haas:fall2020:common:helpances:binaryfileandeof
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| haas:fall2020:common:helpances:binaryfileandeof [2020/08/14 14:54] – created wedge | haas:fall2020:common:helpances:binaryfileandeof [2020/08/14 21:43] (current) – wedge | ||
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| Here is a copy of a reply I had to some questions I suspect many of you may be encountering when dealing with certain file aspects of discrete/ | Here is a copy of a reply I had to some questions I suspect many of you may be encountering when dealing with certain file aspects of discrete/ | ||
| - | <code> | + | <blockquote> |
| - | > I was having trouble finding EOF when reading from my input files last night. Neither the char | + | I was having trouble finding EOF when reading from my input files last night. Neither the char or the unsigned char data types could seem to store EOF when I was reading it in with fgetc(). |
| - | > or the unsigned char data types could seem to store EOF when I was reading it in with fgetc(). | + | </blockquote> |
| - | > | + | |
| - | </code> | + | |
| Yeah, you may notice that **fgetc(3)** will seem to read in a **0xFF** as it encounters the **EOF**. The trick | Yeah, you may notice that **fgetc(3)** will seem to read in a **0xFF** as it encounters the **EOF**. The trick | ||
| Line 14: | Line 12: | ||
| My preferred approach to this is to use **fgetc(3)** in combination with **feof(3)** -- it operates more | My preferred approach to this is to use **fgetc(3)** in combination with **feof(3)** -- it operates more | ||
| - | on the notion of some underlying flag being set when the EOF is encountered. This way, I don't | + | on the notion of some underlying flag being set when the EOF is encountered. This way, I don't have to bother interpreting whether this 0xFF is the critical " |
| - | have to bother interpreting whether this 0xFF is the critical " | + | |
| - | stdio subsystem do it for me. | + | |
| - | <code> | + | <blockquote> |
| - | > Because of this my file reading loop check would never fail and continued to read values after | + | Because of this my file reading loop check would never fail and continued to read values after the end of the file was reached. But once I changed the variable to an integer it recognized EOF and the check utility lit up nicely. Why is this? |
| - | > the end of the file was reached. But once I changed the variable to an integer it recognized EOF | + | </blockquote> |
| - | > and the check utility lit up nicely. Why is this? | + | |
| - | > | + | |
| - | </code> | + | |
| I suspect you are playing with the symbol EOF? As in: | I suspect you are playing with the symbol EOF? As in: | ||
| Line 67: | Line 60: | ||
| Taking our char's -1 and putting it in an int's point of view, we'd have: | Taking our char's -1 and putting it in an int's point of view, we'd have: | ||
| - | * 00000000000000000000000011111111, | + | * 00000000000000000000000011111111, |
| - | significant byte comes last in actual memory representation, | + | |
| If so, (char)-1 is NOT the same binary value as (int)-1, and if EOF is (int)-1, the best we can do | If so, (char)-1 is NOT the same binary value as (int)-1, and if EOF is (int)-1, the best we can do | ||
haas/fall2020/common/helpances/binaryfileandeof.1597416848.txt.gz · Last modified: 2020/08/14 14:54 by wedge
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