vasprintf.c

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/*
 * vasprintf(3)
 * 20020809 entropy@tappedin.com
 * public domain.  no warranty.  use at your own risk.  have a nice day.
 */
 
#include <config.h>
 
#include <stdarg.h>
#include <stdio.h>
 
#if HAVE_STDLIB_H
#include <stdlib.h>
#endif /* HAVE_STDLIB_H */
 
#if HAVE_ERRNO_H
#include <errno.h>
#endif /* HAVE_ERRNO_H */
 
#if HAVE_STRING_H
#include <string.h>
#endif /* HAVE_STRING_H */
 
#if HAVE_UNISTD_H
#include <unistd.h>
#endif /* HAVE_UNISTD_H */
 
#if HAVE_PATHS_H
#include <paths.h>
#endif /* HAVE_PATHS_H */
 
#include <freetds/sysdep_private.h>
#include "replacements.h"
 
#if defined(HAVE__VSNPRINTF) && !defined(HAVE_VSNPRINTF)
#undef HAVE_VSNPRINTF
#undef vsnprintf
#define HAVE_VSNPRINTF 1
#define vsnprintf _vsnprintf
#endif
 
#ifndef _PATH_DEVNULL
#define _PATH_DEVNULL "/dev/null"
#endif
 
#define CHUNKSIZE 512
int
tds_vasprintf(char **ret, const char *fmt, va_list ap)
{
#if HAVE__VSCPRINTF
    int len = _vscprintf(fmt, ap);
 
    if (len >= 0) {
        *ret = malloc(len + 1);
        if (*ret) {
            vsprintf(*ret, fmt, ap);
            return len;
        }
        errno = ENOMEM;
    }
    *ret = NULL;
    return -1;
#elif HAVE_VSNPRINTF
    size_t chunks;
    size_t buflen;
    char *buf;
    int len;
 
    chunks = ((strlen(fmt) + 1) / CHUNKSIZE) + 1;
    buflen = chunks * CHUNKSIZE;
    for (;;) {
        if ((buf = malloc(buflen)) == NULL) {
            errno = ENOMEM;
            *ret = NULL;
            return -1;
        }
        len = vsnprintf(buf, buflen, fmt, ap);
        if (0 <= len && (size_t) len < buflen - 1) {
            break;
        }
        free(buf);
        buflen = (++chunks) * CHUNKSIZE;
        /* 
         * len >= 0 is required for vsnprintf implementations that 
         * return -1 for insufficient buffer
         */
        if (len >= 0 && buflen <= (size_t) len) {
            buflen = len + 1;
        }
    }
    *ret = buf;
    return len;
#else /* HAVE_VSNPRINTF */
#ifdef _REENTRANT
    FILE *fp;
#else /* !_REENTRANT */
    static FILE *fp = NULL;
#endif /* !_REENTRANT */
    int len;
    char *buf;
 
    *ret = NULL;
 
#ifdef _REENTRANT
 
# ifdef _WIN32
#  error Win32 do not have /dev/null, should use vsnprintf version
# endif
 
    if ((fp = fopen(_PATH_DEVNULL, "w")) == NULL)
        return -1;
#else /* !_REENTRANT */
    if ((fp == NULL) && ((fp = fopen(_PATH_DEVNULL, "w")) == NULL))
        return -1;
#endif /* !_REENTRANT */
 
    len = vfprintf(fp, fmt, ap);
 
#ifdef _REENTRANT
    if (fclose(fp) != 0)
        return -1;
#endif /* _REENTRANT */
 
    if (len < 0)
        return len;
    if ((buf = malloc(len + 1)) == NULL) {
        errno = ENOMEM;
        return -1;
    }
    if (vsprintf(buf, fmt, ap) != len)
        return -1;
    *ret = buf;
    return len;
#endif /* HAVE_VSNPRINTF */
}