decompile random

asm/code_800B540.s

@@ -13961,7 +13961,7 @@ _08011E0A:
 	lsls r1, 3
 	adds r0, r5, r1
 	ldr r0, [r0]
-	bl ReseedRng
+	bl SetRngState
 	b _08011E60
 	.align 2, 0
 _08011E38: .4byte 0x00000414

asm/code_8272724.s

@@ -9,20 +9,20 @@
 
 	.text
 
-	thumb_func_start _08272760
-_08272760:
+	thumb_func_start sub_8272760
+sub_8272760:
 	push {lr}
 	adds r1, r0, 0
 	ldr r0, _08272770
-	bl _08272774
+	bl sub_8272774
 	pop {r0}
 	bx r0
 	.align 2, 0
 _08272770: .4byte 0x02027370
-	thumb_func_end _08272760
+	thumb_func_end sub_8272760
 
-	thumb_func_start _08272774
-_08272774:
+	thumb_func_start sub_8272774
+sub_8272774:
 	push {r4-r7,lr}
 	mov r7, r10
 	mov r6, r9
@@ -156,22 +156,22 @@ _08272860:
 	pop {r4-r7}
 	pop {r0}
 	bx r0
-	thumb_func_end _08272774
+	thumb_func_end sub_8272774
 
-	thumb_func_start _08272870
-_08272870:
+	thumb_func_start sub_8272870
+sub_8272870:
 	push {lr}
 	adds r1, r0, 0
 	ldr r0, _08272880
-	bl _08272884
+	bl sub_8272884
 	pop {r0}
 	bx r0
 	.align 2, 0
 _08272880: .4byte 0x02027370
-	thumb_func_end _08272870
+	thumb_func_end sub_8272870
 
-	thumb_func_start _08272884
-_08272884:
+	thumb_func_start sub_8272884
+sub_8272884:
 	push {r4-r7,lr}
 	mov r7, r10
 	mov r6, r9
@@ -325,22 +325,22 @@ _08272994:
 	pop {r4-r7}
 	pop {r0}
 	bx r0
-	thumb_func_end _08272884
+	thumb_func_end sub_8272884
 
-	thumb_func_start _082729A4
-_082729A4:
+	thumb_func_start sub_82729A4
+sub_82729A4:
 	push {lr}
 	adds r1, r0, 0
 	ldr r0, _082729B4
-	bl _082729B8
+	bl sub_82729B8
 	pop {r0}
 	bx r0
 	.align 2, 0
 _082729B4: .4byte 0x02027370
-	thumb_func_end _082729A4
+	thumb_func_end sub_82729A4
 
-	thumb_func_start _082729B8
-_082729B8:
+	thumb_func_start sub_82729B8
+sub_82729B8:
 	push {r4-r7,lr}
 	mov r7, r8
 	push {r7}
@@ -440,22 +440,22 @@ _08272A5A:
 	pop {r4-r7}
 	pop {r0}
 	bx r0
-	thumb_func_end _082729B8
+	thumb_func_end sub_82729B8
 
-	thumb_func_start _08272A78
-_08272A78:
+	thumb_func_start sub_8272A78
+sub_8272A78:
 	push {lr}
 	adds r1, r0, 0
 	ldr r0, _08272A88
-	bl _08272A8C
+	bl sub_8272A8C
 	pop {r0}
 	bx r0
 	.align 2, 0
 _08272A88: .4byte 0x02027370
-	thumb_func_end _08272A78
+	thumb_func_end sub_8272A78
 
-	thumb_func_start _08272A8C
-_08272A8C:
+	thumb_func_start sub_8272A8C
+sub_8272A8C:
 	push {r4-r7,lr}
 	lsls r2, r1, 3
 	adds r2, r1
@@ -546,6 +546,6 @@ _08272B20:
 	pop {r4-r7}
 	pop {r0}
 	bx r0
-	thumb_func_end _08272A8C
+	thumb_func_end sub_8272A8C
 
 	.align 2, 0 @ Don't pad with nop.

asm/libc.s

@@ -2585,7 +2585,7 @@ _080B39E8:
 	adds r2, r5, 0
 	adds r1, r4, 0
 	adds r3, r7, 0
-	bl sub_80B3D3C
+	bl _dtoa_r
 	adds r7, r0, 0
 	mov r1, r9
 	cmp r1, 0x67
@@ -3034,8 +3034,8 @@ _080B3D30:
 	pop {r4-r7,pc}
 	thumb_func_end sub_80B3BE0
 
-	thumb_func_start sub_80B3D3C
-sub_80B3D3C:
+	thumb_func_start _dtoa_r
+_dtoa_r:
 	push {r4-r7,lr}
 	mov r7, r10
 	mov r6, r9
@@ -4669,7 +4669,7 @@ _080B4A26:
 	mov r9, r4
 	mov r10, r5
 	pop {r4-r7,pc}
-	thumb_func_end sub_80B3D3C
+	thumb_func_end _dtoa_r
 
 	thumb_func_start sub_80B4A34
 sub_80B4A34:

asm/random.s

@@ -1,130 +0,0 @@
-	.include "constants/gba_constants.inc"
-	.include "asm/macros.inc"
-
-	.syntax unified
-
-	.text
-
-	thumb_func_start SeedRng
-SeedRng:
-	push {r4,lr}
-	ldr r4, _08006170
-	ldrb r2, [r0]
-	ldrb r1, [r0, 0x1]
-	muls r2, r1
-	ldrb r3, [r0, 0x2]
-	ldrb r1, [r0, 0x3]
-	muls r1, r3
-	ldr r3, _08006174
-	adds r1, r3
-	adds r2, r1
-	ldrb r1, [r0, 0x4]
-	ldrb r0, [r0, 0x5]
-	muls r0, r1
-	adds r2, r0
-	str r2, [r4]
-	pop {r4}
-	pop {r0}
-	bx r0
-	.align 2, 0
-_08006170: .4byte gUnknown_203B07C
-_08006174: .4byte 0x0000d305
-	thumb_func_end SeedRng
-
-	thumb_func_start Random16
-Random16:
-	ldr r2, _08006188
-	ldr r1, [r2]
-	ldr r0, _0800618C
-	muls r0, r1
-	adds r0, 0x1
-	str r0, [r2]
-	asrs r0, 16
-	bx lr
-	.align 2, 0
-_08006188: .4byte gUnknown_203B07C
-_0800618C: .4byte 0x5d588b65
-	thumb_func_end Random16
-
-	thumb_func_start Random
-Random:
-	push {r4,lr}
-	bl Random16
-	adds r4, r0, 0
-	lsls r4, 16
-	asrs r4, 16
-	bl Random16
-	lsls r0, 16
-	asrs r0, 16
-	lsls r4, 16
-	orrs r4, r0
-	adds r0, r4, 0
-	pop {r4}
-	pop {r1}
-	bx r1
-	thumb_func_end Random
-
-	thumb_func_start RandomCapped
-RandomCapped:
-	push {r4,lr}
-	adds r4, r0, 0
-	bl Random
-	ldr r1, _080061C8
-	ands r0, r1
-	muls r0, r4
-	asrs r0, 16
-	ands r0, r1
-	pop {r4}
-	pop {r1}
-	bx r1
-	.align 2, 0
-_080061C8: .4byte 0x0000ffff
-	thumb_func_end RandomCapped
-
-	thumb_func_start RandomRange
-RandomRange:
-	push {r4,r5,lr}
-	adds r5, r0, 0
-	adds r4, r1, 0
-	cmp r5, r4
-	beq _080061EC
-	cmp r5, r4
-	blt _080061E4
-	subs r0, r5, r4
-	bl RandomCapped
-	adds r0, r4
-	b _080061EC
-_080061E4:
-	subs r0, r4, r5
-	bl RandomCapped
-	adds r0, r5
-_080061EC:
-	pop {r4,r5}
-	pop {r1}
-	bx r1
-	thumb_func_end RandomRange
-
-	thumb_func_start GetRngState
-GetRngState:
-	ldr r0, _080061FC
-	ldr r0, [r0]
-	bx lr
-	.align 2, 0
-_080061FC: .4byte gUnknown_203B07C
-	thumb_func_end GetRngState
-
-	thumb_func_start ReseedRng
-ReseedRng:
-	push {r4,lr}
-	ldr r4, _08006214
-	str r0, [r4]
-	bl Random
-	str r0, [r4]
-	pop {r4}
-	pop {r0}
-	bx r0
-	.align 2, 0
-_08006214: .4byte gUnknown_203B07C
-	thumb_func_end ReseedRng
-
-	.align 2, 0 @ Don't pad with nop.

ld_script.txt

@@ -35,7 +35,7 @@ SECTIONS {
     {
         asm/crt0.o(.text);
         asm/code.o(.text);
-        asm/random.o(.text);
+        src/random.o(.text);
         asm/code_8006218.o(.text);
         src/main.o(.text);
         asm/code_800B540.o(.text);

src/random.c

@@ -0,0 +1,49 @@
+#include "global.h"
+
+extern s32 gRngState;
+
+void SeedRng(u8 *seed)
+{
+    gRngState = 54021 + (seed[0] * seed[1]) + (seed[2] * seed[3]) + (seed[4] * seed[5]);
+}
+
+static s16 Random16(void)
+{
+    gRngState = 1566083941 * gRngState + 1;
+    return gRngState >> 16;
+}
+
+s32 Random(void)
+{
+    s32 r1 = Random16();
+    s32 r2 = Random16();
+    return (r1 << 16) | r2;
+}
+
+// Returns a random number in the range [0, cap).
+s32 RandomCapped(s32 cap)
+{
+    return (((Random() & 0xFFFF) * cap) >> 16) & 0xFFFF;
+}
+
+s32 RandomRange(s32 a, s32 b)
+{
+    if (a == b)
+        return a;
+
+    if (a < b)
+        return RandomCapped(b - a) + a;
+
+    return RandomCapped(a - b) + b;
+}
+
+s32 GetRngState(void)
+{
+    return gRngState;
+}
+
+void SetRngState(s32 state)
+{
+    gRngState = state;
+    gRngState = Random();
+}

sym_ewram2.txt

@@ -82,7 +82,7 @@ gUnknown_203B074: @ 203B074
 gUnknown_203B078: @ 203B078
 	.space 0x4
 
-gUnknown_203B07C: @ 203B07C
+gRngState: @ 203B07C
 	.space 0x4
 
 gUnknown_203B080: @ 203B080