Add sha256sum program.

sha256sum.c

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2017 Stephen Heumann
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>
+#include "sha256.h"
+
+unsigned char buf[0x8000];
+
+int main(int argc, char **argv) {
+    struct sha256_context ctx;
+    FILE *file;
+    size_t count;
+    int i;
+
+    srand(time(NULL));
+
+    if (argc != 2)
+        return EXIT_FAILURE;
+
+    file = fopen(argv[1], "rb");
+    if (file == NULL)
+        return EXIT_FAILURE;
+    
+    sha256_init(&ctx);
+    do {
+        count = (rand() & 0x7FFF) + 1;
+        count = fread(buf, 1, count, file);
+        sha256_update(&ctx, buf, count);
+    } while (count != 0);
+    
+    fclose(file);
+    sha256_finalize(&ctx);
+    
+    for (i = 0; i < 32; i++) {
+        printf("%02x", ctx.hash[i]);
+    }
+    printf("\n");
+    
+    return 0;
+}