C language

The next tools you will build come in a pair, because one (wzip) is a file compression tool, and the other (wunzip) is a file decompression tool. The type of compression used here is a simple form of compression called run-length encoding (RLE). RLE is quite simple: when you encounter n characters of the same type in a row, the compression tool (wzip) will turn that into the number n and a single instance of the character. Thus, if we had a file with the following contents: aaaaaaaaaabbbb the tool would turn it (logically) into: 10a4b However, the exact format of the compressed file is quite important; here, you will write out a 4-byte integer in binary format followed by the single character in ASCII. Thus, a compressed file will consist of

some number of 5-byte entries, each of which is comprised of a 4-byte integer (the run length) and the single character. To write out an integer in binary format (not ASCII), you should use fwrite(). Read the man page for more details. For wzip, all output should be written to standard output (the stdout file stream, which, as with stdin, is already open when the program starts running). Note that typical usage of the wzip tool would thus use shell redirection in order to write the compressed output to a file. For example, to compress the file file.txt into a (hopefully smaller) file.z, you would type: prompt> ./wzip file.txt > file.z The "greater than" sign is a UNIX shell redirection; in this case, it ensures that the output from wzip is written to the file file.z (instead of being printed to the screen). The wunzip tool simply does the reverse of the wzip tool, taking in a compressed file and writing (to standard output again) the uncompressed results. For example, to see the contents of file.txt, you would type:

prompt> ./wunzip file.z wunzip should read in the compressed file (likely using fread()) and print out the uncompressed output to standard output using printf().

wunzip should read in the compressed file (likely using fread()) and print out the uncompressed output to standard output using printf(). Specifically, wzip and wunzip should meet the following requirements: Correct invocation should pass one or more files via the command line to the program; if no files are specified, the program should exit with return code 1 and print "wzip: file1 [file2...]" (followed by a newline) or "wunzip: file1 [file2...]" (followed by a newline) for wzip and wunzip respectively. The format of the compressed file must match the description above exactly (a 4-byte integer followed by a character for each run). If wzip encounters a file that it cannot open, it should print "wzip: cannot open file" (followed by a newline) and exit with status 1. If wunzip encounters a file that it cannot open, it should print "wunzip: cannot open file" (followed by a newline) and exit with status 1. Do note that if multiple files are passed to *wzip, they are compressed into a single compressed output, and when unzipped, will turn into a single uncompressed stream of text (thus, the information that multiple files were originally input into wzip is lost). The same thing holds for wunzip