libcasio/docs/char.md

layout	title
page	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:

{% highlight c linenos %} int casio_open_conv(casio_conv_t *cd, const char *to, const char *from); int casio_close_conv(casio_conv_t cd); {% endhighlight %}

The to and from parameters of the casio_open_conv() function 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 casio_conv() function, defined this way:

{% highlight c linenos %} int casio_conv(casio_conv_t cd, const char **in_buffer, size_t *in_left, const char **out_buffer, size_t *out_left); {% endhighlight %}

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:

{% highlight c linenos %} #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",
		casio_strerror(err));
	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",
		casio_strerror(err));
	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",
		casio_strerror(err));
	goto fail;
}

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

fail: /* Close the conversion descriptor. */ casio_close_conv(cd); return (err != 0); } {% endhighlight %}