add stripped-down & slightly-modified version of LibTomCrypt SHA256

src/sha256.h

@@ -0,0 +1,34 @@
+/* public api for Thomas Pornin's BearSSL SHA-256 implementation */
+
+/** @file
+ *  SHA-256 hash API.
+ */
+
+#ifndef __LIBSTROPHE_SHA256_H__
+#define __LIBSTROPHE_SHA256_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* make sure the stdint.h types are available */
+#include "ostypes.h"
+
+typedef struct {
+    uint64_t length;
+    uint32_t state[8], curlen;
+    uint8_t buf[64];
+} sha256_context;
+
+#define SHA256_DIGEST_SIZE 32
+
+void sha256_init(sha256_context *md);
+void sha256_process(sha256_context *md, const uint8_t *in, size_t inlen);
+void sha256_done(sha256_context *md, uint8_t *out);
+
+void sha256_hash(const uint8_t *data, size_t len, uint8_t *digest);
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __LIBSTROPHE_SHA256_H__ */