Decompile code_800FD970 (#141)

* Decompile code_800FD970

* Comment cleanups, ensure formatter won't cause a matching issue later

2 files changed, 86 insertions, 1 deletions

diff --git a/src/code/code_800FD970.c b/src/code/code_800FD970.c
new file mode 100644
index 000000000..ba981a07b
--- /dev/null
+++ b/src/code/code_800FD970.c
@@ -0,0 +1,85 @@
+#include <ultra64.h>
+#include <global.h>
+
+// The latest generated random number, used to generate the next number in the sequence.
+u32 randomNumber = 1;
+
+// Space to store a value to be re-interpreted as a float.
+u32 floatStore;
+
+/**
+ * Gets the next integer in the sequence of pseudo-random numbers.
+ */
+u32 Math_Rand_Next() {
+    return randomNumber = (randomNumber * 1664525) + 1013904223;
+}
+
+/**
+ * Seeds the pseudo-random number generator by providing a starting value.
+ */
+void Math_Rand_Seed(u32 seed) {
+    randomNumber = seed;
+}
+
+/**
+ * Returns a pseudo-random floating-point number between 0.0f and 1.0f, by generating 
+ * the next integer and masking it to an IEEE-754 compliant floating-point number 
+ * between 1.0f and 2.0f, returning the result subtract 1.0f.
+ */
+f32 Math_Rand_ZeroOne() {
+    randomNumber = (randomNumber * 1664525) + 1013904223;
+    floatStore = ((randomNumber >> 9) | 0x3F800000);
+    return *((f32*)&floatStore) - 1.0f;
+}
+
+/**
+ * Returns a pseudo-random floating-point number between -0.5f and 0.5f by the same
+ * manner in which Math_Rand_ZeroOne generates its result.
+ */
+f32 Math_Rand_Centered() {
+    randomNumber = (randomNumber * 1664525) + 1013904223;
+    floatStore = ((randomNumber >> 9) | 0x3F800000);
+    return *((f32*)&floatStore) - 1.5f;
+}
+
+/**
+ * Seeds a pseudo-random number at rndNum with a provided seed.
+ */
+void Math_Rand_Seed_Variable(u32* rndNum, u32 seed) {
+    *rndNum = seed;
+}
+
+/**
+ * Generates the next pseudo-random integer from the provided rndNum.
+ */
+u32 Math_Rand_Next_Variable(u32* rndNum) {
+    return *rndNum = (*rndNum * 1664525) + 1013904223;
+}
+
+/**
+ * Generates the next pseudo-random floating-point number between 0.0f and
+ * 1.0f from the provided rndNum.
+ */
+f32 Math_Rand_ZeroOne_Variable(u32* rndNum) {
+    u32 next;
+
+    next = (*rndNum * 1664525) + 1013904223;
+    // clang-format off
+    *rndNum = next; floatStore = (next >> 9) | 0x3F800000;
+    // clang-format on
+    return *((f32*)&floatStore) - 1.0f;
+}
+
+/**
+ * Generates the next pseudo-random floating-point number between -0.5f and
+ * 0.5f from the provided rndNum.
+ */
+f32 Math_Rand_Centered_Variable(u32* rndNum) {
+    u32 next;
+
+    next = (*rndNum * 1664525) + 1013904223;
+    // clang-format off
+    *rndNum = next; floatStore = (next >> 9) | 0x3F800000;
+    // clang-format on
+    return *((f32*)&floatStore) - 1.5f;
+}
diff --git a/src/code/z_play.c b/src/code/z_play.c
index 291c993ad..1ee3e00b4 100644
--- a/src/code/z_play.c
+++ b/src/code/z_play.c
@@ -339,7 +339,7 @@ void Gameplay_Init(GlobalContext* globalCtx) {
     gTrnsnUnkState = 0;
     globalCtx->transitionMode = 0;
     func_8008E6A0(&globalCtx->sub_7B8);
-    func_800FD9A0((u32)osGetTime());
+    Math_Rand_Seed((u32)osGetTime());
     Matrix_Init(&globalCtx->state);
     globalCtx->state.main = Gameplay_Main;
     globalCtx->state.destroy = Gameplay_Destroy;