add read call

kernel/syscall/handler.cc

@@ -48,7 +48,7 @@ extern "C" size_t syscall_handler(size_t sysnum, size_t p1, size_t p2,
             Syscall::Skeleton::write(Guard::enter().vault(), p1, (char*)p2, p3);
             break;
         case Syscall::ID::READ:
-            ;
+            return Syscall::Skeleton::read(Guard::enter().vault(), 0, (void*) p2, p3);
             break;
         case Syscall::ID::SEM_INIT:
             Syscall::Skeleton::sem_init(Guard::enter().vault(), p1, p2);

kernel/syscall/skeleton.cc

@@ -34,10 +34,17 @@ size_t write(Vault &vault, uint32_t id, const void *buffer, size_t size) {
     return 0;
 }
 
-size_t read(Vault &vault, uint32_t id) {
-	(void)vault;
-	(void)id;
-	return 0;
+size_t read(Vault &vault, uint32_t id, void *buf, size_t len) {
+    size_t read_cnt = 0;
+    while(read_cnt <= len){
+        Key key;
+        vault.keys.consume(key);
+        if(key.valid())
+            ((char*)buf)[read_cnt++] = key.ascii();
+        else
+            return read_cnt;
+    }
+    return len;
 }
 
 void sleep(Vault &vault, size_t ms) {

kernel/syscall/skeleton.h

@@ -15,7 +15,7 @@ size_t test(Vault &vault, size_t p1, size_t p2, size_t p3, size_t p4,
 
 int getpid(Vault &vault);
 size_t write(Vault &vault, uint32_t id, const void *buffer, size_t size);
-size_t read(Vault &vault, uint32_t id);
+size_t read(Vault &vault, uint32_t id, void *buf, size_t len);
 void sleep(Vault &vault, size_t ms);
 bool sem_init(Vault &vault, size_t id, uint32_t value);
 bool sem_destroy(Vault &vault, size_t id);

kernel/user/app2/kappl.cc

@@ -1,6 +1,7 @@
 // vim: set noet ts=4 sw=4:
 
 #include "./kappl.h"
+#include "../../syscall/stub.h"
 
 #include "../../device/textstream.h"
 extern TextStream kout;