vgabios: Introduce text_address().

Factor out code that calculates the text mode address of a given
character.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

3 files changed, 24 insertions, 36 deletions

diff --git a/vgasrc/vgabios.c b/vgasrc/vgabios.c
index d0efc11..400e296 100644
--- a/vgasrc/vgabios.c
+++ b/vgasrc/vgabios.c
@@ -104,9 +104,7 @@ set_cursor_pos(struct cursorpos cp)
         return;
 
     // Calculate the memory address
-    int address = (GET_BDA(video_pagesize) * page
-                   + (x + y * GET_BDA(video_cols)) * 2);
-    stdvga_set_cursor_pos(address);
+    stdvga_set_cursor_pos((int)text_address(cp));
 }
 
 static struct cursorpos
@@ -136,11 +134,9 @@ set_active_page(u8 page)
     if (!vmode_g)
         return;
 
-    // Get cursor pos for the given page
-    struct cursorpos cp = get_cursor_pos(page);
-
     // Calculate memory address of start of page
-    int address = GET_BDA(video_pagesize) * page;
+    struct cursorpos cp = {0, 0, page};
+    int address = (int)text_address(cp);
     vgahw_set_displaystart(vmode_g, address);
 
     // And change the BIOS page
@@ -150,7 +146,7 @@ set_active_page(u8 page)
     dprintf(1, "Set active page %02x address %04x\n", page, address);
 
     // Display the cursor, now the page is active
-    set_cursor_pos(cp);
+    set_cursor_pos(get_cursor_pos(page));
 }
 
 static void
diff --git a/vgasrc/vgabios.h b/vgasrc/vgabios.h
index 645e0e2..73c0697 100644
--- a/vgasrc/vgabios.h
+++ b/vgasrc/vgabios.h
@@ -105,6 +105,7 @@ struct vgamode_s *get_current_mode(void);
 int vga_set_mode(int mode, int flags);
 
 // vgafb.c
+void *text_address(struct cursorpos cp);
 void vgafb_move_chars(struct vgamode_s *vmode_g, struct cursorpos dest
                       , struct cursorpos src, struct cursorpos movesize);
 void vgafb_clear_chars(struct vgamode_s *vmode_g, struct cursorpos dest
diff --git a/vgasrc/vgafb.c b/vgasrc/vgafb.c
index 3c6065c..31bf5de 100644
--- a/vgasrc/vgafb.c
+++ b/vgasrc/vgafb.c
@@ -343,6 +343,15 @@ vgafb_read_pixel(u16 x, u16 y)
  * Text ops
  ****************************************************************/
 
+// Return the fb offset for the given character address when in text mode.
+void *
+text_address(struct cursorpos cp)
+{
+    int stride = GET_BDA(video_cols) * 2;
+    u32 pageoffset = GET_BDA(video_pagesize) * cp.page;
+    return (void*)pageoffset + cp.y * stride + cp.x * 2;
+}
+
 // Move characters on screen.
 void
 vgafb_move_chars(struct vgamode_s *vmode_g, struct cursorpos dest
@@ -353,15 +362,10 @@ vgafb_move_chars(struct vgamode_s *vmode_g, struct cursorpos dest
         return;
     }
 
-    int cheight = 1;
-    int cwidth = 2;
-    int stride = GET_BDA(video_cols) * cwidth;
-    void *dest_far = (void*)(dest.y * cheight * stride + dest.x * cwidth);
-    void *src_far = (void*)(src.y * cheight * stride + src.x * cwidth);
-    u32 pageoffset = GET_BDA(video_pagesize) * dest.page;
-    u16 seg = GET_GLOBAL(vmode_g->sstart);
-    memmove_stride(seg, dest_far + pageoffset, src_far + pageoffset
-                   , movesize.x * cwidth, stride, movesize.y * cheight);
+    int stride = GET_BDA(video_cols) * 2;
+    memmove_stride(GET_GLOBAL(vmode_g->sstart)
+                   , text_address(dest), text_address(src)
+                   , movesize.x * 2, stride, movesize.y);
 }
 
 // Clear are of screen.
@@ -374,15 +378,10 @@ vgafb_clear_chars(struct vgamode_s *vmode_g, struct cursorpos dest
         return;
     }
 
-    int cheight = 1;
-    int cwidth = 2;
-    int stride = GET_BDA(video_cols) * cwidth;
-    void *dest_far = (void*)(dest.y * cheight * stride + dest.x * cwidth);
+    int stride = GET_BDA(video_cols) * 2;
     u16 attr = ((ca.use_attr ? ca.attr : 0x07) << 8) | ca.car;
-    u32 pageoffset = GET_BDA(video_pagesize) * dest.page;
-    u16 seg = GET_GLOBAL(vmode_g->sstart);
-    memset16_stride(seg, dest_far + pageoffset, attr
-                    , clearsize.x * cwidth, stride, clearsize.y * cheight);
+    memset16_stride(GET_GLOBAL(vmode_g->sstart), text_address(dest), attr
+                    , clearsize.x * 2, stride, clearsize.y);
 }
 
 // Write a character to the screen.
@@ -398,11 +397,7 @@ vgafb_write_char(struct cursorpos cp, struct carattr ca)
         return;
     }
 
-    int cheight = 1;
-    int cwidth = 2;
-    int stride = GET_BDA(video_cols) * cwidth;
-    int addr = cp.y * cheight * stride + cp.x * cwidth;
-    void *dest_far = (void*)(GET_BDA(video_pagesize) * cp.page + addr);
+    void *dest_far = text_address(cp);
     if (ca.use_attr) {
         u16 dummy = (ca.attr << 8) | ca.car;
         SET_FARVAR(GET_GLOBAL(vmode_g->sstart), *(u16*)dest_far, dummy);
@@ -425,12 +420,8 @@ vgafb_read_char(struct cursorpos cp)
         goto fail;
     }
 
-    int cheight = 1;
-    int cwidth = 2;
-    int stride = GET_BDA(video_cols) * cwidth;
-    int addr = cp.y * cheight * stride + cp.x * cwidth;
-    u16 *src_far = (void*)(GET_BDA(video_pagesize) * cp.page + addr);
-    u16 v = GET_FARVAR(GET_GLOBAL(vmode_g->sstart), *src_far);
+    u16 *dest_far = text_address(cp);
+    u16 v = GET_FARVAR(GET_GLOBAL(vmode_g->sstart), *dest_far);
     struct carattr ca = {v, v>>8, 0};
     return ca;