From d4f5abbf38d5a50cfc71af9ad235e4093da4afe9 Mon Sep 17 00:00:00 2001
From: Ashelyn Rose <git@tempest.dev>
Date: Fri, 2 Jun 2023 23:45:22 -0600
Subject: [PATCH] memory free

---
 index.html         |  2 +-
 src/entrypoint.wat |  5 +++
 src/io.wat         | 16 ++++++---
 src/memory.wat     | 83 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 101 insertions(+), 5 deletions(-)
diff --git a/index.html b/index.html
index 8cabda6..a15c564 100644
--- a/index.html
+++ b/index.html
@@ -3,7 +3,7 @@
   <body>
     <script type="text/javascript">
       WebAssembly.instantiateStreaming(fetch("./output.wasm"), {
-        wasi_unstable: {
+        wasi_snapshot_preview1: {
           proc_exit: (i) => {throw new Error('err ' + i)},
           fd_write: (a, b, c, d) => console.log('writing something')
         }
diff --git a/src/entrypoint.wat b/src/entrypoint.wat
index 7e9d1c7..f88f26b 100644
--- a/src/entrypoint.wat
+++ b/src/entrypoint.wat
@@ -7,6 +7,7 @@
 
   call $memory_init
 
+  ;; allocate string location
   i32.const 13
   call $memory_alloc
   local.set $stringLocation
@@ -22,6 +23,10 @@
   i32.const 13 ;; length
   call $print
 
+  ;; free string
+  local.get $stringLocation
+  call $memory_free
+
   call $proc_exit
   unreachable
 )
diff --git a/src/io.wat b/src/io.wat
index 545faa7..140db88 100644
--- a/src/io.wat
+++ b/src/io.wat
@@ -1,5 +1,4 @@
-;; Currently using a hard-coded struct at location 0
-(import "wasi_unstable" "fd_write" (func $fd_write (param $file_descriptor i32) (param $io_vectors i32) (param $io_vecnum i32) (param $num_written_ptr i32) (result i32)))
+(import "wasi_snapshot_preview1" "fd_write" (func $fd_write (param $file_descriptor i32) (param $io_vectors i32) (param $io_vecnum i32) (param $num_written_ptr i32) (result i32)))
 
 (func $print (param $location i32) (param $length i32) (result i32)
   (local $structLoc i32)
@@ -35,10 +34,19 @@
   call $fd_write
   local.tee $resultCode
 
-  ;; if 0 code, make sure all bytes were written
+  local.get $structLoc ;; free calling struct
+  call $memory_free
+
+  local.get $resultLoc ;; get bytes written on stack
+  i32.load
+  local.get $resultLoc ;; free bytes written location
+  call $memory_free
+  local.set $resultLoc ;; put in result variable
+
+  ;; if code was 0, make sure all bytes were written
   i32.eqz
   if
-    local.get $resultLoc
+    local.get $resultLoc ;; should be value, not pointer any more
     local.get $length
     i32.lt_u
     if
diff --git a/src/memory.wat b/src/memory.wat
index bb589f0..63ce91b 100644
--- a/src/memory.wat
+++ b/src/memory.wat
@@ -16,6 +16,8 @@
   call $memory_markBlockSize
 )
 
+;; this runs into issue when allocating the final block in memory
+;; our end spot is not aligned with our block size rounding
 (func $memory_alloc (export "alloc") (param $requestedBytes i32) (result i32)
   (local $blockAddr i32)
   local.get $requestedBytes
@@ -45,6 +47,87 @@
   return
 )
 
+(func $memory_free (export "free_block") (param $pointer i32)
+  (local $startPointer i32)
+  (local $blockSize i32)
+  (local $temp i32)
+
+  ;; start with the direct block
+  local.get $pointer
+  i32.const 4
+  i32.sub
+  local.tee $startPointer
+  call $memory_getUsableSizeOfBlock
+  i32.const 8
+  i32.add
+  local.set $blockSize
+
+  ;; check block before
+  local.get $startPointer
+  i32.const 4
+  i32.sub
+  local.tee $temp
+  call $memory_isBlockUsed
+  i32.eqz
+  local.get $temp
+  i32.const 4 ;; start of allocateable memory
+  i32.ge_u
+  i32.and
+
+  if
+    ;; update start of block
+    local.get $temp
+    local.get $temp
+    call $memory_getUsableSizeOfBlock
+    i32.const 4
+    i32.add
+    i32.sub
+    local.tee $startPointer
+
+    ;; update size
+    call $memory_getUsableSizeOfBlock
+    local.get $blockSize
+    i32.const 8
+    i32.add
+    i32.add
+    local.set $blockSize
+  end
+
+  ;; check block after
+  local.get $startPointer
+  local.get $blockSize
+  i32.add
+  local.tee $temp
+
+  memory.size ;; first make sure it's inside memory
+  i32.const 16
+  i32.shl
+  i32.lt_u
+
+  if
+    ;; check if not used
+    local.get $temp
+    call $memory_isBlockUsed
+    i32.eqz
+
+    if
+      ;; update size
+      local.get $temp
+      call $memory_getUsableSizeOfBlock
+      local.get $blockSize
+      i32.const 8
+      i32.add
+      i32.add
+      local.set $blockSize
+    end
+  end
+
+  ;; re-init block
+  local.get $startPointer
+  local.get $blockSize
+  call $memory_markBlockSize
+)
+
 ;; returns address of boundary word for first free block
 (func $memory_findFreeBlock (export "findFree") (param $minimumBytes i32) (result i32)
   (local $memorySize i32)
