Make exceptions easier to translate to error codes

Avoid throwing base Botan::Exception type, as it is difficult to
determine what the error is in that case.

Add Exception::error_code and Exception::error_type which allows
(for error code) more information about the error and (for error type)
allows knowing the error type without requiring a sequence of catches.

See GH #1742

3 files changed, 7 insertions, 4 deletions

diff --git a/src/lib/math/bigint/big_io.cpp b/src/lib/math/bigint/big_io.cpp
index 803e1cc4a..90c2253e9 100644
--- a/src/lib/math/bigint/big_io.cpp
+++ b/src/lib/math/bigint/big_io.cpp
@@ -20,7 +20,7 @@ std::ostream& operator<<(std::ostream& stream, const BigInt& n)
    if(stream.flags() & std::ios::hex)
       base = BigInt::Hexadecimal;
    else if(stream.flags() & std::ios::oct)
-      throw Exception("Octal output of BigInt not supported");
+      throw Invalid_Argument("Octal output of BigInt not supported");
 
    if(n == 0)
       stream.write("0", 1);
diff --git a/src/lib/math/bigint/bigint.h b/src/lib/math/bigint/bigint.h
index bd63425fd..64e408798 100644
--- a/src/lib/math/bigint/bigint.h
+++ b/src/lib/math/bigint/bigint.h
@@ -37,11 +37,14 @@ class BOTAN_PUBLIC_API(2,0) BigInt final
 
      /**
      * DivideByZero Exception
+     *
+     * In a future release this exception will be removed and its usage
+     * replaced by Invalid_Argument
      */
-     class BOTAN_PUBLIC_API(2,0) DivideByZero final : public Exception
+     class BOTAN_PUBLIC_API(2,0) DivideByZero final : public Invalid_Argument
         {
         public:
-           DivideByZero() : Exception("BigInt divide by zero") {}
+           DivideByZero() : Invalid_Argument("BigInt divide by zero") {}
         };
 
      /**
diff --git a/src/lib/math/numbertheory/numthry.cpp b/src/lib/math/numbertheory/numthry.cpp
index bb86f5ce0..a8dfe8eaf 100644
--- a/src/lib/math/numbertheory/numthry.cpp
+++ b/src/lib/math/numbertheory/numthry.cpp
@@ -351,7 +351,7 @@ BigInt inverse_euclid(const BigInt& n, const BigInt& mod)
 word monty_inverse(word input)
    {
    if(input == 0)
-      throw Exception("monty_inverse: divide by zero");
+      throw Invalid_Argument("monty_inverse: divide by zero");
 
    word b = input;
    word x2 = 1, x1 = 0, y2 = 0, y1 = 1;