decompile rng

asm/contest.s

@@ -850,7 +850,7 @@ sub_80D7DE8: @ 80D7DE8
 	adds r0, r5
 	ldr r1, =sub_80D80C8
 	str r1, [r0]
-	ldr r1, =gUnknown_03005D80
+	ldr r1, =gRngValue
 	ldr r0, =gUnknown_030060B8
 	ldr r0, [r0]
 	str r0, [r1]
@@ -2191,7 +2191,7 @@ sub_80D8A88: @ 80D8A88
 	strb r0, [r1, 0x10]
 	ldr r0, [r2]
 	ldr r1, [r0]
-	ldr r0, =gUnknown_03005D80
+	ldr r0, =gRngValue
 	ldr r0, [r0]
 	str r0, [r1, 0x18]
 	ldr r0, =gUnknown_02039F2A
@@ -5369,7 +5369,7 @@ _080DA65C:
 	bl sub_80DF750
 _080DA668:
 	ldr r1, =gUnknown_030060B8
-	ldr r0, =gUnknown_03005D80
+	ldr r0, =gRngValue
 	ldr r0, [r0]
 	str r0, [r1]
 	ldr r4, =gStringVar4

asm/contest_link_80FC4F4.s

@@ -416,7 +416,7 @@ _080FC830:
 	lsls r0, 24
 	cmp r0, 0
 	beq _080FC880
-	ldr r0, =gUnknown_03005D80
+	ldr r0, =gRngValue
 	movs r1, 0x4
 	bl sub_80FC4F4
 	cmp r0, 0x1
@@ -429,7 +429,7 @@ _080FC858:
 	lsls r0, 24
 	cmp r0, 0
 	beq _080FC880
-	ldr r0, =gUnknown_03005D80
+	ldr r0, =gRngValue
 	ldr r4, =gUnknown_020223C4
 	adds r1, r4, 0
 	movs r2, 0x4

asm/rng.s

@@ -1,65 +0,0 @@
-	.include "asm/macros.inc"
-	.include "constants/constants.inc"
-
-	.syntax unified
-
-	.text
-
-	thumb_func_start Random
-@ u16 GenerateRandomNumber()
-Random: @ 806F5CC
-	ldr r2, =gUnknown_03005D80
-	ldr r1, [r2]
-	ldr r0, =0x41c64e6d
-	muls r0, r1
-	ldr r1, =0x00006073
-	adds r0, r1
-	str r0, [r2]
-	ldr r2, =gUnknown_020249C0
-	ldr r1, [r2]
-	adds r1, 0x1
-	str r1, [r2]
-	lsrs r0, 16
-	bx lr
-	.pool
-	thumb_func_end Random
-
-	thumb_func_start SeedRng
-@ void SeedRng(u16 seed)
-SeedRng: @ 806F5F8
-	lsls r0, 16
-	lsrs r0, 16
-	ldr r1, =gUnknown_03005D80
-	str r0, [r1]
-	ldr r1, =gUnknown_020249BC
-	movs r0, 0
-	strb r0, [r1]
-	bx lr
-	.pool
-	thumb_func_end SeedRng
-
-	thumb_func_start SeedRng2
-SeedRng2: @ 806F610
-	lsls r0, 16
-	lsrs r0, 16
-	ldr r1, =gUnknown_03005D84
-	str r0, [r1]
-	bx lr
-	.pool
-	thumb_func_end SeedRng2
-
-	thumb_func_start Random2
-Random2: @ 806F620
-	ldr r2, =gUnknown_03005D84
-	ldr r1, [r2]
-	ldr r0, =0x41c64e6d
-	muls r0, r1
-	ldr r1, =0x00006073
-	adds r0, r1
-	str r0, [r2]
-	lsrs r0, 16
-	bx lr
-	.pool
-	thumb_func_end Random2
-
-	.align 2, 0 @ Don't pad with nop.

asm/rom_8034C54.s

@@ -13834,7 +13834,7 @@ _0803C628:
 	ldrb r0, [r0]
 	cmp r0, 0
 	bne _0803C690
-	ldr r1, =gUnknown_03005D80
+	ldr r1, =gRngValue
 	ldr r0, =gUnknown_0203BD30
 	ldr r0, [r0]
 	str r0, [r1]
@@ -71061,7 +71061,7 @@ sub_805C158: @ 805C158
 	cmp r0, 0
 	bne _0805C194
 	ldr r1, =gUnknown_0203BD30
-	ldr r0, =gUnknown_03005D80
+	ldr r0, =gRngValue
 	ldr r0, [r0]
 	str r0, [r1]
 	bl sub_805D19C

asm/rom_8184DA4.s

@@ -96,7 +96,7 @@ sub_8184E58: @ 8184E58
 	cmp r0, 0x1
 	bne _08184EA0
 	ldr r1, =gUnknown_0203BD2C
-	ldr r0, =gUnknown_03005D80
+	ldr r0, =gRngValue
 	ldr r0, [r0]
 	str r0, [r1]
 	ldr r4, =gUnknown_0203C7AE
@@ -111,7 +111,7 @@ sub_8184E58: @ 8184E58
 _08184EA0:
 	cmp r0, 0x2
 	bne _08184EAC
-	ldr r0, =gUnknown_03005D80
+	ldr r0, =gRngValue
 	ldr r1, =gUnknown_0203BD2C
 	ldr r1, [r1]
 	str r1, [r0]

asm/rom_81BAD84.s

@@ -60550,7 +60550,7 @@ _081DA284:
 	lsls r0, 24
 	cmp r0, 0
 	beq _081DA2D4
-	ldr r0, =gUnknown_03005D80
+	ldr r0, =gRngValue
 	movs r1, 0x4
 	bl sub_80FC4F4
 	cmp r0, 0x1
@@ -60563,7 +60563,7 @@ _081DA2AC:
 	lsls r0, 24
 	cmp r0, 0
 	beq _081DA2D4
-	ldr r0, =gUnknown_03005D80
+	ldr r0, =gRngValue
 	ldr r4, =gUnknown_020223C4
 	adds r1, r4, 0
 	movs r2, 0x4

include/rng.h

@@ -0,0 +1,18 @@
+#ifndef GUARD_RNG_H
+#define GUARD_RNG_H
+
+extern u32 gRngValue;
+extern u32 gRng2Value;
+
+//Returns a 16-bit pseudorandom number
+u16 Random(void);
+u16 Random2(void);
+
+//Returns a 32-bit pseudorandom number
+#define Random32() (Random() | (Random() << 16))
+
+//Sets the initial seed value of the pseudorandom number generator
+void SeedRng(u16 seed);
+void SeedRng2(u16 seed);
+
+#endif // GUARD_RNG_H

ld_script.txt

@@ -60,7 +60,7 @@ SECTIONS {
         asm/pokemon_2.o(.text);
         asm/pokemon_3.o(.text);
         asm/trig.o(.text);
-        asm/rng.o(.text);
+        src/rng.o(.text);
         asm/util.o(.text);
         asm/blend_palette.o(.text);
         asm/daycare.o(.text);

src/rng.c

@@ -0,0 +1,35 @@
+#include "global.h"
+#include "rng.h"
+
+// The number 1103515245 comes from the example implementation of rand and srand
+// in the ISO C standard.
+
+extern u32 gRngValue;
+extern u32 gRng2Value;
+
+EWRAM_DATA u8 sUnknown = 0;
+EWRAM_DATA u32 sRandCount = 0;
+
+u16 Random()
+{
+    gRngValue = 1103515245 * gRngValue + 24691;
+    sRandCount++;
+    return gRngValue >> 16;
+}
+
+void SeedRng(u16 seed)
+{
+    gRngValue = seed;
+    sUnknown = 0;
+}
+
+void SeedRng2(u16 seed)
+{
+    gRng2Value = seed;
+}
+
+u16 Random2(void)
+{
+    gRng2Value = 1103515245 * gRng2Value + 24691;
+    return gRng2Value >> 16;
+}

sym_common.txt

@@ -267,10 +267,10 @@ gUnknown_03005D78: @ 3005D78
 gUnknown_03005D7C: @ 3005D7C
 	.space 0x4
 
-gUnknown_03005D80: @ 3005D80
+gRngValue: @ 3005D80
 	.space 0x4
 
-gUnknown_03005D84: @ 3005D84
+gRng2Value: @ 3005D84
 	.space 0x4
 
 gUnknown_03005D88: @ 3005D88

sym_ewram.txt

@@ -699,12 +699,9 @@ gUnknown_0202499C: @ 202499C
 gUnknown_020249B4: @ 20249B4
 	.space 0x8
 
-gUnknown_020249BC: @ 20249BC
+	.include "src/rng.o"
-	.space 0x4
-
-gUnknown_020249C0: @ 20249C0
-	.space 0x4
 
+	.align 2
 gUnknown_020249C4: @ 20249C4
 	.space 0x64