+#include <stdio.h>
+#include <stdlib.h>
+#ifdef PINTOS
+#include <syscall.h>
+#else
+#include "posix-compat.h"
+#endif
+#include "arc4.h"
+
+#define CHUNK_SIZE (63 * 1024) /* Max file size. */
+#define CHUNK_CNT 8 /* 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;
+
+ printf ("page-merge-par) init\n");
+
+ 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 void
+sort (void)
+{
+ pid_t children[CHUNK_CNT];
+ size_t i;
+
+ for (i = 0; i < CHUNK_CNT; i++)
+ {
+ char fn[128];
+ char cmd[128];
+ int fd;
+
+ printf ("(page-merge-par) sort chunk %zu\n", i);
+
+ /* Write this chunk to a file. */
+ snprintf (fn, sizeof fn, "buf%d", i);
+ create (fn, CHUNK_SIZE);
+ fd = open (fn);
+ if (fd < 0)
+ {
+ printf ("(page-merge-par) open() failed\n");
+ exit (1);
+ }
+ write (fd, buf1 + CHUNK_SIZE * i, CHUNK_SIZE);
+ close (fd);
+
+ /* Sort with subprocess. */
+ snprintf (cmd, sizeof cmd, "child-sort %s", fn);
+ children[i] = exec (cmd);
+ if (children[i] == -1)
+ {
+ printf ("(page-merge-par) exec() failed\n");
+ exit (1);
+ }
+ }
+
+ for (i = 0; i < CHUNK_CNT; i++)
+ {
+ char fn[128];
+ int fd;
+
+ if (join (children[i]) != 123)
+ {
+ printf ("(page-merge-par) join(exec()) returned bad value\n");
+ exit (1);
+ }
+
+ /* Read chunk back from file. */
+ snprintf (fn, sizeof fn, "buf%d", i);
+ fd = open (fn);
+ if (fd < 0)
+ {
+ printf ("(page-merge-par) open() failed\n");
+ exit (1);
+ }
+ read (fd, buf1 + CHUNK_SIZE * i, CHUNK_SIZE);
+ close (fd);
+ }
+}
+
+/* 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;
+
+ printf ("(page-merge-par) merge\n");
+
+ /* 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 void
+verify (void)
+{
+ size_t buf_idx;
+ size_t hist_idx;
+
+ printf ("(page-merge-par) verify\n");
+
+ 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)
+ {
+ printf ("(page-merge-par) bad value %d in byte %zu\n",
+ buf2[buf_idx], buf_idx);
+ exit (1);
+ }
+ buf_idx++;
+ }
+ }
+
+ printf ("(page-merge-par) success, buf_idx=%zu\n", buf_idx);
+}
+
+int
+main (void)
+{
+ printf ("(page-merge-par) begin\n");
+ init ();
+ sort ();
+ merge ();
+ verify ();
+ printf ("(page-merge-par) end\n");
+ return 0;
+}