add multihash.h

extracts info about multihash from binary multihash

Makefile

@@ -19,7 +19,7 @@ TARGET_BIN = multihash
 MAIN = src/main.c
 MAIN_O = $(MAIN:.c=.o)
 
-SRCS = src/hashes.c src/errors.c
+SRCS = src/hashes.c src/errors.c src/multihash.c
 OBJS = $(SRCS:.c=.o)
 
 src/%.o: src/%.c

include/mh/errors.h

@@ -6,7 +6,7 @@
 #define MH_E_UNKNOWN_CODE -1
 #define MH_E_TOO_SHORT -2
 #define MH_E_TOO_LONG -3
-#define MH_E_LEN_NOT_SUPPORTED -4
+#define MH_E_VARINT_NOT_SUPPORTED -4
 
 #define MH_E_LAST -5
 

include/mh/hashes.h

@@ -35,12 +35,3 @@ const char *mh_hash_name(int hash);
 
 // returns length in bytes or if returns is < 0 it is an error
 int mh_hash_default_length(int hash);
-
-int mh_hash_length(const unsigned char multihash[], int len, int *hash_length);
-
-int mh_hash_function(const unsigned char multihash[], int len, int *hash);
-
-
-
-
-

include/mh/multihash.h

@@ -0,0 +1,10 @@
+#ifndef MH_HULTIHASH_H
+#define MH_HULTIHASH_H
+
+// returns hash code or error (which is < 0)
+int mh_multihash_hash(const unsigned char multihash[], int len);
+
+// returns length of multihash or error (which is < 0)
+int mh_multihash_length(const unsigned char multihash[], int len);
+
+#endif /* end of include guard */

src/errors.c

@@ -7,12 +7,12 @@ const char *mh_error_string(int code) {
 		case MH_E_UNKNOWN_CODE:
 			return "unknown multihash code";
 		case MH_E_TOO_SHORT:
-			return "multihash too short. must be > 3 bytes";
+			return "multihash too short. must be > 2 bytes";
 		case MH_E_TOO_LONG:
 			return "multihash too long. must be < 129 bytes";
-		case MH_E_LEN_NOT_SUPPORTED:
+		case MH_E_VARINT_NOT_SUPPORTED:
-			return "multihash does not yet support"
+			return "c-multihash does not yet support"
-				" digsets linger than 127 bytes";
+				" varint encoding";
 		default:
 			return "unknown error code";
 	}

src/multihash.c

@@ -0,0 +1,39 @@
+#include "mh/multihash.h"
+
+#include "mh/hashes.h"
+#include "mh/errors.h"
+
+#define VARINT_MASK (1 << 7)
+
+static int check_multihash(const unsigned char mh[], int len) {
+	if (len < 3) {
+		return MH_E_TOO_SHORT;
+	} else if (len >= 129) {
+		return MH_E_TOO_LONG;
+	} else if (mh[0] & VARINT_MASK) {
+		// In near future multihash format will be
+		// extended with varints, this is how we are protecting
+		// against it.
+		return MH_E_VARINT_NOT_SUPPORTED;
+	} else if (mh[1] & VARINT_MASK) {
+		return MH_E_VARINT_NOT_SUPPORTED;
+	}
+	return MH_E_NO_ERROR;
+}
+
+
+// returns hash code or error (which is < 0)
+int mh_multihash_hash(const unsigned char mh[], int len) {
+	if (check_multihash(mh, len))
+		return check_multihash(mh, len);
+	return (int) mh[0];
+}
+
+
+// returns length of multihash or error (which is < 0)
+int mh_multihash_length(const unsigned char mh[], int len) {
+	if (check_multihash(mh, len))
+		return check_multihash(mh, len);
+	return (int) mh[1];
+}
+

tests/c/minunit.h

@@ -1,7 +1,8 @@
 #include <stdio.h>
 
 #define mu_assert(message, test) do { if (!(test)) return message; } while (0)
-#define mu_run_test(test) do { char *message = test(); tests_run++; \
+#define mu_run_test(test) do { char *message; printf(" - run: %s\n", #test); \
+	message = test(); tests_run++; \
 	if (message) return message; } while (0)
 int tests_run = 0;
 static char *mu_all_tests(void);

tests/c/test_multihash_decoding.c

@@ -0,0 +1,42 @@
+#include <string.h>
+#include "minunit.h"
+#include "mh/multihash.h"
+
+#include "mh/hashes.h"
+
+#include "examples.h"
+
+char error_buf[256];
+
+static char *test_multihash_hash_decoding_works(void) {
+	mu_assert("sha1 multihash is detected as sha1",
+		mh_multihash_hash(sha1_example, sizeof(sha1_example))
+		== MH_H_SHA1);
+	mu_assert("sha2 multihash is detected as sha2",
+		mh_multihash_hash(sha2_example, sizeof(sha2_example))
+		== MH_H_SHA2_256);
+	mu_assert("sha3 multihash is detected as sha3",
+		mh_multihash_hash(sha3_example, sizeof(sha3_example))
+		== MH_H_SHA3_512);
+	return NULL;
+}
+
+static char *test_multihash_length_decoding_works(void) {
+	mu_assert("sha1 multihash has correct length",
+		mh_multihash_length(sha1_example, sizeof(sha1_example))
+		== mh_hash_default_length(MH_H_SHA1));
+	mu_assert("sha2 multihash has correct length",
+		mh_multihash_length(sha2_example, sizeof(sha2_example))
+		== mh_hash_default_length(MH_H_SHA2_256));
+	mu_assert("sha3-512 multihash has correct length",
+		mh_multihash_length(sha3_example, sizeof(sha3_example))
+		== mh_hash_default_length(MH_H_SHA3_512));
+	return NULL;
+}
+
+static char *mu_all_tests(void) {
+	mu_run_test(test_multihash_hash_decoding_works);
+	mu_run_test(test_multihash_length_decoding_works);
+	return NULL;
+}
+