add sha256sum support code

src/common/checksum.c

@@ -0,0 +1,74 @@
+/* this is a cleaned-up version of
+ * http://adamlamers.com/?p=5
+ */
+
+#include <stdio.h>
+#include <malloc.h>
+#include <errno.h>
+
+#include "checksum.h"
+
+void
+sha256_hash_string (unsigned char hash[SHA256_DIGEST_LENGTH], char outputBuffer[65])
+{
+	int i = 0;
+	for (i = 0; i < SHA256_DIGEST_LENGTH; i++)
+	{
+		sprintf(outputBuffer + (i * 2), "%02x", hash[i]);
+	}
+	outputBuffer[64] = 0;
+}
+
+void
+sha256 (char *string, char outputBuffer[65])
+{
+	int i;
+	unsigned char hash[SHA256_DIGEST_LENGTH];
+	SHA256_CTX sha256;
+
+	SHA256_Init (&sha256);
+	SHA256_Update (&sha256, string, strlen(string));
+	SHA256_Final (hash, &sha256);
+
+	for (i = 0; i < SHA256_DIGEST_LENGTH; i++)
+	{
+		sprintf (outputBuffer + (i * 2), "%02x", hash[i]);
+	}
+	outputBuffer[64] = 0;
+}
+
+int
+sha256_file (char *path, char outputBuffer[65])
+{
+	int bytesRead;
+	unsigned char *buffer;
+	unsigned char hash[SHA256_DIGEST_LENGTH];
+	SHA256_CTX sha256;
+
+	FILE *file = fopen (path, "rb");
+	if (!file)
+	{
+		return -534;
+	}
+
+	SHA256_Init (&sha256);
+	buffer = malloc (BUFSIZE);
+	bytesRead = 0;
+
+	if (!buffer)
+	{
+		return ENOMEM;
+	}
+
+	while ((bytesRead = fread (buffer, 1, BUFSIZE, file)))
+	{
+		SHA256_Update (&sha256, buffer, bytesRead);
+    }
+
+    SHA256_Final (hash, &sha256);
+    sha256_hash_string (hash, outputBuffer);
+
+	fclose (file);
+    free (buffer);
+    return 0;
+}

src/common/checksum.h

@@ -0,0 +1,6 @@
+#include <openssl/sha.h>
+#define BUFSIZE 32768
+
+void sha256_hash_string (unsigned char hash[SHA256_DIGEST_LENGTH], char outputBuffer[65]);
+void sha256 (char *string, char outputBuffer[65]);
+int sha256_file (char *path, char outputBuffer[65]);