Reworked I/O methodology

Instead of passing function pointers, we're passing structs with context
now. The idea is the same, I/O functions require some struct with a
function pointer and some generic memory that only the output device
cares about. I/O just calls it.

VGA has been reworked to accomodate this change, as well as default
outputs being created for low-overhead use (such as interrupt handlers).

include/io.h

@@ -8,11 +8,17 @@
 #define IO_H
 #include <stdint.h>
 
-int putc(int (*)(char), char);
-int print(int (*)(char), const char*);
-int println(int (*)(char), const char*);
-int printhex(int (*)(char), uint32_t);
-int prindec(int (*)(char), uint32_t out);
-int printf(int (*)(char), const char* fmt, ...);
+typedef struct char_writer_s char_writer_t;
+struct char_writer_s {
+    int (*putChar)(void* ctx, char out);
+    void* ctx;
+};
+
+int putc(char_writer_t*, char);
+int print(char_writer_t*, const char*);
+int println(char_writer_t*, const char*);
+int printhex(char_writer_t*, uint32_t);
+int prindec(char_writer_t*, uint32_t out);
+int printf(char_writer_t*, const char* fmt, ...);
 
 #endif

include/serial.h

@@ -6,12 +6,15 @@
 #ifndef SERIAL_H
 #define SERIAL_H
 #include "asm.h"
+#include "io.h"
 #include <stdint.h>
 
 typedef struct SerialState_s {
     uint16_t port;
 } SerialState_t;
 
+extern char_writer_t* default_COM;
+
 /**
  * @brief Initialize a serial port for communication
  * @param port The serial port number to initialize

include/vga.h

@@ -7,34 +7,37 @@
 #define VGA_H
 #define VGA_GRID_COLS 80
 #define VGA_GRID_ROWS 25
+#define DEFAULT_ATTRIBUTES 0x0F00 
 #include <stdint.h>
 #include <stdarg.h>
-
+#include "io.h"
 /*
  * CONSTANTS AND VARIABLES
  */
 
 //Information on the VGA buffer
-
 extern volatile uint16_t* const vga_buffer;
 
-//grid is top left origin. This is our cursor!
-extern int cursor_col;
-extern int cursor_row;
-extern uint16_t vga_attributes; // Black background, White foreground
+typedef struct vga_ctx_s {
+    int cursor_col;
+    int cursor_row;
+    uint16_t attributes;
+} vga_ctx_t;
 
+//grid is top left origin. This is our cursor!
+extern uint16_t vga_attributes; // Black background, White foreground
+extern char_writer_t* default_vga;
 
 /*
  * Functions
  */
 
-//Clear the VGA buffer
+//Clear the VGA buffer, context optional
+void vga_clear_ctx(vga_ctx_t* ctx);
 void vga_clear();
-//Put a character in the VGA buffer and move the cursor to the right by one
-void vga_set_attributes(uint8_t attributes);
 //Write character c to cursor
 //Implements IO generic ASCII output
-int vga_out(char c);
+int vga_out(void* ctx, char c);
 
 
 #endif

src/interrupt_handlers.c

@@ -1,26 +1,34 @@
 #include "interrupt_handlers.h"
 #include "vga.h"
 #include "io.h"
+#include "serial.h"
 void generic_isr_handler(StateSnapshot_t* cpu_state) {
     //We made it to C for our interrupt! For now, let's just print our interrupt to the screen.
+    //What's cookin for outputs?
+    char_writer_t* out = 0;
+    if(default_COM) {
+        out = default_COM;
+    } else if(default_vga) {
+        out = default_vga;
+        vga_clear_ctx(default_vga->ctx);
+    }
     switch(cpu_state->interrupt_id) {
-        
-
         default:
-            vga_clear();
-            printf(vga_out, "INTERRUPT TRIGGERED! Info below.\n");
-            printf(vga_out, "Int_ID|ERR: %X|%X\n", cpu_state->interrupt_id, cpu_state->error_code);
-            printf(vga_out, "EFLAGS|CS|EIP: %X|%X|%X\n", cpu_state->eflags, cpu_state->cs,cpu_state->eip);
-            printf(vga_out, "GP Registers:\neax:%X\nebx:%X\necx:%X\nedx:%X\nesp:%X\nebp:%X\nesi:%X\nedi:%X\n",
-                       cpu_state->eax,
-                       cpu_state->ebx,
-                       cpu_state->ecx,
-                       cpu_state->edx,
-                       cpu_state->esp,
-                       cpu_state->ebp,
-                       cpu_state->esi,
-                       cpu_state->edi);
-            printf(vga_out, "HALT!");
-            while(1);
+            if(out){
+                printf(out, "INTERRUPT TRIGGERED! Info below.\n");
+                printf(out, "Int_ID|ERR: %X|%X\n", cpu_state->interrupt_id, cpu_state->error_code);
+                printf(out, "EFLAGS|CS|EIP: %X|%X|%X\n", cpu_state->eflags, cpu_state->cs,cpu_state->eip);
+                printf(out, "GP Registers:\neax:%X\nebx:%X\necx:%X\nedx:%X\nesp:%X\nebp:%X\nesi:%X\nedi:%X\n",
+                           cpu_state->eax,
+                           cpu_state->ebx,
+                           cpu_state->ecx,
+                           cpu_state->edx,
+                           cpu_state->esp,
+                           cpu_state->ebp,
+                           cpu_state->esi,
+                           cpu_state->edi);
+                printf(out, "HALT!");
+                while(1);
+            }
     }
 }

src/io.c

@@ -2,39 +2,39 @@
 #include "kttools.h"
 #include <stdarg.h>
 
-int printhex(int (*sendDataFnc)(char), uint32_t out) {
+int printhex(char_writer_t* writer, uint32_t out) {
     char buff[9];
     i_to_str(out, buff, 9, 0x10);
-    return print(sendDataFnc, buff);
+    return print(writer, buff);
 }
 
-int printdec(int (*sendDataFnc)(char), uint32_t out) {
+int printdec(char_writer_t* writer, uint32_t out) {
     char buff[11];
     i_to_str(out, buff, 11, 10);
-    return print(sendDataFnc, buff);
+    return print(writer, buff);
 }
 
-int putc(int (*sendDataFnc)(char), char out) {
-    return sendDataFnc(out);
+int putc(char_writer_t* writer, char out) {
+    return writer->putChar(writer->ctx, out);
 }
 
-int print(int (*sendDataFnc)(char), const char* out) {
+int print(char_writer_t* writer, const char* out) {
 	int ret = 0;
     for (int i = 0; out[i] != '\0' && !ret; i++)
-        ret = putc(sendDataFnc, out[i]);
+        ret = putc(writer, out[i]);
     return ret;
 }
 
-int println(int (*sendDataFnc)(char), const char* out) {
-    int ret = print(sendDataFnc, out);
+int println(char_writer_t* writer, const char* out) {
+    int ret = print(writer, out);
     if(ret)
         return ret;
-    ret = print(sendDataFnc, "\n");
+    ret = print(writer, "\n");
     return ret;
 }
 
 /**
- * @brief Print a format string to the outstream function.
+ * @brief Print a format string to the outwriter function.
  *
  *  Print some format string to the output given in sendDataFnc. Supports a few format strings in C format.
  *  
@@ -45,7 +45,7 @@ int println(int (*sendDataFnc)(char), const char* out) {
  *
  */
 
-int printf(int (*sendDataFnc)(char), const char* fmt, ...) {
+int printf(char_writer_t* writer, const char* fmt, ...) {
     va_list args;
     va_start(args, fmt);
     int ret = 0;
@@ -54,17 +54,17 @@ int printf(int (*sendDataFnc)(char), const char* fmt, ...) {
             fmt++;
             switch(*fmt) {
                 case 'X':
-                    ret = print(sendDataFnc, "0x");
+                    ret = print(writer, "0x");
                 case 'x':    
-                    ret = printhex(sendDataFnc, va_arg(args,uint32_t));
+                    ret = printhex(writer, va_arg(args,uint32_t));
                     break;
                 case 'd':
-                    ret = printdec(sendDataFnc, va_arg(args,uint32_t));
+                    ret = printdec(writer, va_arg(args,uint32_t));
                     break;
 
             }
         } else {
-            sendDataFnc(*fmt);
+            ret = putc(writer,*fmt);
         }
         fmt++;
         if(ret)

src/main.c

@@ -1,8 +1,4 @@
 //Our own code, at this point...
-//Output table:
-//0: VGA
-//1: COM1
-#define OUTPUT_TYPE 1
 #include <stdint.h>
 #include "vga.h"
 #include "io.h"
@@ -16,35 +12,30 @@ void kern_main(uint32_t multiboot_magic, mb_info_t* multiboot_info)
     //First interrupts.
     setup_idt();
  
-    //Let's pick an output schema.
-    int (*outWriter)(char) = 0;
-    int comstatus = 1234;
-    switch(OUTPUT_TYPE) {
-        case 1:
-            comstatus = serial_init(COM1);
-            if(comstatus) {
-                //Fail...
-                break; 
-            }
-            outWriter = serial_send8;
-            break;
-    }
-    //VGA is selected or the selected option failed, falling back 
-    if(outWriter == 0){
-        outWriter = vga_out;
-        vga_clear();
-    }
+    //Let's get some output schemas ready.
     
-    printf(outWriter, "Entry eax:%X\n", multiboot_magic);
+    //VGA prep
+    vga_ctx_t vga_ctx;
+    vga_ctx.attributes = DEFAULT_ATTRIBUTES;
+    vga_ctx.cursor_row = 0;
+    vga_ctx.cursor_col = 0;
+    char_writer_t vga_writer;
+    vga_writer.ctx = &vga_ctx;
+    vga_writer.putChar = vga_out;
+    default_vga = &vga_writer;
+    vga_clear_ctx(&vga_ctx);
+
+
+    printf(&vga_writer, "Entry eax:%X\n", multiboot_magic);
 
     if(multiboot_magic != 0x2BADB002) {
-        println(outWriter, writerState, "Bootloader not multiboot1 compliant! Needed for mmap, etc. Can't work without it, kthxbye!");
+        println(&vga_writer, "Bootloader not multiboot1 compliant! Needed for mmap, etc. Can't work without it, kthxbye!");
         return;
     } else {
-        println(outWriter, writerState, "Multiboot detected! Continuing...");
+        println(&vga_writer, "Multiboot detected! Continuing...");
     }
 
-    printf(outWriter, writerState, "MEM_LOWER:%X\n", multiboot_info->mem_lower);
-    printf(outWriter, writerState"MEM_UPPER:%X\n", multiboot_info->mem_upper);
+    printf(&vga_writer, "MEM_LOWER:%X\n", multiboot_info->mem_lower);
+    printf(&vga_writer, "MEM_UPPER:%X\n", multiboot_info->mem_upper);
 }
 

src/serial.c

@@ -1,6 +1,7 @@
 #include "serial.h"
 #include <stdint.h>
 
+char_writer_t* default_COM = 0;
 
 int serial_init(uint16_t port) {
     //disable interrupts when messing with it

src/vga.c

@@ -1,22 +1,29 @@
 #include "vga.h"
 #include "kttools.h"
 #include <stddef.h>
-
 /*
  * VARS
  */
 
-int cursor_col = 0;
-int cursor_row = 0;
 volatile uint16_t* const vga_buffer = (uint16_t*)0xB8000;
-uint16_t vga_attributes = 0x0F00;
+char_writer_t* default_vga = 0;
 
 /*
  * FUNCTIONS
  */
 
-void vga_clear() {
-	for (int col = 0; col < VGA_GRID_COLS; col ++) {
+void cga_clear() {
+    vga_clear_ctx(0);
+}
+
+void vga_clear_ctx(vga_ctx_t* ctx) {
+    uint16_t vga_attributes = DEFAULT_ATTRIBUTES;
+    if(ctx) {
+        ctx->cursor_col = 0;
+        ctx->cursor_row = 0;
+        vga_attributes = ctx->attributes;
+    }
+    for (int col = 0; col < VGA_GRID_COLS; col ++) {
 		for (int row = 0; row < VGA_GRID_ROWS; row ++) {
             //works out to iterating every cell
 			const size_t index = (VGA_GRID_COLS * row) + col;
@@ -30,26 +37,24 @@ void vga_clear() {
 	}
 }
 
-int vga_out(char c)
+int vga_out(void* ctx, char c)
 {
+    vga_ctx_t* vga_ctx = (vga_ctx_t*) ctx;
     //Check for some freaky escape character first
     if(c == '\n') {
-        cursor_col = 0;
+        vga_ctx->cursor_col = 0;
         //mod implements wraparound
-        cursor_row = (cursor_row + 1) % (VGA_GRID_ROWS-1);
+        vga_ctx->cursor_row = (vga_ctx->cursor_row + 1) % (VGA_GRID_ROWS-1);
         return 0;
     }
         //Calculate where in the vga buffer to put the character
-		const size_t index = (VGA_GRID_COLS * cursor_row) + cursor_col;
+		const size_t index = (VGA_GRID_COLS * vga_ctx->cursor_row) + vga_ctx->cursor_col;
         //VGA buffer cell consists of the first half attributes, second half character
-		vga_buffer[index] = vga_attributes | c;
-		cursor_col++;
+		vga_buffer[index] = vga_ctx->attributes | c;
+		vga_ctx->cursor_col++;
     return 0;
 }	
 
-void vga_set_attributes(uint8_t attributes) {
-     vga_attributes = ((uint16_t)attributes) << 8;
-}