From 5072f2c51e2b886cf8aaa8550dbf814d1a7828e6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Felix=20Quei=C3=9Fner?= <git@mq32.de>
Date: Sat, 21 May 2016 19:26:08 +0200
Subject: [PATCH] Adds single-byte memory interface to the VM.

---
 prototypes/supervm/vm.c | 42 +++++++++++++++++++++++++++++++++++++++++
 prototypes/supervm/vm.h | 13 +++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/prototypes/supervm/vm.c b/prototypes/supervm/vm.c
index 9a10a09..0323ef9 100644
--- a/prototypes/supervm/vm.c
+++ b/prototypes/supervm/vm.c
@@ -7,6 +7,20 @@ static void cmd_copy(CommandInfo *info)
 	info->output = info->input0;
 }
 
+// |  1 | STORE       | output = MEMORY[input0] = input1     |
+// |  2 | LOAD        | output = MEMORY[input0]              |
+
+static void cmd_load(Process *p, CommandInfo *info)
+{
+	info->output = vm_read_byte(p, info->input0);
+}
+
+static void cmd_store(Process *p, CommandInfo *info)
+{
+	vm_write_byte(p, info->input0, info->input1);
+	info->output = info->input1;
+}
+
 static void cmd_math(CommandInfo *info)
 {
 	switch(info->additional)
@@ -97,6 +111,8 @@ int vm_step_process(Process *process)
 		switch(instr.command)
 		{
 			case VM_CMD_COPY: cmd_copy(&info); break;
+			case VM_CMD_STORE: cmd_store(process, &info); break;
+			case VM_CMD_LOAD: cmd_load(process, &info); break;
 			case VM_CMD_MATH: cmd_math(&info); break;
 			case VM_CMD_SYSCALL: vm_syscall(process, &info); break;
 			case VM_CMD_HWIO: vm_hwio(process, &info); break;
@@ -154,3 +170,29 @@ uint32_t vm_peek(Process *process)
 	vm_assert(process != NULL, "process must not be NULL.");
 	return process->stack[process->stackPointer];
 }
+
+
+
+
+
+uint8_t vm_read_byte(Process *process, uint32_t address)
+{
+	vm_assert(process != NULL, "process must not be NULL.");
+	
+	uint32_t page  = address / process->mmap.pageSize;
+	uint32_t index = address % process->mmap.pageSize;
+	vm_assert(page < process->mmap.length, "Out of memory.");
+	
+	return process->mmap.pages[page][index];
+}
+
+void vm_write_byte(Process *process, uint32_t address, uint8_t value)
+{
+	vm_assert(process != NULL, "process must not be NULL.");
+	
+	uint32_t page  = address / process->mmap.pageSize;
+	uint32_t index = address % process->mmap.pageSize;
+	vm_assert(page < process->mmap.length, "Out of memory.");
+	
+	process->mmap.pages[page][index] = value;
+}
\ No newline at end of file
diff --git a/prototypes/supervm/vm.h b/prototypes/supervm/vm.h
index e1c4caa..71452d1 100644
--- a/prototypes/supervm/vm.h
+++ b/prototypes/supervm/vm.h
@@ -140,6 +140,19 @@ uint32_t vm_pop(Process *process);
  */
 uint32_t vm_peek(Process *process);
 
+/**
+ * Reads a byte from process memory.
+ * @arg process
+ * @arg address The address to read from.
+ */
+uint8_t vm_read_byte(Process *process, uint32_t address);
+
+/**
+ * Writes a byte to process memory.
+ * @arg process
+ * @arg address The address to read from.
+ */
+void vm_write_byte(Process *process, uint32_t address, uint8_t value);
 
 // The following functions need to be host-implemented.