ls: fix alignment when month names have varying widths

Reported by Samuel Thibault and Stéphane Raimbault, as the glibc fr_FR
locale has recently changed to use the official but variable width
abbreviated month names. Other glibc locales also have variable widths.
http://sourceware.org/ml/libc-locales/2008-q1/msg00035.html
http://sourceware.org/bugzilla/show_bug.cgi?id=9859
* NEWS: Mention the fix
* gl/lib/mbsalign.c: A new module to align and truncate a
string in a specified number of screen cells, while handling
multi-byte characters appropriately.
* gl/lib/mbsalign.h: Ditto
* gl/modules/mbsalign: Ditto
* bootstrap.conf: Reference the new module
* src/ls.c (abmon_init): New function, precompute the abbreviated
months aligned left in a minimum width column <= 5 screen cells.
(align_nstrftime): New function, replace the first %b in the
format specification to strftime with the precomputed month string.
Note using the cached month strings speeds up `ls -lU` by around 17%
on glibc-2.7-2 on linux at least.  Also if we implement this function
using heap storage rather than automatic storage, and use snprintf
instead of strcpy, ls will slow down by 2% and 1% respectively
(i.e. a net gain of 14% rather than 17%).
* tests/ls/abmon-align: A new test to test ls alignment for
various formats and locales
* tests/Makefile.am: Reference the new test

1 files changed, 236 insertions, 0 deletions

diff --git a/gl/lib/mbsalign.c b/gl/lib/mbsalign.c
new file mode 100644
index 000000000..bf90e0569
--- /dev/null
+++ b/gl/lib/mbsalign.c
@@ -0,0 +1,236 @@
+/* Align/Truncate a string in a given screen width
+   Copyright (C) 2009 Free Software Foundation, Inc.
+
+   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 3 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, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Pádraig Brady.  */
+
+#include <config.h>
+#include "mbsalign.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <limits.h>
+#include <wchar.h>
+#include <wctype.h>
+
+#ifndef MIN
+# define MIN(a, b) ((a) < (b) ? (a) : (b))
+#endif
+
+/* Replace non printable chars.
+   Return 1 if replacement made, 0 otherwise.  */
+
+static bool
+wc_ensure_printable (wchar_t *wchars)
+{
+  bool replaced = false;
+  wchar_t *wc = wchars;
+  while (*wc)
+    {
+      if (!iswprint ((wint_t) *wc))
+        {
+          *wc = 0xFFFD; /* L'\uFFFD' (replacement char) */
+          replaced = true;
+        }
+      wc++;
+    }
+  return replaced;
+}
+
+/* Truncate wchar string to width cells.
+ * Returns number of cells used.  */
+
+static size_t
+wc_truncate (wchar_t *wc, size_t width)
+{
+  size_t cells = 0;
+  int next_cells = 0;
+
+  while (*wc)
+    {
+      next_cells = wcwidth (*wc);
+      if (next_cells == -1) /* non printable */
+        {
+          *wc = 0xFFFD; /* L'\uFFFD' (replacement char) */
+          next_cells = 1;
+        }
+      if (cells + next_cells > width)
+        break;
+      cells += next_cells;
+      wc++;
+    }
+  *wc = L'\0';
+  return cells;
+}
+
+/* FIXME: move this function to gnulib as it's missing on:
+   OpenBSD 3.8, IRIX 5.3, Solaris 2.5.1, mingw, BeOS  */
+
+static int
+rpl_wcswidth (const wchar_t *s, size_t n)
+{
+  int ret = 0;
+
+  while (n-- > 0 && *s != L'\0')
+    {
+      int nwidth = wcwidth (*s++);
+      if (nwidth == -1)             /* non printable */
+        return -1;
+      if (ret > (INT_MAX - nwidth)) /* overflow */
+        return -1;
+      ret += nwidth;
+    }
+
+  return ret;
+}
+
+/* Write N_SPACES space characters to DEST while ensuring
+   nothing is written beyond DEST_END. A terminating NUL
+   is always added to DEST.
+   A pointer to the terminating NUL is returned.  */
+
+static char*
+mbs_align_pad (char *dest, const char* dest_end, size_t n_spaces)
+{
+  /* FIXME: Should we pad with "figure space" (\u2007)
+     if non ascii data present?  */
+  while (n_spaces-- && (dest < dest_end))
+    *dest++ = ' ';
+  *dest = '\0';
+  return dest;
+}
+
+/* Align a string, SRC, in a field of *WIDTH columns, handling multi-byte
+   characters; write the result into the DEST_SIZE-byte buffer, DEST.
+   ALIGNMENT specifies whether to left- or right-justify or to center.
+   If SRC requires more than *WIDTH columns, truncate it to fit.
+   When centering, the number of trailing spaces may be one less than the
+   number of leading spaces. The FLAGS parameter is unused at present.
+   Return the length in bytes required for the final result, not counting
+   the trailing NUL.  A return value of DEST_SIZE or larger means there
+   wasn't enough space.  DEST will be NUL terminated in any case.
+   Return (size_t) -1 upon error (invalid multi-byte sequence in SRC,
+   or malloc failure).
+   Update *WIDTH to indicate how many columns were used before padding.  */
+
+size_t
+mbsalign (const char *src, char *dest, size_t dest_size,
+          size_t *width, mbs_align_t align, int flags)
+{
+  size_t ret = -1;
+  size_t src_size = strlen (src) + 1;
+  char *newstr = NULL;
+  wchar_t *str_wc = NULL;
+  const char *str_to_print = src;
+  size_t n_cols = src_size - 1;
+  size_t n_used_bytes = n_cols; /* Not including NUL */
+  size_t n_spaces = 0;
+  bool conversion = false;
+  bool wc_enabled = false;
+
+  /* In multi-byte locales convert to wide characters
+     to allow easy truncation. Also determine number
+     of screen columns used.  */
+  if (MB_CUR_MAX > 1)
+    {
+      size_t src_chars = mbstowcs (NULL, src, 0);
+      if (src_chars == (size_t) -1)
+        goto mbsalign_cleanup;
+      src_chars += 1; /* make space for NUL */
+      str_wc = malloc (src_chars * sizeof (wchar_t));
+      if (str_wc == NULL)
+        goto mbsalign_cleanup;
+      if (mbstowcs (str_wc, src, src_chars) > 0)
+        {
+          str_wc[src_chars - 1] = L'\0';
+          wc_enabled = true;
+          conversion = wc_ensure_printable (str_wc);
+          n_cols = rpl_wcswidth (str_wc, src_chars);
+        }
+    }
+
+  /* If we transformed or need to truncate the source string
+     then create a modified copy of it.  */
+  if (conversion || (n_cols > *width))
+    {
+      newstr = malloc (src_size);
+      if (newstr == NULL)
+        goto mbsalign_cleanup;
+      str_to_print = newstr;
+      if (wc_enabled)
+        {
+          n_cols = wc_truncate (str_wc, *width);
+          n_used_bytes = wcstombs (newstr, str_wc, src_size);
+        }
+      else
+        {
+          n_cols = *width;
+          n_used_bytes = n_cols;
+          memcpy (newstr, src, n_cols);
+          newstr[n_cols] = '\0';
+        }
+    }
+
+  if (*width > n_cols)
+    n_spaces = *width - n_cols;
+
+  /* indicate to caller how many cells needed (not including padding).  */
+  *width = n_cols;
+
+  /* indicate to caller how many bytes needed (not including NUL).  */
+  ret = n_used_bytes + (n_spaces * 1);
+
+  /* Write as much NUL terminated output to DEST as possible.  */
+  if (dest_size != 0)
+    {
+      char *dest_end = dest + dest_size - 1;
+      size_t start_spaces = n_spaces / 2 + n_spaces % 2;
+      size_t end_spaces = n_spaces / 2;
+
+      switch (align)
+        {
+        case MBS_ALIGN_CENTER:
+          start_spaces = n_spaces / 2 + n_spaces % 2;
+          end_spaces = n_spaces / 2;
+          break;
+        case MBS_ALIGN_LEFT:
+          start_spaces = 0;
+          end_spaces = n_spaces;
+          break;
+        case MBS_ALIGN_RIGHT:
+          start_spaces = n_spaces;
+          end_spaces = 0;
+          break;
+        }
+
+      dest = mbs_align_pad (dest, dest_end, start_spaces);
+      dest = mempcpy(dest, str_to_print, MIN (n_used_bytes, dest_end - dest));
+      dest = mbs_align_pad (dest, dest_end, end_spaces);
+    }
+
+mbsalign_cleanup:
+
+  free (str_wc);
+  free (newstr);
+
+  return ret;
+}
+/*
+ * Local variables:
+ *  indent-tabs-mode: nil
+ * End:
+ */