98 lines
3.5 KiB
C
98 lines
3.5 KiB
C
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#define _POSIX_C_SOURCE 200809L // needed for strdup extension
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "movies.h"
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/* Given a string (possibly read-only) of IMDB movie data
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(formatted as "Title,Year,Genre"), create a movie_t object
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based on the appropriate fields. */
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movie_t
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split_data (char *csv)
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{
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movie_t movie;
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char *temp = strdup (csv);
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char *token = strtok (temp, ",");
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movie.title = strdup (token); // make a copy the first token as the title
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char *year_str = strtok (NULL, ",");
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char *endptr;
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movie.year = strtol (year_str, &endptr, 10);
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char *genre = strtok (NULL, ",");
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movie.genre = strdup (genre);
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free (temp);
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return movie;
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}
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/* Build a dynamically allocated string from a movie_t object as follows:
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"Title [Year] - Genre"
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*/
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char *
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merge_data (movie_t movie)
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{
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// There are a few ways to merge strings in C. One approach is to start with
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// a base string on the heap and repeatedly grow and append the string. In
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// pseudocode, it might look like this:
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//
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// str = strdup ("Hello");
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// str = realloc (str, ...length...); // grow
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// strncat (str, " World", ...length...); // concatenate
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// str = realloc (str, ...length...); // grow
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// strncat (str, " Again", ...length...); // concatenate
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//
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// This is the C equivalent of something like this in Java:
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//
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// str = "Hello";
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// str += " World";
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// str += " Again";
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//
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// Another (generally more efficient) way to do this is to use snprintf(),
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// for formatting a string. If you are not familiar with snprintf(), you
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// should be familiar with its cousin, printf(). Consider the following
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// line of code, which prints three string variables to the screen:
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//
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// printf ("%s %s %s\n", str1, str2, str3);
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//
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// You do the exact same thing with snprintf(), but add two variables at
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// the beginning: the destination buffer (i.e., where do you want the
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// final string in memory) and the length:
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//
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// snprintf (buffer, length, "%s %s %s\n", str1, str2, str3);
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//
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// The original strings str1, str2, and str3 are unmodified, because their
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// contents are copied into the buffer. snprintf() also has a great built-in
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// feature that strncat() doesn't: it works with more than just strings!
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//
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// int num = 42;
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// char *str = "My favorite number is ";
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// snprintf (message, length, "%s%d\n", str, num);
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//
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// Just remember that the message/buffer variable must be a pointer to a
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// writable portion of memory where you have allocated enough space to store
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// the combined string.
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// HINT: When doing string manipulation, you should use a variable to keep
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// explicit track of the string length. C string lengths are not inherently
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// stored anywhere.
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size_t len = 1; // always keep track of the null byte
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// +10 byte space for yeaar, spaces, brackets, and dash
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len += strlen (movie.title) + 10 + strlen (movie.genre);
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// Use one of the two techniques above to allocated enough space for the
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// merged string. You should NOT rely on any length unless its exact value
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// is known. For instance, you can assume that " [Year] - " adds 10 bytes,
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// but you cannot assume anything about the length of the genre or title.
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// As such, you need to compute those lengths using strlen(). Do not forget
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// to account for the null byte.
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char *result = calloc (len, sizeof (char));
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snprintf (result, len, "%s [%d] - %s", movie.title, movie.year, movie.genre);
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return result;
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}
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