HuidaeCho / libaprintf

Aligned printf C library

Libaprintf

Libaprintf is the aligned printf C library. Functionally, it is similar to the CJK Format Python 3 module.

In the C language, the strlen() of a CJK character is not 1 because strlen() returns the byte length of a string and CJK characters use more than one byte per character. For example, strlen("가") returns 3 because Hangul syllable Ga (가) consists of 0xEA, 0xB0, and 0x80. The same byte length applies to printf()'s string specifier (%s). Again, "가" in printf("%-10s|", "가") will consume three bytes internally and leave seven spaces resulting in

The pipe character (|) is at column 10, not at 11 (10 characters from %-10s plus |) as in

This misalignment issue occurs because CJK characters' byte length (3) and display length (2) are different.

The libaprintf library tries to fix this problem and defines the following functions:

• int count_wide_chars(const char *str) counts the number of wide characters in a string,
• int count_wide_chars_in_cols(const char *str, int ncols, int *nbytes) counts the numbers of wide characters and bytes in a string in a number of columns,
• int aprintf(const char *format, ...) adjusts the width of string specifiers to the display space instead of the number of bytes for wide characters and printf them using the adjusted display width,
• int faprintf(FILE *stream, const char *format, ...) is the fprintf() version of aprintf(),
• int saprintf(char *str, const char *format, ...) is the sprintf() version of aprintf(), and
• int snaprintf(char *str, size_t size, const char *format, ...) is the snprintf() version of aprintf().

Installation

# build the library and test
make

# test
./test

License

Copyright (C) 2020, Huidae Cho <https://idea.isnew.info>

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.