Character encoding and conversions

libcasio has its own portable character encoding conversion, resembling iconv. It supports Unicode transformation formats (UTF-8, UTF-16, UTF-32) and CASIO’s proprietary character encoding named FONTCHARACTER according to the SDK it published in 2006 for the fx-9860G.

The character conversion utilities are defined in <libcasio/char.h>, but as usual, including <libcasio.h> for everything is recommended.

Opening and closing a conversion descriptor

The conversion descriptor is the main object that will keep track of the conversion steps and status. Here are the main functions to manage it:

type casio_conv_t

The conversion descriptor type.

int casio_open_conv(casio_conv_t *cd, char const *to, char const *from)

Open the conversion descriptor.

The to and from parameters are the string identifiers of the source and destination encodings for the conversion. For example, use casio_open_conv(&cd, "utf-8", "utf-32") to open a descriptor that will be able to convert UTF-32 encoded data into UTF-8 encoded data.

Converting formats

Once the conversion descriptor is opened, you can use the following function:

int casio_conv(casio_conv_t cd, char const **in_buffer, size_t *in_left, char **out_buffer, size_t *out_left)

In the same fashion than iconv, this function is made for being called several times, usually because you read from a stream and write to another stream — although you can use it to convert data all at once.

Here is a simple example using two buffers:

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <libcasio.h>

int main(void)
        int err = 0; casio_conv_t cd = NULL;
        uint32_t buf0[] = {'H', 'e', 'l', 'l', 'o'};
        size_t buf0_size = 5 * sizeof(uint32_t);
        uint32_t buf1[] = {' ', 'w', 'o', 'r', 'l', 'd', '!'};
        size_t buf1_size = 7 * sizeof(uint32_t);
        char bufdata[30], *buf = &bufdata;
        size_t outsize = 29; /* let space for the end zero */

        /* Open the conversion descriptor. */
        err = casio_open_conv(&cd, "utf-8", "utf-32");
        if (err) {
                fprintf(stderr, "Could not open the conversion desc.: %s",
                goto fail;

        /* Convert the first buffer. */
        err = casio_conv(cd, &buf0, &buf0_size, &buf, &outsize);
        if (err) {
                fprintf(stderr, "Could not convert the first buffer: %s",
                goto fail;

        /* Convert the second buffer. */
        err = casio_conv(cd, &buf1, &buf1_size, &buf, &outsize);
        if (err) {
                fprintf(stderr, "Could not convert the second buffer: %s",
                goto fail;

        /* Print the buffer. */
        *buf = '\0';
        fputs(bufdata, stdout);

        /* Close the conversion descriptor. */
        return (err != 0);