Make README as Markdown format

README.md

@@ -0,0 +1,66 @@
+Initialisation
+--------------
+
+Before you can use libbase58 for base58check, you must provide a SHA256
+function. The required function signature is:
+
+	bool my_sha256(void *digest, const void *data, size_t datasz)
+
+Simply assign your function to b58_sha256_impl:
+
+	b58_sha256_impl = my_sha256;
+
+This is only required if base58check is used. Raw base58 does not need SHA256.
+
+
+Decoding Base58
+---------------
+
+Simply allocate a buffer to store the binary data in, and set a variable with
+the buffer size, and call the b58tobin function:
+
+	bool b58tobin(void *bin, size_t *binsz, const char *b58, size_t b58sz)
+
+The "canonical" base58 byte length will be assigned to binsz on success, which
+may be larger than the actual buffer if the input has many leading zeros.
+Regardless of the canonical byte length, the full binary buffer will be used.
+If b58sz is zero, it will be initialised with strlen(b58); note that a true
+zero-length base58 string is not supported here.
+
+
+Validating Base58Check
+----------------------
+
+After calling b58tobin, you can validate base58check data using the b58check
+function:
+
+	int b58check(const void *bin, size_t binsz, const char *b58, size_t b58sz)
+
+Call it with the same buffers used for b58tobin. If the return value is
+negative, an error occurred. Otherwise, the return value is the base58check
+"version" byte from the decoded data.
+
+
+Encoding Base58
+---------------
+
+Allocate a string to store the base58 content, create a size_t variable with the
+size of that allocation, and call:
+
+	bool b58enc(char *b58, size_t *b58sz, const void *data, size_t binsz)
+
+Note that you must pass a pointer to the string size variable, not the size
+itself. When b58enc returns, the variable will be modified to contain the actual
+number of bytes used (including the null terminator). If encoding fails for any
+reason, or if the string buffer is not large enough for the result, b58enc will
+return false. Otherwise, it returns true to indicate success.
+
+
+Encoding Base58Check
+--------------------
+
+Targeting base58check is done similarly to raw base58 encoding, but you must
+also provide a version byte:
+
+	bool b58check_enc(char *b58c, size_t *b58c_sz, uint8_t ver,
+	                  const void *data, size_t datasz)