PSET4 If statement returns false on recover.c

Question

The if statement given for recover.c for some reason keeps returning false and I'm not sure exactly what I'm doing wrong here.

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Answer 1

One thing that's wrong: char filename[1];. How "big" is a file name? Bigger than 1. (and don't forget the null-byte, sprintf creates a valid string, ie null terminated). That's not causing this problem, but it's a memory leak/buffer overflow waiting to happen.

An other (bigger) thing is: back-to-back reads. Here fread(buffer, MEM_BLOCK, 1, input); then here while (fread(buffer, 1, MEM_BLOCK, input) == MEM_BLOCK);. It's probably always returning false because it never finds a jpg sig.

An other (even bigger) thing is: int buffer[MEM_BLOCK];. An int is length 4, so this is reading (and writing) 4 * MEM_BLOCK bytes. You need to use a byte type. Get a hint from bmp.h in resize exercise.

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