Extend JKBigInteger to initialize using binary data (e.g. from NSData).

JKBigInteger/JKBigInteger.h

@@ -19,6 +19,8 @@
 - (id)initWithString:(NSString *)string andRadix:(int)radix;
 - (id)initWithCString:(char *)cString;
 - (id)initWithCString:(char *)cString andRadix:(int)radix;
+- (id)initWithUnsignedByteArray:(const unsigned char*)byteArray andSize:(int)size;
+- (id)initWithSignedByteArray:(const unsigned char*)byteArray andSize:(int)size;
 
 - (id)add:(JKBigInteger *)bigInteger;
 - (id)subtract:(JKBigInteger *)bigInteger;
@@ -50,6 +52,7 @@
 - (NSString *)description;
 
 - (unsigned int)countBytes;
+- (unsigned int)countSignedBytes;
 - (void)toByteArraySigned: (unsigned char*) byteArray;
 - (void)toByteArrayUnsigned: (unsigned char*) byteArray;
 

JKBigInteger/JKBigInteger.m

@@ -102,6 +102,45 @@ - (id)initWithCoder:(NSCoder *)decoder {
 
     return self;
 }
+
+- (id)initWithUnsignedByteArray:(const unsigned char *)byteArray andSize:(int)size {
+
+    self = [super init];
+
+    if (self) {
+        //allocate a buffer large enough to read this value
+        if (MP_OKAY != mp_init_size(&m_value, size))
+            return nil;
+
+        //read the value
+        if (MP_OKAY != mp_read_unsigned_bin(&m_value, byteArray, size)) {
+            mp_clear(&m_value);
+            return nil;
+        }
+    }
+
+    return self;
+}
+
+- (id)initWithSignedByteArray:(const unsigned char *)byteArray andSize:(int)size {
+
+    self = [super init];
+
+    if (self) {
+        //allocate a buffer large enough to read this value
+        if (MP_OKAY != mp_init_size(&m_value, size))
+            return nil;
+
+        //read the value
+        if (MP_OKAY != mp_read_signed_bin(&m_value, byteArray, size)) {
+            mp_clear(&m_value);
+            return nil;
+        }
+    }
+
+    return self;
+}
+
 - (void)encodeWithCoder:(NSCoder *)encoder {
 
     mp_clamp(&m_value);
@@ -399,6 +438,11 @@ - (unsigned int)countBytes {
     return (unsigned int) mp_unsigned_bin_size(&m_value);
 }
 
+/* Returns the number of bytes required to store this JKBigInteger as signed binary */
+- (unsigned int)countSignedBytes {
+    return (unsigned int) mp_signed_bin_size(&m_value);
+}
+
 /* Retrieves the signed [big endian] format of this JKBigInteger */
 - (void)toByteArraySigned: (unsigned char*) byteArray {
     mp_to_signed_bin(&m_value, byteArray);

Unit Tests/Unit_Tests.m

@@ -84,6 +84,39 @@ - (void)testEqual2 {
     XCTAssertEqual(result, NSOrderedSame, @"Test equal 2 failed!");
 }
 
+- (void)testInitWithUnsignedByteArray {
+    JKBigInteger *int1 = [[JKBigInteger alloc] initWithString:@"939202309485773939498585839393498477393984"];
+    NSMutableData* data = [[NSMutableData alloc] initWithCapacity:[int1 countBytes]];
+    data.length = [int1 countBytes];
+
+    [int1 toByteArrayUnsigned:[data mutableBytes]];
+    JKBigInteger *result = [[JKBigInteger alloc] initWithUnsignedByteArray:[data bytes] andSize:(int)[data length]];
+
+    XCTAssertEqualObjects([result stringValueWithRadix:10], [int1 stringValueWithRadix:10]);
+}
+
+- (void)testInitWithSignedByteArray0 {
+    JKBigInteger *int1 = [[JKBigInteger alloc] initWithString:@"939202309485773939498585839393498477393984"];
+    NSMutableData* data = [[NSMutableData alloc] initWithCapacity:[int1 countBytes]];
+    data.length = [int1 countSignedBytes];
+
+    [int1 toByteArraySigned:[data mutableBytes]];
+    JKBigInteger *result = [[JKBigInteger alloc] initWithSignedByteArray:[data bytes] andSize:(int)[data length]];
+
+    XCTAssertEqualObjects([result stringValueWithRadix:10], [int1 stringValueWithRadix:10]);
+}
+
+- (void)testInitWithSignedByteArray1 {
+    JKBigInteger *int1 = [[JKBigInteger alloc] initWithString:@"-939202309485773939498585839393498477393984"];
+    NSMutableData* data = [[NSMutableData alloc] initWithCapacity:[int1 countBytes]];
+    data.length = [int1 countSignedBytes];
+
+    [int1 toByteArraySigned:[data mutableBytes]];
+    JKBigInteger *result = [[JKBigInteger alloc] initWithSignedByteArray:[data bytes] andSize:(int)[data length]];
+
+    XCTAssertEqualObjects([result stringValueWithRadix:10], [int1 stringValueWithRadix:10]);
+}
+
 // Auto generated tests below
 
 - (void)testAdd0 {