[pre-lexer 03/21] i18n: New function recode_substring_pool().

[Ben Pfaff]

Occasionally it is necessary to recode a string that might contain a null
byte.  This function is useful in such a case.
---
 src/libpspp/i18n.c |   63 ++++++++++++++++++++++++++++++++++++++--------------
 src/libpspp/i18n.h |   33 +++++----------------------
 2 files changed, 52 insertions(+), 44 deletions(-)

diff --git a/src/libpspp/i18n.c b/src/libpspp/i18n.c
index c0deb11..4934617 100644
--- a/src/libpspp/i18n.c
+++ b/src/libpspp/i18n.c
@@ -32,6 +32,7 @@
 #include "libpspp/hmapx.h"
 #include "libpspp/hash-functions.h"
 #include "libpspp/pool.h"
+#include "libpspp/str.h"
 #include "libpspp/version.h"
 
 #include "gl/localcharset.h"
@@ -99,14 +100,16 @@ recode_string (const char *to, const char *from,
 /* Uses CONV to convert the INBYTES starting at IP into the OUTBYTES starting
    at OP, and appends a null terminator to the output.
 
-   Returns true if successful, false if the output buffer is too small. */
-static bool
+   Returns the output length if successful, -1 if the output buffer is too
+   small. */
+static ssize_t
 try_recode (iconv_t conv,
             const char *ip, size_t inbytes,
-            char *op, size_t outbytes)
+            char *op_, size_t outbytes)
 {
   /* FIXME: Need to ensure that this char is valid in the target encoding */
   const char fallbackchar = '?';
+  char *op = op_;
 
   /* Put the converter into the initial shift state, in case there was any
      state information left over from its last usage. */
@@ -118,14 +121,14 @@ try_recode (iconv_t conv,
       {
       case EINVAL:
         if (outbytes < 2)
-          return false;
+          return -1;
         *op++ = fallbackchar;
-        *op++ = '\0';
-        return true;
+        *op = '\0';
+        return op - op_;
 
       case EILSEQ:
         if (outbytes == 0)
-          return false;
+          return -1;
         *op++ = fallbackchar;
         outbytes--;
         ip++;
@@ -133,7 +136,7 @@ try_recode (iconv_t conv,
         break;
 
       case E2BIG:
-        return false;
+        return -1;
 
       default:
         /* should never happen */
@@ -143,10 +146,10 @@ try_recode (iconv_t conv,
       }
 
   if (outbytes == 0)
-    return false;
+    return -1;
 
   *op = '\0';
-  return true;
+  return op - op_;
 }
 
 /* Converts the string TEXT, which should be encoded in FROM-encoding, to a
@@ -165,14 +168,34 @@ char *
 recode_string_pool (const char *to, const char *from,
                     const char *text, int length, struct pool *pool)
 {
-  size_t outbufferlength;
-  iconv_t conv ;
+  struct substring out;
 
   if ( text == NULL )
     return NULL;
 
   if ( length == -1 )
-     length = strlen(text);
+     length = strlen (text);
+
+  out = recode_substring_pool (to, from, ss_buffer (text, length), pool);
+  return out.string;
+}
+
+/* Converts the string TEXT, which should be encoded in FROM-encoding, to a
+   dynamically allocated string in TO-encoding.  Any characters which cannot be
+   converted will be represented by '?'.
+
+   The returned string will be null-terminated and allocated on POOL.
+
+   This function's behaviour differs from that of g_convert_with_fallback
+   provided by GLib.  The GLib function will fail (returns NULL) if any part of
+   the input string is not valid in the declared input encoding.  This function
+   however perseveres even in the presence of badly encoded input. */
+struct substring
+recode_substring_pool (const char *to, const char *from,
+                       struct substring text, struct pool *pool)
+{
+  size_t outbufferlength;
+  iconv_t conv ;
 
   if (to == NULL)
     to = default_encoding;
@@ -183,14 +206,20 @@ recode_string_pool (const char *to, const char *from,
   conv = create_iconv (to, from);
 
   if ( (iconv_t) -1 == conv )
-    return xstrdup (text);
+    {
+      struct substring out;
+      ss_alloc_substring (&out, text);
+      return out;
+    }
 
   for ( outbufferlength = 1 ; outbufferlength != 0; outbufferlength <<= 1 )
-    if ( outbufferlength > length)
+    if ( outbufferlength > text.length)
       {
         char *output = pool_malloc (pool, outbufferlength);
-        if (try_recode (conv, text, length, output, outbufferlength))
-          return output;
+        ssize_t output_len = try_recode (conv, text.string, text.length,
+                                         output, outbufferlength);
+        if (output_len >= 0)
+          return ss_buffer (output, output_len);
         pool_free (pool, output);
       }
 
diff --git a/src/libpspp/i18n.h b/src/libpspp/i18n.h
index e2663a0..37bd944 100644
--- a/src/libpspp/i18n.h
+++ b/src/libpspp/i18n.h
@@ -1,5 +1,5 @@
 /* PSPP - a program for statistical analysis.
-   Copyright (C) 2006 Free Software Foundation, Inc.
+   Copyright (C) 2006, 2010 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
@@ -26,36 +26,15 @@ void  i18n_init (void);
 
 struct pool;
 
-
-/* 
-Converts the string TEXT, which should be encoded in FROM-encoding, to a
-dynamically allocated string in TO-encoding.   Any characters which cannot
-be converted will be represented by '?'.
-
-LENGTH should be the length of the string or -1, if null terminated.
-
-The returned string will be allocated on POOL.
-
-This function's behaviour differs from that of g_convert_with_fallback provided
-by GLib.  The GLib function will fail (returns NULL) if any part of the input
-string is not valid in the declared input encoding.  This function however 
perseveres
-even in the presence of badly encoded input.
-*/
-char *recode_string_pool (const char *to, const char *from,
-                         const char *text, int length, struct pool *pool);
-
-
-
-/* Similar to recode_string_pool, but allocates the returned value on the heap 
instead of 
-   in a pool.  It is the caller's responsibility to free the returned value. */
 char *recode_string (const char *to, const char *from,
-                     const char *text, int len);
-
+                     const char *text, int len);
+char *recode_string_pool (const char *to, const char *from,
+                         const char *text, int length, struct pool *);
+struct substring recode_substring_pool (const char *to, const char *from,
+                                        struct substring text, struct pool *);
 
 bool valid_encoding (const char *enc);
 
-/* Return the decimal separator according to the
-   system locale */
 char get_system_decimal (void);
 
 const char * get_default_encoding (void);
-- 
1.7.1