From 3ef1b77304ec49ec2527d8cc3e17e1d0dd220720 Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Sat, 5 Jan 2019 13:04:05 -0500
Subject: Refactor QUtil::utf8_to_ascii

---
 libqpdf/QUtil.cc               | 59 ++++++++++++++++++++++++------------------
 libtests/qtest/qutil/qutil.out |  6 ++---
 libtests/qutil.cc              |  2 +-
 3 files changed, 38 insertions(+), 29 deletions(-)

diff --git a/libqpdf/QUtil.cc b/libqpdf/QUtil.cc
index ba4aea2c..04b9b190 100644
--- a/libqpdf/QUtil.cc
+++ b/libqpdf/QUtil.cc
@@ -893,20 +893,32 @@ QUtil::parse_numrange(char const* range, int max)
     return result;
 }
 
-enum encoding_e { e_utf16 };
+enum encoding_e { e_utf16, e_ascii };
 
 static
 std::string
-transcode_utf8(std::string const& utf8_val, encoding_e encoding)
+transcode_utf8(std::string const& utf8_val, encoding_e encoding,
+               char unknown)
 {
-    std::string result = "\xfe\xff";
+    std::string result;
+    if (encoding == e_utf16)
+    {
+        result += "\xfe\xff";
+    }
     size_t len = utf8_val.length();
     for (size_t i = 0; i < len; ++i)
     {
         unsigned char ch = static_cast<unsigned char>(utf8_val.at(i));
         if (ch < 128)
         {
-            result += QUtil::toUTF16(ch);
+            if (encoding == e_utf16)
+            {
+                result += QUtil::toUTF16(ch);
+            }
+            else
+            {
+                result.append(1, ch);
+            }
         }
         else
         {
@@ -923,7 +935,14 @@ transcode_utf8(std::string const& utf8_val, encoding_e encoding)
             if (((bytes_needed > 5) || (bytes_needed < 1)) ||
                 ((i + bytes_needed) >= len))
             {
-                result += "\xff\xfd";
+                if (encoding == e_utf16)
+                {
+                    result += "\xff\xfd";
+                }
+                else
+                {
+                    result.append(1, unknown);
+                }
             }
             else
             {
@@ -941,7 +960,14 @@ transcode_utf8(std::string const& utf8_val, encoding_e encoding)
                     codepoint <<= 6;
                     codepoint += (ch & 0x3f);
                 }
-                result += QUtil::toUTF16(codepoint);
+                if (encoding == e_utf16)
+                {
+                    result += QUtil::toUTF16(codepoint);
+                }
+                else
+                {
+                    result.append(1, unknown);
+                }
             }
         }
     }
@@ -951,28 +977,11 @@ transcode_utf8(std::string const& utf8_val, encoding_e encoding)
 std::string
 QUtil::utf8_to_utf16(std::string const& utf8)
 {
-    return transcode_utf8(utf8, e_utf16);
+    return transcode_utf8(utf8, e_utf16, 0);
 }
 
 std::string
 QUtil::utf8_to_ascii(std::string const& utf8, char unknown_char)
 {
-    std::string ascii_value;
-    for (size_t i = 0; i < utf8.length(); ++i)
-    {
-        unsigned char ch = static_cast<unsigned char>(utf8.at(i));
-        if (ch < 128)
-        {
-            ascii_value.append(1, ch);
-        }
-        else if ((ch & 0xc0) == 0x80)
-        {
-            // Ignore subsequent byte of UTF-8 encoded character
-        }
-        else
-        {
-            ascii_value.append(1, unknown_char);
-        }
-    }
-    return ascii_value;
+    return transcode_utf8(utf8, e_ascii, unknown_char);
 }
diff --git a/libtests/qtest/qutil/qutil.out b/libtests/qtest/qutil/qutil.out
index f47301e4..ca146c15 100644
--- a/libtests/qtest/qutil/qutil.out
+++ b/libtests/qtest/qutil/qutil.out
@@ -48,9 +48,9 @@ HAGOOGAMAGOOGLE: 0
 0x7fffffff -> ff fd
 0x80000000 -> ff fd
 ---- utf8_to_ascii
-Does π have fingers?
-Does ? have fingers?
-Does * have fingers?
+¿Does π have fingers?
+?Does ? have fingers?
+*Does * have fingers?
 ---- whoami
 quack1
 quack2
diff --git a/libtests/qutil.cc b/libtests/qutil.cc
index de51da58..364eae1c 100644
--- a/libtests/qutil.cc
+++ b/libtests/qutil.cc
@@ -222,7 +222,7 @@ void to_utf16_test()
 
 void utf8_to_ascii_test()
 {
-    char const* input = "Does \317\200 have fingers?";
+    char const* input = "\302\277Does \317\200 have fingers?";
     std::cout << input
               << std::endl
               << QUtil::utf8_to_ascii(input)
-- 
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