Add QUtil::hex_decode

1 files changed, 44 insertions, 0 deletions

diff --git a/libqpdf/QUtil.cc b/libqpdf/QUtil.cc
index 93374568..1cc5449a 100644
--- a/libqpdf/QUtil.cc
+++ b/libqpdf/QUtil.cc
@@ -290,6 +290,50 @@ QUtil::hex_encode(std::string const& input)
     return result;
 }
 
+std::string
+QUtil::hex_decode(std::string const& input)
+{
+    std::string result;
+    size_t pos = 0;
+    for (std::string::const_iterator p = input.begin(); p != input.end(); ++p)
+    {
+        char ch = *p;
+        bool skip = false;
+        if ((*p >= 'A') && (*p <= 'F'))
+        {
+            ch -= 'A';
+            ch += 10;
+        }
+        else if ((*p >= 'a') && (*p <= 'f'))
+        {
+            ch -= 'a';
+            ch += 10;
+        }
+        else if ((*p >= '0') && (*p <= '9'))
+        {
+            ch -= '0';
+        }
+        else
+        {
+            skip = true;
+        }
+        if (! skip)
+        {
+            if (pos == 0)
+            {
+                result.push_back(ch << 4);
+                pos = 1;
+            }
+            else
+            {
+                result.back() += ch;
+                pos = 0;
+            }
+        }
+    }
+    return result;
+}
+
 void
 QUtil::binary_stdout()
 {