src/lib/printf-format-fix.c

	printf-format-fix.c revision 1dcf22e98ba8310e8daa8c9297936c6f3a645e7a
/* Copyright (c) 2002-2014 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "printf-format-fix.h"

static const char *
fix_format_real(const char *fmt, const char *p, unsigned int *len_r)
{
    const char *errstr;
    char *buf;
    unsigned int len1, len2, len3;

    i_assert((size_t)(p - fmt) < INT_MAX);
    i_assert(p[0] == '%' && p[1] == 'm');

    errstr = strerror(errno);

    /* we'll assume that there's only one %m in the format string.
       this simplifies the code and there's really no good reason to have
       it multiple times. Callers can trap this case themselves. */
    len1 = p - fmt;
    len2 = strlen(errstr);
    len3 = strlen(p + 2);

    /* @UNSAFE */
    buf = t_buffer_get(len1 + len2 + len3 + 1);
    memcpy(buf, fmt, len1);
    memcpy(buf + len1, errstr, len2);
    memcpy(buf + len1 + len2, p + 2, len3 + 1);

    *len_r = len1 + len2 + len3;
    return buf;
}

static const char *
printf_format_fix_noalloc(const char *format, unsigned int *len_r)
{
    const char *p;
    const char *ret = format;

    for (p = format; *p != '\0'; ) {
        if (*p++ == '%') {
            switch (*p) {
            case 'n':
                i_panic("%%n modifier used");
            case 'm':
                if (ret != format)
                    i_panic("%%m used twice");
                ret = fix_format_real(format, p-1, len_r);
                break;
            case '\0':
                i_panic("%% modifier missing in '%s'", format);
            }
            p++;
        }
    }

    if (ret == format)
        *len_r = p - format;
    return ret;
}

const char *printf_format_fix_get_len(const char *format, unsigned int *len_r)
{
    const char *ret;

    ret = printf_format_fix_noalloc(format, len_r);
    if (ret != format)
        t_buffer_alloc(*len_r + 1);
    return ret;
}

const char *printf_format_fix(const char *format)
{
    const char *ret;
    unsigned int len;

    ret = printf_format_fix_noalloc(format, &len);
    if (ret != format)
        t_buffer_alloc(len + 1);
    return ret;
}

const char *printf_format_fix_unsafe(const char *format)
{
    unsigned int len;

    return printf_format_fix_noalloc(format, &len);
}