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# include <stdlib.h>
# include <stdio.h>
# include <string.h>
# include <ctype.h>
# include <limits.h>
/*
* See ../README.md
*/
/*
* Run as: cc -o ch-1.o ch-1.c; ./ch-1.o < input-file
*/
/*
* Copied from https://gist.github.com/w-vi/7e98342181776162b1a3
*/
char * slurpfile (char * filename) {
FILE * fp;
char * source;
long bufsize;
size_t len;
if ((fp = fopen (filename, "r")) == NULL) {
fprintf (stderr, "Failed to open %s\n", filename);
exit (1);
}
/*
* Get the size of the file:
* - seek to the end of the file
* - use ftell to get the offset from the start
* - seek back to the beginning
*/
if (fseek (fp, 0L, SEEK_END) != 0) {
fprintf (stderr, "seek() failed for %s\n", filename);
exit (1);
}
if ((bufsize = ftell (fp)) == -1) {
fprintf (stderr, "ftell() failed for %s\n", filename);
exit (1);
}
if (fseek (fp, 0L, SEEK_SET) != 0) {
fprintf (stderr, "seek() failed for %s\n", filename);
exit (1);
}
/*
* Allocate memory for content of the file
*/
if ((source = (char *) malloc (sizeof (char) * (bufsize + 1))) == NULL) {
fprintf (stderr, "malloc() failed for %s\n", filename);
exit (1);
}
/*
* And read it in
*/
if ((len = fread (source, sizeof (char), bufsize, fp)) == 0) {
fprintf (stderr, "fread() failed for %s\n", filename);
exit (1);
}
source [++ len] = '\0';
return source;
}
/*
* Use four arrays:
* - filenames: names of files read
* - content: pointers to content of files read
* - content_ptr: pointers to unreturned content
* - content_size: number of characters not returned yet
*/
size_t read_files = 0;
char ** filenames = NULL;
char ** content = NULL;
char ** content_ptr = NULL;
size_t * content_size = NULL;
char * readN (char * filename, int amount) {
ssize_t found = -1;
char * out;
/*
* Check whether we've already found the file --
* if so, set its position in "found".
*/
for (size_t i = 0; i < read_files; i ++) {
if (strncmp (filename, filenames [i], PATH_MAX) == 0) {
/*
* Found the file
*/
found = i;
break;
}
}
/*
* Not found; all filename, content of file, and size to
* the end of the arrays.
*/
if (found < 0) {
found = read_files ++;
/*
* Allocate memory
*/
if ((filenames = (char **)
realloc (filenames, read_files * sizeof (char *))) == NULL) {
fprintf (stderr, "malloc() failed for %s\n", filename);
exit (1);
}
if ((content = (char **)
realloc (content, read_files * sizeof (char *))) == NULL) {
fprintf (stderr, "malloc() failed for %s\n", filename);
exit (1);
}
if ((content_ptr = (char **)
realloc (content_ptr, read_files * sizeof (char *))) == NULL) {
fprintf (stderr, "malloc() failed for %s\n", filename);
exit (1);
}
if ((content_size = (size_t *)
realloc (content_size, read_files * sizeof (size_t))) == NULL) {
fprintf (stderr, "malloc() failed for %s\n", filename);
exit (1);
}
/*
* Set data
*/
if ((filenames [found] = (char *)
malloc (sizeof (char) * (strlen (filename) + 1))) == NULL) {
fprintf (stderr, "malloc() failed for %s\n", filename);
exit (1);
}
stpncpy (filenames [found], filename, strlen (filename));
filenames [found] [strlen (filename)] = '\0';
content [found] = slurpfile (filename);
content_ptr [found] = content [found];
content_size [found] = strlen (content [found]);
/*
* Remove any trailing new lines
*/
while (content [found] [content_size [found] - 1] == '\n') {
content [found] [-- content_size [found]] = '\0';
}
}
/*
* Now 'found' points to the place where the content
* of the file is.
*/
/*
* Cannot return more than we have.
*/
if (content_size [found] < amount) {
amount = content_size [found];
}
/*
* Allocate memory for the return value
*/
if ((out = (char *) malloc (sizeof (char) * (amount + 1))) == NULL) {
fprintf (stderr, "malloc() failed for %s\n", filename);
exit (1);
}
/*
* Copy the amount of data, make sure it's NUL terminated.
*/
stpncpy (out, content_ptr [found], amount);
out [amount] = '\0';
/*
* Adjust the pointer and size left
*/
content_ptr [found] += amount;
content_size [found] -= amount;
return out;
}
int main (void) {
char * line = NULL;
size_t len = 0;
size_t strlen;
/*
* Iterate over the lines of input; parse each line into
* a file name and an amount. Call readN for each line.
*/
while ((strlen = getline (&line, &len, stdin)) != -1) {
char * line_ptr = line;
char * filename;
int amount;
if ((filename = (char *) malloc (PATH_MAX * sizeof (char))) == NULL) {
fprintf (stderr, "malloc() failed\n");
exit (1);
}
if (sscanf (line_ptr, "%s %d", filename, &amount) != 2) {
fprintf (stderr, "Could not parse input\n");
exit (1);
}
printf ("%s\n", readN (filename, amount));
free (filename);
}
/*
* Release memory
*/
free (line);
for (size_t i = 0; i < read_files; i ++) {
free (filenames [i]);
free (content [i]);
}
free (filenames);
free (content);
free (content_ptr);
free (content_size);
return (0);
}
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