New module 'unistr/u16-to-u8'.

[gnulib.git] / lib / unistr / u16-to-u8.c

diff --git a/lib/unistr/u16-to-u8.c b/lib/unistr/u16-to-u8.c
new file mode 100644 (file)
index 0000000..c88db79
--- /dev/null
+++ b/lib/unistr/u16-to-u8.c
@@ -0,0 +1,138 @@
+/* Convert UTF-16 string to UTF-8 string.
+   Copyright (C) 2002, 2006 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2002.
+
+   This program 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, 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+   USA.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include "unistr.h"
+
+#define FUNC u16_to_u8
+#define SRC_UNIT uint16_t
+#define DST_UNIT uint8_t
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+DST_UNIT *
+FUNC (const SRC_UNIT *s, size_t n, DST_UNIT *resultbuf, size_t *lengthp)
+{
+  const SRC_UNIT *s_end = s + n;
+  /* Output string accumulator.  */
+  DST_UNIT *result;
+  size_t allocated;
+  size_t length;
+
+  if (resultbuf != NULL)
+    {
+      result = resultbuf;
+      allocated = *lengthp;
+    }
+  else
+    {
+      result = NULL;
+      allocated = 0;
+    }
+  length = 0;
+  /* Invariants:
+     result is either == resultbuf or == NULL or malloc-allocated.
+     If length > 0, then result != NULL.  */
+
+  while (s < s_end)
+    {
+      ucs4_t uc;
+      int count;
+
+      /* Fetch a Unicode character from the input string.  */
+      count = u16_mbtouc_safe (&uc, s, s_end - s);
+      if (count < 0)
+       {
+         if (!(result == resultbuf || result == NULL))
+           free (result);
+         errno = EILSEQ;
+         return NULL;
+       }
+      s += count;
+
+      /* Store it in the output string.  */
+      count = u8_uctomb (result, uc, allocated - length);
+      if (count == -1)
+       {
+         if (!(result == resultbuf || result == NULL))
+           free (result);
+         errno = EILSEQ;
+         return NULL;
+       }
+      if (count == -2)
+       {
+         DST_UNIT *memory;
+
+         allocated = (allocated > 0 ? 2 * allocated : 12);
+         if (length + 6 > allocated)
+           allocated = length + 6;
+         if (result == resultbuf || result == NULL)
+           memory = (DST_UNIT *) malloc (allocated * sizeof (DST_UNIT));
+         else
+           memory =
+             (DST_UNIT *) realloc (result, allocated * sizeof (DST_UNIT));
+
+         if (memory == NULL)
+           {
+             if (!(result == resultbuf || result == NULL))
+               free (result);
+             errno = ENOMEM;
+             return NULL;
+           }
+         if (result == resultbuf && length > 0)
+           memcpy ((char *) memory, (char *) result,
+                   length * sizeof (DST_UNIT));
+         result = memory;
+         count = u8_uctomb (result, uc, allocated - length);
+         if (count < 0)
+           abort ();
+       }
+      length += count;
+    }
+
+  if (length == 0)
+    {
+      if (result == NULL)
+       {
+         /* Return a non-NULL value.  NULL means error.  */
+         result = (DST_UNIT *) malloc (1);
+         if (result == NULL)
+           {
+             errno = ENOMEM;
+             return NULL;
+           }
+       }
+    }
+  else if (result != resultbuf && length < allocated)
+    {
+      /* Shrink the allocated memory if possible.  */
+      DST_UNIT *memory;
+
+      memory = (DST_UNIT *) realloc (result, length * sizeof (DST_UNIT));
+      if (memory != NULL)
+       result = memory;
+    }
+
+  *lengthp = length;
+  return result;
+}