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diff --git a/32_kvs/README b/32_kvs/README new file mode 100644 index 0000000..35b0a18 --- /dev/null +++ b/32_kvs/README @@ -0,0 +1,118 @@ +For the next 4 problems, you will be doing one slightly larger program, which +we will cut up into 4 discretely testable pieces. + +The big picture is that your program will read two types of input files. +The first type of input file (which your program will read one of) will have the format: + +key1=value1 +key2=value2 +.... +keyN=valueN + +That is, it might say + +Jean Luc Picard=Captain +Will Riker=Commander +Beverly Crusher=Commander +Data=Lt. Commander +Geordi LaForge=Lt. Commander +Worf=Lt. Commander +Deanna Troi=Commander + +Note that the division between the key and the value is the first equals sign (the +values could have = in them, but the keys cannot. So a=b=c, would have a key of a, and +a value of b=c). + +The second type of input file will contain a list of lines (which will typically match +the keys from the first input file). Your program will read one or more of this +type of file. For example, it might contain: + +Jean Luc Picard +Will Riker +Worf +Deanna Troi +Q + +For each such input file that your program reads, it will print out the counts +of the values for the corresponding keys (or <unknown> for anything that did not +match any known key from the first input file). E.g. given the above to input files, +it would print to the corresponding output file (which will be named the same +as the input file, but with ".count" appended to the name). + +Captain: 1 +Commander: 2 +Lt. Commander: 1 +<unknown> : 1 + + + + +In thinking about our program, we might come up with the following +generalized high-level algorithm: + + //read the key/value pairs from the file named by argv[1] (call the result kv) + //count from 2 to argc (call the number you count i) + //count the values that appear in the file named by argv[i], using kv as the key/value pair + // (call this result c) + //compute the output file name from argv[i] (call this outName) + //open the file named by outName (call that f) + //print the counts from c into the FILE f + //close f + //free the memory for outName and c + //free the memory for kv + +This high-level algorithm suggests many functions which we can split our task into. +We will cut them up into 4 groups to make the 4 problems of this assignment: + +The first step (this problem): + - read the key/value pairs from a file + - free the memory for the key/value pairs + +The second step (next problem): + - compute the output file name + +The third step (problem after that): + - print the counts to a file + - free the memory for the counts + +The fourth step (the problem after that): + - compute the counts of values that appear in a particular input file + +Each subsequent problem will have more details about it. + +For this particular problem, you will need to: + + - read the key/value pairs from a file + - free the memory for the key/value pairs + +To start with this problem, you are going to want to define two structs, in the +file kv.h. The first one (struct _kvpair_t) should define the structure for +one key/value pair. The second should define the structure for an +array of key/value pairs (hint: you will want to include the length of the +array in this structure). + +Now you will want to write the four functions in kv.c. + +In readKVs, you will want to open the file, read the lines of text, split them into +key/value pairs, add the resulting pairs to an array (hint: realloc it to make it larger +each time), close the file, and return the kvarray_t * that has your array. + +Remember that you will want to abstract out complex steps into functions (you should +see at least 2 pieces to naturally pull out into their own functions). + +Next, you will write freeKVs, which should free all the memory allocated by readKVs. +That is, freeKVs(readKVs(filename)) should not leak any memory. + +Third, write printKVs which should take a kvarray_t *, and print out + + "key = '%s' value = '%s'\n" +for each key/value pair in the array, with the first %s being whatever the key is, +and the second being whatever value (e.g., key = 'Jean Luc Picard' value = 'Captain'). + +Finally, write the lookupValue function, which takes a kvarray_t * and a char * (string). +The char * that is passed in represents a key. This function searches the kvarray_t +for a matching key, and if found, returns the corresponding value. If no match is found, +this function returns NULL. + +Once you complete these functions, test them using the main in kv_test.c before +proceeding to the next problem. |