From b96dd51d3349961189d4ab1bc2a5c45deff21c09 Mon Sep 17 00:00:00 2001
From: Steven Smith <Steveice10@gmail.com>
Date: Sat, 21 Nov 2015 10:37:22 -0800
Subject: [PATCH] Dynamically determine heap sizes.

---
 libctru/include/3ds/os.h              | 42 ++++++++++++++++++++++++++-
 libctru/source/os.c                   |  6 ++++
 libctru/source/system/allocateHeaps.c | 14 +++++++--
 3 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/libctru/include/3ds/os.h b/libctru/include/3ds/os.h
index 34b4754..e9b26c5 100644
--- a/libctru/include/3ds/os.h
+++ b/libctru/include/3ds/os.h
@@ -17,7 +17,16 @@
 /// Retrieves the revision version from a packed system version.
 #define GET_VERSION_REVISION(version) (((version)>> 8)&0xFF)
 
-/*! OS_VersionBin. Format of the system version: "<major>.<minor>.<build>-<nupver><region>" */
+/// Memory regions.
+typedef enum
+{
+	MEMREGION_ALL = 0,         ///< All regions.
+	MEMREGION_APPLICATION = 1, ///< APPLICATION memory.
+	MEMREGION_SYSTEM = 2,      ///< SYSTEM memory.
+	MEMREGION_BASE = 3,        ///< BASE memory.
+} MemRegion;
+
+/// OS_VersionBin. Format of the system version: "<major>.<minor>.<build>-<nupver><region>"
 typedef struct
 {
 	u8 build;
@@ -78,6 +87,37 @@ static inline u32 osGetKernelVersion(void)
 	return (*(vu32*)0x1FF80000) & ~0xFF;
 }
 
+/**
+ * @brief Gets the size of the specified memory region.
+ * @param region Memory region to check.
+ * @return The size of the memory region, in bytes.
+ */
+static inline u32 osGetMemRegionSize(MemRegion region)
+{
+	if(region == MEMREGION_ALL) {
+		return osGetMemRegionSize(MEMREGION_APPLICATION) + osGetMemRegionSize(MEMREGION_SYSTEM) + osGetMemRegionSize(MEMREGION_BASE);
+	} else {
+		return *(vu32*) (0x1FF80040 + (region - 1) * 0x4);
+	}
+}
+
+/**
+ * @brief Gets the number of used bytes within the specified memory region.
+ * @param region Memory region to check.
+ * @return The number of used bytes of memory.
+ */
+s64 osGetMemRegionUsed(MemRegion region);
+
+/**
+ * @brief Gets the number of free bytes within the specified memory region.
+ * @param region Memory region to check.
+ * @return The number of free bytes of memory.
+ */
+static inline s64 osGetMemRegionFree(MemRegion region)
+{
+	return (s64) osGetMemRegionSize(region) - osGetMemRegionUsed(region);
+}
+
 /**
  * @brief Gets the current time.
  * @return The number of milliseconds since 1st Jan 1900 00:00.
diff --git a/libctru/source/os.c b/libctru/source/os.c
index 8bbc0cc..abd93e4 100644
--- a/libctru/source/os.c
+++ b/libctru/source/os.c
@@ -51,6 +51,12 @@ void* osConvertOldLINEARMemToNew(const void* addr) {
 	return 0;
 }
 
+s64 osGetMemRegionUsed(MemRegion region) {
+	s64 mem_used;
+	svcGetSystemInfo(&mem_used, 0, region);
+	return mem_used;
+}
+
 //---------------------------------------------------------------------------------
 static datetime_t getSysTime(void) {
 //---------------------------------------------------------------------------------
diff --git a/libctru/source/system/allocateHeaps.c b/libctru/source/system/allocateHeaps.c
index 6bfcb62..0d7859c 100644
--- a/libctru/source/system/allocateHeaps.c
+++ b/libctru/source/system/allocateHeaps.c
@@ -1,6 +1,7 @@
 #include <3ds/types.h>
 #include <3ds/svc.h>
 #include <3ds/env.h>
+#include <3ds/os.h>
 
 extern char* fake_heap_start;
 extern char* fake_heap_end;
@@ -13,9 +14,16 @@ u32 __ctru_linear_heap_size;
 void __attribute__((weak)) __system_allocateHeaps() {
 	u32 tmp=0;
 
-	// Retrieve heap sizes.
-	__ctru_heap_size = envGetHeapSize();
-	__ctru_linear_heap_size = envGetLinearHeapSize();
+	if(envIsHomebrew()) {
+		// Use launcher-provided heap information.
+		__ctru_heap_size = envGetHeapSize();
+		__ctru_linear_heap_size = envGetLinearHeapSize();
+	} else {
+		// Distribute available memory into halves, aligning to page size.
+		u32 size = (osGetMemRegionFree(MEMREGION_APPLICATION) / 2) & 0xFFFFF000;
+		__ctru_heap_size = size;
+		__ctru_linear_heap_size = size;
+	}
 
 	// Allocate the application heap
 	__ctru_heap = 0x08000000;