {
        error("cannot read server.host", "");
    }

    toml_array_t* portarray = toml_array_in(server, "port");
    if (!portarray) {
        error("cannot read server.port", "");
    }

    printf("host: %s\n", host.u.s);
    printf("port: ");
    for (int i = 0; ; i++) {
        toml_datum_t port = toml_int_at(portarray, i);
        if (!port.ok) break;
        printf("%d ", (int)port.u.i);
    }
    printf("\n");

    // 4. Free memory
    free(host.u.s);
    toml_free(conf);
    return 0;
}

Accessing Table Content

TOML tables are dictionaries where lookups are done using string keys. In general, all access functions on tables are named toml_*_in(...).

In the normal case, you know the key and its content type, and retrievals can be done using one of these functions:

toml_string_in(tab, key);
toml_bool_in(tab, key);
toml_int_in(tab, key);
toml_double_in(tab, key);
toml_timestamp_in(tab, key);
toml_table_in(tab, key);
toml_array_in(tab, key);

You can also interrogate the keys in a table using an integer index:

toml_table_t* tab = toml_parse_file(...);
for (int i = 0; ; i++) {
    const char* key = toml_key_in(tab, i);
    if (!key) break;
    printf("key %d: %s\n", i, key);
}

Accessing Array Content

TOML arrays can be deref-ed using integer indices. In general, all access methods on arrays are named toml_*_at().

To obtain the size of an array:

int size = toml_array_nelem(arr);

To obtain the content of an array, use a valid index and call one of these functions:

toml_string_at(arr, idx);
toml_bool_at(arr, idx);
toml_int_at(arr, idx);
toml_double_at(arr, idx);
toml_timestamp_at(arr, idx);
toml_table_at(arr, idx);
toml_array_at(arr, idx);

toml_datum_t

Some toml_*_at and toml_*_in functions return a toml_datum_t structure. The ok flag in the structure indicates if the function call was successful. If so, you may proceed to read the value corresponding to the type of the content.

For example:

toml_datum_t host = toml_string_in(tab, "host");
if (host.ok) {
	printf("host: %s\n", host.u.s);
	free(host.u.s);   /* FREE applies to string and timestamp types only */
}

** IMPORTANT: if the accessed value is a string or a timestamp, you must call free(datum.u.s) or free(datum.u.ts) respectively after usage. **

Building and installing

A normal make suffices. You can also simply include the toml.c and toml.h files in your project.

Invoking make install will install the header and library files into /usr/local/{include,lib}.

Alternatively, specify make install prefix=/a/file/path to install into /a/file/path/{include,lib}.

Testing

To test against the standard test set provided by BurntSushi/toml-test:

% make
% cd test1
% bash build.sh   # do this once
% bash run.sh     # this will run the test suite

To test against the standard test set provided by iarna/toml:

% make
% cd test2
% bash build.sh   # do this once
% bash run.sh     # this will run the test suite