ExtendedAttributes.m

//
//  ExtendedAttributes.m
//  Textus
//
//  Created by Jiang Jiang on 9/18/09.
//

#import "ExtendedAttributes.h"

#import <sys/xattr.h>

@implementation NSURL (ExtendedAttributes)

- (NSArray*)allXattrKeys {
  NSMutableArray* allKeys = [NSMutableArray array];
  size_t dataSize =
      listxattr([[self path] fileSystemRepresentation], NULL, ULONG_MAX, 0);
  if (dataSize == ULONG_MAX)
    return allKeys;  // Empty list.

  NSMutableData* listBuffer = [NSMutableData dataWithLength:dataSize];
  dataSize = listxattr([[self path] fileSystemRepresentation],
		       [listBuffer mutableBytes],
		       [listBuffer length],
		       0);
  char* nameStart = [listBuffer mutableBytes];
  int x;
  for (x = 0; x < dataSize; x++) {
    if (((char*)[listBuffer mutableBytes])[x] == 0) {
      NSString* str = @(nameStart);
      nameStart = [listBuffer mutableBytes] + x + 1;
      [allKeys addObject:str];
    }
  }

  return allKeys;
}

- (NSUInteger)unsignedIntegerFromXattrKey:(NSString*)key {
  const char* path = [[self path] fileSystemRepresentation];
  char dataBuf[256];
  size_t dataSize = getxattr(path, [key UTF8String], dataBuf, 256, 0, 0);

  if (dataSize) {
    dataBuf[dataSize] = '\0';
    return strtol(dataBuf, NULL, 10);
  }
  return 0;
}

- (void)setUnsignedInteger:(NSUInteger)num forXattrKey:(NSString*)key {
  const char* path = [[self path] fileSystemRepresentation];
  const char* buf = [[NSString stringWithFormat:@"%lu", num] UTF8String];

  setxattr(path, [key UTF8String], buf, strlen(buf), 0, 0);
}

// -----------------------------------------------------------------------------
//      setData:forKey:atPath:
//              Set the xattr with name key to a block of raw binary data.
//              path is the file whose xattr you want to set.
// -----------------------------------------------------------------------------

- (void)setData:(NSData*)data forXattrKey:(NSString*)key {
  setxattr([[self path] fileSystemRepresentation],
	   [key UTF8String],
	   [data bytes],
	   [data length],
	   0,
	   0);
}

- (NSMutableData*)dataForXattrKey:(NSString*)key {
  size_t dataSize = getxattr([[self path] fileSystemRepresentation],
			     [key UTF8String],
			     NULL,
			     ULONG_MAX,
			     0,
			     0);
  if (dataSize == ULONG_MAX)
    return nil;
  NSMutableData* data = [NSMutableData dataWithLength:dataSize];
  getxattr([[self path] fileSystemRepresentation],
	   [key UTF8String],
	   [data mutableBytes],
	   [data length],
	   0,
	   0);
  return data;
}

- (NSString*)stringFromXattrKey:(NSString*)key {
  NSMutableData* data = [self dataForXattrKey:key];
  return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
}

- (void)setString:(NSString*)str forXattrKey:(NSString*)key {
  NSData* data = [str dataUsingEncoding:NSUTF8StringEncoding];

  if (!data)
    [NSException raise:NSCharacterConversionException
		format:@"Couldn't convert string to UTF8 for xattr storage."];

  [self setData:data forXattrKey:key];
}

@end