BigInt::to_u32bit failed on 32-bit integers. GH #220

3 files changed, 51 insertions, 2 deletions

diff --git a/doc/news.rst b/doc/news.rst
index 214e93962..41277760a 100644
--- a/doc/news.rst
+++ b/doc/news.rst
@@ -4,6 +4,9 @@ Release Notes
 Version 1.11.19, Not Yet Released
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+* BigInt::to_u32bit would fail if the value was exactly 32 bits.
+  GH #220
+
 Version 1.11.18, 2015-07-05
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
diff --git a/src/lib/math/bigint/bigint.cpp b/src/lib/math/bigint/bigint.cpp
index c9aa1d981..045117cbd 100644
--- a/src/lib/math/bigint/bigint.cpp
+++ b/src/lib/math/bigint/bigint.cpp
@@ -142,7 +142,7 @@ u32bit BigInt::to_u32bit() const
    {
    if(is_negative())
       throw Encoding_Error("BigInt::to_u32bit: Number is negative");
-   if(bits() >= 32)
+   if(bits() > 32)
       throw Encoding_Error("BigInt::to_u32bit: Number is too big to convert");
 
    u32bit out = 0;
diff --git a/src/tests/test_bigint.cpp b/src/tests/test_bigint.cpp
index f6ae2a654..2bd7df2a7 100644
--- a/src/tests/test_bigint.cpp
+++ b/src/tests/test_bigint.cpp
@@ -17,7 +17,7 @@
 #include <cstdlib>
 #include <iterator>
 
-
+#include <sstream>
 #include <botan/bigint.h>
 #include <botan/exceptn.h>
 #include <botan/numthry.h>
@@ -26,6 +26,50 @@ using namespace Botan;
 
 namespace {
 
+void test_failure(const char* function, const char* file, int line,
+                  const std::string& what_failed)
+   {
+   std::cout << "FAIL " << function << " " << file << ":" << line << " "
+             << what_failed << std::endl;
+   }
+
+#define BOTAN_TEST(lhs, rhs, msg) try {                                    \
+   ++tests_run;                                                            \
+   const auto lhs_val = lhs;                                               \
+   const auto rhs_val = rhs;                                               \
+   const bool cmp = lhs_val == rhs_val;                                    \
+   if(!cmp)                                                                \
+      {                                                                    \
+      std::ostringstream fmt;                                              \
+      fmt << "expr '" << #lhs << " == " << #rhs << "' false, "             \
+          << "actually " << lhs_val << " " << rhs_val                      \
+          << " (" << msg << ")";                                           \
+      test_failure(BOTAN_CURRENT_FUNCTION, __FILE__, __LINE__, fmt.str()); \
+      ++tests_failed;                                                      \
+      }                                                                    \
+   }                                                                       \
+   catch(std::exception& e)                                                \
+      {                                                                    \
+      std::ostringstream fmt;                                              \
+      fmt << "exception '" << e.what() << "' (" << msg << ")";             \
+      test_failure(BOTAN_CURRENT_FUNCTION, __FILE__, __LINE__, fmt.str()); \
+      ++tests_failed;                                                      \
+      }
+
+size_t test_bigint_to_u32bit()
+   {
+   size_t tests_run = 0, tests_failed = 0;
+
+   for(size_t i = 0; i != 32; ++i)
+      {
+      const u32bit in = 1 << i;
+      BOTAN_TEST(in, BigInt(in).to_u32bit(), "In range round trips");
+      }
+
+   test_report("BigInt to_u32bit", tests_run, tests_failed);
+   return tests_failed;
+   }
+
 void strip_comments(std::string& line)
    {
    if(line.find('#') != std::string::npos)
@@ -303,6 +347,8 @@ size_t test_bigint()
    bool first = true;
    size_t counter = 0;
 
+   total_errors += test_bigint_to_u32bit();
+
    auto& rng = test_rng();
 
    while(!test_data.eof())