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vasprintf.c

/*###########################################################################
  #                                                                           #
  #                                vasprintf                                  #
  #                                                                           #
  #               Copyright (c) 2002-2003 David TAILLANDIER                   #
  #                                                                           #
  ###########################################################################*/

/*

This software is distributed under the GNU General Public Licence.

This software is also released under the modified BSD licence in
another file (same source-code, only license differ).

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 2 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, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA


====================

Hacked from xnprintf version of 29th December 2002 to provide only
vasprintf by Reuben Thomas <rrt@sc3d.org> for Zile.

====================


'printf' function family use the following format string:

%[flag][width][.prec][modifier]type

%% is the escape sequence to print a '%'
%  followed by an unknown format will print the characters without
trying to do any interpretation

flag:   none   +     -     #     (blank)
width:  n    0n    *
prec:   none   .0    .n     .*
modifier:    F N L h l    ('F' and 'N' are ms-dos/16-bit specific)
type:  d i o u x X f e g E G c s p n


The function needs to allocate memory to store the full text before to
actually writting it.  i.e if you want to fnprintf() 1000 characters, the
functions will allocate 1000 bytes.
This behaviour can be modified: you have to customise the code to flush the
internal buffer (writing to screen or file) when it reach a given size. Then
the buffer can have a shorter length. But what? If you really need to write
HUGE string, don't use printf!
During the process, some other memory is allocated (1024 bytes minimum)
to handle the output of partial sprintf() calls. If you have only 10000 bytes
free in memory, you *may* not be able to nprintf() a 8000 bytes-long text.

note: if a buffer overflow occurs, exit() is called. This situation should
never appear ... but if you want to be *really* sure, you have to modify the
code to handle those situations (only one place to modify).
A buffer overflow can only occur if your sprintf() do strange things or when
you use strange formats.

*/

#include "config.h"

#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <ctype.h>
#include <limits.h>

#define ALLOC_CHUNK 2048
#define ALLOC_SECURITY_MARGIN 1024   /* big value because some platforms have very big 'G' exponent */
#if ALLOC_CHUNK < ALLOC_SECURITY_MARGIN
#    error  !!! ALLOC_CHUNK < ALLOC_SECURITY_MARGIN !!!
#endif
/* note: to have some interest, ALLOC_CHUNK should be much greater than ALLOC_SECURITY_MARGIN */

/*
 *  To save a lot of push/pop, every variable are stored into this
 *  structure, which is passed among nearly every sub-functions.
 */
typedef struct {
  const char * src_string;        /* current position into intput string */
  char *       buffer_base;       /* output buffer */
  char *       dest_string;       /* current position into output string */
  size_t       buffer_len;        /* length of output buffer */
  size_t       real_len;          /* real current length of output text */
  size_t       pseudo_len;        /* total length of output text if it were not limited in size */
  size_t       maxlen;
  va_list      vargs;             /* pointer to current position into vargs */
  char *       sprintf_string;
  FILE *       fprintf_file;
} xprintf_struct;

/*
 *  Realloc buffer if needed
 *  Return value:  0 = ok
 *               EOF = not enought memory
 */
static int realloc_buff(xprintf_struct *s, size_t len)
{
  char * ptr;

  if (len + ALLOC_SECURITY_MARGIN + s->real_len > s->buffer_len) {
    len += s->real_len + ALLOC_CHUNK;
    ptr = (char *)realloc((void *)(s->buffer_base), len);
    if (ptr == NULL) {
      s->buffer_base = NULL;
      return EOF;
    }

    s->dest_string = ptr + (size_t)(s->dest_string - s->buffer_base);
    s->buffer_base = ptr;
    s->buffer_len = len;

    (s->buffer_base)[s->buffer_len - 1] = 1; /* overflow marker */
  }

  return 0;
}

/*
 *  Prints 'usual' characters    up to next '%'
 *                            or up to end of text
 */
static int usual_char(xprintf_struct * s)
{
  size_t len;

  len = strcspn(s->src_string, "%");     /* reachs the next '%' or end of input string */
  /* note: 'len' is never 0 because the presence of '%' */
  /* or end-of-line is checked in the calling function  */

  if (realloc_buff(s,len) == EOF)
    return EOF;

  memcpy(s->dest_string, s->src_string, len);
  s->src_string += len;
  s->dest_string += len;
  s->real_len += len;
  s->pseudo_len += len;

  return 0;
}

/*
 *  Return value: 0 = ok
 *                EOF = error
 */
static int print_it(xprintf_struct *s, size_t approx_len,
                    const char *format_string, ...)
{
  va_list varg;
  int vsprintf_len;
  size_t len;

  if (realloc_buff(s,approx_len) == EOF)
    return EOF;

  va_start(varg, format_string);
  vsprintf_len = vsprintf(s->dest_string, format_string, varg);
  va_end(varg);

  /* Check for overflow */
  assert((s->buffer_base)[s->buffer_len - 1] == 1);

  if (vsprintf_len == EOF) /* must be done *after* overflow-check */
    return EOF;

  s->pseudo_len += vsprintf_len;
  len = strlen(s->dest_string);
  s->real_len += len;
  s->dest_string += len;

  return 0;
}

/*
 *  Prints a string (%s)
 *  We need special handling because:
 *     a: the length of the string is unknown
 *     b: when .prec is used, we must not access any extra byte of the
 *        string (of course, if the original sprintf() does... what the
 *        hell, not my problem)
 *
 *  Return value: 0 = ok
 *                EOF = error
 */
static int type_s(xprintf_struct *s, int width, int prec,
                  const char *format_string, const char *arg_string)
{
  size_t string_len;

  if (arg_string == NULL)
    return print_it(s, (size_t)6, "(null)", 0);

  /* hand-made strlen() whitch stops when 'prec' is reached. */
  /* if 'prec' is -1 then it is never reached. */
  string_len = 0;
  while (arg_string[string_len] != 0 && (size_t)prec != string_len)
    string_len++;

  if (width != -1 && string_len < (size_t)width)
    string_len = (size_t)width;

  return print_it(s, string_len, format_string, arg_string);
}

/*
 *  Read a serie of digits. Stop when non-digit is found.
 *  Return value: the value read (between 0 and 32767).
 *  Note: no checks are made against overflow. If the string contain a big
 *  number, then the return value won't be what we want (but, in this case,
 *  the programmer don't know whatr he wants, then no problem).
 */
static int getint(const char **string)
{
  int i = 0;

  while (isdigit(**string) != 0) {
    i = i * 10 + (**string - '0');
    (*string)++;
  }

  if (i < 0 || i > 32767)
    i = 32767; /* if we have i==-10 this is not because the number is */
  /* negative; this is because the number is big */
  return i;
}

/*
 *  Read a part of the format string. A part is 'usual characters' (ie "blabla")
 *  or '%%' escape sequence (to print a single '%') or any combination of
 *  format specifier (ie "%i" or "%10.2d").
 *  After the current part is managed, the function returns to caller with
 *  everything ready to manage the following part.
 *  The caller must ensure than the string is not empty, i.e. the first byte
 *  is not zero.
 *
 *  Return value:  0 = ok
 *                 EOF = error
 */
static int dispatch(xprintf_struct *s)
{
  const char *initial_ptr;
  char format_string[24]; /* max length may be something like  "% +-#032768.32768Ld" */
  char *format_ptr;
  int flag_plus, flag_minus, flag_space, flag_sharp, flag_zero;
  int width, prec, modifier, approx_width;
  char type;
  /* most of those variables are here to rewrite the format string */

#define SRCTXT  (s->src_string)
#define DESTTXT (s->dest_string)

  /* incoherent format string. Characters after the '%' will be printed with the next call */
#define INCOHERENT()         do {SRCTXT=initial_ptr; return 0;} while (0)     /* do/while to avoid */
#define INCOHERENT_TEST()    do {if(*SRCTXT==0)   INCOHERENT();} while (0)    /* a null statement  */

  /* 'normal' text */
  if (*SRCTXT != '%')
    return usual_char(s);

  /* we then have a '%' */
  SRCTXT++;
  /* don't check for end-of-string ; this is done later */

  /* '%%' escape sequence */
  if (*SRCTXT == '%') {
    if (realloc_buff(s, (size_t)1) == EOF) /* because we can have "%%%%%%%%..." */
      return EOF;
    *DESTTXT = '%';
    DESTTXT++;
    SRCTXT++;
    (s->real_len)++;
    (s->pseudo_len)++;
    return 0;
  }

  /* '%' managing */
  initial_ptr = SRCTXT;   /* save current pointer in case of incorrect */
  /* 'decoding'. Points just after the '%' so the '%' */
  /* won't be printed in any case, as required. */

  /* flag */
  flag_plus = flag_minus = flag_space = flag_sharp = flag_zero = 0;

  for (;; SRCTXT++) {
    if (*SRCTXT == ' ')
      flag_space = 1;
    else if (*SRCTXT == '+')
      flag_plus = 1;
    else if (*SRCTXT == '-')
      flag_minus = 1;
    else if (*SRCTXT == '#')
      flag_sharp = 1;
    else if (*SRCTXT == '0')
      flag_zero = 1;
    else
      break;
  }

  INCOHERENT_TEST();    /* here is the first test for end of string */

  /* width */
  if (*SRCTXT == '*') {         /* width given by next argument */
    SRCTXT++;
    width = va_arg(s->vargs, int);
    if ((size_t)width > 0x3fffU) /* 'size_t' to check against negative values too */
      width = 0x3fff;
  } else if (isdigit(*SRCTXT)) /* width given as ASCII number */
    width = getint(&SRCTXT);
  else
    width = -1;                 /* no width specified */

  INCOHERENT_TEST();

  /* .prec */
  if (*SRCTXT == '.') {
    SRCTXT++;
    if (*SRCTXT == '*') {       /* .prec given by next argument */
      prec = va_arg(s->vargs, int);
      if ((size_t)prec >= 0x3fffU) /* 'size_t' to check against negative values too */
        prec = 0x3fff;
    } else {                    /* .prec given as ASCII number */
      if (isdigit(*SRCTXT) == 0)
        INCOHERENT();
      prec = getint(&SRCTXT);
    }
    INCOHERENT_TEST();
  } else
    prec = -1;                  /* no .prec specified */

  /* modifier */
  if (*SRCTXT == 'L' || *SRCTXT == 'h' || *SRCTXT == 'l') {
    modifier = *SRCTXT;
    SRCTXT++;
    if (modifier=='l' && *SRCTXT=='l') {
      SRCTXT++;
      modifier = 'L';  /* 'll' == 'L'      long long == long double */
    } /* only for compatibility ; not portable */
    INCOHERENT_TEST();
  } else
    modifier = -1;              /* no modifier specified */

  /* type */
  type = *SRCTXT;
  if (strchr("diouxXfegEGcspn",type) == NULL)
    INCOHERENT();               /* unknown type */
  SRCTXT++;

  /* rewrite format-string */
  format_string[0] = '%';
  format_ptr = &(format_string[1]);

  if (flag_plus) {
    *format_ptr = '+';
    format_ptr++;
  }
  if (flag_minus) {
    *format_ptr = '-';
    format_ptr++;
  }
  if (flag_space) {
    *format_ptr = ' ';
    format_ptr++;
  }
  if (flag_sharp) {
    *format_ptr = '#';
    format_ptr++;
  }
  if (flag_zero) {
    *format_ptr = '0';
    format_ptr++;
  } /* '0' *must* be the last one */

  if (width != -1) {
    sprintf(format_ptr, "%i", width);
    format_ptr += strlen(format_ptr);
  }

  if (prec != -1) {
    *format_ptr = '.';
    format_ptr++;
    sprintf(format_ptr, "%i", prec);
    format_ptr += strlen(format_ptr);
  }

  if (modifier != -1) {
    *format_ptr = modifier;
    format_ptr++;
  }

  *format_ptr = type;
  format_ptr++;
  *format_ptr = 0;

  /* vague approximation of minimal length if width or prec are specified */
  approx_width = width + prec;
  if (approx_width < 0) /* because width == -1 and/or prec == -1 */
    approx_width = 0;

  switch (type) {
    /* int */
  case 'd':
  case 'i':
  case 'o':
  case 'u':
  case 'x':
  case 'X':
    switch (modifier) {
    case -1 :
      return print_it(s, (size_t)approx_width, format_string, va_arg(s->vargs, int));
    case 'l':
      return print_it(s, (size_t)approx_width, format_string, va_arg(s->vargs, long int));
    case 'h':
      return print_it(s, (size_t)approx_width, format_string, va_arg(s->vargs, int));
      /* 'int' instead of 'short int' because default promotion is 'int' */
    default:
      INCOHERENT();
    }

    /* char */
  case 'c':
    if (modifier != -1)
      return print_it(s, (size_t)approx_width, format_string, va_arg(s->vargs, int));
    INCOHERENT();
    /* 'int' instead of 'char' because default promotion is 'int' */

    /* math */
  case 'e':
  case 'f':
  case 'g':
  case 'E':
  case 'G':
    switch (modifier) {
    case -1 : /* because of default promotion, no modifier means 'l' */
    case 'l':
      return print_it(s, (size_t)approx_width, format_string, va_arg(s->vargs, double));
    case 'L':
      return print_it(s, (size_t)approx_width, format_string, va_arg(s->vargs, long double));
    default:
      INCOHERENT();
    }

    /* string */
  case 's':
    return type_s(s, width, prec, format_string, va_arg(s->vargs, const char*));

    /* pointer */
  case 'p':
    if (modifier == -1)
      return print_it(s, (size_t)approx_width, format_string, va_arg(s->vargs, void *));
    INCOHERENT();

    /* store */
  case 'n':
    if (modifier == -1) {
      int * p;
      p = va_arg(s->vargs, int *);
      if (p != NULL) {
        *p = s->pseudo_len;
        return 0;
      }
      return EOF;
    }
    INCOHERENT();

  } /* switch */

  INCOHERENT();                 /* unknown type */

#undef INCOHERENT
#undef INCOHERENT_TEST
#undef SRCTXT
#undef DESTTXT
}

/*
 *  Return value: number of *virtually* written characters
 *                EOF = error
 */
static int core(xprintf_struct *s)
{
  size_t len, save_len;
  char *dummy_base;

  /* basic checks */
  if ((int)(s->maxlen) <= 0) /* 'int' to check against some conversion */
    return EOF;           /* error for example if value is (int)-10 */
  s->maxlen--;      /* because initial maxlen counts final 0 */
  /* note: now 'maxlen' _can_ be zero */

  if (s->src_string == NULL)
    s->src_string = "(null)";

  /* struct init and memory allocation */
  s->buffer_base = NULL;
  s->buffer_len = 0;
  s->real_len = 0;
  s->pseudo_len = 0;
  if (realloc_buff(s, (size_t)0) == EOF)
    return EOF;
  s->dest_string = s->buffer_base;

  /* process source string */
  for (;;) {
    /* up to end of source string */
    if (*(s->src_string) == 0) {
      *(s->dest_string) = 0;    /* final 0 */
      len = s->real_len + 1;
      break;
    }

    if (dispatch(s) == EOF)
      goto free_EOF;

    /* up to end of dest string */
    if (s->real_len >= s->maxlen) {
      (s->buffer_base)[s->maxlen] = 0; /* final 0 */
      len = s->maxlen + 1;
      break;
    }
  }

  /* for (v)asnprintf */
  dummy_base = s->buffer_base;
  save_len = 0;                 /* just to avoid a compiler warning */

  dummy_base = s->buffer_base + s->real_len;
  save_len = s->real_len;

  /* process the remaining of source string to compute 'pseudo_len'. We
   * overwrite again and again, starting at 'dummy_base' because we don't
   * need the text, only char count. */
  while(*(s->src_string) != 0) { /* up to end of source string */
    s->real_len = 0;
    s->dest_string = dummy_base;
    if (dispatch(s) == EOF)
      goto free_EOF;
  }

  s->buffer_base = (char *)realloc((void *)(s->buffer_base), save_len + 1);
  if (s->buffer_base == NULL)
    return EOF; /* should rarely happen because we shrink the buffer */
  return s->pseudo_len;

  free(s->buffer_base);
  return s->pseudo_len;

 free_EOF:
  if (s->buffer_base != NULL)
    free(s->buffer_base);
  return EOF;
}

int vasprintf(char **ptr, const char *format_string, va_list vargs)
{
  xprintf_struct s;
  int retval;

  s.src_string = format_string;
#ifdef va_copy
  va_copy (s.vargs, vargs);
#else
#ifdef __va_copy
  __va_copy (s.vargs, vargs);
#else
  memcpy (&s.vargs, vargs, sizeof (va_list));
#endif /* __va_copy */
#endif /* va_copy */
  s.maxlen = (size_t)INT_MAX;

  retval = core(&s);
  va_end(s.vargs);
  if (retval == EOF) {
    *ptr = NULL;
    return EOF;
  }

  *ptr = s.buffer_base;
  return retval;
}

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