Add/test is_ascii_alphabet.

Author: evoskuil

include/bitcoin/system/unicode/ascii.hpp

@@ -49,6 +49,9 @@ BC_API bool has_mixed_ascii_case(const std::string_view& text) NOEXCEPT;
 /// True if all characters are in the ASCII subset of UTF8 [<128].
 BC_API bool is_ascii(const std::string_view& text) NOEXCEPT;
 
+/// True if all characters are in the ASCII subset 'a'..'z' and 'A'..'Z'.
+BC_API bool is_ascii_alphabet(const std::string_view& text) NOEXCEPT;
+
 /// True if all characters are in the ASCII subset '0'..'9' with a leading '-'
 /// character if specified. Leaving zeroes allowed, including after negative.
 BC_API bool is_ascii_numeric(const std::string_view& text) NOEXCEPT;

src/unicode/ascii.cpp

@@ -33,6 +33,14 @@ bool is_ascii(const std::string_view& text) NOEXCEPT
     return std::all_of(text.begin(), text.end(), is_ascii_character);
 }
 
+bool is_ascii_alphabet(const std::string_view& text) NOEXCEPT
+{
+    if (text.empty())
+        return true;
+
+    return std::all_of(text.begin(), text.end(), is_ascii_alpha);
+}
+
 bool is_ascii_numeric(const std::string_view& text) NOEXCEPT
 {
     if (text.empty())

test/unicode/ascii.cpp

@@ -328,6 +328,30 @@ BOOST_AUTO_TEST_CASE(ascii__is_ascii_numeric__decimal_numeric__false)
     BOOST_REQUIRE(!is_ascii_numeric("-.42"));
 }
 
+// is_ascii_alphabet
+
+BOOST_AUTO_TEST_CASE(ascii__is_ascii_alphabet__empty__true)
+{
+    BOOST_REQUIRE(is_ascii_alphabet(""));
+}
+
+BOOST_AUTO_TEST_CASE(ascii__is_ascii_alphabet__numeric__false)
+{
+    BOOST_REQUIRE(!is_ascii_alphabet("0123456789"));
+}
+
+BOOST_AUTO_TEST_CASE(ascii__is_ascii_alphabet__alphabet_true)
+{
+    BOOST_REQUIRE(is_ascii_alphabet("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"));
+}
+
+BOOST_AUTO_TEST_CASE(ascii__is_ascii_alphabet__padded_alphabet_false)
+{
+    BOOST_REQUIRE(!is_ascii_alphabet(" abc"));
+    BOOST_REQUIRE(!is_ascii_alphabet("abc "));
+    BOOST_REQUIRE(!is_ascii_alphabet(" abc "));
+}
+
 // ascii_to_lower
 
 BOOST_AUTO_TEST_CASE(ascii__ascii_to_lower__empty__empty)