AcceleratedCryptographicHash: Use platform capabilities

Introduce a CNG version for Windows, a CommonCrypto
version for macOS and a GnuTLS version for Linux, as
we're using gnutls _anyway_.

src/mac/acceleratedcryptographichash_commoncrypto.cpp

@@ -0,0 +1,53 @@
+/*
+ * Use CommonCrypto on macOS for SHA256
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright (C) 2024 Raspberry Pi Ltd
+ */
+
+#include "acceleratedcryptographichash.h"
+
+#include <CommonCrypto/CommonDigest.h>
+
+struct AcceleratedCryptographicHash::Impl {
+    explicit Impl(QCryptographicHash::Algorithm algo) {
+        if (method != QCryptographicHash::Sha256)
+            throw std::runtime_error("Only sha256 implemented");
+
+        CC_SHA256_Init(&_sha256);
+    }
+
+    void addData(const char *data, int length)
+    {
+        CC_SHA256_Update(&_sha256, data, length);
+    }
+
+    void addData(const QByteArray &data)
+    {
+        addData(data.constData(), data.size());
+    }
+
+    QByteArray result() {
+        unsigned char binhash[CC_SHA256_DIGEST_LENGTH];
+        CC_SHA256_Final(binhash, &_sha256);
+        return QByteArray((char *) binhash, sizeof binhash);
+    }
+
+private:
+    CC_SHA256_CTX _sha256;
+};
+
+AcceleratedCryptographicHash::AcceleratedCryptographicHash(QCryptographicHash::Algorithm method)
+    : p_Impl(std::make_unique<impl>(method)) {}
+
+AcceleratedCryptographicHash::~AcceleratedCryptographicHash() = default;
+
+void AcceleratedCryptographicHash::addData(const char *data, int length) {
+    p_Impl->addData(data, length);
+}
+void AcceleratedCryptographicHash::addData(const QByteArray &data) {
+    p_Impl->addData(data);
+}
+QByteArray AcceleratedCryptographicHash::result() {
+    return p_Impl->result();
+}