[SOLVED] CS代考计算机代写 file system /* Generates about 1 MB of random data that is then divided into

/* Generates about 1 MB of random data that is then divided into
16 chunks.A separate subprocess sorts each chunk in
sequence.Then we merge the chunks and verify that the result
is what it should be. */

#include
#include “tests/arc4.h”
#include “tests/lib.h”
#include “tests/main.h”

/* This is the max file size for an older version of the Pintos
file system that had 126 direct blocks each pointing to a
single disk sector.We could raise it now. */
#define CHUNK_SIZE (126 * 512)
#define CHUNK_CNT 16/* Number of chunks. */
#define DATA_SIZE (CHUNK_CNT * CHUNK_SIZE)/* Buffer size. */

unsigned char buf1[DATA_SIZE], buf2[DATA_SIZE];
size_t histogram[256];

/* Initialize buf1 with random data,
then count the number of instances of each value within it. */
static void
init (void)
{
struct arc4 arc4;
size_t i;

msg (“init”);

arc4_init (&arc4, “foobar”, 6);
arc4_crypt (&arc4, buf1, sizeof buf1);
for (i = 0; i < sizeof buf1; i++)histogram[buf1[i]]++;}/* Sort each chunk of buf1 using a subprocess. */static voidsort_chunks (void){size_t i;create (“buffer”, CHUNK_SIZE);for (i = 0; i < CHUNK_CNT; i++) {pid_t child;int handle;msg (“sort chunk %zu”, i);/* Write this chunk to a file. */quiet = true;CHECK ((handle = open (“buffer”)) > 1, “open ”buffer””);
write (handle, buf1 + CHUNK_SIZE * i, CHUNK_SIZE);
close (handle);

/* Sort with subprocess. */
CHECK ((child = exec (“child-sort buffer”)) != -1,
“exec ”child-sort buffer””);
CHECK (wait (child) == 123, “wait for child-sort”);

/* Read chunk back from file. */
CHECK ((handle = open (“buffer”)) > 1, “open ”buffer””);
read (handle, buf1 + CHUNK_SIZE * i, CHUNK_SIZE);
close (handle);

quiet = false;
}
}

/* Merge the sorted chunks in buf1 into a fully sorted buf2. */
static void
merge (void)
{
unsigned char *mp[CHUNK_CNT];
size_t mp_left;
unsigned char *op;
size_t i;

msg (“merge”);

/* Initialize merge pointers. */
mp_left = CHUNK_CNT;
for (i = 0; i < CHUNK_CNT; i++)mp[i] = buf1 + CHUNK_SIZE * i;/* Merge. */op = buf2;while (mp_left > 0)
{
/* Find smallest value. */
size_t min = 0;
for (i = 1; i < mp_left; i++)if (*mp[i] < *mp[min])min = i;/* Append value to buf2. */*op++ = *mp[min];/* Advance merge pointer. Delete this chunk from the set if it’s emptied. */ if ((++mp[min] – buf1) % CHUNK_SIZE == 0)mp[min] = mp[–mp_left]; }}static voidverify (void) {size_t buf_idx;size_t hist_idx;msg (“verify”);buf_idx = 0;for (hist_idx = 0; hist_idx < sizeof histogram / sizeof *histogram; hist_idx++){while (histogram[hist_idx]– > 0)
{
if (buf2[buf_idx] != hist_idx)
fail (“bad value %d in byte %zu”, buf2[buf_idx], buf_idx);
buf_idx++;
}
}

msg (“success, buf_idx=%’zu”, buf_idx);
}

void
test_main (void)
{
init ();
sort_chunks ();
merge ();
verify ();
}