Opening a strait binary file with iOS - ios

Question

I wrote a custom file type that data from my Java program gets saved to. I want to get the data out on an iPod/Pad/Phone. So far I wrote this file for reading strait byte values from a file and changing them into NSStrings and integers.
#import "BinaryFileReader.h"
#implementation BinaryFileReader
- (id)init {
self = [super init];
return self;
}
- (id)initWithLocation:(NSString*)filepath {
if ((self = [super init])) {
_file = [NSFileHandle fileHandleForReadingAtPath:filepath];
_fileOffset = 0;
if (_file == nil)
NSLog(#"%#%#",#"Failed to open file at path:",filepath);
}
return self;
}
- (void)close {
[_file closeFile];
}
- (int)readInt {
[_file seekToFileOffset:_fileOffset];
_databuffer = [_file readDataOfLength:4];
_fileOffset+=4;
return (int)[_databuffer bytes];
}
- (NSString*)readNSString {
int length = [self readInt];
[_file seekToFileOffset:_fileOffset];
_databuffer = [_file readDataOfLength:length];
_fileOffset+=length;
return [[NSString alloc] initWithData:_databuffer encoding:NSUTF8StringEncoding];
}
- (NSMutableArray*)readNSMutableArrayOfNSString {
NSMutableArray* array = [[NSMutableArray alloc] init];
int arrayLength = [self readInt];
int length;
for (int i=0; i<arrayLength; i++) {
length = [self readInt];
[_file seekToFileOffset:_fileOffset];
_databuffer = [_file readDataOfLength:length];
_fileOffset+=length;
[array addObject:[[NSString alloc] initWithData:_databuffer encoding:NSUTF8StringEncoding]];
}
return array;
}
#end
Now when I try to use this to read NSStrings or integers it does not come up with the right values. I assume since both NSStrings and integers are coming up wrong it's something in the readInt method. Anyone see something glaringly obvious that I've missed here?
Edit:
The file format that I am trying to read starts with a string. That string, when read with readNSString, is the correct string but the first 1/3 of the string is missing.
Java code:
public void saveItem() {
try {
byte[] bytes;
FileOutputStream output;
if (countOccurrences(location.getPath(),'.')==1) {
System.out.println("Option 1");
output = new FileOutputStream(location+"/"+name+".dtb");
} else {
output = new FileOutputStream(location);
}
bytes = name.getBytes("UTF-8");
output.write(bytes.length);
output.write(bytes);
output.write(otherNames.length);
for (int i=0;i<otherNames.length;i++) {
bytes = otherNames[i].getBytes("UTF-8");
output.write(bytes.length);
output.write(bytes);
}
bytes = description.getBytes("UTF-8");
output.write(bytes.length);
output.write(bytes);
bytes = XactCode.getBytes("UTF-8");
output.write(bytes.length);
output.write(bytes);
bytes = SymbilityCode.getBytes("UTF-8");
output.write(bytes.length);
output.write(bytes);
output.write(averageLowPrice);
output.write(averageHighPrice);
output.write(averageLifeExpectancy);
output.close();
bytes = null;
} catch (Exception e) {
e.printStackTrace();
}
}

Answer 1

The reason this does not work is the way you are casting the NSData to int. The bytes methods returns a pointer to the actual data, which you will need to deference to get the actual value (otherwise you will just be getting the memory address of the pointer).
I tried two ways:
int test = 64;
NSData *data = [NSData dataWithBytes:&test length:4];
int test2 = (int)[data bytes]; //This gave me 170382992
and
int test = 64;
NSData *data = [NSData dataWithBytes:&test length:4];
int test2 = *((int *)[data bytes]); //This gave me 64