glibc/libio/strfile.h
Florian Weimer e88b9f0e5c stdio-common: Convert vfprintf and related functions to buffers
vfprintf is entangled with vfwprintf (of course), __printf_fp,
__printf_fphex, __vstrfmon_l_internal, and the strfrom family of
functions.  The latter use the internal snprintf functionality,
so vsnprintf is converted as well.

The simples conversion is __printf_fphex, followed by
__vstrfmon_l_internal and __printf_fp, and finally
__vfprintf_internal and __vfwprintf_internal.  __vsnprintf_internal
and strfrom* are mostly consuming the new interfaces, so they
are comparatively simple.

__printf_fp is a public symbol, so the FILE *-based interface
had to preserved.

The __printf_fp rewrite does not change the actual binary-to-decimal
conversion algorithm, and digits are still not emitted directly to
the target buffer.  However, the staging buffer now uses bytes
instead of wide characters, and one buffer copy is eliminated.

The changes are at least performance-neutral in my testing.
Floating point printing and snprintf improved measurably, so that
this Lua script

  for i=1,5000000 do
      print(i, i * math.pi)
  end

runs about 5% faster for me.  To preserve fprintf performance for
a simple "%d" format, this commit has some logic changes under
LABEL (unsigned_number) to avoid additional function calls.  There
are certainly some very easy performance improvements here: binary,
octal and hexadecimal formatting can easily avoid the temporary work
buffer (the number of digits can be computed ahead-of-time using one
of the __builtin_clz* built-ins). Decimal formatting can use a
specialized version of _itoa_word for base 10.

The existing (inconsistent) width handling between strfmon and printf
is preserved here.  __print_fp_buffer_1 would have to use
__translated_number_width to achieve ISO conformance for printf.

Test expectations in libio/tst-vtables-common.c are adjusted because
the internal staging buffer merges all virtual function calls into
one.

In general, stack buffer usage is greatly reduced, particularly for
unbuffered input streams.  __printf_fp can still use a large buffer
in binary128 mode for %g, though.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2022-12-19 18:56:54 +01:00

111 lines
3.7 KiB
C

/* Copyright (C) 1993-2022 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>.
As a special exception, if you link the code in this file with
files compiled with a GNU compiler to produce an executable,
that does not cause the resulting executable to be covered by
the GNU Lesser General Public License. This exception does not
however invalidate any other reasons why the executable file
might be covered by the GNU Lesser General Public License.
This exception applies to code released by its copyright holders
in files containing the exception. */
#ifndef STRFILE_H_
#define STRFILE_H_
#include "libioP.h"
typedef void *(*_IO_alloc_type) (size_t);
typedef void (*_IO_free_type) (void*);
struct _IO_str_fields
{
/* These members are preserved for ABI compatibility. The glibc
implementation always calls malloc/free for user buffers if
_IO_USER_BUF or _IO_FLAGS2_USER_WBUF are not set. */
_IO_alloc_type _allocate_buffer_unused;
_IO_free_type _free_buffer_unused;
};
/* This is needed for the Irix6 N32 ABI, which has a 64 bit off_t type,
but a 32 bit pointer type. In this case, we get 4 bytes of padding
after the vtable pointer. Putting them in a structure together solves
this problem. */
struct _IO_streambuf
{
FILE _f;
const struct _IO_jump_t *vtable;
};
typedef struct _IO_strfile_
{
struct _IO_streambuf _sbf;
struct _IO_str_fields _s;
} _IO_strfile;
/* frozen: set when the program has requested that the array object not
be altered, reallocated, or freed. */
#define _IO_STR_FROZEN(FP) ((FP)->_f._flags & _IO_USER_BUF)
typedef struct
{
_IO_strfile f;
/* This is used for the characters which do not fit in the buffer
provided by the user. */
char overflow_buf[64];
} _IO_strnfile;
typedef struct
{
_IO_strfile f;
/* This is used for the characters which do not fit in the buffer
provided by the user. */
wchar_t overflow_buf[64];
} _IO_wstrnfile;
extern const struct _IO_jump_t _IO_wstrn_jumps attribute_hidden;
/* Initialize an _IO_strfile SF to read from narrow string STRING, and
return the corresponding FILE object. It is not necessary to fclose
the FILE when it is no longer needed. */
static inline FILE *
_IO_strfile_read (_IO_strfile *sf, const char *string)
{
sf->_sbf._f._lock = NULL;
_IO_no_init (&sf->_sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
_IO_JUMPS (&sf->_sbf) = &_IO_str_jumps;
_IO_str_init_static_internal (sf, (char*)string, 0, NULL);
return &sf->_sbf._f;
}
/* Initialize an _IO_strfile SF and _IO_wide_data WD to read from wide
string STRING, and return the corresponding FILE object. It is not
necessary to fclose the FILE when it is no longer needed. */
static inline FILE *
_IO_strfile_readw (_IO_strfile *sf, struct _IO_wide_data *wd,
const wchar_t *string)
{
sf->_sbf._f._lock = NULL;
_IO_no_init (&sf->_sbf._f, _IO_USER_LOCK, 0, wd, &_IO_wstr_jumps);
_IO_fwide (&sf->_sbf._f, 1);
_IO_wstr_init_static (&sf->_sbf._f, (wchar_t *)string, 0, NULL);
return &sf->_sbf._f;
}
#endif /* strfile.h. */