Use Windows library for cryptographic checksumscng_backend

Add a new feature to libbb, FEATURE_USE_CNG_API, which enables the
use of the Cryptography API: Next Generation library to calculate
checksums.  It is disabled by default except in the mingw64u default
config, as the API requires Windows 10+ to function.  Usage of this
API provides a size benefit and delegates hardware optimizations to
the operating system cryptography library.

Based on GitHub PR #498 by rfl890.

Saves 4064 bytes in the mingw64u case.

1 files changed, 10 insertions, 0 deletions

diff --git a/libbb/Config.src b/libbb/Config.src
index 61b4601d6..ed6521c33 100644
--- a/libbb/Config.src
+++ b/libbb/Config.src
@@ -37,6 +37,14 @@ config PASSWORD_MINLEN
         help
         Minimum allowable password length.
 
+config FEATURE_USE_CNG_API
+        bool "Use the Windows CNG API for checksums (Windows 10+ only)"
+        default n
+        depends on PLATFORM_MINGW32
+        help
+        Use the in-built Windows CNG API for checksums.
+        This reduces code size, but is only supported on Windows 10+.
+
 config MD5_SMALL
         int "MD5: Trade bytes for speed (0:fast, 3:slow)"
         default 1  # all "fast or small" options default to small
@@ -67,6 +75,7 @@ config SHA1_SMALL
 config SHA1_HWACCEL
         bool "SHA1: Use hardware accelerated instructions if possible"
         default y
+        depends on !FEATURE_USE_CNG_API
         help
         On x86, this adds ~590 bytes of code. Throughput
         is about twice as fast as fully-unrolled generic code.
@@ -74,6 +83,7 @@ config SHA1_HWACCEL
 config SHA256_HWACCEL
         bool "SHA256: Use hardware accelerated instructions if possible"
         default y
+        depends on !FEATURE_USE_CNG_API
         help
         On x86, this adds ~1k bytes of code.