Need help with a loop that gobbles up RAM

I'm trying to get this loop to free all of the memory it uses, but it still gobbles up RAM pretty quickly. Hopefully someone can tell me how I can get the strings deallocating as they should. Basically, the loop writes doubles to a text file, and sometimes it has to write several megabytes of them.

for (int i = 0; i < number_of_samples; i++)
{
    if (print_str == nil)
    {
        print_str = [[NSMutableString alloc] init];
    }

    NSString* add_str = [[NSString alloc] initWithFormat:@"\n%0.06f", number_of_seconds/number_of_samples*i];
    [print_str appendString:add_str];
    [add_str release];

    开发者_开发知识库for (int g = 0; g < number_of_channels; g++)
    {
        add_str = [[NSString alloc] initWithFormat:@"\t%f", data_buffer[g + i*number_of_channels]];
        [print_str appendString:add_str];
        [add_str release];
    }

    if (i % 100 == 0 && i != 0)
    {
        fprintf(c_file_handle, "%s", [print_str UTF8String]);
        [print_str release];
        print_str = nil;
    }
}

---

The only thing you can do with the string is not using the print_str cause it still holds all the strings and occupies memory. Use "a" option in fopen to append data to the file and append the formatted string add_str to the file instead of adding it to the memory buffer.

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Because you're basically using that one string as a temporary buffer, how about allocating it once, and initWithFormatting it as often as you want? Then release it when you're done with the loop.

NSString * add_str = [NSString alloc];

loop... {
    NSString* add_str = [ add_str initWithFormat:@"\n%0.06f", number_of_seconds/number_of_samples*i];
    [print_str appendString:add_str];
}
// end of loop

[add_str release];

---

Instead of creating strings and using fprintf, you might try using NSOutputStream. Your code might look something like this:

NSOutputStream *os = [NSOutputStream outputStreamToFileAtPath:@"/path/to/file.ext"
                                                       append:YES];
[os open];
for (int i = 0; i < number_of_samples; i++) {
    // create a buffer to store the data to write
    [os write:buffer maxLength:bufferLength];
    // release the buffer
}
[os close];

This is a rough sketch - see the documentation for NSStream and NSOutputStream for details.

---

1. You could use [print_str appendFormat:] instead of allocating and releasing a new string each time.

2. When running in tight loops sometimes you need to create an NSAutoRelease pool and periodically drain it and create a new one but I do not see you using any autoreleased objects.

3. Are you able to free the data_buffer as you go or do you use it again later? free(data_buffer[g + i*number_of_channels]);