2 files changed, 29 insertions, 32 deletions

diff --git a/include/swgfx.h b/include/swgfx.h
index 94eb359..005359b 100644
--- a/include/swgfx.h
+++ b/include/swgfx.h
@@ -39,13 +39,13 @@ typedef struct sgPixel { uint8_t r, g, b, a; } sgPixel;
 
 typedef struct swgfx swgfx;
 
-swgfx* sgNew();
+size_t sgMem(int width, int height); // Get memory requirements.
+swgfx* sgNew(int width, int height, void* mem);
 void   sgDel(swgfx**);
 
 // TODO: Write client app first, then implement the functions below in the C file.
 
-void sgColourBuffer(swgfx*, sgVec2i dimensions, sgPixel* buffer);
-void sgPresent     (swgfx*, sgVec2i dimensions, sgPixel* screen);
+void sgPresent(swgfx*, sgVec2i dimensions, sgPixel* screen);
 
 void sgModelId    (swgfx*);
 void sgModel      (swgfx*, sgVec3 position, sgVec3 right, sgVec3 up, sgVec3 forward);
@@ -66,11 +66,3 @@ void sgTrianglesIndexed(swgfx*, size_t numIndices, const sgIdx* indices, const s
 void sgTrianglesIndexedNonUniform(swgfx*, size_t numTris, const sgTriIdx* tris, const sgVec3* positions);
 
 void sgCheck(swgfx*);
-
-// Memory
-#define SG_ALIGN 64
-#define SG_ALIGN_PTR(P) ((uintptr_t)(P) & (~(SG_ALIGN-1)))
-#define SG_ALIGN_ALLOC(COUNT, TYPE) (TYPE*)sgAlloc(1, COUNT * sizeof(TYPE))
-#define SG_FREE(PP) sgFree((void**)PP)
-void* sgAlloc(size_t count, size_t size);
-void  sgFree(void**);
diff --git a/src/swgfx.c b/src/swgfx.c
index 3b9ce29..54f7432 100644
--- a/src/swgfx.c
+++ b/src/swgfx.c
@@ -17,7 +17,6 @@ Coordinate systems:
 #include <assert.h>
 #include <math.h>   // sqrt
 #include <stdint.h>
-#include <stdlib.h>
 #include <string.h>
 
 static constexpr sgVec3 Up3 = (sgVec3){0,1,0};
@@ -361,47 +360,53 @@ static void DrawTriangle3(swgfx* gfx, const sgTri3* tri) {
 }
 
 #define is_pow2_or_0(X) ((X & (X - 1)) == 0)
+#define SG_ALIGN 64
+#define SG_ALLOC(PP_MEM, COUNT, TYPE) (TYPE*)Alloc(PP_MEM, COUNT, sizeof(TYPE))
 
-static size_t align(size_t size) {
+static void* AlignPtr(void* address) {
+  assert(is_pow2_or_0(SG_ALIGN));
+  constexpr size_t mask = SG_ALIGN - 1;
+  return (void*)(((uintptr_t)address + mask) & ~mask);
+}
+
+static size_t Align(size_t size) {
   static_assert(is_pow2_or_0(SG_ALIGN));
   constexpr size_t mask = SG_ALIGN - 1;
   return (size + mask) & (~mask);
 }
 
-void* sgAlloc(size_t count, size_t size) {
-  const size_t total = align(count * size);
-  void* const ptr = aligned_alloc(SG_ALIGN, total);
+static void* Alloc(void** ppMem, size_t count, size_t size) {
+  assert(ppMem);
+  assert(*ppMem);
+  assert(*ppMem == AlignPtr(*ppMem)); // Should already be aligned.
+  const size_t total = Align(count * size);
+  void* ptr = *ppMem;
+  *ppMem = ptr + total;
   memset(ptr, 0, total);
   return ptr;
 }
 
-void sgFree(void** pp) {
-  assert(pp);
-  if (*pp) {
-    free(*pp);
-    *pp = nullptr;
-  }
+size_t sgMem(int width, int height) {
+  return Align(sizeof(swgfx)) +
+         Align(width * height * sizeof(sgPixel)) +
+         (SG_ALIGN - 1); // To make room to align allocations within the buffer.
 }
 
-swgfx* sgNew() {
-  swgfx* gfx = SG_ALIGN_ALLOC(1, swgfx);
+swgfx* sgNew(int width, int height, void* mem) {
+  void* aligned = AlignPtr(mem); // Uses the extra room we made in sgMem().
+  swgfx* gfx  = SG_ALLOC(&aligned, 1, swgfx);
+  gfx->dims   = (sgVec2i){width, height};
+  gfx->colour = SG_ALLOC(&aligned, width * height, sgPixel);
   return gfx;
 }
 
 void sgDel(swgfx** ppSwgfx) {
   assert(ppSwgfx);
   if (*ppSwgfx) {
-    free(*ppSwgfx);
-    *ppSwgfx = 0;
+    *ppSwgfx = nullptr;
   }
 }
 
-void sgColourBuffer(swgfx* gfx, sgVec2i dimensions, sgPixel* buffer) {
-  assert(gfx);
-  gfx->dims   = dimensions;
-  gfx->colour = buffer;
-}
-
 void sgPresent(swgfx* gfx, sgVec2i dimensions, sgPixel* screen) {
   assert(gfx);
   assert(screen);