@@ -0,0 +1,11 @@
+#ifndef PIPE_H
+#define PIPE_H
+
+#include "cedos/file.h"
+
+int pipe_read(int fd, char *buffer, uint32_t size);
+int pipe_write(int fd, char *buffer, uint32_t size);
+
+extern file_operations_t pipe_fops;
+
+#endif

@@ -67,6 +67,12 @@
     //! String of arguments for the process
     char *args;
 
+    //! process stdin
+    int stdin;
+
+    //! process stdout
+    int stdout;
+
     /*
      * String buffers for name and args
      * TODO: eventually move to a malloc solution

@@ -32,7 +32,7 @@
 /*!
  * Spawns a new process, loads it from the given ELF file, and returns its process ID.
  */
-PROCESS_ID sched_spawn(const char *name, char *args);
+PROCESS_ID sched_spawn(const char *name, char *args, int flags);
 
 /*!
  * Return the ID of the current process.

@@ -1,8 +1,12 @@
 #include "cedos/file.h"
 #include "cedos/fat.h"
+#include "cedos/pipe.h"
 
 #include "cedos/drivers/tty.h"
 #include "cedos/core.h"
+
+#include "cedos/sched/sched.h"
+#include "cedos/sched/process.h"
 
 #ifdef DEBUG
 #define PRINT_DBG(...) printk("[" __FILE__ "] " __VA_ARGS__)
@@ -15,7 +19,7 @@
 file_t file_table[256];
 int next_free = 0;
 
-int stdin, stdout, fat_root;
+int stdin, stdout, fat_root, pipe;
 
 int file_init() {
     file_table[next_free].fops = &tty_fops;
@@ -34,6 +38,10 @@ file_table[next_free].stdio_id = 0;
     file_table[next_free].fat_cluster = 0;
     fat_root = next_free++;
 
+    // pipe
+    file_table[next_free].fops = &pipe_fops;
+    pipe = next_free++;
+
     return 0;
 }
 
@@ -45,13 +53,26 @@
     return file_openat(fat_root, pathname, flags);
 }
 
+file_t *get_process_local_file(int fd) {
+    if (fd > 1) { return &file_table[fd]; }
+    
+    PROCESS_ID pid = get_current_process();
+    PRINT_DBG("pid: %i\n", pid);
+    PROCESS *p = get_process(pid);
+
+    if (fd == 0) { return &file_table[p->stdin]; }
+    if (fd == 1) { return &file_table[p->stdout]; }
+
+    return NULL;
+}
+
 int file_openat(int fd, const char *fname, int flags) {
     int new_fd = next_free++;
 
     PRINT_DBG("Given fd: %i\n", fd);
     PRINT_DBG("New fd:   %i\n", new_fd);
 
-    file_t *root = &file_table[fd];
+    file_t *root = get_process_local_file(fd);
     file_t *handle = &file_table[new_fd];
 
     if (root->fops->openat == NULL) { return -1; }
@@ -62,7 +83,7 @@ return new_fd;
 }
 
 int file_read(int fd, char *buffer, uint32_t size) {
-    file_t *file = &file_table[fd];
+    file_t *file = get_process_local_file(fd);
 
     if (file->fops->read == NULL) { return -1; }
 
@@ -70,7 +91,7 @@ file->fops->read(file, buffer, size);
 }
 
 int file_write(int fd, char *buffer, uint32_t size) {
-    file_t *file = &file_table[fd];
+    file_t *file = get_process_local_file(fd);
 
     if (file->fops->write == NULL) { return -1; }
 
@@ -78,7 +99,7 @@ file->fops->write(file, buffer, size);
 }
 
 int file_dir_next(int fd, int index, char *fname_buffer) {
-    file_t *file = &file_table[fd];
+    file_t *file = get_process_local_file(fd);
 
     if (file->fops->dir_next == NULL) { return -1; }
 

@@ -128,7 +128,7 @@ // create test tasks
     printk("Creating tasks.\n");
     
     
-    int pid = sched_spawn("shelf", "Hello World!");
+    int pid = sched_spawn("shelf", "Hello World!", 0);
     assert(pid != -1);
     //sched_spawn("fibonacci.o", "Hello World!");
     //sched_spawn("fibonacci.o", "Hello World!");

@@ -0,0 +1,49 @@
+#include "cedos/file.h"
+#include "cedos/pipe.h"
+#include "cedos/sched/sched.h"
+
+file_operations_t pipe_fops = {
+    NULL,           /* open */
+    NULL,           /* openat */
+    pipe_read,      /* read */
+    pipe_write,     /* write */
+    NULL            /* dir_next */
+};
+
+#define PIPE_BUFFER_SIZE 512
+
+uint8_t pipe_buffer[PIPE_BUFFER_SIZE];
+int read_head = 0;
+int write_head = 0;
+
+uint8_t pipe_readc() {
+    while (write_head == read_head) {
+        sched_yield();
+    }
+
+    int rh_next = (read_head + 1) % PIPE_BUFFER_SIZE;
+    uint8_t res = pipe_buffer[read_head];
+    read_head = rh_next;
+    return res;
+}
+
+void pipe_writec(uint8_t c) {
+    int wh_next = (write_head + 1) % PIPE_BUFFER_SIZE;
+    while (wh_next == read_head) {
+        sched_yield();
+    }
+    pipe_buffer[write_head] = c;
+    write_head = wh_next;
+}
+
+int pipe_read(int fd, char *buffer, uint32_t size) {
+    for (int i = 0; i < size; i++) {
+        buffer[i] = pipe_readc();
+    }
+}
+
+int pipe_write(int fd, char *buffer, uint32_t size) {
+    for (int i = 0; i < size; i++) {
+        pipe_writec(buffer[i]);
+    }
+}

@@ -52,8 +52,12 @@
 /*!
  * Spawn a new process and returns its process ID.
  */
-PROCESS_ID sched_spawn(const char *name, char *args) {
+PROCESS_ID sched_spawn(const char *name, char *args, int flags) {
     crit_enter();
+
+    PRINT_DBG("process name: %s\n", name);
+    PRINT_DBG("process args: %s\n", args);
+    PRINT_DBG("process flags: %i\n", flags);
 
     if (name != NULL) {
         int fd = file_open(name, 0);
@@ -70,6 +74,14 @@ p->ebp = USER_STACK;
     p->esp = USER_STACK - sizeof(SCHED_FRAME);
     p->eflags = PROCESS_STD_EFLAGS;
     p->entry = (PROCESS_MAIN*)(0xDEADBEEF);
+
+    if (flags != 0) {
+        p->stdin = (int)(flags & 0xFF);
+        p->stdout = (int)(flags >> 8);
+    } else {
+        p->stdin = 0;
+        p->stdout = 1;
+    }
     
     // TODO: implement with malloc
     strcpy(p->name_buf, name);
@@ -185,7 +197,7 @@
     current_pid = 0;
 
     // create idle process
-    PROCESS_ID idle = sched_spawn(NULL, NULL);
+    PROCESS_ID idle = sched_spawn(NULL, NULL, 0);
     assert(idle != -1);
 
     return 1;

@@ -38,6 +38,12 @@ interrupt(0x30, res, 4, fname, args, 0);
     return res;
 }
 
+int process_spawn_pipe(const char *fname, const char *args, int stdin, int stdout) {
+    volatile uint32_t res = 0;
+    interrupt(0x30, res, 4, fname, args, stdin | (stdout << 8));
+    return res;
+}
+
 void process_wait(int pid) {
     volatile uint32_t res = 0;
     interrupt(0x30, res, 5, pid, 0, 0);

@@ -9,6 +9,7 @@ int sysprint(const char *fmt, int arg1, int arg2);
 int yield();
 int get_pid();
 int process_spawn(const char *fname, const char *args);
+int process_spawn_pipe(const char *fname, const char *args, int stdin, int stdout);
 void process_wait(int pid);
 
 void graphics_set_mode(int mode);