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POHow to get byte data from file in object c
 

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  1. POHow to get byte data from file in object c
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    <p>I read file from <code>fcntl(fd, F_GLOBAL_NOCACHE, 1);</code> to read file from Disk not from Cache. After reading file, i can only get string data. Now i want to after reading file, i get byte data of file to NSMutableData. How can i do that? Thanks in advance.</p> <pre><code> if (fd) { fcntl(fd, F_GLOBAL_NOCACHE, 1); NSMutableData* myData = [[NSMutableData alloc] init]; while(YES) { // store the length before addition NSUInteger previousLength = [myData length]; // increase the length so we can write more bytes [myData increaseLengthBy:300]; // read bytes from stream directly at the end of our data size_t len = fread([myData mutableBytes] + previousLength, 300, 1, fd); // set data length [myData setLength:previousLength + len]; // if end-of-file exit the loop if (len == 0) { break; } [myData appendBytes:buffer length:len]; } // use your 'myData' NSLog(@"dataFile: %@",myData); [myData release]; </code></pre> <p>Please give me suggestions? thanks</p> <p><strong>UPDATE2:</strong> Now i have another problem: i want to read file direct from disk not from Cache. I used below code but it seem not work, it still read from Cache :</p> <pre><code> NSString *url= [NSString stringWithFormat:@"%@/demo.abc"]; const char *c_sd_url = [url UTF8String]; NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; FILE * fd = fopen(c_sd_url, "rb"); if (fd) { fcntl(fd, F_GLOBAL_NOCACHE, 1); fseek(fd, 0, SEEK_END); long sz = ftell(fd); fseek(fd, 0, SEEK_SET); char *buf = malloc(sz); NSLog(@"before %s",buf); assert(buf != NULL); assert(fread(buf, sz, 1, fd) == 1); NSLog(@"after %s",buf); NSMutableData *data= [NSMutableData dataWithBytesNoCopy:buf length:sz freeWhenDone:YES]; NSLog(@"%@",data); } </code></pre> <p>I used <code>fcntl(fd, F_GLOBAL_NOCACHE, 1);</code> after fopen(). Please give me any suggestion. Thanks much</p>
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    1. COSimplest is to use NSData dataWithContentsOfFile.
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    2. COIf use it , it can read file from Disk not from Cache ?
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    3. CO@Huynhhttkt You don't appear to have read the documentation of that method, which is bad.
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