struct/dstr-putf.c (dstr_vputf): Rewrite to support `%n$...' specs.

[mLib] / struct / dstr-putf.c

/* -*-c-*-
 *
 * `printf'-style formatting for dynamic strings
 *
 * (c) 1999 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of the mLib utilities library.
 *
 * mLib is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * mLib 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 Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with mLib; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Header files ------------------------------------------------------*/

#include "config.h"

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

#ifdef HAVE_FLOAT_H
#  include <float.h>
#endif

#include "darray.h"
#include "dstr.h"

/*----- Tunable constants -------------------------------------------------*/

/*
 * For each format specifier, at least @PUTFSTEP@ bytes are ensured before
 * writing the formatted result.
 */

#define PUTFSTEP 64			/* Buffer size for @putf@ */

/*----- Preliminary definitions -------------------------------------------*/

#define OUTPUT_FMTTYPES(_)						\
  _(i, unsigned int)							\
  _(li, unsigned long)							\
  _(s, char *)								\
  _(p, void *)								\
  _(f, double)								\
  _(Lf, long double)

#define PERCENT_N_FMTTYPES(_)						\
  _(hn, short *)							\
  _(n, int *)								\
  _(ln, long *)

#define FMTTYPES(_)							\
  OUTPUT_FMTTYPES(_)							\
  PERCENT_N_FMTTYPES(_)

enum {
  fmt_unset = 0,
#define CODE(code, ty) fmt_##code,
  FMTTYPES(CODE)
#undef CODE
  fmt__limit
};

typedef struct {
  int fmt;
  union {
#define MEMB(code, ty) ty code;
    FMTTYPES(MEMB)
#undef MEMB
  } u;
} fmtarg;

DA_DECL(fmtarg_v, fmtarg);

enum {
  len_std = 0,
  len_h,
  len_l,
  len_ll,
  len_L
};

#define f_len		0x000fu
#define f_wd		0x0010u
#define f_wdarg		0x0020u
#define f_prec		0x0040u
#define f_precarg	0x0080u
#define f_plus		0x0100u
#define f_minus		0x0200u
#define f_sharp		0x0400u
#define f_zero		0x0800u
#define f_posarg	0x1000u

typedef struct {
  const char *p;
  size_t n;
  unsigned f;
  int fmt, ch;
  int wd, prec;
  int arg;
} fmtspec;

DA_DECL(fmtspec_v, fmtspec);

/*----- Main code ---------------------------------------------------------*/

/* --- @dstr_vputf@ --- *
 *
 * Arguments:	@dstr *d@ = pointer to a dynamic string block
 *		@const char *p@ = pointer to @printf@-style format string
 *		@va_list *ap@ = argument handle
 *
 * Returns:	The number of characters written to the string.
 *
 * Use:		As for @dstr_putf@, but may be used as a back-end to user-
 *		supplied functions with @printf@-style interfaces.
 */

static void set_arg(fmtarg_v *av, size_t i, int fmt)
{
  size_t j, n;

  n = DA_LEN(av);
  if (i >= n) {
    DA_ENSURE(av, i + 1 - n);
    for (j = n; j <= i; j++) DA(av)[j].fmt = fmt_unset;
    DA_UNSAFE_EXTEND(av, i + 1 - n);
  }

  if (DA(av)[i].fmt == fmt_unset) DA(av)[i].fmt = fmt;
  else assert(DA(av)[i].fmt == fmt);
}

int dstr_vputf(dstr *d, const char *p, va_list *ap)
{
  size_t n = d->len;
  size_t sz, mx;
  dstr dd = DSTR_INIT;
  fmtspec_v sv = DA_INIT;
  fmtarg_v av = DA_INIT;
  fmtarg *fa, *fal;
  fmtspec *fs, *fsl;
  unsigned f;
  int i, anext;
  int wd, prec;

  /* --- Initial pass through the input, parsing format specifiers --- *
   *
   * We essentially compile the format string into a vector of @fmtspec@
   * objects, each of which represnts a chunk of literal text followed by a
   * (possibly imaginary, in the case of the final one) formatting directive.
   * Output then simply consists of interpreting these specifiers in order.
   */

  anext = 0;

  while (*p) {
    f = 0;
    DA_ENSURE(&sv, 1);
    fs = &DA(&sv)[DA_LEN(&sv)];
    DA_UNSAFE_EXTEND(&sv, 1);

    /* --- Find the end of this literal portion --- */

    fs->p = p;
    while (*p && *p != '%') p++;
    fs->n = p - fs->p;

    /* --- Some simple cases --- *
     *
     * We might have reached the end of the string, or maybe a `%%' escape.
     */

    if (!*p) { fs->fmt = fmt_unset; fs->ch = 0; break; }
    p++;
    if (*p == '%') { fs->fmt = fmt_unset; fs->ch = '%'; p++; continue; }

    /* --- Pick up initial flags --- */

  flags:
    for (;;) {
      switch (*p) {
	case '+': f |= f_plus; break;
	case '-': f |= f_minus; break;
	case '#': f |= f_sharp; break;
	case '0': f |= f_zero; break;
	default: goto done_flags;
      }
      p++;
    }

    /* --- Pick up the field width --- */

  done_flags:
    i = 0;
    while (isdigit((unsigned char)*p)) i = 10*i + *p++ - '0';

    /* --- Snag: this might have been an argument position indicator --- */

    if (i && *p == '$' && (!f || f == f_zero)) {
      f |= f_posarg;
      fs->arg = i - 1;
      p++;
      goto flags;
    }

    /* --- Set the field width --- *
     *
     * If @i@ is nonzero here then we have a numeric field width.  Otherwise
     * it might be `*', maybe with an explicit argument number.
     */

    if (i) {
      f |= f_wd;
      fs->wd = i;
    } else if (*p == '*') {
      p++;
      if (!isdigit((unsigned char)*p))
	i = anext++;
      else {
	i = *p++ - '0';
	while (isdigit((unsigned char)*p)) i = 10*i + *p++ - '0';
	assert(*p == '$'); p++;
	assert(i > 0); i--;
      }
      f |= f_wd | f_wdarg;
      set_arg(&av, i, fmt_i); fs->wd = i;
    }

    /* --- Maybe we have a precision spec --- */

    if (*p == '.') {
      p++;
      f |= f_prec;
      if (isdigit((unsigned char)*p)) {
	i = *p++ - '0';
	while (isdigit((unsigned char)*p)) i = 10*i + *p++ - '0';
	fs->prec = i;
      } else if (*p != '*')
	fs->prec = 0;
      else {
	p++;
	if (!isdigit((unsigned char)*p))
	  i = anext++;
	else {
	  i = *p++ - '0';
	  while (isdigit((unsigned char)*p)) i = 10*i + *p++ - '0';
	  assert(*p == '$'); p++;
	  assert(i > 0); i--;
	}
	f |= f_precarg;
	set_arg(&av, i, fmt_i); fs->prec = i;
      }
    }

    /* --- Maybe some length flags --- */

    switch (*p) {
      case 'h': f |= len_h; p++; break;
      case 'l': f |= len_l; p++; break;
      case 'L': f |= len_L; p++; break;
    }

    /* --- The flags are now ready --- */

    fs->f = f;

    /* --- At the end, an actual directive --- */

    fs->ch = *p;
    switch (*p++) {
      case '%':
	fs->fmt = fmt_unset;
	break;
      case 'd': case 'i': case 'x': case 'X': case 'o': case 'u':
	switch (f & f_len) {
	  case len_l: fs->fmt = fmt_li; break;
	  default: fs->fmt = fmt_i;
	}
	break;
      case 'e': case 'E': case 'f': case 'F': case 'g': case 'G':
	fs->fmt = (f & f_len) == len_L ? fmt_Lf : fmt_f;
	break;
      case 'c':
	fs->fmt = fmt_i;
	break;
      case 's':
	fs->fmt = fmt_s;
	break;
      case 'p':
	fs->fmt = fmt_p;
	break;
      case 'n':
	switch (f & f_len) {
	  case len_h: fs->fmt = fmt_hn; break;
	  case len_l: fs->fmt = fmt_ln; break;
	  default: fs->fmt = fmt_n;
	}
	break;
      default:
	fprintf(stderr,
		"FATAL dstr_vputf: unknown format specifier `%c'\n", p[-1]);
	abort();
    }

    /* --- Finally sort out the argument --- *
     *
     * If we don't have explicit argument positions then this comes after the
     * width and precision; and we don't know the type code until we've
     * parsed the specifier, so this seems the right place to handle it.
     */

    if (!(f & f_posarg)) fs->arg = anext++;
    set_arg(&av, fs->arg, fs->fmt);
  }

  /* --- Quick pass over the argument vector to collect the arguments --- */

  for (fa = DA(&av), fal = fa + DA_LEN(&av); fa < fal; fa++) {
    switch (fa->fmt) {
#define CASE(code, ty) case fmt_##code: fa->u.code = va_arg(*ap, ty); break;
      FMTTYPES(CASE)
#undef CASE
      default: abort();
    }
  }

  /* --- Final pass through the format string to produce output --- */

  fa = DA(&av);
  for (fs = DA(&sv), fsl = fs + DA_LEN(&sv); fs < fsl; fs++) {
    f = fs->f;

    /* --- Output the literal portion --- */

    if (fs->n) DPUTM(d, fs->p, fs->n);

    /* --- And now the variable portion --- */

    if (fs->fmt == fmt_unset) {
      switch (fs->ch) {
	case 0: break;
	case '%': DPUTC(d, '%'); break;
	default: abort();
      }
      continue;
    }

    DRESET(&dd);
    DPUTC(&dd, '%');

    /* --- Resolve the width and precision --- */

    if (!(f & f_wd))
      wd = 0;
    else {
      wd = (fs->f & f_wdarg) ? *(int *)&fa[fs->wd].u.i : fs->wd;
      if (wd < 0) { wd = -wd; f |= f_minus; }
    }

    if (!(f & f_prec))
      prec = 0;
    else {
      prec = (fs->f & f_precarg) ? *(int *)&fa[fs->prec].u.i : fs->prec;
      if (prec < 0) { prec = 0; f &= ~f_prec; }
    }

    /* --- Write out the flags, width and precision --- */

    if (f & f_plus) DPUTC(&dd, '+');
    if (f & f_minus) DPUTC(&dd, '-');
    if (f & f_sharp) DPUTC(&dd, '#');
    if (f & f_zero) DPUTC(&dd, '0');

    if (f & f_wd) {
      DENSURE(&dd, PUTFSTEP);
      dd.len += sprintf(dd.buf + dd.len, "%d", wd);
    }

    if (f & f_prec) {
      DENSURE(&dd, PUTFSTEP + 1);
      dd.len += sprintf(dd.buf + dd.len, ".%d", prec);
    }

    /* --- Write out the length gadget --- */

    switch (f & f_len) {
      case len_h: DPUTC(&dd, 'h'); break;
      case len_l: DPUTC(&dd, 'l'); break;
      case len_L: DPUTC(&dd, 'L'); break;
      case len_std: break;
      default: abort();
    }

    /* --- And finally the actually important bit --- */

    DPUTC(&dd, fs->ch);
    DPUTZ(&dd);

    /* --- Make sure we have enough space for the output --- */

    sz = PUTFSTEP;
    if (sz < wd) sz = wd;
    if (sz < prec + 16) sz = prec + 16;
    switch (fs->ch) {
      case 'a': case 'A':
      case 'e': case 'E': case 'f': case 'F': case 'g': case 'G':
#ifdef HAVE_FLOAT_H
	if (fs->ch == 'f') {
	  mx = ((fs->f & f_len) == len_L ?
		LDBL_MAX_10_EXP : DBL_MAX_10_EXP) + 16;
	  if (sz < mx) sz = mx;
	}
	break;
#else
	DPUTS(d, "<no float support>");
	continue;
#endif
      case 's':
	if (!(f & f_prec)) {
	  n = strlen(fa[fs->arg].u.s);
	  if (sz < n) sz = n;
	}
	break;
      case 'n':
	switch (fs->fmt) {
#define CASE(code, ty)							\
  case fmt_##code: *fa[fs->arg].u.code = d->len - n; break;
	  PERCENT_N_FMTTYPES(CASE)
#undef CASE
	  default: abort();
	}
	continue;
    }

    /* --- Finally do the output stage --- */

    DENSURE(d, sz + 1);
    switch (fs->fmt) {
#ifdef HAVE_SNPRINTF
#  define CASE(code, ty) case fmt_##code:				\
     i = snprintf(d->buf + d->len, sz + 1, dd.buf, fa[fs->arg].u.code);	\
     break;
#else
#  define CASE(code, ty) case fmt_##code:				\
     i = sprintf(d->buf + d->len, dd.buf, fa[fs->arg].u.code);		\
     break;
#endif
      OUTPUT_FMTTYPES(CASE)
#undef CASE
      default: abort();
    }
    assert(0 <= i && i <= sz); d->len += i;
  }

  /* --- We're done --- */

  DPUTZ(d);
  DDESTROY(&dd);
  return (d->len - n);
}

/* --- @dstr_putf@ --- *
 *
 * Arguments:	@dstr *d@ = pointer to a dynamic string block
 *		@const char *p@ = pointer to @printf@-style format string
 *		@...@ = argument handle
 *
 * Returns:	The number of characters written to the string.
 *
 * Use:		Writes a piece of text to a dynamic string, doing @printf@-
 *		style substitutions as it goes.  Intended to be robust if
 *		faced with malicious arguments, but not if the format string
 *		itself is malicious.
 */

int dstr_putf(dstr *d, const char *p, ...)
{
  int n;
  va_list ap;
  va_start(ap, p);
  n = dstr_vputf(d, p, &ap);
  va_end(ap);
  return (n);
}

/*----- That's all, folks -------------------------------------------------*/