Solved

fread vs. FSRead

Posted on 1997-01-22
1
276 Views
Last Modified: 2013-12-26
Using CW 10 on a 604 based Mac-clone I have a C program that reads a binary file a few bytes at a time. The SIOUX implemented fread() function is almost 10 times faster than the Mac Toolbox function FSRead() at reading the whole file. I would have thought that fread() just calls FSRead() but apparently that's not the case. Is the problem just buffering? Does fread() have built in buffering that FSRead() lacks?
0
Comment
Question by:tlyons
1 Comment
 

Accepted Solution

by:
looker earned 100 total points
ID: 1291362
Yes fread does use an internal buffer for caching file reads. I'm not sure exactly what size the CW10 buffer is but it will be a minimum of 512 bytes and probably 2K or 4K. This buffer is filled on the first fread call, and subsequent fread calls actuall just transfer memory from the buffer to your storage. When the buffer is exhausted, or you position to somewhere in the file outside the buffer, another low level (FSRead call is made to re-fill the buffer).

FSRead on the other hand usesthe volume buffer for each block read into memory before it transfers it to your storage.

You could drastically improve performace by reading block size chunks from disk and reading through that buffer on your own. There is some extra programming involved, but that would also allow you to implement asynchronous I/O to make your code even more efficient. (You can parse one buffer while reading in another from disk.)
0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Expand LInux Boot partition remotly 3 102
Error on moodle after upgrade 3 149
Detect CR LF to each line 12 174
Hibernate methods 2 83
Introduction: The undo support, implementing a stack. Continuing from the eigth article about sudoku.   We need a mechanism to keep track of the digits entered so as to implement an undo mechanism.  This should be a ‘Last In First Out’ collec…
Exception Handling is in the core of any application that is able to dignify its name. In this article, I'll guide you through the process of writing a DRY (Don't Repeat Yourself) Exception Handling mechanism, using Aspect Oriented Programming.
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
Email security requires an ever evolving service that stays up to date with counter-evolving threats. The Email Laundry perform Research and Development to ensure their email security service evolves faster than cyber criminals. We apply our Threat…

762 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question