1 files changed, 276 insertions, 0 deletions
diff --git a/lib/mbsalign.c b/lib/mbsalign.c
new file mode 100644
index 0000000..38face2
--- /dev/null
+++ b/lib/mbsalign.c
@@ -0,0 +1,276 @@
+/* Align/Truncate a string in a given screen width
+   Copyright (C) 2009-2022 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 <https://www.gnu.org/licenses/>.  */
+
+/* Written by Pádraig Brady.  */
+
+#include <config.h>
+#include "mbsalign.h"
+
+#include "minmax.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <limits.h>
+#include <wchar.h>
+#include <wctype.h>
+
+/* Replace non printable chars.
+   Note \t and \n etc. are non printable.
+   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;
+}
+
+/* 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, char const *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.
+   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_MAX upon error (invalid multi-byte sequence in SRC,
+   or malloc failure), unless MBA_UNIBYTE_FALLBACK is specified.
+   Update *WIDTH to indicate how many columns were used before padding.  */
+
+size_t
+mbsalign (char const *src, char *dest, size_t dest_size,
+          size_t *width, mbs_align_t align, int flags)
+{
+  size_t ret = SIZE_MAX;
+  size_t src_size = strlen (src) + 1;
+  char *newstr = NULL;
+  wchar_t *str_wc = NULL;
+  char const *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 (!(flags & MBA_UNIBYTE_ONLY) && MB_CUR_MAX > 1)
+    {
+      size_t src_chars = mbstowcs (NULL, src, 0);
+      if (src_chars == SIZE_MAX)
+        {
+          if (flags & MBA_UNIBYTE_FALLBACK)
+            goto mbsalign_unibyte;
+          else
+            goto mbsalign_cleanup;
+        }
+      src_chars += 1; /* make space for NUL */
+      str_wc = malloc (src_chars * sizeof (wchar_t));
+      if (str_wc == NULL)
+        {
+          if (flags & MBA_UNIBYTE_FALLBACK)
+            goto mbsalign_unibyte;
+          else
+            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 = wcswidth (str_wc, src_chars);
+        }
+    }
+
+  /* If we transformed or need to truncate the source string
+     then create a modified copy of it.  */
+  if (wc_enabled && (conversion || (n_cols > *width)))
+    {
+        if (conversion)
+          {
+             /* May have increased the size by converting
+                \t to \uFFFD for example.  */
+            src_size = wcstombs (NULL, str_wc, 0) + 1;
+          }
+        newstr = malloc (src_size);
+        if (newstr == NULL)
+        {
+          if (flags & MBA_UNIBYTE_FALLBACK)
+            goto mbsalign_unibyte;
+          else
+            goto mbsalign_cleanup;
+        }
+        str_to_print = newstr;
+        n_cols = wc_truncate (str_wc, *width);
+        n_used_bytes = wcstombs (newstr, str_wc, src_size);
+    }
+
+mbsalign_unibyte:
+
+  if (n_cols > *width) /* Unibyte truncation required.  */
+    {
+      n_cols = *width;
+      n_used_bytes = n_cols;
+    }
+
+  if (*width > n_cols) /* Padding required.  */
+    n_spaces = *width - n_cols;
+
+  /* indicate to caller how many cells needed (not including padding).  */
+  *width = n_cols;
+
+  {
+    size_t start_spaces, end_spaces;
+
+    switch (align)
+      {
+      case MBS_ALIGN_LEFT:
+        start_spaces = 0;
+        end_spaces = n_spaces;
+        break;
+      case MBS_ALIGN_RIGHT:
+        start_spaces = n_spaces;
+        end_spaces = 0;
+        break;
+      case MBS_ALIGN_CENTER:
+      default:
+        start_spaces = n_spaces / 2 + n_spaces % 2;
+        end_spaces = n_spaces / 2;
+        break;
+      }
+
+      if (flags & MBA_NO_LEFT_PAD)
+        start_spaces = 0;
+      if (flags & MBA_NO_RIGHT_PAD)
+        end_spaces = 0;
+
+      /* Write as much NUL terminated output to DEST as possible.  */
+      if (dest_size != 0)
+        {
+          size_t space_left;
+          char *dest_end = dest + dest_size - 1;
+
+          dest = mbs_align_pad (dest, dest_end, start_spaces);
+          space_left = dest_end - dest;
+          dest = mempcpy (dest, str_to_print, MIN (n_used_bytes, space_left));
+          mbs_align_pad (dest, dest_end, end_spaces);
+        }
+
+    /* indicate to caller how many bytes needed (not including NUL).  */
+    ret = n_used_bytes + ((start_spaces + end_spaces) * 1);
+  }
+
+mbsalign_cleanup:
+
+  free (str_wc);
+  free (newstr);
+
+  return ret;
+}
+
+/* A wrapper around mbsalign() to dynamically allocate the
+   minimum amount of memory to store the result.
+   Return NULL on failure.  */
+
+char *
+ambsalign (char const *src, size_t *width, mbs_align_t align, int flags)
+{
+  size_t orig_width = *width;
+  size_t size = *width;         /* Start with enough for unibyte mode.  */
+  size_t req = size;
+  char *buf = NULL;
+
+  while (req >= size)
+    {
+      char *nbuf;
+      size = req + 1;           /* Space for NUL.  */
+      nbuf = realloc (buf, size);
+      if (nbuf == NULL)
+        {
+          free (buf);
+          buf = NULL;
+          break;
+        }
+      buf = nbuf;
+      *width = orig_width;
+      req = mbsalign (src, buf, size, width, align, flags);
+      if (req == SIZE_MAX)
+        {
+          free (buf);
+          buf = NULL;
+          break;
+        }
+    }
+
+  return buf;
+}