source: bootcd/isolinux/syslinux-6.03/gpxe/src/core/asprintf.c

#include <stdint.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

FILE_LICENCE ( GPL2_OR_LATER );

/**
 * Write a formatted string to newly allocated memory.
 *
 * @v strp              Pointer to hold allocated string
 * @v fmt               Format string
 * @v args              Arguments corresponding to the format string
 * @ret len             Length of formatted string
 */
int vasprintf ( char **strp, const char *fmt, va_list args ) {
        size_t len;
        va_list args_tmp;

        /* Calculate length needed for string */
        va_copy ( args_tmp, args );
        len = ( vsnprintf ( NULL, 0, fmt, args_tmp ) + 1 );
        va_end ( args_tmp );

        /* Allocate and fill string */
        *strp = malloc ( len );
        if ( ! *strp )
                return -ENOMEM;
        return vsnprintf ( *strp, len, fmt, args );
}

/**
 * Write a formatted string to newly allocated memory.
 *
 * @v strp              Pointer to hold allocated string
 * @v fmt               Format string
 * @v ...               Arguments corresponding to the format string
 * @ret len             Length of formatted string
 */
int asprintf ( char **strp, const char *fmt, ... ) {
        va_list args;
        int len;

        va_start ( args, fmt );
        len = vasprintf ( strp, fmt, args );
        va_end ( args );
        return len;
}