Hi Kristen,

> +
> +char *stk_text_to_html(char *text, int text_len,
> +				const unsigned char *attrs, int attrs_len)
> +{
> +	GString *string = g_string_sized_new(text_len + 1);
> +	int formats[257];  /* maximum number of chars in text + 1 */
> +	int pos = 0, i, j, attr, prev_attr;
> +	guint8 start, end, code, color, len, align;
> +
> +	/* we will need formatting at the position beyond the last char */
> +	for (i = 0; i <= text_len; i++)
> +		formats[i] = STK_TEXT_FORMAT_INIT;
> +

Please note that the same formatting can be used for EMS messages
(23.040).  These messages have a fairly large max-len (255 segments *
~153 characters)  I'd like to have this function useable for EMS
messages as well.

> +	i = 0;
> +
> +	while (i < attrs_len) {

Using a for loop would be nicer here

> +		start = attrs[i++];
> +		len = attrs[i++];
> +		code = attrs[i++];

You might want to be extra paranoid here that attrs_len is a multiple of 4.

> +
> +		if (i < attrs_len)
> +			color = attrs[i++];
> +		else
> +			color = 0;
> +
> +		if (len == 0)
> +			end = text_len;
> +		else
> +			end = start + len;
> +
> +		/* sanity check values */
> +		if (start > end || end > text_len)
> +			continue;
> +
> +		/*
> +		 * if the alignment is the same as either the default
> +		 * or the last alignment used, don't set any alignment
> +		 * value.
> +		 */
> +		if (start == 0)
> +			align = STK_DEFAULT_TEXT_ALIGNMENT;

Are attributes which do not contain start = 0 valid?  If so, you might
take extra care here.

> +		else {
> +			align = (formats[start -1] & 0xFF) &
> +					STK_TEXT_FORMAT_ALIGN_MASK;
> +			if (align == STK_TEXT_FORMAT_NO_ALIGN)
> +				align = STK_DEFAULT_TEXT_ALIGNMENT;
> +		}
> +
> +		if ((code & STK_TEXT_FORMAT_ALIGN_MASK) == align)
> +			code |= STK_TEXT_FORMAT_NO_ALIGN;
> +
> +		attr = code | (color << 8);
> +
> +		for (j = start; j < end; j++)
> +			formats[j] = attr;
> +	}
> +
> +	prev_attr = STK_TEXT_FORMAT_INIT;
> +
> +	while (pos <= text_len) {

A for loop would be more readable here in my opinion

> +		attr = formats[pos];
> +		if (attr != prev_attr) {
> +			if (prev_attr != STK_TEXT_FORMAT_INIT)
> +				end_format(string, prev_attr & 0xFF);
> +
> +			if (attr != STK_TEXT_FORMAT_INIT)
> +				start_format(string, attr & 0xFF,
> +							(attr >> 8) & 0xFF);
> +
> +			prev_attr = attr;
> +		}
> +
> +		if (pos == text_len)
> +			break;
> +
> +		switch (text[pos]) {
> +		case '\n':
> +			g_string_append(string, "<br/>");
> +			break;
> +		case '\r':
> +		{
> +			g_string_append(string, "<br/>");
> +			if ((pos + 1 < text_len) && (text[pos + 1] == '\n'))
> +				pos++;
> +		}

Fallthrough on purpose?

> +		case '<':
> +			g_string_append(string, "&lt;");
> +			break;
> +		case '>':
> +			g_string_append(string, "&gt;");
> +			break;
> +		case '&':
> +			g_string_append(string, "&amp;");
> +			break;
> +		default:
> +			g_string_append_c(string, text[pos]);
> +		}
> +		pos++;
> +	}
> +
> +	/* return characters from string. Caller must free char data */
> +	return g_string_free(string, FALSE);
> +}
> diff --git a/src/stkutil.h b/src/stkutil.h
> index ca4817e..5b3a679 100644
> --- a/src/stkutil.h
> +++ b/src/stkutil.h
> @@ -1635,6 +1635,27 @@ struct stk_envelope {
>  	};
>  };
>  
> +#define STK_TEXT_FORMAT_ALIGN_MASK 0x03
> +#define STK_TEXT_FORMAT_FONT_MASK 0x0C
> +#define STK_TEXT_FORMAT_STYLE_MASK 0xF0
> +#define STK_DEFAULT_TEXT_ALIGNMENT 0x00
> +#define STK_TEXT_FORMAT_INIT -1
> +
> +/* Defined in ETSI 123 40 9.2.3.24.10.1.1 */
> +enum stk_text_format_code {
> +	STK_TEXT_FORMAT_LEFT_ALIGN = 0x00,
> +	STK_TEXT_FORMAT_CENTER_ALIGN = 0x01,
> +	STK_TEXT_FORMAT_RIGHT_ALIGN = 0x02,
> +	STK_TEXT_FORMAT_NO_ALIGN = 0x03,
> +	STK_TEXT_FORMAT_FONT_SIZE_LARGE = 0x04,
> +	STK_TEXT_FORMAT_FONT_SIZE_SMALL = 0x08,
> +	STK_TEXT_FORMAT_FONT_SIZE_RESERVED = 0x0c,
> +	STK_TEXT_FORMAT_STYLE_BOLD = 0x10,
> +	STK_TEXT_FORMAT_STYLE_ITALIC = 0x20,
> +	STK_TEXT_FORMAT_STYLE_UNDERLINED = 0x40,
> +	STK_TEXT_FORMAT_STYLE_STRIKETHROUGH = 0x80,
> +};
> +

All of these enums really belong in the .c file.  There is no other
client which can make use of them.

>  struct stk_command *stk_command_new_from_pdu(const unsigned char *pdu,
>  						unsigned int len);
>  void stk_command_free(struct stk_command *command);
> @@ -1643,3 +1664,5 @@ const unsigned char *stk_pdu_from_response(const struct stk_response *response,
>  						unsigned int *out_length);
>  const unsigned char *stk_pdu_from_envelope(const struct stk_envelope *envelope,
>  						unsigned int *out_length);
> +char *stk_text_to_html(char *text, int text_len,
> +				const unsigned char *attrs, int attrs_len);

Why not const char *text?

Regards,
-Denis