Allow different type lengths to be stored and loaded

In a wasm context not all types are 256 bit like in evm. This would make
easier to store smaller primitives (e.g. i32), since they would not
require padding.

The bigger win is when storing/retrieving dynamically sized arrays. Strings
can be stored under a single key and do not require splitting up into
smaller 32 byte chunks, and arrays do not need to store a size parameter.

Signed-off-by: Sean Young <[email protected]>

eth_interface.md

@@ -207,12 +207,13 @@ value.
 
 ## storageStore
 
-Store 256-bit a value in memory to persistent storage
+Store bytes value in memory to persistent storage
 
 **Parameters**
 
 - `pathOffset` **i32ptr** the memory offset to load the path from (`bytes32`)
-- `valueOffset` **i32ptr** the memory offset to load the value from (`bytes32`)
+- `valueOffset` **i32ptr** the memory offset to load the value from (`bytes`)
+- `valueLen` **i32** the length of the value
 
 **Returns**
 
@@ -225,22 +226,44 @@ Store 256-bit a value in memory to persistent storage
 
 ## storageLoad
 
-Loads a 256-bit a value to memory from persistent storage
+Loads bytes value to memory from persistent storage. No more than
+`resultMaxLength` is loaded. Returns the actual number of bytes loaded.
+Returns 0 if there is nothing stored at the path.
 
 **Parameters**
 
 - `pathOffset` **i32ptr** the memory offset to load the path from (`bytes32`)
-- `resultOffset` **i32ptr** the memory offset to store the result at (`bytes32`)
+- `resultOffset` **i32ptr** the memory offset to store the result at (`bytes`)
+- `resultMaxLength` **i32** the maximum length to load
 
 **Returns**
 
-*nothing*
+- `lengthLoaded` **i32** Actual number of bytes loaded from storage
+
+**Trap conditions**
+
+- load `bytes32` from memory at `pathOffset` results in out of bounds access,
+- store `bytes32` to memory at `resultOffset` results in out of bounds access.
+
+## storageSize
+
+Returns the length of the storage at the path.
+Returns 0 if there is nothing stored at the path.
+
+**Parameters**
+
+- `pathOffset` **i32ptr** the memory offset to load the path from (`bytes32`)
+
+**Returns**
+
+- `size` **i32** Number of bytes at the path
 
 **Trap conditions**
 
 - load `bytes32` from memory at `pathOffset` results in out of bounds access,
 - store `bytes32` to memory at `resultOffset` results in out of bounds access.
 
+
 ## getCaller
 
 Gets caller address and loads it into memory at the given offset. This is