progress

lib/LICENSE_1_0.txt

@@ -0,0 +1,23 @@
+Boost Software License - Version 1.0 - August 17th, 2003
+
+Permission is hereby granted, free of charge, to any person or organization
+obtaining a copy of the software and accompanying documentation covered by
+this license (the "Software") to use, reproduce, display, distribute,
+execute, and transmit the Software, and to prepare derivative works of the
+Software, and to permit third-parties to whom the Software is furnished to
+do so, all subject to the following:
+
+The copyright notices in the Software and this entire statement, including
+the above license grant, this restriction and the following disclaimer,
+must be included in all copies of the Software, in whole or in part, and
+all derivative works of the Software, unless such copies or derivative
+works are solely in the form of machine-executable object code generated by
+a source language processor.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

lib/oam.fab

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2022, Patrick Bene
+ * This file is distributed under the Boost Software License, Version 1.0.
+ * See LICENSE_1_0.txt or https://www.boost.org/LICENSE_1_0.txt 
+ */
+
+// Code for manipulating OAM (Object Attribute Memory),
+// which is the memory that represents sprites.
+// See: https://www.nesdev.org/wiki/PPU_OAM
+
+vars /oam
+    // This array represents the CPU-side copy of OAM.
+    // Make your modifications to it, then call 'ppu_upload_oam' during VBLANK.
+    U[256] oam
+    : +align
+
+// Offsets into OAM, as determined by the hardware:
+ct Int OAM_Y = 0
+ct Int OAM_P = 1
+ct Int OAM_A = 2
+ct Int OAM_X = 3
+
+// Copies 'oam' into PPU memory. Call during VBLANK only.
+fn ppu_upload_oam(U offset)
+: employs /oam
+: +inline
+    fence
+    {OAMADDR}(offset)
+    {OAMDMA}((&oam).b)
+
+// !!! For the following functions: !!!
+// 'index' must be a multiple of 4, otherwise the behavior is undefined.
+
+// Hides every sprite, starting from 'index':
+fn hide_oam(U index)
+: +inline
+    do for(; index; index += 4)
+        oam{OAM_Y + index} = $FF
+
+// The 'set_oam' functions use the '{}' operator for array indexing 
+// instead of '[]', as it's more efficient in this case.
+
+fn set_oam_x(U index, U x)
+: +inline
+    oam{OAM_X + index} = x
+
+fn set_oam_y(U index, U y)
+: +inline
+    oam{OAM_Y + index} = y
+
+fn set_oam_p(U index, U p)
+: +inline
+    oam{OAM_P + index} = p
+
+fn set_oam_a(U index, U a)
+: +inline
+    oam{OAM_A + index} = a
+
+fn set_oam(U index, U x, U y, U p, U a)
+: +inline
+    oam{OAM_Y + index} = y
+    oam{OAM_P + index} = p
+    oam{OAM_A + index} = a
+    oam{OAM_X + index} = x
+

lib/pad.fab

@@ -1,3 +1,12 @@
+/*
+ * Copyright (c) 2022, Patrick Bene
+ * This file is distributed under the Boost Software License, Version 1.0.
+ * See LICENSE_1_0.txt or https://www.boost.org/LICENSE_1_0.txt 
+ */
+
+// Code for reading and handling gamepad button presses.
+// See: https://www.nesdev.org/wiki/Standard_controller
+
 // Gamepad button flags:
 ct U BUTTON_A      = %10000000
 ct U BUTTON_B      = %01000000
@@ -9,19 +18,20 @@ ct U BUTTON_LEFT   = %00000010
 ct U BUTTON_RIGHT  = %00000001
 ct U BUTTON_DPAD   = BUTTON_UP | BUTTON_DOWN | BUTTON_LEFT | BUTTON_RIGHT
 
+// This struct provides an interface to a single gamepad.
+// To use, AND the fields with the button flags above.
 struct Pad
     U held
     U pressed
     U released
 
 vars /pad
     // [0] for the first controller, [1] for the second
-    Pad[2] pads
+    Pad[2] pads = Pad[2]()
 
 // Reads the current gamepad state into 'pads'.
 asm fn read_pads()
-: vars /pad
-: data
+: employs /pad
     default
         ldx &pads.held+0
         ldy #1

lib/palette.fab

@@ -1,3 +1,13 @@
+/*
+ * Copyright (c) 2022, Patrick Bene
+ * This file is distributed under the Boost Software License, Version 1.0.
+ * See LICENSE_1_0.txt or https://www.boost.org/LICENSE_1_0.txt 
+ */
+
+// Code for working with palettes,
+// i.e. the limited set of colors the NES can display at once.
+// See: https://www.nesdev.org/wiki/PPU_palettes
+
 // Copies the global variable 'palette' into the PPU's internal palette memory.
 fn ppu_upload_palette()
     {PPUSTATUS}()
@@ -76,3 +86,4 @@ ct U[25] example_palette = U[25](
     $08, $1A, $2C,
 
     $0F)
+

lib/pbz.fab

@@ -1,7 +1,9 @@
+// TODO
+
+data /pbz
 
 asm fn load_pbz(CC/pbz ptr, U tiles)
-: vars
-: data /pbz
+: employs /pbz
     vars
         U run_mask
     label write_plane

lib/rng.fab

@@ -1,12 +1,24 @@
+/*
+ * Copyright (c) 2022, Patrick Bene
+ * This file is distributed under the Boost Software License, Version 1.0.
+ * See LICENSE_1_0.txt or https://www.boost.org/LICENSE_1_0.txt 
+ */
+
 // RNG means random number generator.
 // This file contains code for generating random numbers.
 
 vars /rng
     U[2] rng_state = U[2](1, 1)
 
+// Helper function for setting 'rng_state'.
+fn seed(UU nonzero)
+: +inline
+    rng_state[0] = nonzero.a
+    rng_state[1] = nonzero.b
+
+// Returns a pseudo-random 8-bit value.
 asm fn rand() U
-: vars /rng
-: data
+: employs /rng
     default
         lda &rng_state+0
         asl
@@ -23,9 +35,17 @@ asm fn rand() U
         sta &return
         rts
 
+// Returns a pseudo-random 16-bit value.
+fn rand16() UU
+: +inline
+    UU result
+    result.a = rand()
+    result.b = rand()
+    return result
+
+// Returns a bitmask that can hold any value less than or equal to argument 'num'.
 asm fn ceil_mask(U num) U
-: vars
-: data
+: employs
     default
         ldx #$FF
         lda &num

lib/string.fab

@@ -1,4 +1,4 @@
-
+// TODO
 
 vars /decompress_string_vars
     CC/strings decompress_string_ptr
@@ -15,8 +15,7 @@ charmap foo("\0\n", "abcdefghijklmnopqrstuvwxyz
 // Decompresses a single character of the string, returning it.
 // 
 asm fn decompress_string() U
-: vars /decompress_string_vars
-: data /strings
+: employs /strings /decompress_string_vars
     vars
         U stack