Fixes in 1998/tomtorfs, add try.sh & format fixes
The author stated that the program assumes EOF is -1 but for systems that do not have this it will fail. This is indeed a valid concern as the standard mandates that it's a value < 0 but it doesn't require it to be -1. The author also stated that the program could fail if 1 is not a return value that indicates error so this was changed to EXIT_FAILURE as the suggested was made. It is possible of course that I missed a place where this should have been updated but I don't believe so. I am unaware of any system where this would be a problem and I don't know why it matters anyway but I made the change as the author stated it could be a problem with portability. The README.md file has been formatted and typo checked. Added try.sh script. This should complete this entry's review.
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@@ -8,26 +8,31 @@ make all
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## To use:
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```sh
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./tomtorfs tomtorfs.c 32 04C11DB7 1 FFFFFFFF FFFFFFFF
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./tomtorfs filename bitwidth polynom reflected init xor
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```
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where:
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```
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filename : file to calculate the CRC of
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bitwidth : width of the CRC in bits (decimal)
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polynom : polynomial used for the CRC (hexadecimal)
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reflected : 0 if the CRC is not reflected, 1 if it is
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init : initial value for the CRC (hexadecimal)
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xor : value to xor the final CRC with (hexadecimal)
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```
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### Try:
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```sh
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echo "abscond conferrable" > file.A
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echo "adorn condolence" > file.B
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echo "adorn condolence too" > file.C
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./tomtorfs file.A 32 04C11DB7 1 FFFFFFFF FFFFFFFF
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./tomtorfs file.B 32 04C11DB7 1 FFFFFFFF FFFFFFFF
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./tomtorfs file.C 32 04C11DB7 1 FFFFFFFF FFFFFFFF
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./try.sh
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```
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## Judges' remarks:
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If you don't believe the program is correct, try and compare the output
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of the program with the value of CRC computed by PKZIP or any other
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of the program with the value of CRCs computed by PKZIP or any other
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archiver that uses the CRC-32 algorithm.
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@@ -47,12 +52,14 @@ xor : value to xor the final CRC with (hexadecimal)
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### Examples
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#### CRC-16:
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```sh
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./tomtorfs filename 16 1021 0 FFFF 0000
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```
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#### CRC-32:
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@@ -60,6 +67,7 @@ xor : value to xor the final CRC with (hexadecimal)
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./tomtorfs filename 32 04C11DB7 1 FFFFFFFF FFFFFFFF
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```
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#### XMODEM:
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```sh
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@@ -67,12 +75,14 @@ xor : value to xor the final CRC with (hexadecimal)
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```
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#### ARC:
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```sh
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./tomtorfs filename 16 8005 1 0000 0000
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```
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### Portability notes
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The program assumes `CHAR_BIT==8`. Results are undefined if `bitwidth >
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@@ -82,11 +92,13 @@ valid exit value to indicate failure (replace them with `EOF` resp.
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No special build options required.
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### Special notes
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Count the number of non-whitespace characters in the source
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file to find out what dark force drove me to write this ;-).
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### Spoiler
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First of all, if you run a C beautifier on the program (thereby of course losing
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@@ -99,26 +111,29 @@ following meanings:
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```
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a = argc
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A = argv
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b = array of unsigned long variables
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b[0] = bit-width of the CRC (argv[2])
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b[1] = CRC polynomial (argv[3])
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b[2] = nonzero if CRC is reflected (argv[4])
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b[3] = initial value of CRC (argv[5])
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b[4] = value final CRC is XORed with (argv[6])
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b[5] = CRC value
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b[6] = byte from file
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b[7] = counter
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b[0] = bit-width of the CRC (argv[2])
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b[1] = CRC polynomial (argv[3])
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b[2] = nonzero if CRC is reflected (argv[4])
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b[3] = initial value of CRC (argv[5])
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b[4] = value final CRC is XORed with (argv[6])
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b[5] = CRC value
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b[6] = byte from file
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b[7] = counter
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B = FILE * through which the file argv[1] is opened
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C = typedef for unsigned long
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```
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The first for loop simply reads the command-line arguments
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in the `b[]` array. The third parameter to `strtoul()` causes
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The first `for` loop simply reads the command-line arguments
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in the `b[]` array. The third parameter to `strtoul(3)` causes
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all arguments to be in base-16 (hex) except the first one,
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which will be in base-10 (decimal).
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The rest of the program "simply" calculates the CRC in `b[5]`
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and then prints it to stdout. The bit reflection loops may
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and then prints it to `stdout`. The bit reflection loops may
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appear a bit tricky at first, but if you have a good look
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at them they should become obvious also.
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@@ -1,11 +1,12 @@
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#include <stdio.h>
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#include <stdlib.h>
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#define exit(a) return EXIT_FAILURE
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int main(int a,char **A){FILE*B;typedef unsigned long C;C b
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[8]; if(!(a==7&&(B= fopen(1[A],"rb")))) return 1;for(7[b]=0
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[8]; if(!(a==7&&(B= fopen(1[A],"rb")))) exit(1); for(7[b]=0
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;7[b]<5;7[b]++)b[7[ b]]=strtoul(A[2+7[b ]],0,16-!7[b]*6);5[
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b]=3[b] ; while ((6[b]= getc(B)
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)!=(C)- 1){if(2 [b])for (7[b]=0
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) !=EOF ){if(2 [b])for (7[b]=0
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;7[b]<4 ;7[b]++ )if(((6 [b]>>7[
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b])^(6[ b]>>(7-7[b])))&1)6[ b] ^=(1
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<<7[b]) ^(1<<(7-7[b]));5[b] ^= 6[b]
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Executable
+23
@@ -0,0 +1,23 @@
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#!/usr/bin/env bash
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#
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# script to demonstrate 1998/tomtorfs
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#
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rm -f file.A file.B file.C
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echo "$ echo abscond conferrable > file.A" 1>&2
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echo "abscond conferrable" > file.A
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echo "$ ./tomtorfs file.A 32 04C11DB7 1 FFFFFFFF FFFFFFFF" 1>&2
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./tomtorfs file.A 32 04C11DB7 1 FFFFFFFF FFFFFFFF
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echo "$ echo adorn condolence > file.B" 1>&2
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echo "adorn condolence" > file.B
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echo "$ ./tomtorfs file.B 32 04C11DB7 1 FFFFFFFF FFFFFFFF" 1>&2
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./tomtorfs file.B 32 04C11DB7 1 FFFFFFFF FFFFFFFF
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echo "$ echo adorn condolence too > file.C" 1>&2
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echo "adorn condolence too" > file.C
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echo "$ ./tomtorfs file.C 32 04C11DB7 1 FFFFFFFF FFFFFFFF" 1>&2
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./tomtorfs file.C 32 04C11DB7 1 FFFFFFFF FFFFFFFF
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rm -f file.A file.B file.C
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@@ -2167,6 +2167,20 @@ There actually is a web page for the tool and this was added to the author
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information for the entry. It has not been added to any JSON file.
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## [1998/tomtorfs](1998/tomtorfs/tomtorfs.c) ([README.md](1998/tomtorfs/README.md]))
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Cody fixed the assumption that `EOF` is `-1` (the author noted that it assumes
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it is `-1` but the standard only guarantees that it's a value `< 0`) and that 1
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is a valid code to return failure (it seems unlikely that it wouldn't be but
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since the author suggested it it was changed to `EXIT_FAILURE`). To make it so
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the lines end at the same columns as the original the `EXIT_FAILURE` change was
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done by redefining `exit(3)` to be `exit(a) return EXIT_FAILURE` and `1` was
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passed to it (`return` was used because the original program had `return 1`).
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Cody also added the [try.sh](1998/tomtorfs/try.sh) script to try out a few
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commands that we recommended.
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## [2000/anderson](2000/anderson/anderson.c) ([README.md](2000/anderson/README.md]))
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Cody changed this entry to use `fgets()` instead of `gets()` to make it safer
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