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Commit a603a40

Browse files
Ch 14: Removed warning messages in my_tail.c
Adjusted buffer references to reflect correct usage of number of buffers loaded
1 parent 74ad90a commit a603a40

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1 file changed

+38
-41
lines changed

1 file changed

+38
-41
lines changed

‎13_File_I_O_Buffering/my_tail.c‎

Lines changed: 38 additions & 41 deletions
Original file line numberDiff line numberDiff line change
@@ -27,6 +27,24 @@ static void usage_error(char *pgm_name, char *msg)
2727
exit(EXIT_FAILURE);
2828
}
2929

30+
/* --------------------------------------------------------------------------
31+
| Free storage associated with dynamic data structures
32+
* -------------------------------------------------------------------------- */
33+
34+
static void free_buffers(char **buffers, int num_blocks)
35+
{
36+
if (buffers == NULL) return;
37+
38+
for (int i = 0; i < num_blocks; i++)
39+
{
40+
if (buffers[i] != NULL)
41+
{
42+
free(buffers[i]);
43+
}
44+
}
45+
free(buffers);
46+
}
47+
3048
/* --------------------------------------------------------------------------
3149
* Main program
3250
* -------------------------------------------------------------------------- */
@@ -159,57 +177,45 @@ int main(int argc, char *argv[])
159177
fprintf(stderr,
160178
"failed to allocate I/O buffer: %m\n");
161179
close(fd);
162-
for (int i = 0; i < num_blocks; i++)
163-
{
164-
if (buffers[i] != NULL)
165-
{
166-
free(buffers[i]);
167-
}
168-
}
169-
free(buffers);
180+
free_buffers(buffers, num_blocks);
170181
exit(EXIT_FAILURE);
171182
}
183+
num_buffers_loaded++;
172184

173185
if (verbosity > 0) fprintf(stderr, "Seeking offset #%ld\n", blk_offset);
174186
if (lseek(fd, (off_t)blk_offset, SEEK_SET) == (off_t)-1) {
175187
fprintf(stderr,
176188
"failed to lseek to offset %ld: %m\n",
177189
blk_offset);
178190
close(fd);
179-
for (int i = 0; i < num_blocks; i++)
180-
{
181-
if (buffers[i] != NULL)
182-
{
183-
free(buffers[i]);
184-
}
185-
}
186-
free(buffers);
191+
free_buffers(buffers, num_blocks);
187192
exit(EXIT_FAILURE);
188193
}
189194

190-
if (verbosity > 0) fprintf(stderr, "Reading block into buffer #%d at %p\n", num_buffers_loaded, buffers[num_buffers_loaded]);
191-
ssize_t bytes_read = read(fd, (void *)(buffers[num_buffers_loaded]), (size_t)block_size);
195+
if (verbosity > 0)
196+
{
197+
fprintf(stderr,
198+
"Reading block into buffer #%d at %p\n",
199+
num_buffers_loaded-1,
200+
buffers[num_buffers_loaded-1]);
201+
}
202+
ssize_t bytes_read = read(fd,
203+
(void *)(buffers[num_buffers_loaded-1]),
204+
(size_t)block_size);
192205

193206
if (bytes_read == -1)
194207
{
195208
fprintf(stderr,
196209
"failed to read from file: %m\n");
197210
close(fd);
198-
for (int i = 0; i < num_blocks; i++)
199-
{
200-
if (buffers[i] != NULL)
201-
{
202-
free(buffers[i]);
203-
}
204-
}
205-
free(buffers);
211+
free_buffers(buffers, num_blocks);
206212
exit(EXIT_FAILURE);
207213
}
208214

209-
buffers[num_buffers_loaded][bytes_read] = '0円'; /* Put in teminating null */
215+
buffers[num_buffers_loaded-1][bytes_read] = '0円'; /* Put in teminating null */
210216

211-
for (cp = buffers[num_buffers_loaded] + bytes_read - 1;
212-
cp >= buffers[num_buffers_loaded];
217+
for (cp = buffers[num_buffers_loaded-1] + bytes_read - 1;
218+
cp >= buffers[num_buffers_loaded-1];
213219
cp--)
214220
{
215221
if (*cp == '\n') num_lines_found++;
@@ -222,8 +228,6 @@ int main(int argc, char *argv[])
222228
}
223229

224230
if (verbosity > 0) fprintf(stderr, "num_lines_found=%d\n", num_lines_found);
225-
226-
num_buffers_loaded++;
227231

228232
if (num_lines_found == num_lines_required) break;
229233

@@ -234,23 +238,16 @@ int main(int argc, char *argv[])
234238
if (cp != NULL)
235239
{
236240
if (verbosity > 0) fprintf(stderr, "print partial buffer at %p\n", cp);
237-
printf(cp);
241+
printf("%s", cp);
238242
for (int i = num_buffers_loaded - 2; i >= 0; i--)
239243
{
240244
if (verbosity > 0) fprintf(stderr, "print buffer #%d at %p\n", i, buffers[i]);
241-
printf(buffers[i]);
245+
printf("%s", buffers[i]);
242246
}
243247
}
244248

245249
close(fd);
246-
for (int i = 0; i < num_blocks; i++)
247-
{
248-
if (buffers[i] != NULL)
249-
{
250-
free(buffers[i]);
251-
}
252-
}
253-
free(buffers);
250+
free_buffers(buffers, num_blocks);
254251

255252
exit(EXIT_SUCCESS);
256253
}

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